Miscellany

Jai Ganesh · 2023-06-10 14:01:26

1804) Coal

Gist

Coal is a sedimentary deposit composed predominantly of carbon that is readily combustible. Coal is black or brownish-black, and has a composition that (including inherent moisture) consists of more than 50 percent by weight and more than 70 percent by volume of carbonaceous material.

Summary

Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is a type of fossil fuel, formed when dead plant matter decays into peat and is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits of coal originate in former wetlands called coal forests that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times. Many significant coal deposits are younger than this and originate from the Mesozoic and Cenozoic eras.

Coal is used primarily as a fuel. While coal has been known and used for thousands of years, its usage was limited until the Industrial Revolution. With the invention of the steam engine, coal consumption increased. In 2020, coal supplied about a quarter of the world's primary energy and over a third of its electricity. Some iron and steel-making and other industrial processes burn coal.

The extraction and use of coal causes premature death and illness. The use of coal damages the environment, and it is the largest anthropogenic source of carbon dioxide contributing to climate change. Fourteen billion tonnes of carbon dioxide was emitted by burning coal in 2020, which is 40% of the total fossil fuel emissions and over 25% of total global greenhouse gas emissions. As part of worldwide energy transition, many countries have reduced or eliminated their use of coal power. The United Nations Secretary General asked governments to stop building new coal plants by 2020. Global coal use peaked in 2013. To meet the Paris Agreement target of keeping global warming below 2 °C (3.6 °F) coal use needs to halve from 2020 to 2030, and "phasing down" coal was agreed upon in the Glasgow Climate Pact.

The largest consumer and importer of coal in 2020 was China, which accounts for almost half the world's annual coal production, followed by India with about a tenth. Indonesia and Australia export the most, followed by Russia.

Details

Coal is one of the most important primary fossil fuels, a solid carbon-rich material that is usually brown or black and most often occurs in stratified sedimentary deposits.

Coal is defined as having more than 50 percent by weight (or 70 percent by volume) carbonaceous matter produced by the compaction and hardening of altered plant remains—namely, peat deposits. Different varieties of coal arise because of differences in the kinds of plant material (coal type), degree of coalification (coal rank), and range of impurities (coal grade). Although most coals occur in stratified sedimentary deposits, the deposits may later be subjected to elevated temperatures and pressures caused by igneous intrusions or deformation during orogenesis (i.e., processes of mountain building), resulting in the development of anthracite and even graphite. Although the concentration of carbon in Earth’s crust does not exceed 0.1 percent by weight, it is indispensable to life and constitutes humankind’s main source of energy.

History of the use of coal

In ancient times

The discovery of the use of fire helped to distinguish humans from other animals. Early fuels were primarily wood (and charcoal derived from it), straw, and dried dung. References to the early uses of coal are meagre. Aristotle referred to “bodies which have more of earth than of smoke” and called them “coal-like substances.” (It should be noted that biblical references to coal are to charcoal rather than to the rock coal.) Coal was used commercially by the Chinese long before it was used in Europe. Although no authentic record is available, coal from the Fushun mine in northeastern China may have been employed to smelt copper as early as 1000 BCE. Stones used as fuel were said to have been produced in China during the Han dynasty (206 BCE–220 CE).

In Europe

Coal cinders found among Roman ruins in England suggest that the Romans were familiar with coal use before 400 CE. The first documented proof that coal was mined in Europe was provided by the monk Reinier of Liège, who wrote (about 1200) of black earth very similar to charcoal used by metalworkers. Many references to coal mining in England and Scotland and on the European continent began to appear in the writings of the 13th century. Coal was, however, used only on a limited scale until the early 18th century, when Abraham Darby of England and others developed methods of using in blast furnaces and forges coke made from coal. Successive metallurgical and engineering developments—most notably the invention of the coal-burning steam engine by James Watt—engendered an almost insatiable demand for coal.

In the New World

Up to the time of the American Revolution, most coal used in the American colonies came from England or Nova Scotia. Wartime shortages and the needs of the munitions manufacturers, however, spurred small American coal-mining operations such as those in Virginia on the James River near Richmond. By the early 1830s mining companies had emerged along the Ohio, Illinois, and Mississippi rivers and in the Appalachian region. As in European countries, the introduction of the steam locomotive gave the American coal industry a tremendous impetus. Continued expansion of industrial activity in the United States and in Europe further promoted the use of coal.

Modern utilization

Coal is an abundant natural resource that can be used as a source of energy, as a chemical source from which numerous synthetic compounds (e.g., dyes, oils, waxes, pharmaceuticals, and pesticides) can be derived, and in the production of coke for metallurgical processes. Coal is a major source of energy in the production of electrical power using steam generation. In addition, gasification and liquefaction of coal produce gaseous and liquid fuels that can be easily transported (e.g., by pipeline) and conveniently stored in tanks. After the tremendous rise in coal use in the early 2000s, which was primarily driven by the growth of China’s economy, coal use worldwide peaked in 2012. Since then coal use has experienced a steady decline, offset largely by increases in natural gas use.

Conversion

In general, coal can be considered a hydrogen-deficient hydrocarbon with a hydrogen-to-carbon ratio near 0.8, as compared with a liquid hydrocarbons ratio near 2 (for propane, ethane, butane, and other forms of natural gas) and a gaseous hydrocarbons ratio near 4 (for gasoline). For this reason, any process used to convert coal to alternative fuels must add hydrogen (either directly or in the form of water).

Gasification refers to the conversion of coal to a mixture of gases, including carbon monoxide, hydrogen, methane, and other hydrocarbons, depending on the conditions involved. Gasification may be accomplished either in situ or in processing plants. In situ gasification is accomplished by controlled, incomplete burning of a coal bed underground while adding air and steam. The gases are withdrawn and may be burned to produce heat or generate electricity, or they may be used as synthesis gas in indirect liquefaction or the production of chemicals.

Coal liquefaction—that is, any process of turning coal into liquid products resembling crude oil—may be either direct or indirect (i.e., by using the gaseous products obtained by breaking down the chemical structure of coal). Four general methods are used for liquefaction: (1) pyrolysis and hydrocarbonization (coal is heated in the absence of air or in a stream of hydrogen), (2) solvent extraction (coal hydrocarbons are selectively dissolved and hydrogen is added to produce the desired liquids), (3) catalytic liquefaction (hydrogenation takes place in the presence of a catalyst—for example, zinc chloride), and (4) indirect liquefaction (carbon monoxide and hydrogen are combined in the presence of a catalyst).

Problems associated with the use of coal

Hazards of mining and preparation

Coal is abundant and inexpensive. Assuming that current rates of usage and production do not change, estimates of reserves indicate that enough coal remains to last more than 200 years. There are, however, a variety of problems associated with the use of coal.

Mining operations are hazardous. Each year hundreds of coal miners lose their lives or are seriously injured. Major mine hazards include roof falls, rock bursts, and fires and explosions. The latter result when flammable gases (such as methane) trapped in the coal are released during mining operations and accidentally are ignited. Methane may be extracted from coal beds prior to mining through the process of hydraulic fracturing (fracking), which involves high-pressure injection of fluids underground in order to open fissures in rock that would allow trapped gas or crude oil to escape into pipes that would bring the material to the surface. Methane extraction was expected to lead to safer mines and provide a source of natural gas that had long been wasted. However, enthusiasm for this technology has been tempered with the knowledge that fracking has also been associated with groundwater contamination. In addition, miners working belowground often inhale coal dust over extended periods of time, which can result in serious health problems—for example, black lung.

Coal mines and coal-preparation plants have caused much environmental damage. Surface mining, or strip mining, destroys natural habitats, and one type of surface mining, known as mountaintop removal mining, dramatically and irreparably alters the topography of the area. Surface areas exposed during mining, as well as coal and rock waste (which were often dumped indiscriminately), weather rapidly, producing abundant sediment and soluble chemical products such as sulfuric acid and iron sulfates. Nearby streams can become clogged with sediment. Iron oxides have stained rocks, and “acid mine drainage” has caused marked reductions in the numbers of plants and animals living in the vicinity. Potentially toxic elements, leached from the exposed coal and adjacent rocks, are released into the environment and may contaminate groundwater supplies. Since the 1970s, stricter laws have significantly reduced the environmental damage caused by coal mining in developed countries, though more-severe damage continues to occur in many developing countries.

Pollution from coal utilization

Coal utilization is associated with various forms of air pollution. During the incomplete burning or conversion of coal, many compounds are produced, some of which are carcinogenic. The burning of coal also produces sulfur and nitrogen oxides that react with atmospheric moisture to produce sulfuric and nitric acids—so-called acid rain. In addition, it produces particulate matter (fly ash) that can be transported by winds for many hundreds of kilometres and solids (bottom ash and slag) that must be disposed of. Trace elements originally present in the coal may escape as volatiles (e.g., chlorine and mercury) or be concentrated in the ash (e.g., math and barium). Densely populated areas that burn coal directly for heating—such as the Mongolian capital, Ulaanbaatar—can suffer from unhealthy levels of air pollution, and areas near coal-burning power plants frequently have poorer air quality. Some of the harmful pollutants can be trapped by using such devices as electrostatic precipitators, baghouses, and scrubbers, but the technology is less common in developing countries. Current research on alternative means for combustion (e.g., fluidized bed combustion, magnetohydrodynamics, and low nitrogen dioxide burners) is expected to provide efficient and environmentally attractive methods for extracting energy from coal. Regardless of the means used for combustion, acceptable ways of disposing of the waste products have to be found.

The burning of coal, like the burning of all fossil fuels (oil and natural gas included), releases large quantities of carbon dioxide (CO2) into the atmosphere and is a major driver of global warming. A potent greenhouse gas, CO2 molecules allow the shorter-wavelength rays from the Sun to enter the atmosphere and strike Earth’s surface, but they do not allow much of the long-wave radiation reradiated from the surface to escape into space. The CO2 absorbs this upward-propagating infrared radiation and reemits a portion of it downward, causing the lower atmosphere to remain warmer than it would otherwise be. According to the Intergovernmental Panel on Climate Change (IPCC), there is substantial evidence that higher concentrations of CO2 and other greenhouse gases due to human activity have increased the mean temperature of Earth since 1950. Indeed, the burning of coal is the single largest contributor to anthropogenic climate change, with much of those emissions coming from the production of electricity using coal-powered plants. Technologies being considered to reduce carbon dioxide levels include biological fixation, cryogenic recovery, disposal in the oceans and aquifers, and conversion to methanol, but most climate scientists urgently advocate for a global transition away from coal in favour of renewable energies like solar and wind power.

Coal types and ranks

Coals may be classified in several ways. One mode of classification is by coal type; such types have some genetic implications because they are based on the organic materials present and the coalification processes that produced the coal. The most useful and widely applied coal-classification schemes are those based on the degree to which coals have undergone coalification. Such varying degrees of coalification are generally called coal ranks (or classes). In addition to the scientific value of classification schemes of this kind, the determination of rank has a number of practical applications. Many coal properties are in part determined by rank, including the amount of heat produced during combustion, the amount of gaseous products released upon heating, and the suitability of the coals for liquefaction or for producing coke.

Coal types

Macerals

Coals contain both organic and inorganic phases. The latter consist either of minerals such as quartz and clays that may have been brought in by flowing water (or wind activity) or of minerals such as pyrite and marcasite that formed in place (authigenic). Some formed in living plant tissues, and others formed later during peat formation or coalification. Some pyrite (and marcasite) is present in micrometre-sized spheroids called framboids (named for their raspberry-like shape) that formed quite early. Framboids are very difficult to remove by conventional coal-cleaning processes.

By analogy to the term mineral, British botanist Marie C. Stopes proposed in 1935 the term maceral to describe organic constituents present in coals. The word is derived from the Latin macerare, meaning “to macerate.” (Mineral names often end in -ite. The corresponding ending for macerals is -inite.) Maceral nomenclature has been applied differently by some European coal petrologists who studied polished blocks of coal using reflected-light microscopy (their terminology is based on morphology, botanical affinity, and mode of occurrence) and by some North American petrologists who studied very thin slices (thin sections) of coal using transmitted-light microscopy. Various nomenclature systems have been used.

Three major maceral groups are generally recognized: vitrinite, liptinite (formerly called exinite), and inertinite. The vitrinite group is the most abundant, constituting as much as 50 to 90 percent of many North American coals. Vitrinites are derived primarily from cell walls and woody tissues. They show a wide range of reflectance values (how the coal reflects light; discussed below), but in individual samples these values tend to be intermediate compared with those of the other maceral groups. Several varieties are recognized—e.g., telinite (the brighter parts of vitrinite that make up cell walls) and collinite (clear vitrinite that occupies the spaces between cell walls).

The liptinite group makes up 5 to 15 percent of many coals. Liptinites are derived from waxy or resinous plant parts, such as cuticles, spores, and wound resins. Their reflectance values are usually the lowest in an individual sample. Several varieties are recognized, including sporinite (spores are typically preserved as flattened spheroids), cutinite (part of cross sections of leaves, often with crenulated surfaces), and resinite (ovoid and sometimes translucent masses of resin). The liptinites may fluoresce (i.e., luminesce because of absorption of radiation) under ultraviolet light, but with increasing rank their optical properties approach those of the vitrinites, and the two groups become indistinguishable.

The inertinite group makes up 5 to 40 percent of most coals. Their reflectance values are usually the highest in a given sample. The most common inertinite maceral is fusinite, which has a charcoal-like appearance with obvious cell texture. The cells may be either empty or filled with mineral matter, and the cell walls may have been crushed during compaction (bogen texture). Inertinites are derived from strongly altered or degraded plant material that is thought to have been produced during the formation of peat; in particular, charcoal produced by a fire in a peat swamp is preserved as fusinite.

Coal rock types

Coals may be classified on the basis of their macroscopic appearance (generally referred to as coal rock type, lithotype, or kohlentype). Four main types are recognized:

* Vitrain, which is characterized by a brilliant black lustre and composed primarily of the maceral group vitrinite, which is derived from the woody tissue of large plants. Vitrain is brittle and tends to break into angular fragments; however, thick vitrain layers show conchoidal fractures (that is, curving fractures that resemble the interior of a seashell) when broken. Vitrain occurs in narrow, sometimes markedly uniform, bright bands that are about 3 to 10 mm (about 0.1 to 0.4 inch) thick. Vitrain probably formed under somewhat drier surface conditions than did the lithotypes clarain and durain. On burial, stagnant groundwater prevented the complete decomposition of the woody plant tissues.
* Clarain, which has an appearance between those of vitrain and durain and is characterized by alternating bright and dull black laminae (thin layers, each commonly less than 1 mm thick). The brightest layers are composed chiefly of the maceral vitrinite and the duller layers of the other maceral groups, liptinite and inertinite. Clarain exhibits a silky lustre less brilliant than that of vitrain. It seems to have originated under conditions that alternated between those in which durain and vitrain formed.
* Durain, which is characterized by a hard granular texture and composed of the maceral groups liptinite and inertinite as well as relatively large amounts of inorganic minerals. Durain occurs in layers more than 3 to 10 mm (about 0.1 to 0.4 inch) thick, although layers more than 10 cm (about 4 inches) thick have been recognized. Durains are usually dull black to dark gray in colour. Durain is thought to have formed in peat deposits below water level, where only liptinite and inertinite components resisted decomposition and where inorganic minerals accumulated from sedimentation.
* Fusain, which is commonly found in silky and fibrous lenses that are only millimetres thick and centimetres long. Most fusain is extremely soft and crumbles readily into a fine, sootlike powder that soils the hands. Fusain is composed mainly of fusinite (carbonized woody plant tissue) and semifusinite from the maceral group inertinite, which is rich in carbon and highly reflective. It closely resembles charcoal, both chemically and physically, and is believed to have been formed in peat deposits swept by forest fires, by fungal activity that generated intense heat, or by subsurface oxidation of coal.

Banded and nonbanded coals

The term coal type is employed to distinguish between banded coals and nonbanded coals. Banded coals contain varying amounts of vitrinite and opaque material. They are made up of less than 5 percent anthraxylon (the translucent glossy jet-black material in bituminous coal) that alternates with thin bands of dull coal called attritus. Banded coals include bright coal, which contains more than 80 percent vitrinite, and splint coal, which contains more than 30 percent opaque matter. The nonbanded varieties include boghead coal, which has a high percentage of algal remains, and cannel coal, which has a high percentage of spores in its attritus (that is, pulverized or finely divided matter). The anthraxylon content in nonbanded coals exceeds 5 percent. The usage of all the above terms is quite subjective.

Ranking by coalification

Hydrocarbon content

The oldest coal-classification system was based on criteria of chemical composition. Developed in 1837 by the French chemist Henri-Victor Regnault, it was improved in later systems that classified coals on the basis of their hydrogen and carbon content. However, because the relationships between chemistry and other coal properties are complex, such classifications are rarely used for practical purposes today.

Chemical content and properties

Coal is divided into a number of ranks to help buyers such as electrical utilities assess the calorific value and volatile matter content of each unit of coal they purchase. The most commonly employed systems of classification are those based on analyses that can be performed relatively easily in the laboratory—for example, determining the percentage of volatile matter lost upon heating to about 950 °C (about 1,750 °F) or the amount of heat released during combustion of the coal under standard conditions (see also coal utilization). ASTM International (formerly the American Society for Testing and Materials) assigns ranks to coals on the basis of fixed carbon content, volatile matter content, and calorific value. In addition to the major ranks (lignite, subbituminous, bituminous, and anthracite), each rank may be divided into coal groups such as high-volatile A bituminous coal. These categories differ slightly between countries; however, the ranks are often comparable with respect to moisture, volatile matter content, and heating value. Other designations, such as coking coal and steam coal, have been applied to coals, and they also tend to differ from country to country.

Virtually all classification systems use the percentage of volatile matter present to distinguish coal ranks. In the ASTM classification, high-volatile A bituminous (and higher ranks) are classified on the basis of their volatile matter content. Coals of lower rank are classified primarily on the basis of their heat values, because of their wide ranges in volatile matter content (including moisture). The agglomerating character of a coal refers to its ability to soften and swell when heated and to form cokelike masses that are used in the manufacture of steel. The most suitable coals for agglomerating purposes are in the bituminous rank.

Coal analyses may be presented in the form of “proximate” and “ultimate” analyses, whose analytical conditions are prescribed by organizations such as ASTM. A typical proximate analysis includes the moisture, ash, volatile matter, and fixed carbon contents. (Fixed carbon is the material, other than ash, that does not vaporize when heated in the absence of air. It is usually determined by subtracting the sum of the first three values—moisture, ash, and volatile matter—in weight percent from 100 percent.) It is important for economic reasons to know the moisture and ash contents of a coal because they do not contribute to the heating value of a coal. In most cases ash becomes an undesirable residue and a source of pollution, but for some purposes (e.g., use as a chemical source or for coal liquefaction) the presence of mineral matter may be desirable. Most of the heat value of a coal comes from its volatile matter, excluding moisture, and fixed carbon content. For most coals it is necessary to measure the actual amount of heat released upon combustion (expressed in megajoules per kilogram or British thermal units per pound).

Ultimate analyses are used to determine the carbon, hydrogen, sulfur, nitrogen, ash, oxygen, and moisture contents of a coal. For specific applications, other chemical analyses may be employed. These may involve, for example, identifying the forms of sulfur present. Sulfur may occur in the form of sulfide minerals (pyrite and marcasite), sulfate minerals (gypsum), or organically bound sulfur. In other cases the analyses may involve determining the trace elements present (e.g., mercury, chlorine), which may influence the suitability of a coal for a particular purpose or help to establish methods for reducing environmental pollution and so forth.

Origin of coal

Coal-forming materials

Plant matter

It is generally accepted that most coals formed from plants that grew in and adjacent to swamps in warm, humid regions. Material derived from these plants accumulated in low-lying areas that remained wet most of the time and was converted to peat through the activity of microorganisms. (It should be noted that peat can occur in temperate regions [e.g., Ireland and the state of Michigan in the United States] and even in subarctic regions [e.g., the Scandinavian countries].) Under certain conditions this organic material continued to accumulate and was later converted into coal. Much of the plant matter that accumulates on the surface of Earth is never converted to peat or to coal, because it is removed by fire or organic decomposition. Hence, the vast coal deposits found in ancient rocks must represent periods during which several favourable biological and physical processes occurred at the same time.

Evidence that coal was derived from plants comes from three principal sources. First, lignites, the lowest coal rank, often contain recognizable plant remains. Second, sedimentary rock layers above, below, and adjacent to coal seams contain plant fossils in the form of impressions and carbonized films (e.g., leaves and stems) and casts of larger parts such as roots, branches, and trunks. Third, even coals of advanced rank may reveal the presence of precursor plant material. When examined microscopically in thin sections or polished blocks, cell walls, cuticles (the outer wall of leaves), spores, and other structures can still be recognized (see below Macerals). Algal and fungal remains also may be present. (Algae are major components in boghead coal, a type of sapropelic coal.)

The fossil record

Anthracite (the highest coal rank) material, which appears to have been derived from algae, is known from the Proterozoic Eon (approximately 2.5 billion to 541 million years ago) of Precambrian time. Siliceous rocks of the same age contain fossil algae and fungi. These early plants were primarily protists (solitary or aggregate unicellular organisms that include yellow-green algae, golden-brown algae, and diatoms) that lived in aqueous environments. By the Silurian Period (443.8 million to 419.2 million years ago), plants had developed the ability to survive on land and had invaded the planet’s coastal areas.

Evidence for coastal forests is preserved in strata of the Ordovician Period (485.4 million to 443.8 million years ago). By the latter half of the Paleozoic Era, plants had undergone extensive evolution and occupied many previously vacant environments (this phenomenon is sometimes called adaptive radiation).

Asia

There were two major eras of coal formation in geologic history. The older includes the Carboniferous Period (extending from 358.9 million to 298.9 million years ago and often divided into the Mississippian and Pennsylvanian subperiods) and the Permian Period (from approximately 298.9 million to 251.9 million years ago) of the Paleozoic Era. Much of the bituminous coal of eastern North America and Europe is Carboniferous in age. Most coals in Siberia, eastern Asia, and Australia are of Permian origin.

The younger era of coal formation began about 145 million years ago, during the Cretaceous Period, and reached its peak approximately 66 million to 2.6 million years ago, during the Paleogene and Neogene periods of the Cenozoic Era. Most of the coals that formed during this later era are lignites and subbituminous (brown) coals. These are widespread in western North America (including Alaska), southern France and central Europe, Japan, and Indonesia.

Late Paleozoic flora included sphenopsids, lycopsids, pteropsids, and the Cordaitales. The sphenopsid Calamites grew as trees in swamps. Calamites had long, jointed stems with sparse foliage. The lycopsids included species of Lepidodendron and Sigillaria (up to 30 metres [about 100 feet] tall) that grew in somewhat drier areas. Pteropsids included both true ferns (Filicineae) and extinct seed ferns (Pteridospermaphyta), which grew in relatively dry environments. The Cordaitales, which had tall stems and long, narrow, palmlike leaves, also favoured drier areas. During the Cretaceous and Cenozoic the angiosperms (flowering plants) evolved, producing a diversified flora from which the younger coals developed.

Formation processes

Peat

Although peat is used as a source of energy, it is not usually considered a coal. It is the precursor material from which coals are derived, and the process by which peat is formed is studied in existing swamps in many parts of the world (e.g., in the Okefenokee Swamp of Georgia, U.S., and along the southwestern coast of New Guinea). The formation of peat is controlled by several factors, including (1) the evolutionary development of plant life, (2) the climatic conditions (warm enough to sustain plant growth and wet enough to permit the partial decomposition of the plant material and preserve the peat), and (3) the physical conditions of the area (its geographic position relative to the sea or other bodies of water, rates of subsidence or uplift, and so forth). Warm moist climates are thought to produce broad bands of bright coal, a type of bituminous coal characterized by its fine banding and high concentrations of nitrogen, sulfur, and moisture. Cooler temperate climates, on the other hand, are thought to produce detrital coal (which is thought to be the remains of preexisting coal beds) with relatively little bright coal.

Initially, the area on which a future coal seam may be developed must be uplifted so that plant growth can be established. Areas near seacoasts or low-lying areas near streams stay moist enough for peat to form, but elevated swamps (some bogs and moors) can produce peat only if the annual precipitation exceeds annual evaporation and little percolation or drainage occurs. Thick peat deposits necessary for coal formation develop at sites where the following conditions exist: slow, continuous subsidence; the presence of such natural structures as levees, beaches, and bars that give protection from frequent inundation; and a restricted supply of incoming sediments that would interrupt peat formation. In such areas the water may become quite stagnant (except for a few rivers traversing the swamp), and plant material can continue to accumulate. Microorganisms attack the plant material and convert it to peat. Very close to the surface where oxygen is still readily available (aerobic, or oxidizing, conditions), the decomposition of the plant material produces mostly gaseous and liquid products. With increasing depth, however, the conditions become increasingly anaerobic (reducing), and molds and peats develop. The process of peat formation—biochemical coalification—is most active in the upper few metres of a peat deposit. Fungi are not found below about 0.5 metre (about 18 inches), and most forms of microbial life are eliminated at depths below about 10 metres (about 30 feet). If either the rate of subsidence or the rate of influx of new sediment increases, the peat will be buried and soon thereafter the coalification process—geochemical coalification—begins. The cycle may be repeated many times, which accounts for the numerous coal seams found in some sedimentary basins.

Coalification

The general sequence of coalification is from lignite to subbituminous to bituminous to anthracite. Since microbial activity ceases within a few metres of Earth’s surface, the coalification process must be controlled primarily by changes in physical conditions that take place with depth. Some coal characteristics are determined by events that occur during peat formation—e.g., charcoal-like material in coal is attributed to fires that occurred during dry periods while peat was still forming.

Three major physical factors—duration, increasing temperature, and increasing pressure—may influence the coalification process. In laboratory experiments artificially prepared coals are influenced by the duration of the experiment, but in nature the length of time is substantially longer and the overall effect of time remains undetermined. Low-rank coal (i.e., brown coal) in the Moscow Basin was deposited during Carboniferous time but was not buried deeply and never reached a higher rank. The most widely accepted explanation is that coalification takes place in response to increasing temperature. In general, temperature increases with depth. This geothermal gradient averages about 30 °C (about 85 °F) per kilometre, but the gradient ranges from less than 10 °C (50 °F) per kilometre in regions undergoing very rapid subsidence to more than 100 °C (212 °F) per kilometre in areas of igneous activity. Measurements of thicknesses of sedimentary cover and corresponding coal ranks suggest that temperatures lower than 200 °C (about 390 °F) are sufficient to produce coal of anthracite rank. The effect of increasing pressure due to depth of burial is not considered to cause coalification. In fact, increasing overburden pressure might have the opposite effect if volatile compounds such as methane that must escape during coalification are retained. Pressure may influence the porosity and moisture content of coal.

Structure and properties of coal

Organic compounds

The plant material from which coal is derived is composed of a complex mixture of organic compounds, including cellulose, lignin, fats, waxes, and tannins. As peat formation and coalification proceed, these compounds, which have more or less open structures, are broken down, and new compounds—primarily aromatic (benzenelike) and hydroaromatic—are produced. In vitrinite these compounds are connected by cross-linking oxygen, sulfur, and molecules such as methylene. During coalification, volatile phases rich in hydrogen and oxygen (e.g., water, carbon dioxide, and methane) are produced and escape from the mass; hence, the coal becomes progressively richer in carbon. The classification of coal by rank is based on these changes—i.e., as coalification proceeds, the amount of volatile matter gradually decreases and the amount of fixed carbon increases. As volatiles are expelled, more carbon-to-carbon linkages occur in the remaining coal until, having reached the anthracite rank, it takes on many of the characteristics of the end product of the metamorphism of carbonaceous material—namely, graphite. Coals pass through several structural states as the bonds between the aromatic nuclei increase.

Properties

Many of the properties of coal are strongly rank-dependent, although other factors such as maceral composition and the presence of mineral matter also influence its properties. Several techniques have been developed for studying the physical and chemical properties of coal, including density measurements, X-ray diffraction, scanning and transmission electron microscopy, infrared spectrophotometry, mass spectroscopy, gas chromatography, thermal analysis, and electrical, optical, and magnetic measurements.

Density

Knowledge of the physical properties of coal is important in coal preparation and utilization. For example, coal density ranges from approximately 1.1 to about 1.5 megagrams per cubic metre, or grams per cubic centimetre (1 megagram per cubic metre equals 1 gram per cubic centimetre). Coal is slightly denser than water (1.0 megagram per cubic metre) and significantly less dense than most rock and mineral matter (e.g., shale has a density of about 2.7 megagrams per cubic metre and pyrite of 5.0 megagrams per cubic metre). Density differences make it possible to improve the quality of a coal by removing most of the rock matter and sulfide-rich fragments by means of heavy liquid separation (fragments with densities greater than about 1.5 megagrams per cubic metre settle out while the coal floats on top of the liquid). Devices such as cyclones and shaker tables also separate coal particles from rock and pyrite on the basis of their different densities.

Porosity

Coal density is controlled in part by the presence of pores that persist throughout coalification. Measurement of pore sizes and pore distribution is difficult; however, there appear to be three size ranges of pores: (1) macropores (diameter greater than 50 nanometres), (2) mesopores (diameter 2 to 50 nanometres), and (3) micropores (diameter less than 2 nanometres). (One nanometre is equal to 10−9 metre.) Most of the effective surface area of a coal—about 200 square metres per gram—is not on the outer surface of a piece of coal but is located inside the coal in its pores. The presence of pore space is important in the production of coke, gasification, liquefaction, and the generation of high-surface-area carbon for purifying water and gases. From the standpoint of safety, coal pores may contain significant amounts of adsorbed methane that may be released during mining operations and form explosive mixtures with air. The risk of explosion can be reduced by adequate ventilation during mining or by prior removal of coal-bed methane.

Reflectivity

An important property of coal is its reflectivity (or reflectance)—i.e., its ability to reflect light. Reflectivity is measured by shining a beam of monochromatic light (with a wavelength of 546 nanometres) on a polished surface of the vitrinite macerals in a coal sample and measuring the percentage of the light reflected with a photometer. Vitrinite is used because its reflectivity changes gradually with increasing rank. Fusinite reflectivities are too high due to its origin as charcoal, and liptinites tend to disappear with increasing rank. Although little of the incident light is reflected (ranging from a few tenths of a percent to 12 percent), the value increases with rank and can be used to determine the rank of most coals without measuring the percentage of volatile matter present.

The study of coals (and coaly particles called phyterals) in sedimentary basins containing oil and/or gas reveals a close relationship between coalification and the maturation of liquid and gaseous hydrocarbons. During the initial stages of coalification (to a reflectivity of almost 0.5 and near the boundary between subbituminous and high-volatile C bituminous coal), hydrocarbon generation produces chiefly methane. The maximum generation of liquid petroleum occurs during the development of high-volatile bituminous coals (in the reflectivity range from roughly 0.5 to about 1.3). With increasing depth and temperature, petroleum liquids break down and, finally, only natural gas (methane) remains. Geologists can use coal reflectivity to anticipate the potential for finding liquid or gaseous hydrocarbons as they explore for petroleum.

Other properties

Other properties, such as hardness, grindability, ash-fusion temperature, and free-swelling index (a visual measurement of the amount of swelling that occurs when a coal sample is heated in a covered crucible), may affect coal mining and preparation, as well as the way in which a coal is used. Hardness and grindability determine the kinds of equipment used for mining, crushing, and grinding coals in addition to the amount of power consumed in their operation. Ash-fusion temperature influences furnace design and operating conditions. The free-swelling index provides preliminary information concerning the suitability of a coal for coke production.

World distribution of coal

General occurrence

Coal is a widespread resource of energy and chemicals. Although terrestrial plants necessary for the development of coal did not become abundant until Carboniferous time (358.9 million to 298.9 million years ago), large sedimentary basins containing rocks of Carboniferous age and younger are known on virtually every continent, including Antarctica. The presence of large coal deposits in regions that now have arctic or subarctic climates (such as Alaska and Siberia) is due to climatic changes and to the tectonic motion of crustal plates that moved ancient continental masses over Earth’s surface, sometimes through subtropical and even tropical regions. Coal is absent in some areas (such as Greenland and much of northern Canada) because the rocks found there predate the Carboniferous Period and these regions, known as continental shields, lacked the abundant terrestrial plant life needed for the formation of major coal deposits.

Resources and reserves

World coal reserves and resources are difficult to assess. Although some of the difficulty stems from the lack of accurate data for individual countries, two fundamental problems make these estimates difficult and subjective. The first problem concerns differences in the definition of terms such as proven reserves (generally only those quantities that are recoverable) and geological resources (generally the total amount of coal present, whether or not recoverable at present).

The proven reserves for any commodity should provide a reasonably accurate estimate of the amount that can be recovered under existing operating and economic conditions. To be economically mineable, a coal bed must have a minimum thickness (about 0.6 metre; 2 feet) and be buried less than some maximum depth (roughly 2,000 metres; 6,600 feet) below Earth’s surface. These values of thickness and depth are not fixed but change with coal quality, demand, the ease with which overlying rocks can be removed (in surface mining) or a shaft sunk to reach the coal seam (in underground mining), and so forth. The development of new mining techniques may increase the amount of coal that can be extracted relative to the amount that cannot be removed. For example, in underground mining (which accounts for about 60 percent of world coal production), conventional mining methods leave behind large pillars of coal to support the overlying rocks and recover only about half of the coal present. On the other hand, longwall mining, in which the equipment removes continuous parallel bands of coal, may recover nearly all the coal present.

The second problem, which concerns the estimation of reserves, is the rate at which a commodity is consumed. When considering the worldwide reserves of coal, the number of years that coal will be available may be more important than the total amount of coal resources. At present rates of consumption, world coal reserves should last more than 300–500 years. A large amount of additional coal is present in Earth but cannot be recovered at this time. These resources, sometimes called “geologic resources,” are even more difficult to estimate, but they are thought to be as much as 15 times greater than the amount of proven reserves.

The quantities of proven coal reserves are typically shown in millions of tons of coal equivalent (MTCE). One ton of coal equivalent equals 1 metric ton (2,205 pounds) of coal with a heating value of 29.3 megajoules per kilogram (12,600 British thermal units per pound). These values suggest that the United States has the largest amount of recoverable coal. Nearly 75 percent of the world’s recoverable coal resources are controlled by five countries: the United States (about 22 percent), Russia (about 15 percent), Australia (14 percent), China (about 13 percent), and India (about 10 percent).

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Jai Ganesh · 2023-06-11 16:16:47

1805) Amoeba

Gist

The term amoeba is used to generally refer to any cell that exhibits an amoeboid movement. An amoeboid movement is one in which the cell forms pseudopods that can be extended and retracted as the cell moves. In this regard, amoebas include cells that are amoeba-like, such as cells of certain fungi, algae, and animals. They are also referred to as amoeboid to allude to their amoeba-like appearance and amoeboid movement.

Summary

Amoeba, also spelled ameba, plural amoebas or amoebae, is any of the microscopic unicellular protozoans of the rhizopodan order Amoebida. The well-known type species, Amoeba proteus, is found on decaying bottom vegetation of freshwater streams and ponds. There are numerous parasitic amoebas. Of six species found in the human alimentary tract, Entamoeba histolytica causes amebic dysentery. Two related free-living genera of increasing biomedical importance are Acanthamoeba and Naegleria, strains of which have been recognized as disease-causing parasites in several vertebrates, including humans.

Amoebas are identified by their ability to form temporary cytoplasmic extensions called pseudopodia, or false feet, by means of which they move about. This type of movement, called amoeboid movement, is considered to be the most primitive form of animal locomotion.

Amoebas are used extensively in cell research for determining the relative functions and interactions of the nucleus and the cytoplasm. Each amoeba contains a small mass of jellylike cytoplasm, which is differentiated into a thin outer plasma membrane, a layer of stiff, clear ectoplasm just within the plasma membrane, and a central granular endoplasm. The endoplasm contains food vacuoles, a granular nucleus, and a clear contractile vacuole. The amoeba has no mouth or math; food is taken in and material excreted at any point on the cell surface. During feeding, extensions of cytoplasm flow around food particles, surrounding them and forming a vacuole into which enzymes are secreted to digest the particles. Oxygen diffuses into the cell from the surrounding water, and metabolic wastes diffuse from the amoeba into the surrounding water. A contractile vacuole, which removes excess water from the amoeba, is absent in most marine and parasitic species. Reproduction is asexual (binary fission).

During adverse environmental periods many amoebas survive by encystment: the amoeba becomes circular, loses most of its water, and secretes a cyst membrane that serves as a protective covering. When the environment is again suitable, the envelope ruptures, and the amoeba emerges.

Details

An amoeba often called an amoeboid, is a type of cell or unicellular organism with the ability to alter its shape, primarily by extending and retracting pseudopods. Amoebae do not form a single taxonomic group; instead, they are found in every major lineage of eukaryotic organisms. Amoeboid cells occur not only among the protozoa, but also in fungi, algae, and animals.

Microbiologists often use the terms "amoeboid" and "amoeba" interchangeably for any organism that exhibits amoeboid movement.

In older classification systems, most amoebae were placed in the class or subphylum Sarcodina, a grouping of single-celled organisms that possess pseudopods or move by protoplasmic flow. However, molecular phylogenetic studies have shown that Sarcodina is not a monophyletic group whose members share common descent. Consequently, amoeboid organisms are no longer classified together in one group.

The best known amoeboid protists are Chaos carolinense and Amoeba proteus, both of which have been widely cultivated and studied in classrooms and laboratories. Other well known species include the so-called "brain-eating amoeba" Naegleria fowleri, the intestinal parasite Entamoeba histolytica, which causes amoebic dysentery, and the multicellular "social amoeba" or slime mould Dictyostelium discoideum.

Shape, movement and nutrition

Amoeba do not have cell walls, which allows for free movement. Amoeba move and feed by using pseudopods, which are bulges of cytoplasm formed by the coordinated action of actin microfilaments pushing out the plasma membrane that surrounds the cell. The appearance and internal structure of pseudopods are used to distinguish groups of amoebae from one another. Amoebozoan species, such as those in the genus Amoeba, typically have bulbous (lobose) pseudopods, rounded at the ends and roughly tubular in cross-section. Cercozoan amoeboids, such as Euglypha and Gromia, have slender, thread-like (filose) pseudopods. Foraminifera emit fine, branching pseudopods that merge with one another to form net-like (reticulose) structures. Some groups, such as the Radiolaria and Heliozoa, have stiff, needle-like, radiating axopodia (actinopoda) supported from within by bundles of microtubules.

Free-living amoebae may be "testate" (enclosed within a hard shell), or "naked" (also known as gymnamoebae, lacking any hard covering). The shells of testate amoebae may be composed of various substances, including calcium, silica, chitin, or agglutinations of found materials like small grains of sand and the frustules of diatoms.

To regulate osmotic pressure, most freshwater amoebae have a contractile vacuole which expels excess water from the cell. This organelle is necessary because freshwater has a lower concentration of solutes (such as salt) than the amoeba's own internal fluids (cytosol). Because the surrounding water is hypotonic with respect to the contents of the cell, water is transferred across the amoeba's cell membrane by osmosis. Without a contractile vacuole, the cell would fill with excess water and, eventually, burst. Marine amoebae do not usually possess a contractile vacuole because the concentration of solutes within the cell are in balance with the tonicity of the surrounding water.

Diet

The food sources of amoebae vary. Some amoebae are predatory and live by consuming bacteria and other protists. Some are detritivores and eat dead organic material.

Amoebae typically ingest their food by phagocytosis, extending pseudopods to encircle and engulf live prey or particles of scavenged material. Amoeboid cells do not have a mouth or cytostome, and there is no fixed place on the cell at which phagocytosis normally occurs.

Some amoebae also feed by pinocytosis, imbibing dissolved nutrients through vesicles formed within the cell membrane.

Size range

The size of amoeboid cells and species is extremely variable. The marine amoeboid Massisteria voersi is just 2.3 to 3 micrometres in diameter, within the size range of many bacteria. At the other extreme, the shells of deep-sea xenophyophores can attain 20 cm in diameter. Most of the free-living freshwater amoebae commonly found in pond water, ditches, and lakes are microscopic, but some species, such as the so-called "giant amoebae" Pelomyxa palustris and Chaos carolinense, can be large enough to see with the naked eye.

Amoebae as specialized cells and life cycle stages

Some multicellular organisms have amoeboid cells only in certain phases of life, or use amoeboid movements for specialized functions. In the immune system of humans and other animals, amoeboid white blood cells pursue invading organisms, such as bacteria and pathogenic protists, and engulf them by phagocytosis.

Amoeboid stages also occur in the multicellular fungus-like protists, the so-called slime moulds. Both the plasmodial slime moulds, currently classified in the class Myxogastria, and the cellular slime moulds of the groups Acrasida and Dictyosteliida, live as amoebae during their feeding stage. The amoeboid cells of the former combine to form a giant multinucleate organism, while the cells of the latter live separately until food runs out, at which time the amoebae aggregate to form a multicellular migrating "slug" which functions as a single organism.

Other organisms may also present amoeboid cells during certain life-cycle stages, e.g., the gametes of some green algae (Zygnematophyceae) and pennate diatoms, the spores (or dispersal phases) of some Mesomycetozoea, and the sporoplasm stage of Myxozoa and of Ascetosporea.

Jai Ganesh · 2023-06-12 14:05:21

1806) Euglena

Summary

Euglena is genus of more than 1,000 species of single-celled flagellated (i.e., having a whiplike appendage) microorganisms that feature both plant and animal characteristics. Found worldwide, Euglena live in fresh and brackish water rich in organic matter and can also be found in moist soils. As photosynthetic protists, Euglena have a taxonomy that is somewhat contentious, and the genus is usually placed in the phylum Euglenozoa. Previous classifications placed the genus in the algal phylum Euglenophyta.

Euglena are characterized by an elongated cell (15–500 micrometres [1 micrometre = {10}^{−6} metre], or 0.0006–0.02 inch) with one nucleus, numerous chloroplasts (cell organelles that contain chlorophyll and are the site of photosynthesis), a contractile vacuole (organelle that regulates the cytoplasm), an eyespot, and one or two flagella. Certain species (e.g., E. rubra) appear red in sunlight because they contain a large amount of carotenoid pigments. Unlike plant cells, Euglena lack a rigid cellulose wall and have a flexible pellicle (envelope) that allows them to change shape. Though they are photosynthetic, most species can also feed heterotrophically (on other organisms) and absorb food directly through the cell surface via phagocytosis (in which the cell membrane entraps food particles in a vacuole for digestion). Food is often stored as a specialized complex carbohydrate known as paramylon, which enables the organisms to survive in low-light conditions. Euglena reproduce asexually by means of longitudinal cell division, in which they divide down their length, and several species produce dormant cysts that can withstand drying.

Some species, especially E. viridis and E. sanguinea, can develop large toxic populations of green or red “blooms” in ponds or lakes with high nitrogen content. E. gracilis is common in laboratory demonstrations, and a number of species are used to study cell growth and metabolism in various environmental conditions.

Details

Euglena is a genus of single cell flagellate eukaryotes. It is the best known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. Species of Euglena are found in fresh water and salt water. They are often abundant in quiet inland waters where they may bloom in numbers sufficient to color the surface of ponds and ditches green (E. viridis) or red (E. sanguinea).

The species Euglena gracilis has been used extensively in the laboratory as a model organism.

Most species of Euglena have photosynthesizing chloroplasts within the body of the cell, which enable them to feed by autotrophy, like plants. However, they can also take nourishment heterotrophically, like animals. Since Euglena have features of both animals and plants, early taxonomists, working within the Linnaean two-kingdom system of biological classification, found them difficult to classify. It was the question of where to put such "unclassifiable" creatures that prompted Ernst Haeckel to add a third living kingdom (a fourth kingdom in toto) to the Animale, Vegetabile (and Lapideum meaning Mineral) of Linnaeus: the Kingdom Protista.

Form and function

When feeding as a heterotroph, Euglena takes in nutrients by osmotrophy, and can survive without light on a diet of organic matter, such as beef extract, peptone, acetate, ethanol or carbohydrates. When there is sufficient sunlight for it to feed by phototrophy, it uses chloroplasts containing the pigments chlorophyll a and chlorophyll b to produce sugars by photosynthesis. Euglena's chloroplasts are surrounded by three membranes, while those of plants and the green algae (among which earlier taxonomists often placed Euglena) have only two membranes. This fact has been taken as morphological evidence that Euglena's chloroplasts evolved from a eukaryotic green alga. Thus, the similarities between Euglena and plants would have arisen not because of kinship but because of a secondary endosymbiosis. Molecular phylogenetic analysis has lent support to this hypothesis, and it is now generally accepted.

Euglena chloroplasts contain pyrenoids, used in the synthesis of paramylon, a form of starch energy storage enabling Euglena to survive periods of light deprivation. The presence of pyrenoids is used as an identifying feature of the genus, separating it from other euglenoids, such as Lepocinclis and Phacus.

Euglena have two flagella rooted in basal bodies located in a small reservoir at the front of the cell. Typically, one flagellum is very short, and does not protrude from the cell, while the other is long enough to be seen with light microscopy. In some species, such as Euglena mutabilis, both flagella are "non-emergent"--entirely confined to the interior of the cell's reservoir--and consequently cannot be seen in the light microscope. In species that possess a long, emergent flagellum, it may be used to help the organism swim. The surface of the flagellum is coated with about 30,000 extremely fine filaments called mastigonemes.

Like other euglenoids, Euglena possess a red eyespot, an organelle composed of carotenoid pigment granules. The red spot itself is not thought to be photosensitive. Rather, it filters the sunlight that falls on a light-detecting structure at the base of the flagellum (a swelling, known as the paraflagellar body), allowing only certain wavelengths of light to reach it. As the cell rotates with respect to the light source, the eyespot partially blocks the source, permitting the Euglena to find the light and move toward it (a process known as phototaxis).

Euglena lacks a cell wall. Instead, it has a pellicle made up of a protein layer supported by a substructure of microtubules, arranged in strips spiraling around the cell. The action of these pellicle strips sliding over one another, known as metaboly, gives Euglena its exceptional flexibility and contractility. The mechanism of this euglenoid movement is not understood, but its molecular basis may be similar to that of amoeboid movement.

In low moisture conditions, or when food is scarce, Euglena forms a protective wall around itself and lies dormant as a resting cyst until environmental conditions improve.

Reproduction

Euglena reproduce asexually through binary fission, a form of cell division. Reproduction begins with the mitosis of the cell nucleus, followed by the division of the cell itself. Euglena divide longitudinally, beginning at the front end of the cell, with the duplication of flagellar processes, gullet and stigma. Presently, a cleavage forms in the anterior, and a V-shaped bifurcation gradually moves toward the posterior, until the two halves are entirely separated.

Reports of sexual conjugation are rare, and have not been substantiated.

Jai Ganesh · 2023-06-13 13:27:27

1807) Physical disability

Gist

Impairment in a person's body structure or function, or mental functioning; examples of impairments include loss of a limb, loss of vision or memory loss. Activity limitation, such as difficulty seeing, hearing, walking, or problem solving.

Details

A physical disability is a limitation on a person's physical functioning, mobility, dexterity or stamina. Other physical disabilities include impairments which limit other facets of daily living, such as respiratory disorders, blindness, epilepsy and sleep disorders.

Causes

Prenatal disabilities are acquired before birth. These may be due to diseases or substances that the mother has been exposed to during pregnancy, embryonic or fetal developmental accidents or genetic disorders.

Perinatal disabilities are acquired between some weeks before to up to four weeks after birth in humans. These can be due to prolonged lack of oxygen or obstruction of the respiratory tract, damage to the brain during birth (due to the accidental misuse of forceps, for example) or the baby being born prematurely. These may also be caused due to genetic disorders or accidents.

Post-natal disabilities are gained after birth. They can be due to accidents, injuries, obesity, infection or other illnesses. These may also be caused due to genetic disorders.

Types

Mobility impairment includes upper or lower limb loss or impairment, poor manual dexterity, and damage to one or multiple organs of the body. Disability in mobility can be a congenital or acquired problem or a consequence of disease. People who have a broken skeletal structure also fall into this category.

Visual impairment is another type of physical impairment. There are hundreds of thousands of people with minor to various serious vision injuries or impairments. These types of injuries can also result in severe problems or diseases such as blindness and ocular trauma. Some other types of vision impairment include scratched cornea, scratches on the sclera, diabetes-related eye conditions, dry eyes and corneal graft, macular degeneration in old age and retinal detachment.

Hearing loss is a partial or total inability to hear. Deaf and hard of hearing people have a rich culture and benefit from learning sign language for communication purposes. People who are only partially deaf can sometimes make use of hearing aids to improve their hearing ability. Speech and language disability: the person with deviations of speech and language processes which are outside the range of acceptable deviation within a given environment and which prevent full social or educational development

Physical impairment can also be attributed to disorders causing, among others, sleep deficiency, chronic fatigue, chronic pain, and seizures.

Additional Information

A disability is a physical or mental problem that makes it difficult or impossible for a person to walk, see, hear, speak, learn, or do other important things. Some disabilities are permanent, or last forever. Others are temporary, or last for only a short time. A disability can be something a person was born with. Or it can be the result of an illness or an accident.

A physical disability is a problem with the body. Physical disabilities may affect the eyes, the ears, the muscles, or the interior organs, such as the heart or lungs. Some people with a physical disability may use a wheelchair to move around.

A mental disability is a problem with the brain, or mind. Mental disabilities include developmental disabilities (mental retardation), mental illness, and learning disabilities, such as dyslexia. A person with a mental disability may have trouble learning or getting along with other people.

With medical treatment or other help, people with disabilities can do many of the things that nondisabled people can do. A person with a missing leg can learn to walk with an artificial leg. Many kinds of mental illness can be treated with medication or other therapies. Organizations in a community can help people with developmental disabilities go to school, work, or live on their own.

Jai Ganesh · 2023-06-14 13:32:05

1808) Paramecium

Gist

Any freshwater protozoan of the genus Paramecium, having an oval body covered with cilia and a ventral ciliated groove for feeding: phylum Ciliophora (ciliates).

Summary

Paramecium, genus of microscopic, are single-celled, and free-living protozoans. Most species can be cultivated easily in the laboratory, making them ideal model organisms, well suited for biological study. Paramecium vary in length from about 0.05 to 0.32 mm (0.002 to 0.013 inch). Their basic shape is an elongated oval with rounded or pointed ends, such as in P. caudatum. The term paramecium is also used to refer to individual organisms in a Paramecium species. Paramecium is the only genus in the family Parameciidae, which resides within the phylum Ciliophora.

Paramecia are completely covered with cilia (fine hairlike filaments) that beat rhythmically to propel them and to direct bacteria and other food particles into their mouths. On the ventral surface an oral groove runs diagonally posterior to the mouth and gullet. Within the gullet, food particles are transformed into food vacuoles, and digestion takes place within each food vacuole; waste material is excreted through the rear end.

A thin layer of ectoplasm (clear, firm cytoplasm) lies directly beneath the pellicle (a flexible body membrane) and encloses the endoplasm (the inner, more fluid portion of the cytoplasm). The endoplasm contains granules, food vacuoles, and crystals of different sizes. Embedded in the ectoplasm are trichocysts (spindle-shaped bodies) that may be released by chemical, electrical, or mechanical means. The precise function of trichocysts is unclear; they may be extruded as a reaction to injury, or they may be used as an anchoring device, as a mechanism of defense, or as a means of capturing prey.

Depending on the species, a paramecium has from one to several contractile vacuoles located close to the surface near the ends of the cell. Contractile vacuoles function in regulating the water content within the cell and may also be considered excretory structures, since the expelled water contains metabolic wastes.

Paramecia have two kinds of nuclei: a large ellipsoidal nucleus called a macronucleus and at least one small nucleus called a micronucleus. Both types of nuclei contain the full complement of genes that bear the hereditary information of the organism. The organism cannot survive without the macronucleus; it cannot reproduce without the micronucleus. The macronucleus is the centre of all metabolic activities of the organism. The micronucleus is a storage site for the germline genetic material of the organism. It gives rise to the macronucleus and is responsible for the genetic reorganization that occurs during conjugation (cross-fertilization).

Strictly speaking, the only type of reproduction in Paramecium is asexual binary fission in which a fully grown organism divides into two daughter cells. Paramecium also exhibits several types of sexual processes. Conjugation consists of the temporary union of two organisms and the exchange of micronuclear elements. Without the rejuvenating effects of conjugation, a paramecium ages and dies. Only opposite mating types, or genetically compatible organisms, can unite in conjugation. P. aurelia has multiple hereditary mating types that form distinct mating groups; once known as syngens, these distinct groups are now considered separate species within the so-called P. aurelia complex. Autogamy (self-fertilization) is a similar process that occurs in one organism. In cytogamy, another type of self-fertilization, two organisms join together but do not undergo nuclear exchange.

Details

Paramecium (also spelled Paramoecium, plural Paramecia) is a genus of eukaryotic, unicellular ciliates, commonly studied as a model organism of the ciliate group. Paramecia are widespread in freshwater, brackish, and marine environments and are often abundant in stagnant basins and ponds. Because some species are readily cultivated and easily induced to conjugate and divide, they have been widely used in classrooms and laboratories to study biological processes. The usefulness of Paramecium as a model organism has caused one ciliate researcher to characterize it as the "white rat" of the phylum Ciliophora.

Historical background

Paramecia were among the first ciliates to be observed by microscopists, in the late 17th century. They were probably known to the Dutch pioneer of protozoology, Antonie van Leeuwenhoek, and were clearly described by his contemporary Christiaan Huygens in a letter from 1678. The earliest known illustration of a Paramecium species was published anonymously in Philosophical Transactions of the Royal Society in 1703.

In 1718, the French mathematics teacher and microscopist Louis Joblot published a description and illustration of a microscopic poisson (fish), which he discovered in an infusion of oak bark in water. Joblot gave this creature the name "Chausson", or "slipper", and the phrase "slipper animalcule" remained in use as a colloquial epithet for Paramecium, throughout the 18th and 19th centuries.

The name "Paramecium" – constructed from the Greek – was coined in 1752 by the English microscopist John Hill, who applied the name generally to "Animalcules which have no visible limbs or tails, and are of an irregularly oblong figure." In 1773, O. F. Müller, the first researcher to place the genus within the Linnaean system of taxonomy, adopted the name Paramecium, but changed the spelling to Paramœcium. C. G. Ehrenberg, in a major study of the infusoria published in 1838, restored Hill's original spelling for the name, and most researchers have followed his lead.

Description

Species of Paramecium range in size from 50 to 330 micrometres (0.0020 to 0.0130 in) in length. Cells are typically ovoid, elongate, or foot- or cigar-shaped.

The body of the cell is enclosed by a stiff but elastic structure called the pellicle. The pellicle consists of an outer cell membrane (plasma membrane), a layer of flattened membrane-bound sacs called alveoli, and an inner membrane called the epiplasm. The pellicle is not smooth, but textured with hexagonal or rectangular depressions. Each of these polygons is perforated by a central aperture through which a single cilium projects. Between the alveolar sacs of the pellicle, most species of Paramecium have closely spaced spindle-shaped trichocysts, explosive organelles that discharge thin, non-toxic filaments, often used for defensive purposes.

Typically, an anal pore (cytoproct) is located on the ventral surface, in the posterior half of the cell. In all species, there is a deep oral groove running from the anterior of the cell to its midpoint. This is lined with inconspicuous cilia which beat continuously, drawing food into the cell. Paramecia are primarily heterotrophic, feeding on bacteria and other small organisms. A few species are mixotrophs, deriving some nutrients from endosymbiotic algae (chlorella) carried in the cytoplasm of the cell.

Osmoregulation is carried out by contractile vacuoles, which actively expel water from the cell to compensate for fluid absorbed by osmosis from its surroundings. The number of contractile vacuoles varies depending on the species.

Movement

A Paramecium propels itself by whip-like movements of the cilia, which are arranged in tightly spaced rows around the outside of the body. The beat of each cilium has two phases: a fast "effective stroke," during which the cilium is relatively stiff, followed by a slow "recovery stroke," during which the cilium curls loosely to one side and sweeps forward in a counter-clockwise fashion. The densely arrayed cilia move in a coordinated fashion, with waves of activity moving across the "ciliary carpet," creating an effect sometimes likened to that of the wind blowing across a field of grain.

The Paramecium spirals through the water as it progresses. When it happens to encounter an obstacle, the "effective stroke" of its cilia is reversed and the organism swims backward for a brief time, before resuming its forward progress. This is called the avoidance reaction. If it runs into the solid object again, it repeats this process, until it can get past the object.

It has been calculated that a Paramecium expends more than half of its energy in propelling itself through the water. This ciliary method of locomotion has been found to be less than 1% efficient. This low percentage is nevertheless close to the maximum theoretical efficiency that can be achieved by an organism equipped with cilia as short as those of the members of Paramecium.

Gathering food

Paramecia feed on microorganisms like bacteria, algae, and yeasts. To gather food, the Paramecium makes movements with cilia to sweep prey organisms, along with some water, through the oral groove (vestibulum, or vestibule), and into the cell. The food passes from the cilia-lined oral groove into a narrower structure known as the buccal cavity (gullet). From there, food particles pass through a small opening called the cytostome, or cell mouth, and move into the interior of the cell. As food enters the cell, it is gathered into food vacuoles, which are periodically closed off and released into the cytoplasm, where they begin circulating through the cell body by the streaming movement of the cell contents, a process called cyclosis or cytoplasmic streaming. As a food vacuole moves along, enzymes from the cytoplasm enter it, to digest the contents. As enzymatic digestion proceeds, the vacuole contents become more acidic. Within five minutes of a vacuole's formation, the pH of its contents drops from 7 to 3. As digested nutrients pass into the cytoplasm, the vacuole shrinks. When the fully digested vacuole reaches the anal pore, it ruptures, expelling its waste contents outside the cell.

Symbiosis

Some species of Paramecium form mutualistic relationships with other organisms. Paramecium bursaria and Paramecium chlorelligerum harbour endosymbiotic green algae, from which they derive nutrients and a degree of protection from predators such as Didinium nasutum. Numerous bacterial endosymbionts have been identified in species of Paramecium. Some intracellular bacteria, known as kappa particles, give Paramecia the ability to kill other strains of Paramecium that lack kappa particles.

Genome

The genome of the species Paramecium tetraurelia has been sequenced, providing evidence for three whole-genome duplications.

In some ciliates, like Stylonychia and Paramecium, only UGA is decoded as a stop codon, while UAG and UAA are reassigned as sense codons (that is, codons that code for standard amino acids), coding for the amino acid glutamic acid.

Learning

The question of whether Paramecia exhibit learning has been the object of a great deal of experimentation, yielding equivocal results. However, a study published in 2006 seems to show that Paramecium caudatum may be trained, through the application of a 6.5 volt electric current, to discriminate between brightness levels. This experiment has been cited as a possible instance of cell memory, or epigenetic learning in organisms with no nervous system.

Jai Ganesh · 2023-06-15 00:11:47

1809) Stadium

Gist

A stadium is a large closed area of land with rows of seats around the sides and often with no roof, used for sports events and musical performances.

Summary

A stadium is an enclosure that combines broad space for athletic games and other exhibitions with large seating capacity for spectators. The name derives from the Greek unit of measurement, the stade, the distance covered in the original Greek footraces (about 600 feet [180 metres]). The course for the footrace in the ancient Olympic Games at Olympia was exactly a stade in length, and the word for the unit of measurement became transferred first to the footrace and then to the place in which the race was run. As a type of structure, the stadium played a significant role in 20th-century construction technology.

Classical stadiums

The first Greek stadiums were long and narrow, in the shape of a U or a horseshoe. They were sometimes cut into the side of a hill, as at Thebes, Epidaurus, and at Olympia, the site of the Olympic Games, which began there in the 8th century BCE. The Greeks also built hippodrome stadiums similar in layout but broad enough to accommodate four-horse chariot races, a feature of the Olympic Games as early as the 7th century BCE.

The design of the Greek stadium was taken over and improved upon by the Romans, who built two types of stadiums: the circus and the amphitheatre. The circus was the Roman version of the hippodrome, a long, narrow, U-shaped structure designed for chariot races. The largest, and doubtless the finest ever built, was the Circus Maximus in Rome. In contrast to the circus, the amphitheatre, one of the most characteristic of all Roman buildings, was oval or round in plan and was completely enclosed on all sides. Intended for gladiatorial contests, in which the precise dimensions of the field were of slight importance, the amphitheatre was designed to afford maximum seating capacity and optimum visual facility for spectators. The giant amphitheatre built in Rome in the 1st century CE is known as the Colosseum. After the fall of Rome, amphitheatres survived for some time until the decline of the cities themselves terminated the spectacles that they had held. Nearly two millennia passed before the form was revived; much smaller, usually temporary stands sufficed for such intervening spectatorial events as the knightly tournaments of the Middle Ages in Europe.

The renewal of large-scale spectator sports came about gradually in the 19th century with the growth of European cities and the revival of interest in athletic contests; symbolically, the great impetus for the design of modern stadiums came from the revival of Olympic competition in 1896.

Modern stadiums

The stadium for the first modern Olympiad in Athens was a reconstruction of the ancient marble stadium built by Herodes Atticus on the site of an even earlier stadium in Athens. The Olympics since that time have provided a major focal point for the development of the modern stadium concept. In each period since the first modern Olympiad, the host country has usually erected a permanent stadium to mark the event. The first stadium of the modern genre was constructed for the IV Olympiad in 1908 at Shepherd’s Bush in London. The stands were partly roofed, and the stadium seated more than 50,000 people. Other Olympic stadiums of architectural note that were built before World War II include those at Stockholm (1912), Colombes, outside Paris (1924), Amsterdam (1927), and Berlin (1936). The Helsinki stadium built for the XII Olympiad (1940), which was canceled by the outbreak of World War II, served as the site for the XV Olympiad in 1952.

Stadiums rivaling the size of those of ancient Rome were constructed in several cities in the first half of the 20th century, notably the vast Strahov Stadium, in Prague, which was completed in 1934 for the Sokol gymnastics exhibition and had a seating capacity of more than 240,000. Other stadiums built to accommodate in excess of 100,000 people include May Day Stadium, in P’yŏngyang, North Korea; Melbourne Cricket Ground, in Melbourne; Aztec Stadium, in Mexico City; Salt Lake Stadium, in Kolkata (Calcutta); and Michigan Stadium, in Ann Arbor, Michigan, U.S. These figures of course denote how many people can be “accommodated”; the official “seating” capacities may be considerably lower.

American football inspired a new type of stadium design, the elliptical bowl, first employed in the Yale Bowl at New Haven, Connecticut, in 1914, and repeated in several other stadiums, including the Rose Bowl and Michigan Stadium. Because the bowl is entirely unsuited to the other principal American sport, baseball, another type of American stadium has evolved for baseball, in which the aim is to supply maximum roofed-seating capacity to protect spectators from the sunlight. A notable pioneer in this trend was triple-tiered Yankee Stadium, New York, built in 1923 (demolished 2009–10).

Design innovations

The shapes of stadiums have varied widely according to the variety of uses for which they were built. Some are rectangular with curved corners, whereas others are elliptical or U-shaped. The building of large stadiums in the 20th century has been greatly facilitated by the use of reinforced concrete; this material has made possible the construction of daring new designs that would previously have been impossible to sustain structurally.

A basic difficulty of the roofed stadium was the interference with visibility by the columns supporting the roof. Dodger Stadium in Los Angeles was the first tiered stadium to provide column-free views from all seats (1959), followed by Shea Stadium in New York, which added field seat sections that rotate around the stadium to permit conversion from a baseball to a football arrangement (1964; demolished 2008). Several other outstanding stadiums have been built for baseball, for example, Wrigley Field in Chicago (1914) and Oriole Park at Camden Yards in Baltimore, Maryland (1992).

A significant development of the mid-20th century was the Astrodome, built in 1965 in Houston, Texas; this was the first major fully roofed stadium. Indoor stadiums of considerable size had been built previously, notably Madison Square Garden in New York City and Chicago Stadium in Chicago (both original structures have been demolished). For the 1960 Olympics in Rome, the leading Italian architect-engineer Pier Luigi Nervi created the Roman sports complex, which included the Palazzetto dello Sport with a ribbed-dome roof. The Astrodome, however, was, by comparison, gigantic, with a seating capacity of 62,000 people and a large playing field under a dome, of transparent plastic panels supported by a steel lattice, that spanned 642 feet (196 metres) and rose 208 feet (63 metres) above the playing field. Within a decade, however, the Astrodome was eclipsed by the New Orleans Superdome, which opened in 1975 with an official seating capacity of 69,065 (though able to accommodate larger numbers); the 30-story structure is topped by a steel-ribbed roof that has a 680-foot (200-metre) clearspan. In the late 1980s stadiums with retractable domes began to appear, most notably Toronto’s Rogers Centre (opened 1989).

An important development was the application of flexible steel cables to span large roof dimensions. Cables contributed significantly to speed of construction, to lightness of roof, and to economy of construction cost in covered stadiums. A modern stadium with this system was built in Minneapolis–St. Paul, Minnesota, and called the Metrodome (opened 1982; demolished 2014). Such cable systems can span large distances; a concept for a 200,000-capacity, covered baseball stadium was developed by Lev Zetlin, an American engineer.

The concept of an enclosed stadium and the desire for greater capacities have led toward the search for improved materials and construction techniques. Modern technology, including that developed in the aerospace industry, already possesses techniques for covering spans of thousands of feet. Such is the potential of the modern stadium design concept that proposals to span all of Manhattan Island have been seriously discussed. It is by no means unrealistic to see today’s roofed stadiums, with their arrays of restaurants, exhibition halls, and other auxiliaries, as the forerunners of completely roofed, weather-controlled cities.

Details

A stadium (pl: stadiums or stadia) is a place or venue for (mostly) outdoor sports, concerts, or other events and consists of a field or stage either partly or completely surrounded by a tiered structure designed to allow spectators to stand or sit and view the event.

Pausanias noted that for about half a century the only event at the ancient Greek Olympic festival was the race that comprised one length of the stadion at Olympia, where the word "stadium" originated.

Most of the stadiums with a capacity of at least 10,000 are used for association football. Other popular stadium sports include gridiron football, baseball, cricket, the various codes of rugby, field lacrosse, bandy, and bullfighting. Many large sports venues are also used for concerts.

Etymology

"Stadium" is the Latin form of the Greek word "stadion", a measure of length equalling the length of 600 human feet. As feet are of variable length the exact length of a stadion depends on the exact length adopted for 1 foot at a given place and time. Although in modern terms 1 stadion = 600 ft (180 m), in a given historical context it may actually signify a length up to 15% larger or smaller.

The equivalent Roman measure, the stadium, had a similar length – about 185 m (607 ft) – but instead of being defined in feet was defined using the Roman standard passus to be a distance of 125 passūs (double-paces).

The English use of stadium comes from the tiered infrastructure surrounding a Roman track of such length.

Most dictionaries provide for both stadiums and stadia as valid English plurals.

History

The oldest known stadium is the Stadium at Olympia in Greece, where the ancient Olympic Games were held from 776 BC. Initially the Games consisted of a single event, a sprint along the length of the stadium.

Greek and Roman stadiums have been found in numerous ancient cities, perhaps the most famous being the Stadium of Domitian, in Rome.

The excavated and refurbished ancient Panathenaic Stadium hosted attempted revivals of the Olympic Games in 1870 and 1875 before hosting the first modern Olympics in 1896, the 1906 Intercalated Games, and some events of the 2004 Summer Olympics. The excavation and refurbishment of the stadium was part of the legacy of the Greek national benefactor Evangelos Zappas, and it was the first ancient stadium to be used in modern times.

Modernity

The first stadiums to be built in the modern era were basic facilities, designed for the single purpose of fitting as many spectators in as possible. With tremendous growth in the popularity of organised sport in the late Victorian era, especially association football in the United Kingdom and baseball in the United States, the first such structures were built. One such early stadium was the Lansdowne Road Stadium, the brainchild of Henry Dunlop, who organised the first All Ireland Athletics Championships. Banned from locating sporting events at Trinity College, Dunlop built the stadium in 1872. "I laid down a cinder running path of a quarter-mile, laid down the present Lansdowne Tennis Club ground with my own theodolite, started a Lansdowne archery club, a Lansdowne cricket club, and last, but not least, the Lansdowne Rugby Football Club – colours red, black and yellow." Some 300 cartloads of soil from a trench beneath the railway were used to raise the ground, allowing Dunlop to use his engineering expertise to create a pitch envied around Ireland.

Other early stadiums from this period in the UK include the Stamford Bridge stadium (opened in 1877 for the London Athletic Club) and Anfield stadium (1884 as a venue for Everton F.C.).

In the U.S., many professional baseball teams built large stadiums mainly out of wood, with the first such venue being the South End Grounds in Boston, opened in 1871 for the team then known as the Boston Beaneaters (now the Atlanta Braves). Many of these parks caught fire, and those that did not proved inadequate for a growing game. All of the 19th-century wooden parks were replaced, some after a few years, and none survive today.

Goodison Park was the first purpose-built association football stadium in the world. Walton-based building firm Kelly brothers were instructed to erect two uncovered stands that could each accommodate 4,000 spectators. A third covered stand accommodating 3,000 spectators was also requested. Everton officials were impressed with the builder's workmanship and agreed two further contracts: exterior hoardings were constructed at a cost of £150 and 12 turnstiles were installed at a cost of £7 each. The stadium was officially opened on 24 August 1892 by Lord Kinnaird and Frederick Wall of the Football Association. No football was played; instead the 12,000 crowd watched a short track and field event followed by music and a fireworks display. Upon its completion the stadium was the first joint purpose-built football stadium in the world.

The architect Archibald Leitch brought his experience with the construction of industrial buildings to bear on the design of functional stadiums up and down the country. His work encompassed the first 40 years of the 20th century. One of his most notable designs was Old Trafford in Manchester. The ground was originally designed with a capacity of 100,000 spectators and featured seating in the south stand under cover, while the remaining three stands were left as terraces and uncovered. It was the first stadium to feature continuous seating along the contours of the stadium.

These early venues, originally designed to host football matches, were adopted for use by the Olympic Games, the first one being held in 1896 in Athens, Greece. The White City Stadium, built for the 1908 Summer Olympics in London is often cited as the first modern seater stadium, at least in the UK. Designed by the engineer J.J. Webster and completed in 10 months by George Wimpey, on the site of the Franco-British Exhibition, this stadium with a seating capacity of 68,000 was opened by King Edward VII on 27 April 1908. Upon completion, the stadium had a running track 24 ft wide (7.3 m) and three laps to the mile (536 m); outside there was a 35-foot-wide (11 m), 660-yard (600 m) cycle track. The infield included a swimming and diving pool. The London Highbury Stadium, built in 1913, was the first stadium in the UK to feature a two-tiered seating arrangement when it was redesigned in the Art Deco style in 1936.

During these decades, parallel stadium developments were taking place in the U.S. The Baker Bowl, a baseball park in Philadelphia that opened in its original form in 1887 but was completely rebuilt in 1895, broke new ground in stadium construction in two major ways. The stadium's second incarnation featured the world's first cantilevered second deck (tier) in a sports venue, and was the first baseball park to use steel and brick for the majority of its construction. Another influential venue was Boston's Harvard Stadium, built in 1903 by Harvard University for its American football team and track and field program. It was the world's first stadium to use concrete-and-steel construction. In 1909, concrete-and-steel construction came to baseball with the opening of Shibe Park in Philadelphia and, a few months later, Forbes Field in Pittsburgh. The latter was the world's first three-tiered sporting venue. The opening of these parks marked the start of the "jewel box" era of park construction. The largest stadium crowd ever was 199,854 people watching the final match of the 1950 World Cup at Rio de Janeiro's Maracanã on 16 July 1950.

Antiquity

Stadiums in ancient Greece and Rome were built for different purposes, and at first only the Greeks built structures called "stadium"; Romans built structures called "circus". Greek stadia were for foot races, whereas the Roman circus was for horse races. Both had similar shapes and bowl-like areas around them for spectators. The Greeks also developed the theatre, with its seating arrangements foreshadowing those of modern stadiums. The Romans copied the theatre, then expanded it to accommodate larger crowds and more elaborate settings. The Romans also developed the double-sized round theatre called amphitheatre, seating crowds in the tens of thousands for gladiatorial combats and beast shows. The Greek stadium and theatre and the Roman circus and amphitheatre are all ancestral to the modern stadium.

Political and economic issues

Modern stadiums, especially the largest among them, are megaprojects that can only be afforded by the largest corporations, wealthiest individuals, or government. Sports fans have a deep emotional attachment to their teams. In North America, with its closed-league "franchise" system, there are fewer teams than cities which would like them. This creates tremendous bargaining power for the owners of teams, whereby owners can threaten to relocate teams to other cities unless governments subsidize the construction of new facilities. In Europe and Latin America, where there are multiple association football clubs in any given city, and several leagues in each country, no such monopoly power exists, and stadiums are built primarily with private money. Outside professional sports, governments are also involved through the intense competition for the right to host major sporting events, primarily the Summer Olympics and the FIFA World Cup (of association football), during which cities often pledge to build new stadiums in order to satisfy the International Olympic Committee (IOC) or FIFA.

Corporate naming

In recent decades, to help take the burden of the massive expense of building and maintaining a stadium, many American and European sports teams have sold the rights to the name of the facility. This trend, which began in the 1970s, but accelerated greatly in the 1990s, has led to sponsors' names being affixed to both established stadiums and new ones. In some cases, the corporate name replaces (with varying degrees of success) the name by which the venue has been known for many years. But many of the more recently built stadiums, like the Volkswagen Arena in Wolfsburg, Germany, have never been known by a non-corporate name. The sponsorship phenomenon has since spread worldwide. There remain a few municipally owned stadiums, which are often known by a name that is significant to their area (for example, Boston's Fenway Park). In recent years, some government-owned stadiums have also been subject to naming-rights agreements, with some or all of the revenue often going to the team(s) that play there.

One consequence of corporate naming has been an increase in stadium name changes, when the namesake corporation changes its name, or if it is the naming agreement simply expires. Phoenix's Chase Field, for example, was previously known as Bank One Ballpark, but was renamed to reflect the takeover of the latter corporation. San Francisco's historic Candlestick Park was renamed as 3Com Park for several years, but the name was dropped when the sponsorship agreement expired, and it was another two years before the new name of Monster Cable Products' Monster Park was applied. Local opposition to the corporate naming of that particular stadium led San Francisco's city council to permanently restore the Candlestick Park name once the Monster contract expired. More recently, in Ireland, there has been huge opposition to the renaming of Dublin's historic Lansdowne Road as the Aviva Stadium. Lansdowne was redeveloped as the Aviva, opening in May 2010.

On the other hand, Los Angeles' Great Western Forum, one of the earliest examples of corporate renaming, retained its name for many years, even after the namesake bank no longer existed, the corporate name being dropped only after the building later changed ownership. This practice has typically been less common in countries outside the United States. A notable exception is the Nippon Professional Baseball league of Japan, in which many of the teams are themselves named after their parent corporations. Also, many newer European football stadiums, such as the University of Bolton and Emirates Stadiums in England and Signal Iduna Park and Allianz Arena in Germany have been corporately named.

This new trend in corporate naming (or renaming) is distinguishable from names of some older venues, such as Crosley Field, Wrigley Field, and the first and second Busch Stadiums, in that the parks were named by and for the club's owner, which also happened to be the name of the company owned by those clubowners. (The current Busch Stadium received its name via a modern naming rights agreement.)

During the 2006 FIFA World Cup in Germany, some stadiums were temporarily renamed because FIFA prohibits sponsorship of stadiums. For example, the Allianz Arena in Munich was called the FIFA World Cup Stadium, Munich during the tournament. Likewise, the same stadium will be known as the "München Arena" during the European Competitions. Similar rules affect the Imtech Arena and Veltins-Arena. This rule applies even if the stadium sponsor is an official FIFA sponsor—the Johannesburg stadium then commercially known as "Coca-Cola Park", bearing the name of one of FIFA's major sponsors, was known by its historic name of Ellis Park Stadium during the 2010 FIFA World Cup. Corporate names are also temporarily replaced during the Olympics.

Environmental issues

Modern stadiums bring several negative environmental issues with their construction. They require thousands of tons of materials to build, they greatly increase traffic in the area around the stadium, as well as maintaining the stadium. The increased traffic around modern stadiums has led to create exposure zones says the Health Effect Institute, exposing 30-40% of people living around the stadium to potential health issues. Many stadiums are attempting to counteract these issues by implementing solar panels, and high efficiency lighting, to reduce their own carbon footprint.

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Jai Ganesh · 2023-06-16 00:07:28

1810) Gardening

Gist

Gardening is the laying out and care of a plot of ground devoted partially or wholly to the growing of plants such as flowers, herbs, or vegetables.

Summary

Gardening is the practice of growing and cultivating plants as part of horticulture. In gardens, ornamental plants are often grown for their flowers, foliage, or overall appearance; useful plants, such as root vegetables, leaf vegetables, fruits, and herbs, are grown for consumption, for use as dyes, or for medicinal or cosmetic use.

Gardening ranges in scale from fruit orchards, to long boulevard plantings with one or more different types of shrubs, trees, and herbaceous plants, to residential back gardens including lawns and foundation plantings, all the way to container gardens grown inside or outside. Gardening may be very specialized, with only one type of plant grown, or involve a variety of plants in mixed plantings. It involves an active participation in the growing of plants, and tends to be labor-intensive, which differentiates it from farming or forestry.

Details

Gardening is the laying out and care of a plot of ground devoted partially or wholly to the growing of plants such as flowers, herbs, or vegetables.

Gardening can be considered both as an art, concerned with arranging plants harmoniously in their surroundings, and as a science, encompassing the principles and techniques of plant cultivation. Because plants are often grown in conditions markedly different from those of their natural environment, it is necessary to apply to their cultivation techniques derived from plant physiology, chemistry, and botany, modified by the experience of the planter. The basic principles involved in growing plants are the same in all parts of the world, but the practice naturally needs much adaptation to local conditions.

The nature of gardening

Gardening in its ornamental sense needs a certain level of civilization before it can flourish. Wherever that level has been attained, in all parts of the world and at all periods, people have made efforts to shape their environment into an attractive display. The instinct and even enthusiasm for gardening thus appear to arise from some primitive response to nature, engendering a wish to produce growth and harmony in a creative partnership with it.

It is possible to be merely an admiring spectator of gardens. However, most people who cultivate a domestic plot also derive satisfaction from involvement in the processes of tending plants. They find that the necessary attention to the seasonal changes, and to the myriad small “events” in any shrubbery or herbaceous border, improves their understanding and appreciation of gardens in general.

A phenomenal upsurge of interest in gardening began in Western countries after World War II. A lawn with flower beds and perhaps a vegetable patch has become a sought-after advantage to home ownership. The increased interest produced an unprecedented expansion of business among horticultural suppliers, nurseries, garden centres, and seedsmen. Books, journals, and newspaper columns on garden practice have found an eager readership, while television and radio programs on the subject have achieved a dedicated following.

Several reasons for this expansion suggest themselves. Increased leisure in the industrial nations gives more people the opportunity to enjoy this relaxing pursuit. The increased public appetite for self-sufficiency in basic skills also encourages people to take up the spade. In the kitchen, the homegrown potato or ear of sweet corn rewards the gardener with a sense of achievement, as well as with flavour superior to that of store-bought produce. An increased awareness of threats to the natural environment and the drabness of many inner cities stir some people to cultivate the greenery and colour around their own doorsteps. The bustle of 20th-century life leads more individuals to rediscover the age-old tranquillity of gardens.

The varied appeal of gardening

The attractions of gardening are many and various and, to a degree perhaps unique among the arts and crafts, may be experienced by any age group and at all levels of ambition. At its most elemental, but not least valuable, the gardening experience begins with the child’s wonder that a packet of seeds will produce a charming festival of colour. At the adult level, it can be as simple as helping to raise a good and edible carrot, and it can give rise to almost parental pride. At higher levels of appreciation, it involves an understanding of the complexity of the gardening process, equivalent to a chess game with nature, because the variables are so many.

The gardening experience may involve visiting some of the world’s great gardens at different seasons to see the relation of individual groups of plants, trees, and shrubs to the whole design; to study the positioning of plants in terms of their colour, texture, and weight of leaf or blossom; and to appreciate the use of special features such as ponds or watercourses, pavilions, or rockeries. Garden visiting on an international scale provides an opportunity to understand the broad cultural influences, as well as the variations in climate and soil, that have resulted in so many different approaches to garden making.

The appeal of gardening is thus multifaceted and wide in range. The garden is often the only place where someone without special training can exercise creative impulses as designer, artist, technician, and scientific observer. In addition, many find it a relaxing and therapeutic pursuit. It is not surprising that the garden, accorded respect as a part of nature and a place of contemplation, holds a special place in the spiritual life of many.

Practical and spiritual aspects of gardening are shown in an impressive body of literature. In Western countries manuals of instruction date to classical Greece and Rome. Images of plants and gardens are profuse in the works of the major poets, from Virgil to Shakespeare, and on to some of the moderns.

Another of gardening’s attractions is that up to a certain level it is a simple craft to learn. The beginner can produce pleasing results without the exacting studies and practice required by, for example, painting or music. Gardens are also forgiving to the inexperienced to a certain degree. Nature’s exuberance will cover up minor errors or short periods of neglect, so gardening is an art practiced in a relatively nonjudgmental atmosphere. While tolerant in many respects, nature does, however, present firm reminders that all gardening takes place within a framework of natural law; and one important aspect of the study of the craft is to learn which of these primal rules are imperatives and which may be stretched.

Control and cooperation

Large areas of gardening development and mastery have concentrated on persuading plants to achieve what they would not have done if left in the wild and therefore “natural” state. Gardens at all times have been created through a good deal of control and what might be called interference. The gardener attends to a number of basic processes: combating weeds and pests; using space to allay the competition between plants; attending to feeding, watering, and pruning; and conditioning the soil. Above this fundamental level, the gardener assesses and accommodates the unique complex of temperature, wind, rainfall, sunlight, and shade found within his own garden boundaries. A major part of the fascination of gardening is that in problems and potential no one garden is quite like another; and it is in finding the most imaginative solutions to challenges that the gardener demonstrates artistry and finds the subtler levels of satisfaction.

Different aesthetics require different balances between controlling nature and cooperating with its requirements. The degree of control depends on the gardener’s objective, the theme and identity he is aiming to create. For example, the English wild woodland style of gardening in the mid-19th century dispensed with controls after planting, and any interference, such as pruning, would have been misplaced. At the other extreme is the Japanese dry-landscape garden, beautifully composed of rock and raked pebbles. The artistic control in this type of garden is so firm and refined that the intrusion of a single “natural” weed would spoil the effect.

Choice of plants

The need for cooperation with nature is probably most felt by the amateur gardener in choosing the plants he wants to grow. The range of plants available to the modern gardener is remarkably rich, and new varieties are constantly being offered by nurseries. Most of the shrubs and flowers used in the Western world are descendants of plants imported from other countries. Because they are nonnative, they present the gardener with some of his most interesting problems but also with the possibility of an enhanced display. Plants that originated in subtropical regions, for example, are naturally more sensitive to frost. Some, like rhododendrons or azaleas, originated in an acid soil, mainly composed of leaf mold. Consequently, they will not thrive in a chalky or an alkaline soil. Plant breeding continues to improve the adaptability of such exotic plants, but the more closely the new habitat resembles the original, the better the plant will flourish. Manuals offer solutions to most such problems, and the true gardener will always enjoy finding his own. In such experiments, he may best experience his work as part of the historical tradition of gardening.

Historical background

Western gardening had its origins in Egypt some 4,000 years ago. As the style spread, it was changed and adapted to different localities and climates, but its essentials remained those of disciplined lines and groupings of plants, usually in walled enclosures. Gardening was introduced into Europe through the expansion of Roman rule and, second, by way of the spread of Islam into Spain. Though clear evidence is lacking, it is presumed that Roman villas outside the confines of Italy contained native and imported plants, hedges, fruit trees, and vines, in addition to herbs for medicinal and culinary purposes.

In medieval times the monasteries were the main repositories of gardening knowledge and the important herbal lore. Though little is certainly known about the design and content of the monastic garden, it probably consisted of a walled courtyard built around a well or an arbour, with colour provided by flowers (some of which, including roses and lilies, served as ecclesiastical symbols), all of which maintained the ancient idea of the garden as a place of contemplation.

The earliest account of gardening in English, The Feate of Gardening, dating from about 1400, mentions the use of more than 100 plants, with instructions on sowing, planting, and grafting of trees and advice on cultivation of herbs such as parsley, sage, fennel, thyme, camomile, and saffron. The vegetables mentioned include turnip, spinach, leek, lettuce, and garlic.

Early gardening was largely for utility. The emergence of the garden as a form of creative display properly began in the 16th century. The Renaissance, with its increased prosperity, brought an upsurge of curiosity about the natural world and, incidentally, stirred interest in composing harmonious forms in the garden.

This awakening took especially firm root in Elizabethan England, which notably developed the idea that gardens were for enjoyment and delight. Echoing the Renaissance outlook, the mood of the period was one of exuberance in gardening, seen in the somewhat playful arrangements of Tudor times, with mazes, painted statuary, and knot gardens (consisting of beds in which various types of plants were separated by dwarf hedges). Flowers began to appear profusely in paintings and, as mentioned above, were used by poets in their verbal images.

This enthusiasm was accompanied by an earnest search for knowledge, and the period saw the birth of botanical science. A leading figure in this work was Carolus Clusius (Charles de l’Écluse), whose botanical skills and introduction of the tulip and other bulbous plants to the botanical gardens at Leiden, Netherlands, laid the foundation for Dutch prominence in international horticulture. The earliest botanical garden was that of Pisa (1543), followed by that of Padua (1545). The first in England was founded at Oxford in 1621, followed by Scotland’s first, at Edinburgh, in 1667. The gardens at Kew, near London, were founded almost a century later, in 1759. These centres of experiment and learning have contributed greatly to the art and science of horticulture.

The advances from the simple medieval style were marked and rapid at this time. The English statesman and scholar Francis Bacon could already, by 1625, advance a sophisticated and almost modern conception of the garden in his essay “On Gardens.” He saw it as a place that should be planted for year-round enjoyment, offering a wide range of experiences through colour, form and scent, exercise and repose. The flower garden, already well established by the early 17th century, was set against a background of tall, clipped hedges and neatly scythed lawns. The taste of the time, as contemporary lists show, was for perfumed varieties such as carnations, lavender, sweet marjoram, musk roses, and poppies.

The plant trade

As interest in gardening developed in Europe, the new trade of nurseryman was established, and the trade became highly important to the spread of knowledge and materials. By the end of the 17th century, nurserymen were relatively numerous in England, France, and the Low Countries, with keen customers among the nobility and gentry for all the exotica they could provide. The catalog of the Tradescant family’s private botanical garden in London listed 1,600 plants in 1656. A number of them had been brought back by the family from visits to Virginia. These early exotica from the New World included now familiar plants such as the Michaelmas daisy, the Virginia creeper, hamamelis, goldenrod, the first perennial lupine, and such fine autumn-colouring trees as liquidambar and the staghorn sumac. The work of the nurserymen thus spread new plants more widely and, as breeding skills developed, contributed to the acclimatizing of foreign imports.

Vegetables and fruits

The history of vegetables is imprecise. Though familiar types, including the radish, turnip, and onion, are known to have been in cultivation from early times, it is fairly supposed that they were meagre and would bear little clear resemblance to modern equivalents. The early range available to European gardens and, later, to those in America, included such native plants as kale, parsnips, and the Brussels sprout family, with peas and broad beans grown as field crops.

The Romans introduced the globe artichoke, leek, cucumber, cabbage, asparagus, and the Mediterranean strain of garlic to their imperial territory wherever these plants would flourish. Among plants imported to Europe from the Americas were the scarlet runner bean and tomato (both originally grown for ornament), corn (maize), and the vastly important potato. The numerous herbs in use were mostly native to European locations. One curiosity to the modern mind is that certain flowers, such as marigolds, violets, and primroses, were used as flavourings in the kitchen.

The cultivation of fruit trees was one of the most advanced skills and interests from the 16th century onward. Pride was taken in variety, and, judging by the opulent still-life paintings of the period, the quality was remarkably high. Among the challenges bravely taken up in the 17th century in northern Europe was the growing of orange and lemon trees, though this was done more for the pleasure of their evergreen qualities than for their fruit. The catalog of the British royal gardens in 1708 shows 14 varieties of cherry, 14 apricots, 58 kinds of peach and nectarine, 33 plums, eight figs, 23 vines, 29 pears, and numerous varieties of apple.

The French style

The most favoured style for great house gardens in Europe during much of this period derived from the influence of the French designer André Le Nôtre, creator of the gardens at Versailles. The French style represented an extreme of formality, with box-edged parterres (elaborate and geometrical beds) typically placed near the residence to provide an arranged view. Trees were grouped in neat plantations or in bold lines along avenues, with terraces and statuary carefully placed to emphasize the architectural symmetry of the grand manner. The widespread adoption of this style among the European nobility and gentry reflected the potency of French cultural influence at the time. It was also related, on a practical basis, to the limited availability of planting materials, especially those offering autumn and winter display.

The change to a more natural style of gardening came about when, in the latter part of the 18th century, the opinion arose among leading gardeners, particularly those of the English gentry, that the formal manner brought with it a certain monotony. The increasing importation of foreign plants also brought with it opportunities for a large-scale transformation.

The plant hunters

The early importation of plants to Europe was managed through informal channels, following the increase in exploration and the spread of empires. Seeds and tubers were sent home by diplomats and missionaries, sea captains and travelers. An example of this type of collecting is afforded by Henry Compton, bishop of London, whose diocese included the American colonies. He was an avid collector, and he corresponded with like-minded experts in Europe and America and thus brought numerous fine plants to his exceptional garden in Fulham, west London. He also encouraged his missionaries to send home seeds. From one such source in Virginia came the Magnolia virginiana, the first magnolia to be cultivated. This was the beginning of what became known as the American garden, based upon magnolias, azaleas, and other woodland species.

As the appetite for exotica developed, plant collecting around the world became more systematized. Expeditions to foreign parts were organized and financed by nurserymen, botanical gardens, or syndicates of private gardeners. The botanist plant hunters thus sent out were exceptional and patient. They were required to endure long voyages and residence for up to several years in an often hostile environment. Their goal was to find the plant in flower, return in due season to collect seed, then see their delicate specimens back to Europe through varying climatic zones.

North America’s potential to yield countless new specimens was recognized early: the first book on American plants, published in London in 1577, was entitled Joyfull Newes out of the New Founde Worlde and was in itself a hint of the excited spirit of contemporary gardening. The jacaranda, flowering catalpa, and wisteria were among the finds made by Compton’s missionaries in the Carolinas. An early resident collector in North America was John Bartram, regarded as the founder of American botany. He settled on a farm near Philadelphia in 1728 and, in 30 years of collecting in the Alleghenies, Carolinas, and other areas of North America, sent some 200 important plants to British gardens in sufficient quantity that they became widespread there.

The extremely rich west coast of North America was not exploited by plant collectors until the early 19th century. The contemporary importance of such discoveries is suggested by the fact that, in their celebrated crossing of the American continent in 1804–06, Lewis and Clark found time to collect the seeds of Mahonia aquifolium and Symphoricarpos racemosus. Perhaps the most distinguished collector among an exceptional fraternity was David Douglas, one of the numerous Scotsmen who contributed to international botany. His expeditions to the North American Far West brought to Europe such important timber trees as the Douglas fir, the Sitka spruce, the Monterey pine, and a number of now familiar shrubs such as Garrya elliptica and Ribes sanguineum. The California annuals he discovered made a lasting impact on the colour of Western gardens. In the 19th century, plant collectors began to explore South America, where two Cornish brothers, William and Thomas Lobb, gained prominence. They are credited with carrying back to Europe the monkey puzzle tree (Araucaria araucana), native to the Andes mountains; the Berberis darwinii; and the Escallonia macrantha.

Collectors went to a number of countries in the 19th century, but the most important area was China. Its flora was more intact than that in the West, because the erosions of the Ice Age had been less severe for climatic reasons, and it had a long history of skilled gardening. Plant collection was difficult, however, because for many years the only foreigners allowed to travel within its borders were Jesuit priests. They aided botanists by sending many specimens to Paris and London. The first professional collector to live in China was William Kerr, who sent out 238 new plants. Real exploration of the interior did not begin until the 1840s. China, Japan, and the Himalayas produced unparalleled riches in rhododendrons, azaleas, flowering cherries, ornamental maples, roses, lilies, primulas, poppies, kerrias, and quinces.

The conditions for transporting plants from such distances had been much improved by Nathaniel B. Ward’s invention of the wardian case, an airtight glass box that protected the plants from sea air and harsh climate. Gradually almost all regions and countries were visited, and new plants and their progeny were dispersed around the Western world. And still the search for new specimens continues.

From the 19th century

By the early 19th century, with the expansion of the horticultural trade, gardening had become international in scope. Numerous handbooks spread knowledge. The founding of new garden and botanical societies, such as the London (later Royal) Horticultural Society, helped to increase interest, encourage science, and raise standards. Such moves signaled the rise of the small leisure gardener; a floral retreat was no longer the sole property of the rich. It now extended from the manor to the small suburban garden.

Gardens in North America had generally been smaller and trimmer than their European counterparts, with box edgings and pleached trees (that is, lines of trees allowed to grow with branches interlaced to form a screen), as seen in the reconstructed gardens of Williamsburg, Virginia. The “natural” gardening style (known on the European continent as the English style), which had overtaken earlier formality, allowed wider use of plant varieties. This approach became the pervasive trend in the west, notably through the views of John Claudius Loudon, whose Encyclopaedia of Gardening (1822) set the pattern of domestic cultivation over a long period with a style known as Gardenesque. His style encouraged the individual qualities of garden elements while ensuring that together they made a harmonious blend.

The natural style was further enhanced by an English artist and landscape architect, Gertrude Jekyll. In her opinion, the first purpose of a garden is to give happiness and repose of mind. With experience derived from the richly floral cottage gardens of Surrey, she developed the idea of supporting plants with an architectural base and allowing them to grow in a free form, encouraging natural shape and creating harmonious relationships of colour.

The period saw much progress in garden equipment and supplies. Heated greenhouses had been in use since the late 17th century, and mass production led to great strides in nursery gardening. The modern, bladed lawn mower was first seen in a design of 1832; in more recent times the application of the jet-engine principle led to the hover mower. Fertilizer development was also important, from the discovery of superphosphate to the devising of modern kinds of foliar feeding.

In the second half of the 20th century, interest in gardening brought in new adherents in unprecedented numbers; they were advised and encouraged by numerous publications and by television and radio programs. Though the process was very gradual, domestic gardening became somewhat more adventurous. Among the more ambitious, designs took a multiplicity of forms, from the Japanese garden, producing an austere magic out of rock and pebble, to the other extreme of the wild country garden, virtually left to seed itself. Increasing numbers of professional designers at their best set high standards to emulate. But the art of gardening still depends on a simple empathy with the needs and nature of living things. Symbolic of this essential, the spade has remained much the same implement that it had been in medieval times.

Types of gardens

The domestic garden can assume almost any identity the owner wishes within the limits of climate, materials, and means. The size of the plot is one of the main factors, deciding not only the scope but also the kind of display and usage. Limits on space near urban centres, as well as the wish to spend less time on upkeep, have tended to make modern gardens ever smaller. Paradoxically, this happens at a time when the variety of plants and hybrids has never been wider. The wise small gardener avoids the temptations of this banquet. Some of the most attractive miniature schemes, such as those seen in Japan or in some Western patio gardens, are effectively based on an austere simplicity of design and content, with a handful of plants given room to find their proper identities.

In the medium- to large-sized garden, the tradition generally continues of dividing the area to serve various purposes: a main ornamental section to enhance the residence and provide vistas; walkways and seating areas for recreation; a vegetable plot; a children’s play area; and features to catch the eye here and there. Because most gardens are mixed, the resulting style is a matter of emphasis rather than exclusive concentration on one aspect. It may be useful to review briefly the main garden types.

Flower gardens

Though flower gardens in different countries may vary in the types of plants that are grown, the basic planning and principles are nearly the same, whether the gardens are formal or informal. Trees and shrubs are the mainstay of a well-designed flower garden. These permanent features are usually planned first, and the spaces for herbaceous plants, annuals, and bulbs are arranged around them. The range of flowering trees and shrubs is enormous. It is important, however, that such plants be appropriate to the areas they will occupy when mature. Thus it is of little use to plant a forest tree that will grow 100 feet (30 metres) high and 50 feet across in a small suburban front garden 30 feet square, but a narrow flowering cherry or redbud tree would be quite suitable.

Blending and contrast of colour as well as of forms are important aspects to consider in planning a garden. The older type of herbaceous border was designed to give a maximum display of colour in summer, but many gardeners now prefer to have flowers during the early spring as well, at the expense of some bare patches later. This is often done by planting early-flowering bulbs in groups toward the front. Mixed borders of flowering shrubs combined with herbaceous plants are also popular and do not require quite so much maintenance as the completely herbaceous border.

Groups of half-hardy annuals, which can withstand low night temperatures, may be planted at the end of spring to fill gaps left by the spring-flowering bulbs. The perpetual-flowering roses and some of the larger shrub roses look good toward the back of such a border, but the hybrid tea roses and the floribunda and polyantha roses are usually grown in separate rose beds or in a rose garden by themselves.

Woodland gardens

The informal woodland garden is the natural descendant of the shrubby “wilderness” of earlier times. The essence of the woodland garden is informality and naturalness. Paths curve rather than run straight and are of mulch or grass rather than pavement. Trees are thinned to allow enough light, particularly in the glades, but irregular groups may be left, and any mature tree of character can be a focal point. Plants are chosen largely from those that are woodlanders in their native countries: rhododendron, magnolia, pieris, and maple among the trees and shrubs; lily, daffodil, and snowdrop among the bulbs; primrose, hellebore, St.-John’s-wort, epimedium, and many others among the herbs.

Rock gardens

Rock gardens are designed to look as if they are a natural part of a rocky hillside or slope. If rocks are added, they are generally laid on their larger edges, as in natural strata. A few large boulders usually look better than a number of small rocks. In a well-designed rock garden, rocks are arranged so that there are various exposures for sun-tolerant plants such as rockroses and for shade-tolerant plants such as primulas, which often do better in a cool, north-facing aspect. Many smaller perennial plants are available for filling spaces in vertical cracks among the rock faces.

The main rocks from which rock gardens are constructed are sandstone and limestone. Sandstone, less irregular and pitted generally, looks more restful and natural, but certain plants, notably most of the dianthuses, do best in limestone. Granite is generally regarded as too hard and unsuitable for the rock garden because it weathers very slowly.

Water gardens

The water garden represents one of the oldest forms of gardening. Egyptian records and pictures of cultivated water lilies date as far back as 2000 BCE. The Japanese have also made water gardens to their own particular and beautiful patterns for many centuries. Many have an ornamental lantern of stone in the centre or perhaps a flat trellis roof of wisteria extending over the water. In Europe and North America, water gardens range from formal pools with rectangular or circular outline, sometimes with fountains in the centre and often without plants or with just one or two water lilies (Nymphaea), to informal pools of irregular outline planted with water lilies and other water plants and surrounded by boggy or damp soil where moisture-tolerant plants can be grown. The pool must contain suitable oxygenating plants to keep the water clear and support any introduced fish. Most water plants, including even the large water lilies, do well in still water two to five feet deep. Temperate water lilies flower all day, but many of the tropical and subtropical ones open their flowers only in the evening.

In temperate countries water gardens also can be made under glass, and the pools can be kept heated. In such cases, more tropical plants, such as the great Victoria amazonica (V. regia) or the lotus (Nelumbo nucifera), can be grown together with papyrus reeds at the edge. The range of moisture-loving plants for damp places at the edge of the pool is great and includes many beautiful plants such as the candelabra primulas, calthas, irises, and osmunda ferns.

Herb and vegetable gardens

Most of the medieval gardens and the first botanical gardens were largely herb gardens containing plants used for medicinal purposes or herbs such as thyme, parsley, rosemary, fennel, marjoram, and dill for savouring foods. The term herb garden is usually used now to denote a garden of herbs used for cooking, and the medicinal aspect is rarely considered. Herb gardens need a sunny position, because the majority of the plants grown are native to warm, dry regions.

The vegetable garden also requires an open and sunny location. Good cultivation and preparation of the ground are important for successful vegetable growing, and it is also desirable to practice a rotation of crops as in farming. The usual period of rotation for vegetables is three years; this also helps to prevent the carryover from season to season of certain pests and diseases.

The old French potager, the prized vegetable garden, was grown to be decorative as well as useful; the short rows with little hedges around and the high standard of cultivation represent a model of the art of vegetable growing. The elaborate parterre vegetable garden at the Château de Villandry is perhaps the finest example in Europe of a decorative vegetable garden.

Specialty gardens

Roof gardens

The modern tendency in architecture for flat roofs has made possible the development of attractive roof gardens in urban areas above private houses and commercial buildings. These gardens follow the same principles as others except that the depth of soil is less, to keep the weight on the rooftop low, and therefore the size of plants is limited. The plants are generally set in tubs or other containers, but elaborate roof gardens have been made with small pools and beds. Beds of flowering plants are suitable, among which may be stood tubs of specimen plants to produce a desired effect.

Scented gardens

Scent is one of the qualities that many people appreciate highly in gardens. Scented gardens, in which scent from leaves or flowers is the main criterion for inclusion of a plant, have been established, especially for the benefit of blind people. Some plants release a strong scent in full sunlight, and many must be bruised or rubbed to yield their fragrance. These are usually grown in raised beds within easy reach of visitors.

Contents of gardens

Permanent elements

The more or less permanent plants available for any garden plan are various grasses for lawns, other ground-cover plants, shrubs, climbers, and trees. More transitory and therefore in need of continued attention are the herbaceous plants, such as the short-lived annuals and biennials, and the perennials and bulbous plants, which resume growth each year.

Lawns and ground covers

Areas of lawn, or turf, provide the green expanse that links all other garden plantings together. The main grasses used in cool areas for fine-textured lawns are fescues (Festuca species), bluegrasses (Poa species), and bent grasses (Agrostis species), often in mixtures. A rougher lawn mixture may contain ryegrass (Lolium species). In drier and subtropical regions, Bermuda grass (Cynodon dactylon) is frequently used, but it does not make nearly as fine a lawn as those seen in temperate regions of higher rainfall.

Ground covers are perennial plants used as grass substitutes in regions where grasses do poorly, or they are sometimes combined with grassy areas to produce a desired design. The deep greens, bronzes, and other colours that ground-cover plants can provide offer pleasing contrasts to the green of a turf. Ground covers, however, are not so durable as lawns and do not sustain themselves as well under foot traffic and other activities. Among the better known plants used as ground covers are Japanese spurge (Pachysandra terminalis), common periwinkle (Vinca minor), lily of the valley (Convallaria majalis), ajuga, or bugleweed (Ajuga reptans), many stonecrops (Sedum species), dichondra (Dichondra repens), and many ivies (Hedera species).

Shrubs and vines (climbers)

Smaller woody plants, such as shrubs and bushes, have several stems arising from the base. These plants attain heights up to about 20 feet (6 metres). They often form the largest part of modern gardens, because their cultivation requires less labour than that of herbaceous plants, and some flowering shrubs have extended blooming periods. Among the popular garden shrubs are lilac (Syringa vulgaris), privet (Ligustrum species), spirea (Spiraea species), honeysuckle (Lonicera species), forsythia (Forsythia species), mock orange (Philadelphus species), and hydrangea (Hydrangea species).

Bushlike azaleas and rhododendrons (both of which are species of Rhododendron) provide colourful blossoms in spots where there is semishade.

Climbers are often useful in softening the sharp lines of buildings, fences, and other structures. They can provide shade as an awning or cover on an arbour or garden house. Some species are also useful as ground covers on steep slopes and terraces. Among the many woody perennial climbers for the garden are the ivies, trumpet creeper (Bignonia, or Campsis, radicans), clematis (Clematis species), wisteria (Wisteria sinensis), climbing roses, annual herbaceous vines such as morning glory (Ipomoea species), and ornamental gourds, the last of which can provide rapid but temporary coverage of unsightly objects.

Trees

Trees are the most permanent features of a garden plan. The range of tree sizes, shapes, and colours is vast enough to suit almost any gardening scheme, from shrubby dwarf trees to giant shade trees, from slow to rapid growers, from all tones of green to bronzes, reds, yellows, and purples. A balance between evergreen trees, such as pines and spruces, and deciduous trees, such as oaks, maples, and beeches, can provide protection and visual interest throughout the year.

Transitory elements

Herbaceous plants

Herbaceous plants, which die down annually and have no woody stem aboveground, are readily divided into three categories, as mentioned earlier: (1) Annuals, plants that complete their life cycle in one year, are usually grown from seed sown in the spring either in the place they are to flower or in separate containers, from which they are subsequently moved into their final position. Annuals flower in summer and die down in winter after setting seed. Many brilliantly coloured ornamental plants as well as many weeds belong in this category. Examples of annuals are petunia and lobelia. (2) Biennials are plants sown from seed one year, generally during the summer. They flower the second season and then die. Examples are wallflower and sweet william. (3) Herbaceous perennials are those that die down to the ground each year but whose roots remain alive and send up new top growth each year. They are an important group in horticulture, whether grown as individual plants or in the assembly of the herbaceous border. Because they flower each year, they help to create the structure of the garden’s appearance, so their placement must be considered carefully. Examples are delphinium and lupine.

Bulbous plants

For horticultural purposes, bulbous plants are defined to include those plants that have true bulbs (such as the daffodil), those with corms (such as the crocus), and a few that have tubers or rhizomes (such as the dahlia or iris). A bulb is defined as a modified shoot with a disklike basal plate and above it a number of fleshy scales that take the place of leaves and contain foods such as starch, sugar, and some proteins. Each year a new stem arises from the centre. A corm consists of the swollen base of a stem, generally rounded or flattened at the top and covered with a membranous tunic in which reserve food materials are stored. A tuber or rhizome is not the base of the stem but rather a swollen part of an underground stem; it is often knobbly. All such plants have evolved in places where they can survive in a semidormant state over long unfavourable seasons, either cold mountain winters or long droughty summers.

The principles of gardening

Soil is the basic element in the cultivation of all plants, although soilless growth in water, with or without gravel or sand, enriched with suitable chemicals (hydroponics) can be very successful.

Soil consists of particles, mainly mineral, derived from the breakdown of rocks and other substances together with organic matter. In the pore spaces between the particles, both water (containing dissolved salts) and air circulate. The air contains more carbon dioxide and less oxygen than does the atmosphere. Minute living organisms are also present in soil in immense quantities and are what make it “alive.” Plants must penetrate this pore space to reach much of their nourishment.

The soil must be managed for fertility (the ability to supply plant nutrients) and physical condition. Nutrients must be supplied and released in forms available to the plant. Sixteen elements are necessary for plant growth. Three of these, carbon, oxygen, and hydrogen, are provided through water and air; the other 13 are provided through the soil. The elements required in relatively large amounts are called major elements: nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. The minerals required in small quantities are called trace elements: iron, boron, manganese, zinc, molybdenum, copper, and chlorine.

Soils can be roughly divided into three main types on the basis of their usefulness horticulturally, but many areas contain a mixture.

Clays

Clays, in which the particles are very fine, are called in horticulture heavy soils, because it is difficult to turn them over with a spade. They can be very fertile but tend to be lacking in good drainage, holding their water closely adhered to the soil particles; therefore, they cannot be worked when wet, and under pressure they tend to compact tightly, driving out the air. During drought they tend to become hard and even to develop large cracks so that they cannot be worked satisfactorily. Clay soils can be lightened with as much humus as can be dug into them. Humus may be any decayed organic matter, such as farmyard manure, leaf mold, or compost made from kitchen scraps and grass clippings.

Sands and gravels

Sands and gravels are opposite in properties to clay. The soil particles are large, and the soils are called light because they are easy to work and turn in nearly all weather. Since their water-holding capacity is very low, however, they tend to dry out quickly. They are “hungry” soils requiring great quantities of manures, humus, and fertilizers to keep them prolific.

Peats and heaths

Peats and heaths are usually very acid and ill-drained. They result where conditions have prevented the complete breakdown of old vegetable matter into humus, generally because of poor aeration and surplus acid bog water. Much peat is derived from the decaying roots of sphagnum moss, useful for mulching in the garden. A heath soil is generally less fertile, consisting of a large mixture of sand with the peat and tending to be very low in mineral content and in water-retaining capacity.

The ideal garden soil is a medium loam consisting of a mixture of clay and sand, fairly rich in humus and easily worked, and not forming large clods when dry. The consistency of the soil is important, for a porous, properly tilled soil provides a medium through which roots can penetrate readily and rapidly. Another factor of importance in soils is the degree of acidity or alkalinity. Soil alkalinity is usually derived from free calcium carbonate or a similar alkaline salt. Soil reaction can be modified. It may be made more alkaline by adding one of the organic salts, of which calcium is best, in the form of lime. Acidity may be increased by adding hydrogen, in the form of sulfur compounds such as ammonia sulfate or superphosphate.

Feeding: fertilizing and watering

Maximum return can be obtained only from soil with an ample supply of elements necessary for plant growth, combined with sufficient moisture to enable them to be dissolved and absorbed through the plant hairs.

Treatment with farmyard manure or garden compost can supply the majority of these requirements. Because manure and compost are scarce in urban areas it is often necessary to use mineral fertilizers as well as organics. The soil is such a complex substance that all fertilizers must be applied in moderation and in balance with each other according to the deficiencies of the soil and the requirements of the particular crop. Different crops have different fertilizer needs. Manures are generally best dug into the ground in autumn in a temperate climate but also may be used as mulches in spring to control weeds. A mulch is a surface layer of organic matter that helps the several needs of feeding, conserving moisture, and controlling weeds. Black polyethylene sheeting is now widely used for all the mulching functions except feeding.

Watering of newly placed plants and of all plants during periods of drought is an essential gardening chore. Deep and thorough watering—not simply sprinkling the soil surface—can result in greatly improved growth. Water is essential in itself, but it also makes minerals available to plants in solution, the only form usable by plants. About one inch of water applied each week to the soil surface will percolate down about six inches; this is a minimal subsistence amount for many herbaceous garden plants, and small trees and shrubs require more. Proper watering once a week encourages deep penetration of roots, which in turn enables plants to survive dry surface conditions.

Drainage

Drainage is the other important side of water management. All plants need water but the amount needed varies, and if plants are forced to absorb more than they need, a form of drowning occurs. The symptoms are most easily seen in overwatered pot plants but are also visible to an experienced eye in badly drained corners of a garden. Roots require air as well as water and depend on subsurface water to bring the necessary oxygen. In large private gardens and in commercial gardens, buried earthenware piping is commonly used. In smaller gardens drainage can be readily achieved by the use of sumps, that is, holes dug to a depth of about four feet in affected places. The bottom half of the sump is filled with stones, through which excess water drains. Such measures may greatly improve the potential of a garden and the workability of its soil.

Protecting plants

Most plants have a precise level of tolerance to cold, below which they are killed. Many plants from tropical or subtropical regions cannot survive frost and are killed by temperatures below 32 °F (0 °C). These are called frost-tender. Others, called half-hardy, can withstand a few degrees of frost. Fortunately, many of the best garden plants are completely hardy, a quality often encouraged by careful breeding, and will withstand any low temperatures likely to be reached in temperate regions.

Various measures can be taken to give frost protection, from the simple ones appropriate for smaller gardens to the elaborate coverings used to protect valuable horticultural crops. Removing weeds that shade the soil increases the amount of heat stored during the day. Well-drained soil is less susceptible. Any shield against wind in frosty weather enhances survival capability. The simplest form of protection is a wrapping to keep warmer air around the plant. This can be a mulch (leaves, soil, ashes) placed over the crown of a slightly tender plant in winter or a shield of sacking for leaf-shedding plants (not as desirable for evergreens, which utilize their leaves all the year).

Glass structures such as greenhouses or outdoor frames can provide additional protection for tender plants. Such structures can be heated and the temperature regulated by a thermostat to any required degree. Thus, in temperate regions, orchids and other tropical plants can be grown so that they flower throughout the winter, many being forced to flower earlier than their normal season by the higher temperature. Greenhouses are divided by gardeners into four rough categories: (1) The cold house, in which there is no supplementary heating and which is suitable only for plants that will not be killed by a few degrees of frost (such as alpines or potted bulbous plants). The combination of heat from the sun and protection from wind will keep such a house appreciably warmer than the temperature outside. (2) The coolhouse, in which the minimum temperature is kept to 45 °F (7 °C). Most amateurs’ greenhouses fall into this class, and a very large range of plants can be grown in them. (3) The intermediate house, in which the minimum temperature is kept at 55 or 60 °F (13 or 16 °C) and which is suitable for a wide range of orchids. (4) The hothouse, or stove house, in which the minimum temperature is kept above 60 °F (16 °C) and in which tropical plants such as anthuriums and cattleyas (a genus of the orchid family) can be grown.

Training and pruning

Training, the orienting of the plant in space, is achieved by techniques that direct the shape, size, and direction of plant growth. It may be accomplished by use of supports to which plants can be bent, twisted, or fastened. Pruning, the judicious cutting away of plant parts, is performed for other purposes: to contain size, to encourage fruiting in orchard trees, or to improve the appearance of ornamental trees and shrubs. It is one of the most important horticultural arts.

Where trees and shrubs are left to grow naturally, they often become much too large for their space in the garden. Also they may grow lanky and misshapen and have much dead growth. Where a branch or shoot is cut, it will often be induced to make a number of young shoots from below the cut, and these are likely to flower more freely than the older branches. Fruit trees in particular when pruned annually often give fruit of finer quality, larger in size, freer of disease, and of better colour. The two basic pruning cuts are known as heading back and thinning out. Heading back consists of cutting back the terminal portion of a branch to a bud; thinning out is the complete removal of a branch to a lateral or main trunk. Heading back, usually followed by the stimulation of lateral budbreak below the cut, produces a bushy, compact plant, suitable for a hedgerow, and it is often used to rejuvenate shrubs that have become too large or that flower poorly. Thinning out, which encourages longer growth of the remaining terminals by reducing lateral branches, tends to open up the plant, producing a longer plant. In general, pruning, started when the plant is young, obviates the need for drastic and risky remedial pruning later of a large, old, or misshapen bush or tree.

Particular spatial arrangements may increase light utilization, facilitate harvesting or disease control, or improve productivity and quality. Thus, training and pruning form an essential part of fruit growing throughout the life of the plant. Special attention is given in the formative years to obtain desired shape and structure. The key to training is the point on the main stem from which branches form. In the central-leader system of training, the trunk forms a central axis with branches distributed laterally up and down and around the stem. In the open-centre or vase system, the main stem is terminated and growth forced through a number of branches originating close to the upper end of the trunk. An intermediate system is called the modified-leader system. In espalier systems plants are trained to grow flat along a wire or trellis. Properly executed espaliers are extremely attractive as ornamentals. Espaliers in combination with dwarfing rootstocks allow high-density orchards that are very productive on a per-unit-area basis, with the fruit close to the ground for easy harvest. Extensive pruning is required annually to maintain the system.

There are a number of physiological responses to training and pruning. Orientation of the plant may have a marked effect on growth and fruiting. Thus fruit trees planted on an inclined angle become dwarfed and flower earlier; training branches in a horizontal position produces the same effect. This effect is achieved naturally when a heavy fruit load bends a limb down. The main effects of pruning are achieved by altering the root–shoot balance. Thus an explosion of vegetative growth normally occurs after extensive shoot pruning. Severely pruned plants, especially if they are in the juvenile stage of growth, tend to remain vegetative. Similarly the slowdown of vegetative growth by root pruning encourages flowering.

The training of plants to grow in unnatural shapes for ornamental purposes is called topiary. In Roman and Renaissance times, when ingenious topiary was in high fashion, plants were trained to unusual and fantastic shapes such as beasts, ships, and building facades. Though more modestly, hedges and shrubs are still trained to geometric shapes in formal gardens.

Another extreme form of training is the Japanese art of bonsai, the creation of dwarfed potted trees by a combination of pruning (both roots and tops) and restricted nutrition. Living trees more than 100 years old and only a few feet high are grown in special containers arranged to resemble the natural landscape.

Propagation

New plants are produced either from seed or by the techniques of division, taking cuttings, grafting, budding, or layering. For the ordinary gardener, propagation is a relatively simple but interesting process normally used for economic provision of more versions of favourite plants, as part of exchanges with other gardeners, or as a wise precaution against winter losses.

Propagation by cuttings is the most common practice. Young shoots of the current season are usually the most successful at rooting. Roses are usually propagated by budding, in which a bud from the rose desired is inserted in rootstock (that part of the plant tissue from which a root can form) just above ground level. Fruit trees are usually propagated by layering, in which a young shoot is pegged down in the ground with the end twisted upward almost at right angles; the lower side of the wood just before the twist is wounded so as to induce rooting. When this has taken place, the layer is severed from the parent.

Control of weeds

Controlling weeds is a basic, and probably the most arduous, factor of cultivation and has been carried on from the time the earliest nomads settled down to an agricultural life. It has always been necessary to free the chosen crops of competition from other plants. For smaller weeds hoeing is practicable. The weeds are cut off by the action of the hoe and left to wither on the surface. Hand weeding, by pulling out individual weeds, is often necessary in gardens, particularly the rock garden, in seed boxes, and in the herbaceous border or among annuals. Chemical and biological control of weeds developed greatly after World War II and has made much mechanical cultivation unnecessary.

Control of pests and diseases

Damage to plants is most often caused by pests such as insects, mites, eelworms, and other small creatures but may also be caused by mammals such as deer, rabbits, and mice. Damage by disease is that caused by fungi, bacteria, and viruses.

Prevention is generally better than cure, and constant vigilance is necessary to prevent a pest infestation or a disease outbreak. Control can be obtained by the use of chemical sprays, dusts, and fumigants, but some of these are so potent that they should be used only by the experienced operator. Considerable evidence is available regarding the possible harmful long-term effects on the biological chain of excessive use of some of these noxious chemicals, particularly the hydrocarbons. Some control can be obtained through good garden practices: clearing up all dead and diseased material and burning it; pruning and thinning so that a reasonable circulation of air is obtained through the plants; and crop rotation. Some control may also be obtained through natural biological predators. The breeding of plants immune to certain pests and diseases is also a valuable means of control.

Mechanical aids

Mechanical devices to aid the gardener include tillers, lawn mowers, hedge cutters, sprinklers, and a variety of more esoteric equipment that has made gardening an easier pursuit. Such machines are not a substitute for good judgment and technique in the garden, however, nor will they give anyone a completely labour-free garden. They do enable a considerably larger area to be cultivated and maintained than if all labour is performed by hand.

Jai Ganesh · 2023-06-17 00:11:22

1811) Diving

Gist

Diving is the sport of jumping or falling into water from a platform or springboard, usually while performing acrobatics. Diving is an internationally recognized sport that is part of the Olympic Games. In addition, unstructured and non-competitive diving is a recreational pastime.

Competitors possess many of the same characteristics as gymnasts and dancers, including strength, flexibility, kinaesthetic judgment and air awareness. Some professional divers were originally gymnasts or dancers as both the sports have similar characteristics to diving. Dmitri Sautin holds the record for most Olympic diving medals won, by winning eight medals in total between 1992 and 2008.

Summary

Diving is a sport of plunging into water, usually head foremost, performed with the addition of gymnastic and acrobatic stunts. In its more elaborate, acrobatic form, diving originated in Europe early in the 19th century as a diversion of gymnasts and as a competitive sport in the late 19th century. It became a part of the swimming program of the Olympic Games in 1904 and developed rapidly through the first half of the 20th century. Synchronized diving, a competition in which two divers simultaneously perform a dive, emerged and became part of the Olympic program in 2000.

In competition, dives are performed from a firm platform 5 or 10 metres (16.4 or 32.8 feet) above the water or from an elastic springboard 1 or 3 metres high. In Olympic contests only the 10-metre platform and 3-metre springboard are used. Dives performed in competition are listed, together with a rating of their degree of difficulty of performance, in a table published by the Fédération Internationale de Natation Amateur (International Amateur Swimming Federation; founded 1908), the world governing body of amateur aquatic sports. Contestants are required to do certain of the listed dives, as well as several of their own choice. At least three but not more than 10 judges score each dive, with attention paid to takeoff, bearing of the body in the air, execution of the prescribed movements, and entry into the water. The scores for each dive are totaled and multiplied by the degree of difficulty. The diver with the highest total score for all dives at the end of the contest is the winner. In the springboard competition, men make 17 dives, women 15. Platform events require 16 dives from men and 14 from women. In synchronized competitions, participants make 10 dives and are judged on their synchronicity with each other as well as their individual execution of the dive.

Competitive dives are divided into five groups, with the addition of arm-stand dives done from fixed platforms only. The first includes the forward dives, in which the person faces the water, dives out from the edge of the board or platform, and rotates forward one-half or more turns before entering the water. The second comprises the backward dives, in which the diver stands at the edge, facing away from the water, then springs and rotates backward. The third is the reverse group, in which the diver takes off in the forward position but then reverses his spin toward the board. In the fourth group, the inward dives, the diver stands on the edge of the platform and springs backward but rotates forward, again toward the board. The fifth classification is that of the twisting dives, in which the diver rotates the body on its long axis while performing one of the other four types of dives—as in a forward 11/2 somersault with 3 twists. The five voluntary dives comprise one selected from each group.

The majority of dives included in the roster may be executed in three distinct positions: straight, pike, or tuck. In the straight position, the body is held extended, with no flexion at the hips or knees. In the pike position, there is a bend at the hips but no knee flexion. In the tuck position, both hips and knees are flexed and the body resembles a ball. The most complicated dives may be done in free (any) position, a loose but graceful combination of the others.

Additional Information

What is Diving?

Diving is a sport where athletes jump or fall into water from a platform or springboard while performing acrobatic routines.

As such, competitors similar characteristics as gymnasts, including strength, flexibility, balance, power, and air awareness.

By whom, where and when was Diving invented?

The sport of diving became popular in Sweden and Germany in the 18th and 19th centuries, and was primarily practised by gymnasts who started performing tumbling routines into the water.

In the late 19th century, a group of Swedish divers visited Great Britain. They put on diving displays that proved hugely popular and led to the formation of the first diving organisation, the Amateur Diving Association, in 1901.

What are the rules of Diving?

There are two types of diving board at the Olympics: springboard and platform.

Springboard diving takes place on a flexible board three metres above the water that propels athletes upwards.

Platform boards sit 10 metres above the water and are rigid, meaning that athletes have to generate their own power, or simply drop into their routine.

There are both individual and synchronised (featuring two athletes) events for both springboard and platform diving at the Olympics. Men compete over six rounds, while women compete over five.

Individual dives are scored by a panel of seven World Aquatics-appointed judges, who rate the dive based on the starting position, the take-off, the flight, and the entry into the water. The top two and bottom two scores are eliminated, and the final three scores are added together and multiplied by the degree of difficulty rating of the dive to achieve the total score for that dive.

The highest overall combined score at the end is declared the winner.

It is the same process for synchronised diving, except there are 11 judges: six grading the divers’ execution, and five grading synchronisation.

What is the hardest Olympic dive?

The reverse 4½ somersault in the pike position rated at 4.8 is considered to be the hardest dive routine, but competitors could attempt more difficult dives.

Why do Olympic divers shower after every dive?

Divers shower or jump in a jacuzzi after they compete in order to keep their muscles warm and reduce the chance of any strains or cramps.

Diving and the Olympics

Diving was included in the Olympic Games for the first time at the Olympic Games St. Louis 1904. The springboard and platform events have been included since the 1908 Olympic Games in London. Since the Stockholm Games in 1912, women have taken part in the diving events.

The first Olympic competitions differed from those which exist nowadays, notably with respect to the height of the platforms and springboards. The diving programme has been relatively stable since the 1928 Games in Amsterdam: men and women take part in 10-metre high-dive and 3-metre springboard events. In 2000, the Sydney Games witnessed the entrance of synchronised diving on both the springboard and the platform.

This discipline was first dominated by the USA, with four-time Olympic gold medallist Greg Louganis considered one of the sport’s finest athletes ever. But this domination started to waver with the emergence of the People’s Republic of China at the end of the 1980s. Since then, the Asian powerhouse has dominated the sport of diving across the men’s and women’s disciplines.

Best Divers to watch

The latest star off China’s impressive conveyor belt of diving talent is Wang Zongyuan.

He won 3m synchronised Olympic gold alongside Xie Siyi and individual 3m silver at Tokyo 2020 before becoming world champion in both disciplines in 2022.

Wang’s compatriot, Cao Yuan, boasts one of the most impressive and diverse diving resumes ever with three Olympic golds (10m synchro at London 2012, 3m springboard at Rio 2016, and 10m platform at Tokyo 2020), as well as four world championship titles.

On the women’s side, Chen Yuxi delivered gold and silver in the 10m synchro and platform respectively at Tokyo 2020, before winning both titles at the 2022 Worlds, while teenager Quan Hongchan won 10m platform Olympic gold before taking out the 10m synchro Worlds title alongside Yuxi.

Outside of China, Great Britain has posed the most consistent challenge to China, with Tom Daley winning 10m synchro Olympic gold in Tokyo alongside Matty Lee, while Jack Laugher took home the 3m synchro gold medal at Rio 2016.

Diving Competition Rules at Paris 2024

There will once again be two events in diving at Paris 2024: 3m springboard and 10m platform.

A maximum of 136 athletes (68 of each gender) will compete in diving at Paris 2024 - the exact same number as Tokyo 2020.

There will be individual and synchronised competitions in both, meaning four gold medals overall are up for grabs.

There will be three rounds for each competition, including preliminaries, semi-finals, and a final.

Jai Ganesh · 2023-06-18 00:08:57

1812) Magic

Gist

The secret power that some people believe can make strange or impossible things happen if you say special words or do special things.
2. The art of doing tricks that seem impossible in order to entertain people.

Summary

Magic, sometimes spelled magick, is an ancient practice rooted in rituals, spiritual divinations, and/or cultural lineage—with an intention to invoke, manipulate, or otherwise manifest supernatural forces, beings, or entities in the natural world. It is a categorical yet often ambiguous term which has been used to refer to a wide variety of beliefs and practices, frequently considered separate from both religion and science.

Although connotations have varied from positive to negative at times throughout history, magic continues to have an important religious and medicinal role in many cultures today.

Within Western culture, magic has been linked to ideas of the Other, foreignness, and primitivism; indicating that it is "a powerful marker of cultural difference" and likewise, a non-modern phenomenon. During the late nineteenth and early twentieth century, Western intellectuals perceived the practice of magic to be a sign of a primitive mentality and also commonly attributed it to marginalised groups of people.

In modern occultism and neopagan religions, many self-described magicians and witches regularly practice ritual magic; defining magic as a technique for bringing about change in the physical world through the force of one's will. This definition was popularised by Aleister Crowley (1875–1947), an influential British occultist, and since that time other religions (e.g. Wicca and LaVeyan Satanism) and magical systems (e.g. chaos magick) have adopted it.

Magic, which encompasses the subgenres of illusion, stage magic, and close up magic, among others, is a performing art in which audiences are entertained by tricks, effects, or illusions of seemingly impossible feats, using natural means. It is to be distinguished from paranormal magic which are effects claimed to be created through supernatural means. It is one of the oldest performing arts in the world.

Modern entertainment magic, as pioneered by 19th-century magician Jean-Eugène Robert-Houdin, has become a popular theatrical art form. In the late 19th and early 20th centuries, magicians such as Maskelyne and Devant, Howard Thurston, Harry Kellar, and Harry Houdini achieved widespread commercial success during what has become known as "the Golden Age of Magic". During this period, performance magic became a staple of Broadway theatre, vaudeville, and music halls. Magic retained its popularity in the television age, with magicians such as Paul Daniels, David Copperfield, Criss Angel, Doug Henning, Penn & Teller, David Blaine, and Derren Brown modernizing the art form.

The world's largest-selling publication for magicians, Magic magazine, curated a list of the "100 most influential magicians of the 20th century" to have contributed to the modern development of the art of magic. According to the magician-culled list titled "Those Who Most Affected The Art in America", Houdini holds the first rank. Then, in decreasing order, Dai Vernon, David Copperfield, Harry Blackstone, Doug Henning, Tarbell, Cardini, Mark Wilson, Siegfried and Roy, and finally Thurston at number 10.

Details

Magic is a concept used to describe a mode of rationality or way of thinking that looks to invisible forces to influence events, effect change in material conditions, or present the illusion of change. Within the Western tradition, this way of thinking is distinct from religious or scientific modes; however, such distinctions and even the definition of magic are subject to wide debate.

Nature and scope

Practices classified as magic include divination, astrology, incantations, alchemy, sorcery, spirit mediation, and necromancy. The term magic is also used colloquially in Western popular culture to refer to acts of conjuring and sleight of hand for entertainment. The purpose of magic is to acquire knowledge, power, love, or wealth; to heal or ward off illness or danger; to guarantee productivity or success in an endeavour; to cause harm to an enemy; to reveal information; to induce spiritual transformation; to trick; or to entertain. The effectiveness of magic is often determined by the condition and performance of the magician, who is thought to have access to unseen forces and special knowledge of the appropriate words and actions to manipulate those forces.

Phenomena associated or confused with magic include forms of mysticism, medicine, paganism, heresy, witchcraft, shamanism, Vodou, and superstition. Magic is sometimes divided into the "high" magic of the intellectual elite, bordering on science, and the "low" magic of common folk practices. A distinction is also made between "black" magic, used for nefarious purposes, and "white" magic, ostensibly used for beneficial purposes. Although these boundaries are often unclear, magical practices have a sense of "otherness" because of the supernatural power that is believed to be channeled through the practitioner, who is a marginalized or stigmatized figure in some societies and a central one in others.

Elements of magic:

Spells

The performance of magic involves words (e.g, spells, incantations, or charms) and symbolic numbers that are thought to have innate power, natural or man-made material objects, and ritual actions performed by the magician or other participants. A spell or incantation is believed to draw power from spiritual agencies to accomplish magic. Knowledge of spells or symbolic numbers is often secret (occult), and the possessor of such knowledge can be either greatly revered or feared. In some cases, the spell is the most highly regarded component of the magical rite or ceremony. The Trobriand Islanders of Melanesia, for example, regarded using the right words in the right way as essential to the efficacy of the rite being performed. Among the Maori of New Zealand the power of words is thought to be so important that mistakes in public recitations are believed to cause disasters for individuals or the community. Moreover, like the medieval European charms that used archaic languages and parts of the Latin liturgy, spells often employ an esoteric vocabulary that adds to the respect accorded rites. Belief in the transformative power of words is also common in many religions. Shamans, spirit mediums, and mystics, for example, repeat specific sounds or syllables to achieve an ecstatic state of contact with spiritual forces or an enlightened state of consciousness. Even modern magic for entertainment retains a residual of the spell with its use of the term abracadabra.

Material

Much anthropological literature refers to the objects used in magic as "medicines," hence the popular use of the term medicine man for magician. These medicines include herbs, animal parts, gemstones, sacred objects, or props used in performance and are thought to be potent in themselves or empowered by incantations or rituals. In some cases, medicines that are intended to heal are physiologically effective; for example, the poppy is used widely as an anesthetic, willow bark is used by some Chinese as an analgesic, and garlic and onions were used as antibiotics in medieval Europe. Other medicines that are meant to cause harm, such as toad extracts and bufadienolides, are, in fact, known poisons. Other materials have a symbolic relationship to the intended outcome, as with divination from animal parts. In scapulamancy (divination from a sheep shoulder bone), for example, the sheep’s bone reflects the macrocosmic forces of the universe. In sorcery a magician may employ something belonging to the intended victim (e.g., hair, nail parings, or a piece of clothing) as part of the ritual. The rite itself may be symbolic, as with the drawing of protective circles in which to call up spirits, the sprinkling of water on the ground to make rain, or the destruction of a wax image to harm a victim. Plants or other objects can also symbolize desired outcomes: in rites to ensure a canoe’s speed, the Trobriand use light vegetable leaves to represent the ease with which the craft will glide over the water; the Zande of South Sudan place a stone in a tree fork to postpone the setting of the sun; and many Balkan peoples once swallowed gold to cure jaundice.

Rites and condition of the performer

Because magic is based on performance, ritual and the magician’s knowledge and ability play a significant role in its efficacy. The performance of magic also presumes an audience, either the spiritual forces addressed, the patient-client, or the community. Both the magician and the rite itself are concerned with the observance of taboos and the purification of the participants. Magicians, like priests presiding over religious rituals, observe restrictions of diet or sexual activity to demarcate the rite from ordinary and profane activities and to invest it with sanctity. Modern magicians’ success with entertaining audiences is dependant primarily on their performance skills in manipulating material objects to create an illusion.

Functions

Foremost among the many roles magic plays are its “instrumental” and “expressive” functions. Based in the attempt to influence nature or human behaviour, magic’s instrumental function is measured by its efficacy in achieving the desired result. Anthropologists identify three main types of instrumental magic: the productive, the protective, and the destructive. Productive magic is employed to solicit a successful outcome from human labour or nature, such as bountiful hunt or harvest or good weather. Protective magic aims to defend an individual or community from the vagaries of nature and the evil of others. The use of amulets to ward off contagious diseases or the recitation of charms before a journey are examples of this protective function. Lastly, destructive magic, or sorcery, is intended to harm others, often is motivated by envy, and is socially disruptive. Consequently, the use of countermagic against sorcery may relieve some social tension within a community.

Magic’s expressive function results from the symbolic and social meanings attached to its practices, though its performers may not necessarily be aware of this function. Magic can provide a sense of group identity through shared rituals that give power or strength to members. At the same time, it can isolate the magician as a special person within or on the margins of society. Magic can also serve as a creative outlet or form of entertainment. It is, therefore, inseparable from the total system of thought, belief, and practice in a given society.

Definitional issues: magic, religion, and science

The term magic cannot be defined in isolation because of its broad parameters, important role in many societies, and interactions with related phenomena. Magic is a generic label used by outsiders (theoretically, objective observers) to describe specific practices in societies in which this word or its conceptual equivalent may not even exist. As a result, diverse phenomena are lumped together on the assumption that they operate in the same way. This artificial construct of magic also exists only in relation to what it is not—primarily, religion and science as alternate modes of rationality. Such definitions of magic privilege cultures with a strong scientific orientation and stigmatize those that practice magic instead of religion. Consequently, defining magic and identifying magicians requires an understanding of the cultural contexts in which these labels are used.

Although magic has an ambiguous relationship with Western religion and science, it is rooted in the main institutional, social, and intellectual traditions in Western history. Moreover, modern attempts to arrive at a universal definition of magic reflect a Western bias. In particular, 18th- and 19th-century views on cultural and historical evolution set magic apart from religion and science. In a model developed by the British anthropologist Sir James Frazer (1854–1941), magic is characterized as an early stage in human development, superseded first by religion and then by science. The debate over the relationship between magic, religion, and science that dominated much of the discussion about magic throughout the 20th century is evident in the fieldwork of anthropologists, the theories of sociologists of religion, and critiques by postmodernists. Consequently, research in comparative religions, history, and anthropology in the second half of the 20th century moved away from the evolutionary model toward more context-sensitive interpretations, while other studies developed new models for cross-cultural comparison. Nonetheless, the magic-religion-science model retains considerable interpretive power, and the dichotomies used to distinguish magic from religion or science are pervasive in popular discourse.

Magic and religion

Magic continues to be widely perceived as an archaic worldview, a form of superstition lacking the intrinsic spiritual value of religion or the rational logic of science. Religion, according to seminal anthropologist Sir Edward Burnett Tylor (1832–1917), involves a direct, personal relationship between humans and spiritual forces; in religion’s highest form, that relationship is with a personal, conscious omnipotent spiritual being. Magic, on the other hand, is characterized as external, impersonal, and mechanical, involving technical acts of power. Magic seeks to manipulate spiritual powers, while religious prayer supplicates spiritual forces, a distinction explored by Bronisław Malinowski (1884–1942) in his work on the Trobriand Islanders. Moreover, according to Émile Durkheim (1858–1917), religion is communal because its adherents, bound together by shared belief, form a church. Magic, on the other hand, involves no permanent ties between believers and only temporary ties between individuals and the magicians who perform services for them. The fieldwork of A.R. Radcliffe-Brown (1881–1955) among the Andaman Islanders, however, has made clear that magic, too, may have a communal dimension.

Magic and science

Although magic is similar in some respects to science and technology, it approaches efficacy (the ability to produce a desired material outcome) differently. Magic, like religion, is concerned with invisible, nonempirical forces; yet, like science, it also makes claims to efficacy. Unlike science, which measures outcomes through empirical and experimental means, magic invokes a symbolic cause-effect relationship. Moreover, like religion and unlike science, magic has an expressive function in addition to its instrumental function. Magical rainmaking strategies, for example, may or may not be efficacious, but they serve the expressive purpose of reinforcing the social importance of rain and farming to a community.

Subcategories of magic

The view of magic as pre-religious or nonscientific has contributed both to subtle distinctions between magic and other practices and to the recognition of subcategories of magic. Notably, anthropologists distinguish magic from witchcraft, defining the former as the manipulation of an external power by mechanical or behavioral means to affect others and the latter as an inherent personal quality that allows the witch to achieve the same ends. However, the line between the two is not always clear, and in some parts of the world an individual may operate in both ways. Similarly, the distinction between "black" magic and "white" magic is obscure since both practices often use the same means and are performed by the same person. Scholars also distinguish between magic and divination, whose purpose is not to influence events but to predict or understand them. Nevertheless, the mystical power of diviners may be thought to be the same as that behind magic. Ultimately, despite these distinctions and the variety of unique roles that practitioners play in their own societies, most end up classified under the universal term magician. Often even religious figures such as priests, shamans, and prophets are identified as magicians because many of their activities include acts defined as "magical" by modern scholars.

In the end, distinctions between magic and religion or science are harder to make in practice than in theory; scholars therefore use labels such as magico-religious to describe activities or persons who cross this artificial dividing line. Similarly, the boundary between magic and science is permeable, since the modern scientific method (observation and experimentation) evolved from forms of scientific magic such as alchemy and astrology. Thus, the evolutionary model, which draws sharp distinctions between magic, religion, and science, cannot account for the essential similarity between various phenomena. Moreover, dichotomies that define magic in relation to other phenomena are reductionist, often ignoring the meaningful structures and beliefs that inform these practices in their native context.

Conceptual history

The claim that magic is found in all human societies rests on a definition that is rooted in Western cultural assumptions, and both these assumptions and the use of the term magic have undergone change over time and place. Consequently, to understand beliefs and practices in other societies that appear similar to European magic, it is necessary to apply the context-sensitive and comparative methods that become increasingly important in the study of anthropology, history, and religion.

History of magic in Western worldviews

The Western conception of magic is rooted in the ancient Judeo-Christian and Greco-Roman heritage. The tradition took further shape in northern Europe during the medieval and early modern period before spreading to other parts of the globe through European exploration and colonialism after 1500. The view of Western civilization as a story of progress includes the magic-religion-science paradigm that traces the "rise" and "decline" of magic and then religion, along with the final triumph of science—a model now challenged by scholars. Moreover, the very origins of the word magic raise questions about ways in which one person’s religion is another person’s magic, and vice versa.

Ancient Mediterranean world

The root word for magic (Greek: mageia; Latin: magia) derives from the Greek term magoi, which refers to a Median tribe in Persia and their religion, Zoroastrianism. The Greco-Roman tradition held that magicians possessed arcane or secret knowledge and the ability to channel power from or through any of the polytheistic deities, spirits, or ancestors of the ancient pantheons. Indeed, many of the traditions associated with magic in the Classical world derive from a fascination with ancient Middle Eastern beliefs and are concerned with a need for countermagic against sorcery. Spells uttered by sorcerers and addressed to gods, to fire, to salt, and to grain are recorded from Mesopotamia and Egypt. These texts also reveal the practice of necromancy, invoking the spirits of the dead, who were regarded as the last defense against evil magic. Greco-Egyptian papyruses from the 1st to the 4th century CE, for example, include magical recipes involving animals and animal substances, along with instructions for the ritual preparations necessary to ensure the efficacy of the spells. Divination took many forms—from the Etruscan art of haruspicina (reading entrails of animal sacrifices) to the Roman practice of augury (interpreting the behaviour of birds)—and was widely practiced as a means of determining propitious times to engage in specific activities; it often played a role in political decision making. Ancient Roman society was particularly concerned with sorcery and countersorcery, contests associated with the development of competitive new urban classes whose members had to rely on their own efforts in both material and magical terms to defeat their rivals and attain success.

Ambivalence toward magic carried into the early Christian era of the Roman Empire and its subsequent heirs in Europe and Byzantium. In the Gospel According to Matthew, the Magi who appeared at the birth of Jesus Christ were both Persian foreigners of Greco-Roman conception and wise astrologers. As practitioners of a foreign religion, they seemed to validate the significance of Jesus’ birth. However, magus, the singular form of magi, has a negative connotation in the New Testament in the account of Simon Magus (Acts 8:9–25), the magician who attempted to buy the miraculous power of the disciples of Christ. In medieval European Christian legends, his story developed into a dramatic contest between true religion, with its divine miracles, and false demonic magic, with its illusions. Nonetheless, belief in the reality of occult powers and the need for Christian counterrituals persisted, for example, in the Byzantine belief in the "evil eye" cast by the envious, which was thought to be demonically inspired and from which Christians needed protection through divine remedies.

Medieval Europe

During the period of Europe’s conversion to Christianity (c. 300–1050), magic was strongly identified with paganism, the label Christian missionaries used to demonize the religious beliefs of Celtic, Germanic, and Scandinavian peoples. Church leaders simultaneously appropriated and Christianized native practices and beliefs. For example, medicinal remedies found in monastic manuscripts combined Christian formulas and rites with Germanic folk rituals to empower natural ingredients to cure ailments caused by poisons, elf-attack, demonic possession, or other invisible forces. Another Christianized practice, bibliomancy (divination through the random selection of a biblical text), was codified in the 11th-century Divinatory Psalter of the Orthodox Slavs. Although co-opted and condemned by Christian leaders of this period, magic survived in a complex relationship with the dominant religion. Similar acculturation processes occurred in later conversions in Latin America and Africa, where indigenous beliefs in spiritual forces and magical practices coexist, sometimes uneasily, with Christian theology.

Sites associated with ancient Mesopotamian history

Mesopotamian religion: The magical arts

In high medieval Europe (c. 1050–1350), the battle between religion and magic occurred as the struggle against heresy, the church’s label for perverted Christian belief. Magicians, like heretics, were believed to distort or abuse Christian rites to do the Devil’s work. By the 15th century, belief in the reality of human pacts with the Devil and the magical powers acquired through them contributed to the persecution of those accused of actually harming others with their magic. Also in the high Middle Ages the demonization of Muslims and Jews contributed to the suspicion of the "other.” Marginal groups were routinely accused of ritual baby-killing. In lurid accounts of the “blood libel,” Jews were charged with stealing Christian children for sacrifice. Similar accusations were made against witches by Christians and against Christians by the ancient Romans.

Although magic was widely condemned during the Middle Ages, often for political or social reasons, the proliferation of magic formulas and books from the period indicates its widespread practice in various forms. Richard Kieckhefer has identified two major categories of magic: "low" magic includes charms (prayers, blessings, adjurations), protective amulets and talismans, sorcery (the misuse of medical and protective magic), divination and popular astrology, trickery, and medical magic through herbs and animals; and "high," or intellectual, magic, includes more learned forms of astrology, astral magic, alchemy, books of secrets, and necromancy. There is also evidence of courtly interest in magic, particularly that involving automatons and gemstones. Moreover, magic served as a literary device of the time, notably the presence of Merlin in the Arthurian romances. Although medieval European magic retained its sense of otherness by borrowing from Jewish practices and Arabic scientific sources such as the astral magic manual Picatrix, it also drew from the mainstream Christian tradition. Necromancy, for example, used Latin Christian rites and formulas to compel the spirits of the dead to obey.

Late medieval and early modern Europe

By the late Middle Ages (c. 1350–1450) and into the early modern period (c. 1450–1750), magic was regarded as part of a widespread and dangerously antisocial demonic cult that included the condemned practices of sorcery, necromancy, and witchcraft. Accused heretics, witches, and magicians were subject to inquisitions designed to uncover these cult connections and to destroy the means of transmission (e.g., the burning of condemned books and/or the “guilty” parties). The influential manual Malleus maleficarum (“The Hammer of Witches,” 1486) by Jacob Sprenger and Henry Krämer describes witchcraft in great detail (e.g, the witches’ sabbath, a midnight assembly in fealty to the Devil); moreover, this oft-reprinted volume is responsible for the misogynist association of witchcraft with women that becomes the dominant characteristic in the early modern period. This conspiracy theory of demonic magic contributed to the early modern "witch craze” that occurred at a time of growing tension between magic, religion, and nascent science.

Nonetheless, despite the persecution of “black” magic and its alleged practitioners, forms of "white" magic persisted in Europe on the boundaries between magic, mysticism, and emerging empiricism. During the Renaissance there was renewed interest in ancient Middle Eastern practices, Neoplatonic mysticism, and Arabic texts on alchemy and astrology. Pico della Mirandola sought hidden knowledge in Jewish Kabbala, a mystical practice for unlocking the divine secrets contained in written and unwritten Hebrew Scriptures. Marsilio Ficino studied astral magic and the power of music to channel cosmic influences, while Giordano Bruno explored the mystical traditions of Hermeticism, based on works of the legendary Alexandrian prophet of the 1st–3rd century Hermes Trismegistus. Although generally tolerated because their practices were perceived to be within the main Judaic and Christian Hermetic tradition, practitioners of alchemy were sometimes considered to be evil magicians who acquired their knowledge through a pact with the Devil (as in the Faust legends). When magical activities of intellectual dilettantes proved, or appeared, to be antisocial, the results were more often put down to simple trickery—as in the case of the 18th-century charlatan Alessandro, conte di Cagliostro (Giuseppe Balsamo).

European traditions and the modern world

The European fascination with the magical traditions of the ancient Middle East was extended to those of East and South Asia when Europeans made contact with these regions in the early modern period. Orientalism, as literary and cultural critic Edward Said labeled this phenomenon, has its roots in the sense of the "other" found in the earliest definitions of magic (notably the Magi as Persian foreigners) and in the Renaissance penchant for Egyptian, Hebrew, and Arabic materials. Intrigued by the exotic otherness of Eastern societies, modern European philosophers experimented with the progressive model of magic-science-religion. Georg Wilhelm Friedrich Hegel, for example, viewed 19th-century India as an immature civilization, in part because Hindu consciousness lacked the categories of logic Hegel valued.

A popular “scientific” worldview prevails in modern Western societies that suggests the triumph of human reason. Enlightenment rationalism and the scientific revolution—ironically rooted in Renaissance experiments in magic and motivated in part by Reformation pragmatism—led to the modern triumph of scientific reasoning over magic, evident, for example, in 19th-century exposés of magic tricksters as charlatans. Notably, spirit rappers, mediums who “conversed” with spirits who replied by knocking on a table, were easily exposed as the ones doing the knocking. Modern popular magic has appeared in the realm of entertainment, generally as a plot device in stories and movies, as tricks aimed at children, and as mysterious sleight-of-hand illusions in magic shows that delight the audience’s sense perceptions and challenge their reasoning ability. The fascination with occult knowledge and mystical powers derived from nonmainstream or foreign sources persists in the West in astrological charts in newspapers, theories of interplanetary aliens and government conspiracies to hide them, occult rituals in some New Age religions, and interest in traditional practices that have an esoteric flavour, such as feng shui (geomancy, the traditional Asian practice of aligning graves, homes, and temples with cosmic forces). This persistence suggests, in part, the impact of globalization on postmodern worldviews challenging the dominance of a strictly scientific mode of rationality.

Globalization of the magic concept

Western conceptions of magic, religion, and science were exported to other parts of the globe in the modern period by traders, conquerors, missionaries, anthropologists, and historians. European travelers in the 16th–19th centuries functioned as primitive ethnographers whose written observations are invaluable historical resources. However, their accounts, often coloured by their Judeo-Christian assumptions about religion versus magic, illuminate how indigenous peoples were treated as "children" to be educated or, in the case of some conquerors, as subhuman races to be enslaved. During the latter part of the 19th century, anthropologists began to analyze magic and its part in the evolution of the world’s religions. Their work was characterized by a fundamental distinction rooted in the magic-religion-science evolutionary model: the world is divided between historical, literate urbanized cultures, or “civilizations” (for example, the ancient traditions of East and South Asia) and nonliterate, tribal archaic, or "primitive," societies (such as those found in parts of Africa, the Americas, and Oceania). Historians viewed complex societies characterized by urbanization, centralization, and written traditions as more advanced and measured their progress as civilizations according to the evolutionary model. Nomadic, tribal, agricultural, or nonurbanized societies with strong oral traditions were often perceived by early European observers as developmentally stagnant people without history. While these views are no longer accepted, their residual effect is still felt in the way magic, religion, and science are conceptualized. Anthropologists of religion traditionally distinguished between the “religion” practiced by the world’s main faiths, which often marginalize magic as superstition, and the beliefs of small nonliterate societies in which “magic” may in fact be central to religious belief. Here the distinction between religion and magic seems unfounded. Indeed, as some postcolonial societies endeavour to distance themselves from Western logic, ancient religious traditions are pivotal to the reassertion of cultural identity and autonomy. West African Vodun (Vodou), which spread to the Caribbean, the Americas, and elsewhere, is one example of an indigenous religious practice that is tied to cultural identity in art, music, and literature and used subversively as a rallying point for postcolonial resistance to Western modes of rationality.

World cultures

The Western concept of magic as a set of beliefs, values, and practices that are not fully religious or scientific does not find its equivalent in non-Western languages and cultures; conversely, concepts found in other cultures may be untranslatable into English or a Western framework. For example, Hawaiian historian David Malo (c. 1793–1853), discussing Christianity and traditional Hawaiian religion, found hoˋomana (to make, to do, or to imbue with supernatural, divine, or miraculous power) the closest translation for English religion, contrary to its characterization by Westerners as a magical component in Polynesian beliefs. Furthermore, a modern Japanese dictionary uses a transliteration, majikku, for the English word magic. It also uses the English word magic to translate several Japanese words beginning with ma-, the kanji character representing a vengeful spirit of the dead (in East Asian folk belief, an ancestor not cared for properly; in Buddhist cosmology, an evil demonic figure). While superficially similar to the Christian notion of magic as demonic, the cosmologies regarding these demons differ significantly. Moreover, ma- does not have the range of meanings that magic has in Western thought.

On the other hand, specific practices identified as magic—e.g., divination, spells, spirit mediation—are found worldwide, even if the word magic is not. For example, in China various practices such as divination through oracle bones, offerings to dead ancestors, and feng shui can be classified as either magic, religion, or science, but it is questionable whether these categories have any validity in Chinese thought; rather these so-called magical practices are an intrinsic part of the worldviews expressed in China’s main religious and philosophical systems (ancestor worship, Confucianism, Daoism, and Buddhism). In modern China, some communities deal with crisis by combining seemingly contradictory practices—including supplication and coercion of gods, appeals to ancestral spirits, folk cures, and modern inoculations. Such syncretism has been common in East Asia; notably, in 6th-century Japan the native nature worship of Shinto blended with imported forms of Buddhism without the kind of conflict that occurred during the conversion of Europe to Christianity. In modern East Asia, conflict between magic, religion, and science introduced by Western concepts of magic occurs alongside a strong tradition of syncretism that blends empirical science with practices that Westerners often perceive as unscientific magic or religious superstition.

Asian religious traditions such as Hinduism, Buddhism, and Daoism teach that material life is illusory. This mode of rationality focuses on understanding the principles and spiritual forces that lie behind physical experience. Consequently, adepts in these traditions who have achieved a level of understanding of these cosmic forces often appear to have the ability to manipulate physical reality in ways that seem magical. The point of demonstrations by street magicians and snake charmers in India is to show the illusory quality of material reality in order to draw attention to the universal, timeless, and cosmic. Purposeful deception in magic is thus used to illustrate the deceptiveness of human apprehensions of reality. The mystical component of magic is also clear in Tantra and other esoteric and nonconformist sects of Hinduism or Buddhism, which use mystical words, symbols, and diagrams in their rituals. Whether these practices are magic or religion depends upon one’s point of view.

Postcolonial points of views

Anthropological and sociological studies of modern nonliterate societies in the Americas, Oceania, and Africa have given rise to new global terminology. Beginning in the second half of the 20th century, some sociologists and anthropologists turned the tables on earlier scholarship by applying the methods used for examining extant nonliterate (“primitive”) societies to literate, urban societies of the past, which previously had been evaluated by the criteria reserved for the study of “civilizations.” For example, the phenomenon of shamanism and the word shaman, as defined by Mircea Eliade (1907–86) in his exploration of ecstatic states, has been applied not only to “primitive” cultures but to premodern Christian Europe. Likewise the term mana (“power”), appropriated from Melanesian and Polynesian cultures by Émile Durkheim and Marcel Mauss (1872–1950), has been widely applied to magical practices in historical civilizations, including that of Classical Rome.

History of magic theories:

Foundations

Because of the impact of anthropological theory on the study of magic, its development and history bear reviewing. The first important figure in this line of inquiry was Sir Edward Burnett Tylor, whose Primitive Culture (1871) regarded magic as a "pseudo-science" in which the "savage" postulated a direct cause-effect relationship between the magical act and the desired outcome. Tylor regarded magic as "one of the most pernicious delusions that ever vexed mankind," but he did not approach it as superstition or heresy. Instead he studied it as a phenomenon based on the "symbolic principle of magic," a scheme of thought founded on a rational process of analogy. He also realized that magic and religion are parts of a total system of thought. Although he believed that magic and animistic beliefs became less prevalent in the later stages of history, he did not view magic and religion as alternative stages in the evolutionary development of mankind.

That conclusion would be left for Sir James Frazer in The Golden Bough (1890), in which he ordered magic, religion, and science in a grandiose evolutionary scheme. Magic preceded religion because, according to Frazer, the former was logically more simple. This notion, however, was a based on his erroneous assumption that the Australian Aborigines, examples of a “primitive” people, believed in magic but not in religion.

Sociological theories

Another line of theorists, including sociologists Durkheim and Mauss, widened the discussion by defining magic in terms of its social function. In The Elementary Forms of the Religious Life (1912), Durkheim argued that magical rites involved the manipulation of sacred objects by the magician on behalf of individual clients; the socially cohesive significance of religious rites proper (by priests) was therefore largely lacking. Durkheim’s views were furthered by A.R. Radcliffe-Brown in the The Andaman Islanders (1922) and to a lesser extent by Malinowski in Argonauts of the Western Pacific (1922) and Magic, Science and Religion (1925). Radcliffe-Brown posited that the function of magic was to express the social importance of the desired event, while Malinowski regarded magic as directly and essentially concerned with the psychological needs of the individual.

Subsequent studies of the working of systems of magic, especially in Africa and Oceania, built upon the work of Malinowski and Radcliffe-Brown along with that of Sir Edward Evans-Pritchard in Witchcraft, Oracles and Magic Among the Azande (1937). In his seminal book, Evans-Pritchard demonstrated that magic is an integral part of religion and culture used to explain events that cannot otherwise be understood or controlled. The Zande of South Sudan accept magic, together with witchcraft and oracles, as a normal part of nature and society. These phenomena form a closed logical system, each part of which buttresses the other and provides a rational system of causation.

Psychological theories

These anthropological and sociological approaches focused on magic as a social phenomenon, but the role of individual psychology was implicit in the views of Tylor and Frazer and brought out more in the work of Malinowski, who frequently offered psychological explanations for belief in magic. Sigmund Freud’s influential view of magic as the earliest phase in the development of religious thought (Totem and Taboo, 1918) followed Frazer’s model and posited an essential similarity between the thought of children, neurotics, and “savages.” According to Freud, all three assumed that wish or intention led automatically to the fulfillment of the desired end. This reductionist view, based on outmoded notions about "primitive" cultures, was revised as the result of new field research. Although Claude Lévi-Strauss also initially equated these three groups, he later modified this view in his analysis of the work of Mauss, which focuses on the structural linguistics of terms such as mana that are deployed in the study of magic. His work, therefore, laid the foundation for later deconstructions of the concept of magic.

Comparative religions

The rise of the study of comparative religion led to new theories that accounted for both world religions and localized belief systems. The work of Eliade, including his study of shamanism, is an important and influential example of this approach, as is that of Ninian Smart, who devised a seven-dimensional (experiential, mythic, doctrinal, ethical, ritual, social, and material) worldview analysis for cross-cultural comparison that can be applied to different belief systems, whether called magic or religion. Likewise, Judaic scholar Jacob Neusner suggested the neutral rubric "modes of rationality" to avoid pejorative comparisons between systems of thought otherwise classified as magic, religion, science, or philosophy. The broader base established by the comparative religions approach avoids the difficulties of distinguishing urban literate from nonurban nonliterate societies and the perils of the magic-religion-science progression.

Postmodern dialogue

Postmodern scholarship continues to challenge older anthropological notions. The work of such anthropologists as Victor Turner (1920–83), Clifford Geertz, and Marshall Sahlins has had a wide impact on the social sciences and humanities. Central to the challenge to the traditional magic-religion-science paradigm was Magic, Science, Religion, and the Scope of Rationality (1990), in which Stanley Jeyaraja Tambiah deconstructs the European history of the progress model and the work of anthropologists from Tylor forward. Other anthropologists have questioned the model of the rise and decline of magic in European thought articulated in Keith Thomas’s groundbreaking Religion and the Decline of Magic (1971), a study of early modern England, and Valerie Flint’s The Rise of Magic in Early Medieval Europe (1991). Notably, anthropologist Hildred Geertz challenged Thomas’s universalized conceptions of religion and magic, and scholars have questioned the rise and fall model by suggesting that the terminology is culture-specific and the historical circumstances much more complex than the simple pattern presented. These cross-disciplinary debates, along with the rejection of the Western magic-religion-science paradigm, have contributed to more sensitive treatments of magical practices in diverse societies.

Conclusion

The study of magic as a distinct cultural phenomenon has a long history in anthropological, sociological, and historical studies. Although some distinctions between magic and other religious or scientific activities may be useful, magic cannot be studied in isolation as it once was. Practices classified as magic represent essentially an aspect or reflection of the worldview held by a particular people at a particular point in their own historical development. Magic, like religion and science, is thus a part of a culture’s total worldview.

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Jai Ganesh · 2023-06-19 00:17:21

1813) Archery

Gist

Archery is the sport, practice, or skill of using a bow to shoot arrows. The word comes from the Latin arcus, meaning bow. Historically, archery has been used for hunting and combat. In modern times, it is mainly a competitive sport and recreational activity. A person who practices archery is typically called an archer, bowman, or toxophilite.

Summary

What is archery?

Archery is one of the oldest sports still practised, and is closely linked to the development of civilisation. Using bows and arrows, the sport as a history dating back thousands of years. As a cultural advance, it was comparable to the discovery of fire and the invention of the wheel.

By whom, where and when was archery invented?

Archery was the favourite sport of the Egyptian pharaohs during the 18th dynasty (1567-1320 BC). Many centuries later, some of the earliest recorded archery tournaments took place during the Zhou dynasty (1046 - 256 BC) in China. Such events were attended by Chinese nobility. Much later, English writers honoured the longbow for famous contributions to their country’s victories in the battles of Crécy, Agincourt and Poitiers.

In 1200 BC, the Hittites and Assyrians shot their bows from chariots, becoming fearsome opponents in battle. They made their bows with tendon, horn and wood, and also developed a new re-curved shape. This made their bows shorter and more powerful, making them easier to handle for an archer on horseback.

What are the rules of archery?

That depends on the type of archery being practised as sport, with different disciplines and rules regarding the type of bow that can be used. At the Olympics, outdoor target archery is practised with recurve bows. This sees athletes fire at targets 70 metres away, with competitors going head-to-head to win set points (with 2 points for winning a set or 1 point for tying a set), with the first to 6 set points winning the match. Other types of archery for sport include field archery, indoor archery, and para archery. Other bows that may be used include a compound bow or a barebow.

How is archery scored?

Each arrow can score from 0 to 10 points, with 10 points for hitting the smallest rings of the target. If the arrow is touching a line separating two scoring zones, the higher score counts. There is often also an inner-most ring, which also awards 10 points but is used as a tie-breaker if needed. After each set of three arrows per competitor, the archer with more points wins the set and picks up 2 set points in the match.

Archery and the Olympics

Archery first appeared in the Olympic Games in 1900, was contested again in 1904, 1908, and 1920, then again—after an absence of 52 years—from 1972 to the present. The most decorated archer in Olympic history is Hubert Van Innis of Belgium, who competed in 1900 and 1920, winning six gold and three silver medals.

Currently, five events are on the archery programme at each Olympic Games: men's and women's individual and team events, and a mixed team event.

Best archers to watch

The Republic of Korea produces some of the world's best archers, and has dominated the sport since the country hosted the 1988 Games in Seoul. The country has won 43 medals (27 gold medals) up to the Olympic Games Tokyo 2020, and athletes representing the Republic of Korea currently hold all five active Olympic records. An San, who won three golds at Tokyo 2020 in 2021, is a part of three of them, holding the women's individual ranking round, women's team ranking round, and mixed team ranking round records.

Archery competition rules and event format at Paris 2024

All archers will compete in a ranking round of 72 arrows, meaning a maximum score of 720 is possible. The top 64 will qualify in each individual event, in a seeded single-elimination bracket.

Meanwhile, the results of all three archers representing a team will be added together to obtain a team ranking result in the men's and women's team events, with the 12 teams then competing in a seeded single-elimination bracket.

The ranking score of each NOC's top male and top female archer will be added together to obtain a mixed team ranking result, with the top 16 NOCs progressing to a seeded single-elimination bracket.

Details

Archery is a sport involving shooting arrows with a bow, either at an inanimate target or in hunting.

History

From prehistoric times, the bow was a principal weapon of war and of the hunt throughout the world, except in Australia. Recreational archery also was practiced, along with military, among the ancient Egyptians and Greeks, one instance of the latter being the competition in which Odysseus won the hand of Penelope. The Huns, Seljuq Turks, Mongols, and other nomadic horse archers dominated large parts of Asia for about 15 centuries from the 1st century CE. English longbowmen achieved glorious military victories in the Hundred Years’ War (1337–1453), while on continental Europe the crossbow became widely used, especially in Switzerland, parts of Germany, France, and the Low Countries. In Europe the bow and arrow were displaced by firearms as a military weapon in the 16th century. By the time the Spanish Armada attempted to invade England in 1588, an English county troop levy consisted of one-third bowmen to two-thirds soldiers with guns, and by century’s end the bow had been almost abandoned as a weapon.

The bow was retained as a hunting weapon, and archery continued to be practiced as a sport in England by both royalty and the general public. The earliest English archery societies dated from the 16th and 17th centuries. The prince of Wales, afterward George IV, became the patron of the Toxophilite Society in 1787 and set the prince’s lengths of 100 yards (91 metres), 80 yards (73 metres), and 60 yards (55 metres); these distances are still used in the British men’s championship York round (six dozen, four dozen, and two dozen arrows shot at each of the three distances). These recreational activities with the bow evolved into the modern sport of archery. In 1844 the first of the Grand National Archery Meetings—the British championships—was held at York, and the Grand National Archery Society became the governing body of the sport in the United Kingdom. International rules were standardized in 1931 with the founding of the Fédération Internationale de Tir à l’Arc (FITA; Federation of International Target Archery) in Paris.

The first American archery organization was the United Bowmen of Philadelphia, founded in 1828. In the early days the sport was, as in England, a popular upper- and middle-class recreation. In the 1870s many archery clubs sprang up, and in 1879 eight of them formed the National Archery Association of the United States. In 1939 the National Field Archery Association of the United States was established to promote hunting, roving, and field archery. The number of archers around the world increased phenomenally after 1930, led by remarkable growth in the United States. By the late 20th century there were probably more than 10 million American participants in all forms of the sport. Their ranks included those who use the bow to hunt game; those who engage in shooting at targets of several kinds at various distances for accuracy; and those who strive for ever-greater distances in “flight” shooting.

The bow was almost certainly the earliest mechanical device to achieve greater speed in a projectile than could be attained by throwing it. It does this by accumulating energy in the bow limbs while drawing (pulling the bowstring back), storing it temporarily while holding and aiming, and releasing the stored energy by converting it to energy of flight in the arrow. Initially, and probably for millennia, bows were made of a single material, usually wood (self bows), including those in which two pieces were fastened together to make the equivalent of a single long stave. Later, some bows were made of several materials, such as wood and horn glued together in layers (composite bows) and reinforced with bands of sinew. The short self bows used in Europe until the late Middle Ages were weak weapons that gave way to the technically superior longbow beginning in the 11th century. The English longbow, made of wood from the English yew tree (Taxus baccata), became famous in legend and history for the victories it won over the French at the battles of Crécy, Poitiers, and Agincourt during the Hundred Years’ War. Composite bows made of wood, horn, and sinew were used throughout much of Asia during the same period.

Up to about 1930 the history of Western archery as a sport was the history of the longbow. This bow had disadvantages, however. It was subject to differing conditions of temperature and humidity, it needed to be left unstrung when not in use, and using it was an art. The bow that replaced it in the mid-20th century was a composite design made of laminated wood, plastic, and fibreglass that was little affected by changes of temperature and humidity. The limbs of the composite bow are laminated, with a thin strip of wood serving as a core for facing and backing strips of fibreglass that are secured to it with epoxy glue. The bow’s rigid middle section gives the archer a good grip, and its thin, wide, fibreglass limbs are exceedingly strong. The composite bow gives superior accuracy, velocity, and distance in comparison to the longbow. Using a modern bow, target archers of equal skill can score an average 30 to 40 percent higher than they can with the longbow. The modern composite bow shoots farther than the longbow: a maximum distance of more than 775 metres (850 yards) has been obtained with it, compared to about 275 metres (300 yards) for the longbow. The efficiency (the percentage of energy in a fully drawn bow that is transferred to the arrow at the moment of loose) of the modern bow doubles that of the longbow, the velocity of the arrow with the new bow reaching 65 metres (213 feet) per second as opposed to 45 metres (150 feet) per second. The wooden arrows used by archers for millennia have been replaced by ones made from aluminum-alloy or fibreglass tubing, and plastic fins have replaced feathers. The arrows’ points are made of steel, and nylon is used for the bowstring.

A more recent innovation is the compound bow, which uses a system of cables and pulleys to make the bow easier to draw. Compound bows have achieved increasing popularity since a two-pulley design was introduced in the 1960s. They are used in field archery, in hunting, and in international target archery competition. See also bow and arrow.

Equipment

The modern target bow varies in length according to the height of the archer but averages 173 cm (68 inches). Similarly, arrows vary, but an average arrow is 56 cm (22 inches). The drawing force of a bow—that is, the energy required to draw back an arrow to the fullest—varies from 14 to 23 kg (30 to 50 pounds) for men and from 9 to 18 kg (20 to 40 pounds) for women. The archer usually carries arrows in a quiver, a container hung over the shoulder or slung from the belt. A glove or finger protector shields the fingers used to draw the bowstring back, and a bracer is fitted to the inside forearm of the bow arm to protect against the released bowstring. In Western nations, the so-called Mediterranean draw is used to draw and loose the arrow; this is executed by pulling the string back with three fingers, the first being above and the second and third below the nocked arrow. In right-handed shooting, the arrow is shot from the left side of the bow.

An outdoor archery range is most desirably laid out on level turf north to south, with shooting done to the north. Some competitions, however, take place indoors. A target is usually a boss of tightly coiled straw rope about 1.22 metres (4 feet) in diameter on which is stretched a canvas face with concentric scoring rings (British, 5 rings; FITA, 10), scored 9, 7, 5, 1 outward from the centre (British; also used in the United States) and 10 through 1 (FITA). Target sizes vary at different distances.

Additional pieces of equipment have become common with the increasing popularity of the sport. These include devices attached to the bow, such as stabilizers (long rods that project from the bow), torque flight compensators (shorter rods with weights attached), counterweight rods, and lens-less bowsights (devices used for aiming). When these devices are allowed, competition is called freestyle; when they are not, it is known as bare bow.

Competition

The main forms of competitive archery are field archery and target archery. In field archery, competitors shoot arrows at different-sized targets set at varying and undetermined distances around a course. In target archery, competitors shoot a specified number of arrows at set distances at a target with established scoring values. A round is a target-shooting competitive event in which a specified number of arrows are shot at a specified distance, and scoring is done after the round or rounds. Principal kinds of rounds include the American round, Hereford round, National round, and York round. FITA round distances are 90, 70, 50, and 30 metres (295, 230, 164, and 98 feet) for men and 70, 60, 50, and 30 metres for women, and the standard FITA round for both men and women consisted of 36 arrows per round being shot at each distance. Since the 1930s the FITA specifications have been those most widely used. (See also FITA round.)

Archery events for men were held in the Olympic Games in 1900, 1904, 1908, and 1920 and for women in 1904 and 1908. They were then suspended until the 1972 Games, when they were reintroduced for both men and women and continued thereafter. World championship matches have been held on either an annual or biennial basis from 1931 (except during World War II), when FITA, the international governing body of the sport, was organized. FITA events (including Olympic Games from 1972) are shot at metric distances, and from 1957 to 1985 in double FITA rounds. In 1985, to improve archery as a spectator sport, a new championship round known as the grand FITA round, with single-elimination matches, was adopted. The grand FITA round first appeared in the Olympic Games in 1988, when team competition was introduced to the program. The 1992 Olympic Games saw the debut of the FITA Olympic round, a championship round of single-elimination, head-to-head matches.

Other forms of sport archery

Clout shooting originated at least as early as the late 16th century and is mainly British. Flight shooting was practiced in England at the end of the 16th century and was also popular in Turkey with a composite bow.

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Jai Ganesh · 2023-06-20 00:22:12

1814) Boating

Gist

Boating is the activity of travelling on water in a boat for pleasure.

Summary

Boating is the leisurely activity of travelling by boat, or the recreational use of a boat whether powerboats, sailboats, or man-powered vessels (such as rowing and paddle boats), focused on the travel itself, as well as sports activities, such as fishing or waterskiing. It is a popular activity, and there are millions of boaters worldwide.

Types of boats

Boats (boat types) can be categorized into 3 different types of board categories: unpowered, motor boats, and sailboats. Recreational boats (sometimes called pleasure craft, especially for less sporting activities) fall into several broad categories, and additional subcategories. Broad categories include dinghies (generally under 16 feet (5 m) powered by sail, small engines, or muscle power) usually made from hardwood or inflatable rubber. paddle sports boats (kayaks, rowing shells, canoes), runabouts (15–25 ft. (5–8 m) powerboats with either outboard, sterndrive, or inboard engines), daysailers (14–25 Ft. (4–8 m) sailboats, frequently with a small auxiliary engine), cruisers (25–65 ft. (8–20 m) powerboats with cabins), and cruising and racing sailboats (25–65 Ft. (8–20 m) sailboats with auxiliary engines). Center console (18 to 75 ft. (18-23m) power boats that have a large interior typically used for fishing, with its high speed performance design and engine also used in water sports. Deck Boats (25-35 ft.(8-11m) that characterized with an open deck area and used typically for leisure activities. Lifeboats (smaller, quicker water crafts equipped with emergency equipment in which to help voyagers in case of emergency in the water.

Details

A boat is a watercraft of a large range of types and sizes, but generally smaller than a ship, which is distinguished by its larger size, shape, cargo or passenger capacity, or its ability to carry boats.

Small boats are typically found on inland waterways such as rivers and lakes, or in protected coastal areas. However, some boats, such as the whaleboat, were intended for use in an offshore environment. In modern naval terms, a boat is a vessel small enough to be carried aboard a ship.

Boats vary in proportion and construction methods with their intended purpose, available materials, or local traditions. Canoes have been used since prehistoric times and remain in use throughout the world for transportation, fishing, and sport. Fishing boats vary widely in style partly to match local conditions. Pleasure craft used in recreational boating include ski boats, pontoon boats, and sailboats. House boats may be used for vacationing or long-term residence. Lighters are used to move cargo to and from large ships unable to get close to shore. Lifeboats have rescue and safety functions.

Boats can be propelled by manpower (e.g. rowboats and paddle boats), wind (e.g. sailboats), and inboard/outboard motors (including gasoline, diesel, and electric).

History

After Homo erectus possibly used watercraft more than a million years ago to cross straits between landmasses, boats have served as transportation far into pre-historic times. Circumstantial evidence, such as the early settlement of Australia over 40,000 years ago, findings in Crete dated 130,000 years ago and in Flores dated to 900,000 years ago, suggest that boats have been used since pre-historic times.[non sequitur] The earliest boats are thought to have been dugouts, dubious – discuss] and the oldest boats found by archaeological excavation date from around 7,000 to 10,000 years ago. The oldest recovered boat in the world, the Pesse canoe, found in the Netherlands, is a dugout made from the hollowed tree trunk of a Pinus sylvestris that was constructed somewhere between 8200 and 7600 BC. This canoe is exhibited in the Drents Museum in Assen, Netherlands. Other very old dugout boats have also been recovered. Rafts have operated for at least 8,000 years. A 7,000-year-old seagoing reed boat has been found at site H3 in Kuwait. Boats were used between 4000 and 3000 BC in Sumer, where a 4000-year old boat has been excavated at Uruk, ancient Egypt, and in the Indian Ocean.

Boats played an important role in the commerce between the Indus Valley civilization and Mesopotamia. Evidence of varying models of boats has also been discovered at various Indus Valley archaeological sites. Uru craft originate in Beypore, a village in south Calicut, Kerala, in southwestern India. This type of mammoth wooden ship was constructed solely of teak, with a transport capacity of 400 tonnes. The ancient Arabs and Greeks used such boats as trading vessels.

The historians Herodotus, Pliny the Elder, and Strabo record the use of boats for commerce, travel, and military purposes.

Types

Boats can be categorized by their means of propulsion. These divide into:

* Unpowered. This involves drifting with the tide or a river current.
* Powered by the crew-members on board, using oars, paddles or a punting pole or quant.
* Powered by sail.
* Towed – either by humans or animals from a river or canal bank (or in very shallow water, by walking on the sea or river bed) or by another vessel.
* Powered by machinery, such as internal combustion engines, steam engines or by batteries and an electric motor.

Any one vessel may use more than one of these methods at different times or in combination.

A number of large vessels are usually referred to as boats. Submarines are a prime example. Other types of large vessels which are traditionally called boats include Great Lakes freighters, riverboats, and ferryboats. Though large enough to carry their own boats and heavy cargoes, these vessels are designed for operation on inland or protected coastal waters.

Terminology

The hull is the main, and in some cases only, structural component of a boat. It provides both capacity and buoyancy. The keel is a boat's "backbone", a lengthwise structural member to which the perpendicular frames are fixed. On some boats a deck covers the hull, in part or whole. While a ship often has several decks, a boat is unlikely to have more than one. Above the deck are often lifelines connected to stanchions, bulwarks perhaps topped by gunnels, or some combination of the two. A cabin may protrude above the deck forward, aft, along the centerline, or covering much of the length of the boat. Vertical structures dividing the internal spaces are known as bulkheads.

The forward end of a boat is called the bow, the aft end the stern. Facing forward the right side is referred to as starboard and the left side as port.

Building materials

Until the mid-19th century most boats were made of natural materials, primarily wood, although reed, bark and animal skins were also used. Early boats include the bound-reed style of boat seen in Ancient Egypt, the birch bark canoe, the animal hide-covered kayak and coracle and the dugout canoe made from a single log.

By the mid-19th century, many boats had been built with iron or steel frames but still planked in wood. In 1855 ferro-cement boat construction was patented by the French, who coined the name "ferciment". This is a system by which a steel or iron wire framework is built in the shape of a boat's hull and covered over with cement. Reinforced with bulkheads and other internal structure it is strong but heavy, easily repaired, and, if sealed properly, will not leak or corrode.

As the forests of Britain and Europe continued to be over-harvested to supply the keels of larger wooden boats, and the Bessemer process (patented in 1855) cheapened the cost of steel, steel ships and boats began to be more common. By the 1930s boats built entirely of steel from frames to plating were seen replacing wooden boats in many industrial uses and fishing fleets. Private recreational boats of steel remain uncommon. In 1895 WH Mullins produced steel boats of galvanized iron and by 1930 became the world's largest producer of pleasure boats.

Mullins also offered boats in aluminum from 1895 through 1899 and once again in the 1920s, but it wasn't until the mid-20th century that aluminium gained widespread popularity. Though much more expensive than steel, aluminum alloys exist that do not corrode in salt water, allowing a similar load carrying capacity to steel at much less weight.

Around the mid-1960s, boats made of fiberglass (aka "glassfibre") became popular, especially for recreational boats. Fiberglass is also known as "GRP" (glass-reinforced plastic) in the UK, and "FRP" (for fiber-reinforced plastic) in the US. Fiberglass boats are strong, and do not rust, corrode, or rot. Instead, they are susceptible to structural degradation from sunlight and extremes in temperature over their lifespan. Fiberglass structures can be made stiffer with sandwich panels, where the fiberglass encloses a lightweight core such as balsa or foam.

Cold molding is a modern construction method, using wood as the structural component. In one cold molding process, very thin strips of wood are layered over a form. Each layer is coated with resin, followed by another directionally alternating layer laid on top. Subsequent layers may be stapled or otherwise mechanically fastened to the previous, or weighted or vacuum bagged to provide compression and stabilization until the resin sets. An alternative process uses thin sheets of plywood shaped over a disposable male mold, and coated with epoxy.

Additional Information

Boating is one of the most popular family sports. Although people have enjoyed pleasure boating for hundreds of years, its popularity increased dramatically in the 20th century, particularly in North America, Western Europe, and Australasia.

The term boat includes the shell—a slender, highly stylized vessel used exclusively in racing contests; the flat-bottomed punt, which is usually propelled by pushing a pole against the bottom of a stream; and a wide variety of primitive craft used by native peoples in various parts of the world. Also classified as boats are working craft such as the fisherman’s dory and the scow used for hauling sand or other bulk cargoes—both flat-bottomed vessels—and the lifeboat found on ships.

Thousands of years ago people discovered that they could use a log to support their weight on water. By this means they could cross the rivers and lakes which were obstacles to their progress. Soon they found that they could support themselves better by making a raft of several logs. In time they learned to hollow out single logs to form crude canoes and to use the power of the wind with sails.

Nobody knows when or where these first steps were taken. It is only known that as far back as man can trace the story, there were boats of some sort. The first white men in America found the Indians paddling their graceful birchbark canoes up and down the streams. Much of the pioneers’ exploring was made possible by the use of such canoes—so light that they could be carried long distances over the rough trails, or portages, that separated one river or lake from another (see canoeing).

One of the most curious of primitive boats is the coracle. The Romans found it in use in the British Isles when they invaded them more than 2,000 years ago. Today the coracle is still used in parts of Wales and Ireland. This vessel is made of waterproof canvas attached to a wooden frame. To form the frame, thin strips of beech or ash are interwoven and bent upward. The vessel is usually large enough for only one person.

A boat similar to the coracle is the gufa, used today on the Tigris and Euphrates rivers of Iraq. The gufa is a circular, basketlike craft woven of willow twigs and smeared with tar for waterproofing.

Among the best of the primitive sailing craft is the prau, which is still in use in certain waters of Indonesia. A typical prau is a long, narrow canoe, upcurved and pointed at both ends. One of its sides is flat; the other, curved. From the curved side projects the outrigger—a floating spar connected to the canoe by two shorter spars. The triangular sail is supported by a mast that rises midway between the ends of the boat.

Catamaran

The primitive catamaran is found in the South Pacific and off the coast of India. In some regions this vessel is made of three logs lashed together. The middle log is longer than the other two and is pointed to form a prow. In other areas the catamaran consists of two canoe hulls attached parallel to each other. In recent years the catamaran design has been widely adopted by Western boatbuilders. The catamaran, they have found, offers smoother riding, is difficult to capsize, and may often be swifter than single-hulled craft of comparable size.

After World War II boating as a popular sport grew at a remarkable rate. The upsurge was due to improved mass-production techniques which have made family-sized boats available at prices well within the budget of the average-income family. The increase in available water areas, as the number of artificial reservoirs rises yearly, has been another factor.

Boating has also been stimulated by the radical improvement in marine engines, particularly outboard motors, and by the introduction of lighter, tougher, more waterproof materials as substitutes for wooden planking in the manufacture of boat hulls. These materials include plywood, aluminum, and fiber glass. The increased popularity of other water sports, such as water-skiing and skin diving, has stimulated interest in boating as well.

Rowing

The easiest, the least expensive, and, in many ways, the safest of the water sports is rowing. Rowboats vary in length from about 7 to 16 feet and are customarily equipped with one pair of oars; longer rowboats sometimes have two pairs. Short, square-ended rowboats are usually called prams.

In competitive rowing—whether the boat is a two-, four-, or eight-man racing shell—there is one oar per man. In single sculling, one man uses two oars. These are both vigorous sports which demand careful training. (See also rowing and sculling.)

Sailing

Sailing is one of the most delightful forms of boating. With a small, simple sailboat, even a child can learn the rudiments of this sport under good weather conditions. To become truly expert at the art of sailing, however, requires patience, endurance, and good judgment.

An ideal boat for the child who is learning to sail is a small catboat. A catboat has a single mast and one sail. Customarily it is gaff-rigged—that is, the sail is four-sided, one of the sides being supported by a gaff, or spar, which extends backward at an angle from the upper part of the mast. When the sail is triangular, with the forward edge of the sail to the mast, the boat is said to be Marconi-rigged—sometimes called jibheaded or Bermuda-rigged.

The shape of a sailboat hull is designed according to the general purpose of the boat and the kind of waters in which it will be sailed. Racing sailboats have sleeker lines than those intended for cruising. On small bodies of water a flat hull is often used. On the Great Lakes and on the ocean a deeper hull is necessary if the boat is to be seaworthy over long distances or in storms and rough water.

Most catboats and other small sailboats are usually made with a centerboard or a dagger board to provide stability and to minimize tipping. In larger boats a keel serves the same purpose. Dagger boards and centerboards are plates that can be raised and lowered through a well in the center of the boat. The dagger board is adjusted vertically. The centerboard swings up and down on a pivot located at the forward end of the well, or centerboard trunk. The keel is an integral, rigid, very heavy timber or plate that extends along the center of the bottom of the boat from front to back.

The most technical problem in sailing is handling the sails to catch the wind. The simplest sail action occurs when a sail is spread so that it is driven square before the wind. Should a north wind blow upon a boat that is headed west with its sail in line with the hull (broadside on to the wind), the wind would press the sail and the boat sideways to the southward. For the boat to go westward, its sail would have to extend southeastward from the mast. The wind would then exert a glancing pressure upon the sail, forcing it southwestward. This southwestward pressure operates in two directions—southward with the wind and westward, the direction in which the boat is headed. Water resistance against the side keeps the boat from drifting too far southward. This drift is called leeway.

Motorboating

Motorboats are classified broadly according to the type of hull and the engine location. The most common hull is the displacement type, which has a prow that cuts through the water and sits low enough to displace its own weight. Planing hulls, which have flat bottoms, are for high-speed boats. At top speeds, the forward part rises clear of the water and the craft rides on the heel of the hull. Engines are either inboard or outboard. The engine of an inboard motorboat is permanently mounted within the hull with the drive shaft passing through the hull. An outboard motorboat has a portable, detachable motor, incorporating drive shaft and propeller, that may be clamped or bolted to the stern or in a well within the hull. Smaller inboard boats that are used mostly for sport are also called speedboats.

All speedboats up to about 1900 were displacement types. In Europe as early as 1907, simple, rectangular flat-bottomed skimmers were being raced. In 1911 an Italian named Enrico Forlanini built the first hydrofoil boat. Hydrofoils are small wings connected by stiltlike struts to the bottom of the hull. As the boat gains speed, the planing surface of the foils forces the entire boat up until it is riding on the foils alone. From early competitive speeds of 20 miles per hour in 1904, race boats developed to the point where unlimited propeller-driven hydroplanes were running heats at well over 100 miles per hour in 1955. In 1978 a jet motorboat at Blowering Dam Lake, Australia, achieved a record-breaking speed of 317.596 miles per hour.

Motorboat racing has become a popular sport. The major competitive divisions are stock inboard, stock outboard, unlimited inboard hydroplane, unlimited outboard hydroplane, offshore, outboard pleasure craft, drag, special events, and predicted log. Each division has several classes.

In addition to speedboats, there are various other types of motorboats. These include cabin cruisers, motor sailers, houseboats, and diverse kinds of utility boats for fishing or recreation. Cabin cruisers usually have both sleeping and dining accommodations. Because family boating has become more and more popular, designs of cabin cruisers have changed to allow for larger cabins with more headroom. Keeping pace, boatyards have become marinas that provide dockage, fuel, water, electricity, and such shoreside facilities as lounges, restaurants, entertainment, laundry service, and even swimming pools.

The motor sailer is what the name implies—a boat that can be driven under power or sail or both. The engine is larger than that found in an auxiliary sailboat, where the power is used primarily for getting in and out of the harbor. The sails on motor sailers are less efficient than those on regular sailboats.

The basic houseboat is a floating home, permanently moored in a sheltered location, with moving possible only by towing. Self-powered ones have been developed from small camper types to large luxury types. Houseboats are generally flat-bottomed and of limited seaworthiness.

Yacht Racing

On American waters, races are held for virtually every size and class of sailboat. The most famous international yachting competition is the America’s Cup race, first held in 1851. The schooner America, representing the United States, defeated several British yachts in a 60-mile race around the Isle of Wight. United States vessels won the next 24 competitions, the first four with schooners. Since 1881, when a sloop beat a British schooner, every competing vessel has been a sloop. J-class sloops (130 feet long) were used until 1958, when 12-meter sloops began to compete. Since 1958 the challenge trophy has been the best four out of seven races, with each race run over a triangular 24-mile course by yachts of the 12-meter class. In a 1988 challenge race, the United States defeated New Zealand, using a catamaran with a rigid sail. New Zealand disputed the victory, but the courts upheld it.

Handicap races are competitions between boats of different designs. The slower a boat’s design, the greater its handicap (the time deducted from the time it takes to complete the race). Thus, a boat of slow design can beat a faster competitor.

Boating Safety

Every person who owns or operates a boat should be familiar with local boating regulations and with the traffic rules for watercraft. Half of all fatal boating accidents result from failure to observe the rules. Information about these regulations may be obtained from local offices of the United States Coast Guard.

Before venturing into deep water in any type of craft, one should be able to swim. Amateur sailors, even if competent swimmers, should wear a life jacket or have one close at hand. All boats should be equipped with a life preserver for each passenger.

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Jai Ganesh · 2023-06-21 00:11:23

1815) Shooting

Gist

The sport of shooting involves firing at targets of various kinds with rifles, handguns, and shotguns. Marksmanship has been practiced, particularly by soldiers, ever since firearms were invented in about 1300. As a competitive sport, however, target shooting is fairly modern because weapons accurate enough for consistent firing were not developed until the 19th century.

Summary

Shooting is the sport of firing at targets of various kinds with rifles, handguns (pistols and revolvers), and shotguns as an exercise in marksmanship.

Early history

Shooting at a mark as a test of skill began with archery, long before the advent of firearms (c. 1300). Firearms were first used in warfare and later in sport shooting (hunting), and because of the shadowy early history of firearms, it is not known when target shooting began. The early history of the sport is largely that of shooting with rifles. The earliest recorded shooting match is one held in Eichstäat, Bavaria, in 1477; the shooters, probably using matchlocks, competed at 200 metres (220 yards).

A Swiss painting from 1504 shows a rifle shooting setup that is quite modern. Contestants fire from enclosed and covered shooting booths at targets in the background. Each target is flanked by a small hut in which a target marker would be concealed during shooting and would later signal by a staff or pole to the shooter and the judges the value of the hit. The judges and scorekeepers are in the right foreground at a table under a roof.

Many German museums have wooden targets dating to 1540 that were made for weddings and were shot at by the guests and then given to the host as a memento. By the 16th century target shooting with rifled arms was a popular pastime in much of Europe, especially in the Germanic countries. Elaborately decorated German wheel locks, presumably intended for target shooting, with rifled bores and quite sophisticated peep or aperture rear sights, appeared late in the 16th century.

Russia

Shooting at a mark was recorded in 1737 when the empress Anna established a target-shooting range at her court. The marks shot at were live birds, and the most proficient marksmen were given gold- and diamond-studded cups. The royal shooting matches became a tradition. In 1806 the Society of Shooting Amateurs, formed in St. Petersburg largely by military officers, had as its chief interest handgun shooting with flintlock pistols. The first shooting range or club was founded, also in St. Petersburg, in 1834 for rifles or handguns, where the public could shoot for a nominal fee. Many more such public shooting grounds had appeared by the 1850s. In the 1890s several shooting societies were formed: the Russian Athletic Society, with a shooting range on club property; the St. Petersburg Club of Sports Amateurs; the St. Petersburg Society of Salon Shooting; and the Riga Shooting Society. In 1897 the Imperial Society of Reglemented Hunting published rules for rifle-shooting competitions, and in the next year held two tournaments with more than 200 shooters in the second. In 1899 the recently formed Southern Russian Shooting Society offered gold and silver award badges in two categories to successful sharpshooters. The first All-Russian Championship shooting competition was held at Kiev in 1913 and a second at Riga in 1914. The success of Soviet marksmen in the Olympic Games and world championships reflected the Russians’ long-held interest in the sport.

The American frontier

Rifle shooting in the North American English colonies was a way of life both on the frontier, as it progressed westward, and in the farming settlements of the Atlantic seaboard, where the rifle was used for protection and hunting as well as for target shooting.

The flintlock Kentucky rifle, produced from about 1750 by American gunsmiths from Germany and Switzerland, provided great accuracy to 180 metres (200 yards), then a long range. Virtually every village and settlement had a shooting match on weekends and holidays, often attracting a hundred or more marksmen. A common target was a piece of board, blackened in the smoke of a fire or charred, on which an X was slashed with a knife, the intersection marking the centre. Shooting at a wooden figure of a bird atop a pole, as crossbowmen had in the Middle Ages, was also popular. Live turkey shooting—the bird tethered behind a box or rock so that only the neck and head showed—was a standard event.

By 1830 shooting clubs were formed both in the heavily populated East and in towns and cities of the Midwest. Target shooting from a bench or rest was established before 1840. In the 1850s a Vermont benchrest shooting club was formed, the National Rifle Club, but regional rather than nationwide, and its members won a high reputation for accuracy with muzzle-loading rifles. In 1871 the National Rifle Association was founded by National Guard officers to improve marksmanship.

Great Britain

Target rifle shooting was a popular sport before 1800. The first book in English on target rifle shooting, Scloppetaria; or, Considerations on the Nature and Use of Rifled Barrell Guns…by a Corporal of Riflemen (pseudonym of Capt. Henry Beaufoy), was published in 1808.

The English military conducted research on various rifles from 1800, especially emphasizing long-range shooting at targets of more than 550 metres (600 yards). When early in the 1850s volunteer rifle brigades for this kind of shooting were formed, they attracted some of the finest shots in the United Kingdom, and long-range shooting became so popular that at the first prize meeting in 1860 of the National Rifle Association, Queen Victoria fired the first shot.

In 1873 an Irish rifle team bested England and Scotland in a match, and then challenged American shooters to a match at ranges of 700, 800, and 900 metres (765.5, 874.8, and 984.2 yards). The match was held on Long Island, New York, in 1874, and though the American team had not shot beyond the 550-metre range, it won.

Interest in long-range shooting grew rapidly in the last third of the 19th century and continued well into the 20th century in all English-speaking countries. International competitions were held frequently with teams from as far afield as Australia and New Zealand traveling to England to compete, as late as the 1930s.

Schuetzen shooting

Of Germanic–Swiss origin, the shooting called Schuetzen was practiced for centuries practically unchanged throughout much of central Europe, and by the 1880s it had become predominantly popular. It was done in the standing, or offhand, position at targets from 90 or 180 metres (98.4 or 196.8 yards) outdoors, and at 23 metres (25.1 yards) indoors. The sport began to decline in Europe and the United States in the 1920s.

After World War I, interest in target rifle shooting grew rapidly with shooting clubs and associations numbering in the thousands. A great part of this growth was in small-bore—.22-calibre rimfire—shooting.

Handguns

Target shooting with handguns roughly parallels that of rifles, but perhaps because they are so much more difficult to aim and shoot accurately, they have never been as widely used. (The handgun is a primary weapon of police forces.) Pistol shooting was included in the modern Olympic Games from their beginning in 1896 and was added to the National Rifle Association championships in Great Britain in 1893 and in the United States in 1900.

Shotguns

Target shooting with shotguns originated as practice for shooting game, usually upland game birds and waterfowl. For many years live pigeons were used, their release at unexpected angles offering good hunting practice. Live-pigeon shooting remained popular in France, Spain, and Italy in the second half of the 20th century. The live birds were replaced first by glass balls and ultimately by “clay pigeons.” The term trapshooting evolved from the box traps from which live pigeons are released. Trapshooting, also known for some time as inanimate bird shooting (especially in England where the Inanimate Bird Shooting Association was founded in 1893), was introduced into the United States about 1830. The sport became popular in Europe in the 19th century, and international competitions were held annually at Monaco and elsewhere. The American sport of skeet shooting was officially named in 1925.

International competition and organization

Shooting has been an Olympic sport since the modern games began in 1896. In the early games there were events for army rifles and service pistols, as well as events for shooting running deer, boar, and live pigeons. Ultimately Olympic Games events became free pistol (from 1936), rapid-fire pistol (from 1948); small-bore rifle, prone and three positions: standing, prone, and kneeling (from 1900 and from 1952, respectively), air rifle (from 1984); clay pigeon (trapshooting) (1900–24, from 1952), skeet shooting (from 1968); and running target: running boar (1900 only, until revived from 1972). Early Olympic shooters were men, but women were not banned, and in the 1976 Games an American woman won the silver medal for rifle (three positions) having won the world’s championship. In 1984, however, three separate events were created for women—sport pistol, air rifle, and small-bore standard rifle (three positions). After the 1992 Games, the mixed gender events were dropped and replaced by skeet shooting, trapshooting, and double target trapshooting events for men and a double target trapshooting event for women.

Although there was a world championship in 1897, later world championships fell under the supervision of the international governing body, the International Shooting Union (ISU), formed in 1907 and reorganized in 1919 and 1946. The organization changed its name to the International Shooting Sport Federation (ISSF) in 1998.

World championship competitions are with the small-bore rifle, free rifle, centre-fire pistol, free-pistol, rapid-fire pistol (.22 calibre), air rifle, air pistol, and shotgun. Running-deer and running-boar matches are fired with .22 rimfire or .222 centre-fire rifles with telescopic sights. All other guns have metal sights. The three positions for small-bore rifle are standing, prone, and kneeling at a range of 50 metres (55 yards). Three-position matches are held at 300 metres (328 yards) in free-rifle and army rifle competitions. Free-pistol matches are at 50 metres; centre-fire and rapid-fire competition is at 25 metres (27.3 yards). Targets are paper—either the concentric bull’s-eye type or, for rapid-fire pistol and running boar and deer, silhouettes.

Details

Shooting is the act or process of discharging a projectile from a ranged weapon (such as a gun, bow, crossbow, slingshot, or blowpipe). Even the acts of launching flame, artillery, darts, harpoons, grenades, rockets, and guided missiles can be considered acts of shooting. When using a firearm, the act of shooting is often called firing as it involves initiating a combustion (deflagration) of chemical propellants.

Shooting can take place in a shooting range or in the field, in shooting sports, hunting, or in combat. The person involved in the shooting activity is called a shooter. A skilled, accurate shooter is a marksman or sharpshooter, and a person's level of shooting proficiency is referred to as their marksmanship.

Competitive shooting

Shooting has inspired competition, and in several countries rifle clubs started to form in the 19th century. Soon international shooting events evolved, including shooting at the Summer and Winter Olympics (from 1896) and World Championships (from 1897). The International Shooting Sport Federation still administers Olympic and non-Olympic rifle, pistol, shotgun, and running target shooting competitions, although there is also a large number of national and international shooting sports controlled by unrelated organizations.

Shooting technique differs depending on factors like the type of firearm used (from a handgun to a precision rifle); the distance to and nature of the target; the required precision; and the available time. Breathing and position play an important role when handling a handgun or a rifle. Some shooting sports, such as IPSC shooting and biathlon also include movement. The prone position, kneeling position, and standing position offer different amounts of support for the shooter.

Hunting with guns

In the United Kingdom shooting often refers to the activity of hunting game birds such as grouse or pheasants, or small game such as rabbits, with guns. A shooter is sometimes referred to as a "gun". Shooting may also refer to the culling of vermin with guns. Clay pigeon shooting is meant to simulate shooting pigeons released from traps after live birds were banned in the United Kingdom in 1921.

Weapons

Shooting most often refers to the use of a gun (firearm or air gun), although it can also be used to describe discharging of any ranged weapons like a bow, crossbow, slingshot, or even blowpipe. The term "weapon" does not necessarily mean it is used as a combat tool, but as a piece of equipment to help the user best achieve the hit on their intended targets.

Shooting is also used in warfare, self-defense, crime, and law enforcement. Duels were sometimes held using guns. Shooting without a target has applications such as celebratory gunfire, 21-gun salute, or firing starting pistols, incapable of releasing bullets.

Restrictions

In many countries, there are restrictions on what kind of firearm can be bought and by whom, leading to debate about how effective such measures are and the extent to which they should be applied. For example, attitudes towards guns and shooting in the United States are very different from those in the United Kingdom and Australia.

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Jai Ganesh · 2023-06-22 00:12:05

1816) Jumping

Gist

Jumping is to push yourself suddenly off the ground and into the air using your legs; to push yourself suddenly off the ground in order to go over something.

Details

Jumping or leaping is a form of locomotion or movement in which an organism or non-living (e.g., robotic) mechanical system propels itself through the air along a ballistic trajectory. Jumping can be distinguished from running, galloping and other gaits where the entire body is temporarily airborne, by the relatively long duration of the aerial phase and high angle of initial launch.

Some animals, such as the kangaroo, employ jumping (commonly called hopping in this instance) as their primary form of locomotion, while others, such as frogs, use it only as a means to escape predators. Jumping is also a key feature of various activities and sports, including the long jump, high jump and show jumping.

Physics

All jumping involves the application of force against a substrate, which in turn generates a reactive force that propels the jumper away from the substrate. Any solid or liquid capable of producing an opposing force can serve as a substrate, including ground or water. Examples of the latter include dolphins performing traveling jumps, and Indian skitter frogs executing standing jumps from water.

Jumping organisms are rarely subject to significant aerodynamic forces and, as a result, their jumps are governed by the basic physical laws of ballistic trajectories. Consequently, while a bird may jump into the air to initiate flight, no movement it performs once airborne is considered jumping, as the initial jump conditions no longer dictate its flight path.

Following the moment of launch (i.e., initial loss of contact with the substrate), a jumper will traverse a parabolic path. The launch angle and initial launch velocity determine the travel distance, duration, and height of the jump. The maximum possible horizontal travel distance for a projectile occurs at a launch angle of 45°, but any launch angle between 35° and 55° will result in ninety percent of the maximum possible distance. However, the jump angle for humans which maximizes horizontal distance travelled is lower at ~23-26°.

Muscles (or other actuators in non-living systems) do physical work, adding kinetic energy to the jumper's body over the course of a jump's propulsive phase. This results in a kinetic energy at launch that is proportional to the square of the jumper's speed. The more work the muscles do, the greater the launch velocity and thus the greater the acceleration and the shorter the time interval of the jump's propulsive phase.

Mechanical power (work per unit time) and the distance over which that power is applied (e.g., leg length) are the key determinants of jump distance and height. As a result, many jumping animals have long legs and muscles that are optimized for maximal power according to the force-velocity relationship of muscles. The maximum power output of muscles is limited, however. To circumvent this limitation, many jumping species slowly pre-stretch elastic elements, such as tendons or apodemes, to store work as strain energy. Such elastic elements can release energy at a much higher rate (higher power) than equivalent muscle mass, thus increasing launch energy to levels beyond what muscle alone is capable of.

A jumper may be either stationary or moving when initiating a jump. In a jump from stationary (i.e., a standing jump), all of the work required to accelerate the body through launch is done in a single movement. In a moving jump or running jump, the jumper introduces additional vertical velocity at launch while conserving as much horizontal momentum as possible. Unlike stationary jumps, in which the jumper's kinetic energy at launch is solely due to the jump movement, moving jumps have a higher energy that results from the inclusion of the horizontal velocity preceding the jump. Consequently, jumpers are able to jump greater distances when starting from a run.

Anatomy

A bullfrog skeleton, showing elongate limb bones and extra joints. Red marks indicate bones substantially elongated in frogs, and joints that have become mobile. Blue indicates joints and bones that have not been modified, or are only somewhat elongated.

Animals use a wide variety of anatomical adaptations for jumping. These adaptations are exclusively concerned with the launch, as any post-launch method of extending range or controlling the jump must use aerodynamic forces, and thus is considered gliding or parachuting.

Aquatic species rarely display any particular specializations for jumping. Those that are good jumpers usually are primarily adapted for speed, and execute moving jumps by simply swimming to the surface at a high velocity. A few primarily aquatic species that can jump while on land, such as mud skippers, do so via a flick of the tail.

Limb morphology

In terrestrial animals, the primary propulsive structure is the legs, though a few species use their tails. Typical characteristics of jumping species include long legs, large leg muscles, and additional limb elements.

Long legs increase the time and distance over which a jumping animal can push against the substrate, thus allowing more power and faster, farther jumps. Large leg muscles can generate greater force, resulting in improved jumping performance. In addition to elongated leg elements, many jumping animals have modified foot and ankle bones that are elongated and possess additional joints, effectively adding more segments to the limb and even more length.

Frogs are an excellent example of all three trends: frog legs can be nearly twice the body length, leg muscles may account for up to twenty percent of body weight, and they have not only lengthened the foot, shin and thigh, but extended the ankle bones into another limb joint and similarly extended the hip bones and gained mobility at the sacrum for a second 'extra joint'. As a result, frogs are the undisputed champion jumpers of vertebrates, leaping over fifty body lengths, a distance of more than eight feet.

Power amplification through stored energy

Grasshoppers use elastic energy storage to increase jumping distance. Although power output is a principal determinant of jump distance (as noted above), physiological constraints limit muscle power to approximately 375 Watts per kilogram of muscle. To overcome this limitation, grasshoppers anchor their legs via an internal "catch mechanism" while their muscles stretch an elastic apodeme (similar to a vertebrate tendon). When the catch is released, the apodeme rapidly releases its energy. Because the apodeme releases energy more quickly than muscle, its power output exceeds that of the muscle that produced the energy.

This is analogous to a human throwing an arrow by hand versus using a bow; the use of elastic storage (the bow) allows the muscles to operate closer to isometric on the force-velocity curve. This enables the muscles to do work over a longer time and thus produce more energy than they otherwise could, while the elastic element releases that work faster than the muscles can. The use of elastic energy storage has been found in jumping mammals as well as in frogs, with commensurate increases in power ranging from two to seven times that of equivalent muscle mass.

Classification

One way to classify jumping is by the manner of foot transfer. In this classification system, five basic jump forms are distinguished:

Jump – jumping from and landing on two feet
Hop – jumping from one foot and landing on the same foot
Leap – jumping from one foot and landing on the other foot
Assemblé – jumping from one foot and landing on two feet
Sissonne – jumping from two feet and landing on one foot

Leaping gaits, which are distinct from running gaits, include cantering, galloping, and stotting or pronging. Some sources also distinguish bounding as a cyclical motion of repeated jumps, used to maintain energy from one jump to the next.

Standing long jump mechanics

The optimal take off angle for a standing long jump (performed by a human) has been theoretically calculated to be ~22.6°, substantially lower than the optimal take off angle for a projectile (i.e. 45°). This is due to take-off speed decreasing with take-off angle due to the jumper's body configuration. It has been shown that experienced parkour athletes use a take off angle of ~25.6°, whereas beginner traceurs use an angle of ~ 34°. Experienced athletes also swing their arms to a greater extent and rock backwards before taking off. These factors help parkour athletes to carry out longer standing long jumps than beginners.

The (official) male standing long jump world record is 371 cm, and the female record is 292 cm (both as of June 2023). These were achieved by Arne Tvervaag and Annelin Mannes respectively. Standing long jump distances range between 146.2 cm and 219.8 cm (10th to 90th percentile) for 18 year old men, and between 100 cm and 157 cm for 18 year old women.

Person jumping on a trampoline

The height of a jump may be increased by using a trampoline or by converting horizontal velocity into vertical velocity with the aid of a device such as a half pipe.

Various exercises can be used to increase an athlete's vertical jumping height. One category of such exercises—plyometrics—employs repetition of discrete jumping-related movements to increase speed, agility, and power.

It has been shown in research that children who are more physically active display more proficient jumping (along with other basic motor skill) patterns.

It is also noted that jumping development in children has a direct relationship with age. As children grow older, it is seen that their jumping abilities in all forms also increase. Jumping development is more easily identifiable in children rather than adults due to the fact that there are less physical differences at a younger age. Adults of the same age may be vastly different in terms of physicality and athleticism making it difficult to see how age affects jumping ability.

In 2021, researchers incorporated ratchets into a robot design and created a robot capable of jumping over thirty meters vertically.

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Jai Ganesh · 2023-06-23 00:14:26

1817) Skating

Summary

Skating is a sport in which bladelike runners or sets of wheels attached to shoes are used for gliding on ice or other surfaces.

Figure skating is a sport in which ice skaters, singly or in pairs, perform freestyle movements of jumps, spins, lifts, and footwork in a graceful manner.

Roller-skating is a recreational and competitive sport in which the participants use special shoes fitted with small wheels to move about on rinks or paved surfaces. Roller-skating sports include speed skating, hockey, figure skating, and dancing competitions similar to the ice-skating sports, as well as the vertical and street-style competitions common to so-called extreme sports.

Speed skating is the the sport of racing on ice skates that originated in the Netherlands, possibly as early as the 13th century. Organized international competition developed in the late 19th century, and the sport was included as a men’s event in the first Winter Olympics in 1924. At the 1960 Games in Squaw Valley, California, U.S., women’s speed-skating events were added.

The blade of the modern speed skate is longer and thinner than that of the hockey or figure skate. When planted on the ice with weight upon it, the blade describes a nearly straight line. Only the last few feet of the stride curve slightly outward as the skate leaves the ice. Length of stride has tended to diminish since the days of the 11- to 16-metre (36- to 52-foot) stride attributed to the English champion William Smart, who was active during the mid-19th century. The modern racing stride rarely exceeds 9 metres (30 feet) and is usually about 5 or 6 metres. In 1996 the clapskate was introduced by speed skaters from the Netherlands. The clapskate features a hinge at the toe of the shoe that allows for greater extension and a longer stride. In order to profit as much as possible from every stride, skaters crouch so that their stomachs and thighs are almost touching. In addition, they wear special skin-tight, hooded suits that cut down air resistance.

International speed skating involves a course with straight sides and curved ends of such a radius that no slackening of speed is necessary. The competitors race two at a time on a two-lane track and race against the clock. Each skater must keep his own course. The advantage of the inner curve is given alternately, and a space (called the crossing line) is left open along the backstretch for the skaters to switch tracks. The 1998 Nagano Olympic Games were the first to require skaters in the 500-metre event to race twice per heat—once in each of the lanes. The times are then combined to determine a winner. The official track measures 400 metres (about one-quarter mile). World championships are decided annually under the supervision of the International Skating Union (ISU) at distances of 500, 1,000, 1,500, 5,000, and 10,000 metres for men and 500, 1,000, 1,500, 3,000, and 5,000 metres for women.

An offshoot of speed skating, which takes place on indoor or outdoor rinks, is short-track speed skating, done indoors on a 111-metre (364-foot) track.

Details

Skating involves any sports or recreational activity which consists of traveling on surfaces or on ice using skates, and may refer to:

a) Ice skating is the self-propulsion and gliding of a person across an ice surface, using metal-bladed ice skates. People skate for various reasons, including recreation (fun), exercise, competitive sports, and commuting. Ice skating may be performed on naturally frozen bodies of water, such as ponds, lakes, canals, and rivers, and on human-made ice surfaces both indoors and outdoors.

Natural ice surfaces used by skaters can accommodate a variety of winter sports which generally require an enclosed area, but are also used by skaters who need ice tracks and trails for distance skating and speed skating. Man-made ice surfaces include ice rinks, ice hockey rinks, bandy fields, ice tracks required for the sport of ice cross downhill, and arenas.

Various formal sports involving ice skating have emerged since the 19th century. Ice hockey, bandy, rinkball, and ringette, are team sports played with, respectively, a flat sliding puck, a ball, and a rubber ring. Synchronized skating is a unique artistic team sport derived from figure skating. Figure skating, ice cross downhill, speed skating, and barrel jumping (a discipline of speed skating), are among the sporting disciplines for individuals.

b) Figure skating is a sport in which individuals, pairs, or groups perform on figure skates on ice. It was the first winter sport to be included in the Olympic Games, when contested at the 1908 Olympics in London. The Olympic disciplines are men's singles, women's singles, pair skating, and ice dance; the four individual disciplines are also combined into a team event, first included in the Winter Olympics in 2014. The non-Olympic disciplines include synchronized skating, Theater on Ice, and four skating. From intermediate through senior-level competition, skaters generally perform two programs (the short program and the free skate), which, depending on the discipline, may include spins, jumps, moves in the field, lifts, throw jumps, death spirals, and other elements or moves.

Figure skaters compete at various levels from beginner up to the Olympic level (senior) at local, regional, sectional, national, and international competitions. The International Skating Union (ISU) regulates international figure skating judging and competitions. These include the Winter Olympics, the World Championships, the World Junior Championships, the European Championships, the Four Continents Championships, the Grand Prix series (senior and junior), and the ISU Challenger Series.

The sport is also associated with show business. Major competitions generally conclude with exhibition galas, in which the top skaters from each discipline perform non-competitive programs. Many skaters, both during and after their competitive careers, also skate in ice shows, which run during the competitive season and the off-season.

c) Speed skating is a competitive form of ice skating in which the competitors race each other in travelling a certain distance on skates. Types of speed skating are long track speed skating, short track speed skating, and marathon speed skating. In the Olympic Games, long-track speed skating is usually referred to as just "speed skating", while short-track speed skating is known as "short track". The International Skating Union (ISU), the governing body of competitive ice sports, refers to long track as "speed skating" and short track as "short track skating".

An international federation was founded in 1892, the first for any winter sport. The sport enjoys large popularity in the Netherlands, Norway and South Korea. There are top international rinks in a number of other countries, including Canada, the United States, Germany, Italy, Japan, Russia, Kazakhstan, China, Belarus and Poland. A World Cup circuit is held with events in those countries plus two events in the Thialf ice hall in Heerenveen, Netherlands.

d) Tour skating is recreational long distance ice skating on natural ice. It is particularly popular in the Netherlands and the Nordic countries. It is becoming more popular in areas of North America such as New England, Southcentral Alaska, and Nova Scotia.

While Nordic skating usually involves tours over open ice on marshes, lakes, rivers, or sea, in the Netherlands skaters follow marked routes on frozen canals and connected lakes. Consequently, there are differences in equipment and skating styles between these two regions. Alaskans often include winter camping on longer journeys of a hundred miles or more.

Nordic skating is a popular activity in Sweden but is also becoming more popular in Finland and Norway, where it is called långfärdsskridskoåkning (in Swedish), retkiluistelu (in Finnish) and turskøyting (in Norwegian). In Canada and the United States this style is often called Nordic skating. Other names used are trip skating and wild skating.

Dutch skating is called toerschaatsen and is regarded by some as a sport in its own right.

e) Roller skating is the act of traveling on surfaces with roller skates. It is a recreational activity, a sport, and a form of transportation. Roller rinks and skate parks are built for roller skating, though it also takes place on streets, sidewalks, and bike paths.

Roller skating originated in the performing arts in the 18th century. It gained widespread popularity starting in the 1880s. Roller skating was very popular in the United States from the 1930s to the 1950s, then again in the 1970s when it was associated with disco music and roller discos. During the 1990s, inline outdoor roller skating became popular.

Sport roller skating includes speed skating, roller hockey, roller derby, figure skating and aggressive quad skating.

f) Skateboarding is an action sport originating in the United States that involves riding and performing tricks using a skateboard, as well as a recreational activity, an art form, an entertainment industry job, and a method of transportation. Skateboarding has been shaped and influenced by many skateboarders throughout the years. A 2009 report found that the skateboarding market is worth an estimated $4.8 billion in annual revenue, with 11.08 million active skateboarders in the world. In 2016, it was announced that skateboarding would be represented at the 2020 Summer Olympics in Tokyo, for both male and female teams.

Since the 1970s, skateparks have been constructed specifically for use by skateboarders, freestyle BMXers, aggressive skaters, and more recently, scooters. However, skateboarding has become controversial in areas in which the activity, although illegal, has damaged curbs, stoneworks, steps, benches, plazas, and parks.

g) A snowskate is a hybrid of a skateboard and a snowboard, intended primarily to allow for skateboard-style tricks on the snow. There are many types depending on the brand or style of snowskate.

Snowskates are now available in four varieties: the single deck variety, the bideck variety, the 4x4 variety, and the powderskate variety. All of the modern snowskates have either a waterproof top grip coating on the deck, or a textured deck to avoid slippage while riding.

Jai Ganesh · 2023-06-24 00:10:39

1818) Skiing

Gist

Skiing is the activity or sport of moving on skis.

Summary

Skiing is the use of skis to glide on snow. Variations of purpose include basic transport, a recreational activity, or a competitive winter sport. Many types of competitive skiing events are recognized by the International Olympic Committee (IOC), and the International Ski Federation (FIS).

History

Skiing has a history of almost five millennia. Although modern skiing has evolved from beginnings in Scandinavia, it may have been practiced more than 100 centuries ago in what is now China, according to an interpretation of ancient paintings. However, this continues to be debated.

The word "ski" comes from the Old Norse word "skíð" which means to "split piece of wood or firewood".

Asymmetrical skis were used in northern Finland and Sweden until at least the late 19th century. On one foot, the skier wore a long straight non-arching ski for sliding, and a shorter ski was worn on the other foot for kicking. The underside of the short ski was either plain or covered with animal skin to aid this use, while the long ski supporting the weight of the skier was treated with animal fat in a similar manner to modern ski waxing.

Early skiers used one long pole or spear. The first description of a skier with two ski poles dates to 1741.

Troops in continental Europe were equipped with skis by 1747.

Skiing was primarily used for transport until the mid-19th century but, since then, it has also become a recreation and sport. Military ski races were held in Norway during the 18th century, and ski warfare was studied in the late 18th century. As equipment evolved and ski lifts were developed during the late 19th and early 20th centuries, two main genres of skiing emerged—Alpine (downhill) skiing and Nordic skiing. The main difference between the two is the type of ski binding (the way in which the ski boots are attached to the skis).

Details

Skiing, recreation, sport, and mode of transportation that involves moving over snow by the use of a pair of long, flat runners called skis, attached or bound to shoes or boots. Competitive skiing is divided into Alpine, Nordic, and freestyle events. Competitions are also held in events such as speed skiing and snowboarding.

History

Skiing for transport, hunting, and war:

Skiing was a prehistoric activity; the oldest known skis date to between 8000 and 7000 BCE and were discovered in Russia. Early skis have been found in many areas of northern Europe: a 4,000-year-old rock carving depicting skis was found near the Arctic Circle in Norway, and hundreds of ski fragments that are 1,000 to 3,500 years old have been found in bogs in Sweden, Norway, and Finland. Some of the first skis were short and broad, resembling snowshoes more than modern skis. Skiing certainly was not confined to Europe, though, as the first written references to skiing are from the Han dynasty (206 BCE–220 CE) and describe skiing in northern China.

Many peoples who lived in climates with snow for many months of the year developed some form of skiing. The Sami (Lapps) believed themselves to be the inventors of skiing, and their use of skis for hunting was renowned from Roman times. In addition, the Vikings used skis from the 9th to the 11th century. Skis are still occasionally used for travel in rural areas of Russia and the Scandinavian countries.

Skiing also has long been employed for military purposes. Norwegian men on skis reconnoitred before the Battle of Oslo (1200). Ski troops were also used in Sweden in 1452, and from the 15th to the 17th century, skis were used in warfare in Finland, Norway, Russia, Poland, and Sweden. Capt. Jens Emmahusen wrote the first skiing manual for Norwegians in 1733. Since 1767 there have been military ski competitions with monetary prizes. These competitions may have been the forerunner of biathlons, which combine skiing and target shooting. Military skiing continued into the 20th century where snow conditions and terrain favoured their use for scouts and for a type of mounted infantry with a first-strike advantage against small objectives. In particular, ski troops fought in both World War I and World War II. Many veterans, especially of World War II, were very active in promoting the sport of skiing after returning to civilian life.

Skiing for recreation and sport

Skiing both as recreation and as a sport was a natural development from its utilitarian applications. One of the first competitions was a cross-country skiing race at Tromsø, Norway, in 1843. There was competitive skiing in California in the 1860s on straight downhill courses, using 12-foot (3.7-metre) skis with only toe straps (the heels were loose). The first big ski-jumping event took place at Christiania (now Oslo) in 1879.

Skiing for sport in Europe, however, primarily developed after the publication of The First Crossing of Greenland (Paa ski over Grønland; 1890), Fridtjof Nansen’s account of his 1888–89 trans-Greenland expedition on skis.

Before the mid-19th century, skiing was limited by the primitive bindings that attached the ski to the boot only at the toe, which made it all but impossible to ski downhill on steep slopes or slopes that required any significant maneuvering. According to tradition (though now subject to debate), about 1860 Norwegian Sondre Nordheim tied wet birch roots around his boots from the toe straps back around the boots’ heels to anchor them firmly to the skis. After drying out, the birch roots became stiff and provided better stability and control than earlier efforts with leather straps had. With this innovation, modern downhill skiing, or Alpine skiing, with its characteristic speed and turns, became possible.

At first, Alpine skiers had to ascend on foot to a height before being able to ski down, which severely limited the number of downhill runs skiers could make in a day, even if they had the energy to keep climbing back up the slope. This changed with the introduction of a succession of devices in the 1930s—from rope tows to chairlifts and gondola lifts—that eliminated exhausting climbs up the slope and made it possible for one to ski downhill four to five times more in a day than earlier skiers could manage.

With the invention and installation of ski lifts in the 1930s, Alpine skiing became an increasingly popular and common activity, first in Europe and North America and then later in Australia, New Zealand, Chile, Argentina, and Japan. In Slovenia there is a tradition of Nordic skiing going back to the 17th century, and in the 1920s and ’30s Alpine skiing was introduced there as well as in Greece, Portugal, Lebanon, Turkey, and Iran. The Pyrenees, which stretch along the frontier between France and Spain, had been the scene of ski competitions before World War I, and skiers had been active in the Atlas Mountains of northwest Africa prior to 1914.

Television coverage of skiing events, which began in the 1950s, also did much to increase the popularity of skiing worldwide. Another factor that contributed to the spread of skiing was the introduction during the late 1950s of snowmaking machines, which guaranteed adequate snow for vacationers when the weather was uncooperative.

Nordic skiing

Ski jumping equipmentJumping skis are longer and wider than other skis. The extra length allows superior tracking down inruns, and the wider construction provides maximum lift during a jump. Jumping skis also have a relatively flat camber to reduce the impact of landing. Jumping boots are similar to freestyle cross-country boots but have higher backs and a lower cut in front to allow the skier to lean forward easily during takeoff and throughout flight. The jumping binding is modified from the standard Nordic binding in two important ways. First, a heel wedge is usually present in back to lift the boot heel off the ski. Second, a cord secures the boot heel to the back of the binding in order to provide additional stability during flight.

Nordic, or classic, skiing consists of techniques and events that evolved in the hilly terrain of Norway and the other Scandinavian countries. The modern Nordic events are the cross-country races (including a relay race) and ski-jumping events. The Nordic combined is a separate test consisting of a 15-km cross-country race and special ski-jumping contest, with the winner determined on the basis of points awarded for performance in both events.

There are numerous factors that differentiate the various individual cross-country races, such as the type of start, the style of skiing, and the distance. With the exception of one event, all cross-country races begin with a staggered start in which competitors are spaced 30 seconds apart. Skiers are thus racing against the clock, not each other directly. Races with pursuit formats, in which one racer or team is given a head start and the other racer or team attempts to catch up, typically involve two runs, with the racers or teams exchanging roles; ultimately, the skiers race against each other rather than the clock. Sprint races of about a kilometre are growing in popularity.

The other important aspect of a cross-country race is the style of skiing. Until the 1970s there was only one style, now called classic, in which skiers follow parallel tracks. A more efficient type of cross-country skiing was popularized by American Bill Koch when he used a “skating” stride, pushing his skis outside the parallel tracks. This innovative style is now used in certain cross-country events. The skating technique requires longer poles and shorter skis than the classic style. It also requires higher boots that give improved ankle support.

Individual Nordic events—in both cross-country skiing and ski jumping—were first included in the Olympics at the Winter Games at Chamonix, France, in 1924.

Alpine skiing

By the start of the 20th century, a second upstart style of skiing competition had joined the older established cross-country skiing races and ski-jumping contests of Nordic skiing. The downhill races of this Alpine skiing, developed in the mountainous terrain of the Alps in central Europe, were generally dismissed by Nordic skiers, who considered their annual cross-country and ski-jumping events at the Holmenkollen Ski Festival near Oslo (from 1892) and the Nordic Games (held quadrennially from 1901 to 1917 and 1922 to 1926) to be the only proper representation of the sport of skiing. In 1930, however, the Nordic skiing countries of Norway, Sweden, and Finland finally withdrew their resistance and allowed Alpine events to be fully sanctioned by skiing’s international governing body, the Fédération Internationale de Ski (FIS; International Ski Federation), which was founded in 1924.

Modern Alpine competitive skiing is divided into four races—slalom, giant slalom, supergiant slalom (super-G), and downhill—each of which is progressively faster and has fewer turns than its predecessor on the list. Super-G and downhill are known as speed events, which are contested in single runs down long, steep, fast courses featuring few and widely spaced turns. The slalom and giant slalom are known as technical events, which challenge the skier’s ability to maneuver over courses marked by closely spaced gates through which both skis must pass; winners of these events are determined by the lowest combined time in two runs on two different courses. The Alpine combined event consists of a downhill and a slalom race, with the winner having the lowest combined time.

Alpine skiing made its Olympic debut at the 1936 Winter Games in Garmisch-Partenkirchen, Germany, where a combined race (featuring both downhill and slalom events) was held. The first giant slalom Olympic competition took place at the 1952 Winter Games in Oslo, and the supergiant slalom was added at the 1988 Winter Games in Calgary, Alberta, Canada. That same year the combined event, which had been removed from the roster of Olympic events in the 1940s, returned as an official event. It was dropped for the 1998 Winter Games in Nagano, Japan, however, in favour of two new events—the combined slalom (a slalom run coupled with a giant slalom run) and the combined downhill (comprising a supergiant slalom run and a downhill run). The 2002 Winter Games in Salt Lake City, Utah, once again featured an event that combined one downhill and two slalom runs. The 2006 Winter Games in Turin, Italy, included combined downhills and slaloms for men and women.

Freestyle skiing

Freestyle skiing focuses on acrobatics and includes three events: acro, aerials, and moguls. Formerly known as ballet, acro was invented in the early 1930s in Europe. Utilizing moves from figure skating and gymnastics, the acro skier performs a 90-second routine set to music, in which jumps, flips, and spins are executed while skiing a 160-metre course on a gently sloping hill (12° to 15° incline). The performance is scored by judges on the basis of artistic impression and technical difficulty. The equipment for acro varies from that of Alpine skiing; the poles are longer and thicker, and the skis are shorter. In recent years acro skiing has been losing out in popularity to the more gymnastic events.

Somersaulting and other tricks were exhibited before World War I, but it was not until about 1950 that such stunts (aerials) were popularized by Norwegian Stein Eriksen, who won a gold medal in the giant slalom at the 1952 Winter Games in Oslo. There are two varieties of aerials: upright and inverted. Flips or any movements where a competitor’s feet are higher than his head are not allowed in upright competition. Instead, the skier performs such jumps as the daffy (with one ski extended forward, the other backward) or the spread eagle. In inverted competition contestants execute flips and somersaults, often reaching heights of some 50 feet (15 metres). The skiers build up speed on the inrun, which leads to various ramps and a landing hill with an incline of 34° to 39° and a length of about 100 feet (30 metres). On the basis of the degree of difficulty, the routine is scored on form and technique (50 percent), takeoff and height (20 percent), and landing (30 percent).

Mogul skiing, the navigation of large bumps (moguls) on the slope, was incorporated into competition shortly after the introduction of aerials. Competing on a steep incline (22° to 32°) over a course of some 660 to 890 feet (about 200 to 270 metres), the mogul skier is scored on speed, turn techniques, and two mandatory upright jumps. There are also freestyle combined competitions in which skiers compete in acro, aerials, and moguls; the winner is determined by the total score of all three events.

Freestyle skiing flourished on North American slopes in the 1950s and ’60s as “hot dog” skiers performed increasingly daring moves. Widespread popularity quickly established skiing as a serious sport. After an appearance at the 1988 Winter Games in Calgary as a demonstration sport, freestyle skiing was approved for Olympic competition. Mogul skiing debuted at the 1992 Winter Games in Albertville, France, and aerial events were added to the 1994 Winter Games in Lillehammer, Norway.

Governing body

In 1924 the Fédération Internationale de Ski (FIS; International Ski Federation) was founded as the world governing body for skiing. World championships sanctioned by the FIS have been held in Nordic events since 1925 for men and since 1954 for women. Women also compete separately from men in cross-country events. There is now a women’s jumping circuit.

World championships have been held in Alpine skiing since 1931, with men and women competing separately. A World Cup in downhill has been awarded since 1967, in slalom since 1970, and in giant slalom since 1975.

The FIS recognized freestyle skiing in 1980 and organized a World Cup for the sport that year. Other sports that have gained FIS recognition include speed skiing, grass skiing (skiing on grass, using a type of skates instead of skis), and telemark (a type of downhill skiing in which the skier’s heel is not bound to the ski, as in cross-country skiing).

Originally, snowboarding competitions were governed by the International Snowboarding Federation (ISF), which was formed in 1991 and began holding world championships in 1992. The FIS recognized snowboarding as a sport in 1994 and began holding its own world championships in snowboarding in 1996. Shortly afterward, the International Olympic Committee recognized the FIS as the official sanctioning body of the sport for Olympic purposes. Three races are recognized for men and women: half-pipe, parallel giant slalom, and snowboard cross.

Skiing equipment

Early skis designed for sport and recreation were made from one piece of wood, often hickory, but laminated constructions began to be used in the 1930s. In the 1950s plastic running surfaces on the bottom of skis increased their speed and durability. By the 1990s skis were typically made by surrounding a foam core with wood, wrapping both layers with fibreglass combined with Kevlar, aluminum, titanium, or carbon for strength, and finally adding a plastic base. As early as the 19th century, Norwegians and others had designed skis with sides that curved up to form parabolic profiles when seen from an end. Parabolic skis began to be widely used in the 1990s and are now standard for all Alpine skis. The unique shape of parabolic skis allows novices and intermediate skiers to master difficult turns more easily. Participation in recreational and competitive skiing continues to increase in popularity among people with disabilities, for whom specially modified equipment has been designed.

Typically the length of men’s and women’s Alpine skis should be close to the height of the skier, though somewhat longer skis can be handled by heavier or more experienced skiers. Alpine skis are generally about 3 inches (7.6 cm) wide. Cross-country skis are somewhat longer, narrower, and lighter than Alpine skis, and freestyle skis are somewhat shorter than Alpine skis. All types of skis—downhill (including slalom), jumping, cross-country (both for racing and touring), and freestyle—are pointed, turned up, and usually slightly wider at the tip (front) and shovel and squared at the tail (rear). They are thickest at the waist (midsection) under the foot and thinnest just before the ends. Skis are built with a camber, or a slight arch, so as to distribute the skier’s weight along the length of the ski. Alpine skis once had a shallow groove running lengthwise along the centre of the bottom to give directional stability, but that feature is no longer necessary with parabolic skis. Alpine skis have sharp steel edges along the bottom to bite into hard snow or ice. Jumping skis are about 8.5 feet (2.6 metres) long and are wider, thicker, and heavier than downhill skis. They ordinarily have three grooves in the bottom and no steel edges.

Close-fitting heavy plastic boots, held firmly by bindings (with release features in case the skier falls), are necessary equipment for all skiers. Alpine and freestyle boots have flat, stiff soles to help maintain precise control of the skis. Lighter, more flexible boots, with a binding that allows the heel to be raised, are worn for jumping and cross-country skiing.

Alpine skiers carry a light pole of metal tubing about 4 feet (1.2 metres) long in each hand. Cross-country skiers typically carry longer and lighter poles. Poles aid the skier in pushing along on level terrain, in climbing, and in maintaining balance when racing downhill or turning. Each pole has a ring or wheel near the bottom, which prevents the point from sinking too deep in the snow.

At one time there were a seemingly endless variety of waxes for coating skis according to exact snow conditions, slopes, and skiing styles, but the development of synthetic resins and polymers for ski coatings has eliminated the use of wax by most skiers. There also have been changes in ski clothing. Synthetic fabrics that wick body moisture away from the body have also improved warmth and comfort on the slopes.

Jai Ganesh · 2023-06-25 00:18:08

1819) Cycling

Gist

Cycling can help to protect you from serious diseases such as stroke, heart attack, some cancers, depression, diabetes, obesity and arthritis. Riding a bike is healthy, fun and a low-impact form of exercise for all ages. Cycling is easy to fit into your daily routine by riding to the shops, park, school or work.

Summary

Cycling, also, when on a two-wheeled bicycle, called bicycling or biking, is the use of cycles for transport, recreation, exercise or sport. People engaged in cycling are referred to as "cyclists", "bicyclists", or "bikers". Apart from two-wheeled bicycles, "cycling" also includes the riding of unicycles, tricycles, quadricycles, recumbent and similar human-powered vehicles (HPVs).

Bicycles were introduced in the 19th century and now number approximately one billion worldwide. They are the principal means of transportation in many parts of the world, especially in densely populated European cities.

History

Cycling became popularlised in Europe and North America in the latter part and especially the last decade of the 19th century. Today, over 50 percent of the human population knows how to ride a bike.

War

The bicycle has been used as a method of reconnaissance as well as transporting soldiers and supplies to combat zones. In this it has taken over many of the functions of horses in warfare. In the Second Boer War, both sides used bicycles for scouting. In World War I, France, Germany, Australia and New Zealand used bicycles to move troops. In its 1937 invasion of China, Japan employed some 50,000 bicycle troops, and similar forces were instrumental in Japan's march or "roll" through Malaya in World War II. Germany used bicycles again in World War II, while the British employed airborne "Cycle-commandos" with folding bikes.

In the Vietnam War, communist forces used bicycles extensively as cargo carriers along the Ho Chi Minh Trail.

The last country known to maintain a regiment of bicycle troops was Switzerland, which disbanded its last unit in 2003.

Equipment

In many countries, the most commonly used vehicle for road transport is a utility bicycle. These have frames with relaxed geometry, protecting the rider from shocks of the road and easing steering at low speeds. Utility bicycles tend to be equipped with accessories such as mudguards, pannier racks and lights, which extends their usefulness on a daily basis. Since the bicycle is so effective as a means of transportation, various companies have developed methods of carrying anything from the weekly shop to children on bicycles. Certain countries rely heavily on bicycles and their culture has developed around the bicycle as a primary form of transport. In Europe, Denmark and the Netherlands have the most bicycles per capita and most often use bicycles for everyday transport.

Road bikes tend to have a more upright shape and a shorter wheelbase, which make the bike more mobile but harder to ride slowly. The design, coupled with low or dropped handlebars, requires the rider to bend forward more, making use of stronger muscles (particularly the gluteus maximus) and reducing air resistance at high speed.

Road bikes are designed for speed and efficiency on paved roads. They are characterized by their lightweight frames, skinny tires, drop handlebars, and narrow saddles. Road bikes are ideal for racing, long-distance riding, and fitness training.

If you plan to ride long distances on paved roads, a road bike is an excellent choice. They are fast and efficient, allowing you to cover a lot of ground quickly. However, they are not suitable for off-road riding or commuting.

The price of a new bicycle can range from US$50 to more than US$20,000 (the highest priced bike in the world is the custom Madone by Damien Hirst, sold at US$500,000), depending on quality, type and weight (the most exotic road bicycles can weigh as little as 3.2 kg (7 lb)). However, UCI regulations stipulate a legal race bike cannot weigh less than 6.8 kg (14.99 lbs). Being measured for a bike and taking it for a test ride are recommended before buying.

The drivetrain components of the bike should also be considered. A middle grade dérailleur is sufficient for a beginner, although many utility bikes are equipped with hub gears. If the rider plans a significant amount of hillclimbing, a triple-chainrings crankset gear system may be preferred. Otherwise, the relatively lighter, simpler, and less expensive double chainring is preferred, even on high-end race bikes. Much simpler fixed wheel bikes are also available.

Many road bikes, along with mountain bikes, include clipless pedals to which special shoes attach, via a cleat, enabling the rider to pull on the pedals as well as push. Other possible accessories for the bicycle include front and rear lights, bells or horns, child carrying seats, cycling computers with GPS, locks, bar tape, fenders (mud-guards), baggage racks, baggage carriers and pannier bags, water bottles and bottle cages.

For basic maintenance and repairs cyclists can carry a pump (or a CO2 cartridge), a puncture repair kit, a spare inner tube, and tire levers and a set of allen keys. Cycling can be more efficient and comfortable with special shoes, gloves, and shorts. In wet weather, riding can be more tolerable with waterproof clothes, such as cape, jacket, trousers (pants) and overshoes and high-visibility clothing is advisable to reduce the risk from motor vehicle users.

Items legally required in some jurisdictions, or voluntarily adopted for safety reasons, include bicycle helmets, generator or battery operated lights, reflectors, and audible signalling devices such as a bell or horn. Extras include studded tires and a bicycle computer.

Bikes can also be heavily customized, with different seat designs and handle bars, for example. Gears can also be customized to better suit the rider's strength in relation to the terrain.

Details

Cycling is use of a bicycle for sport, recreation, or transportation. The sport of cycling consists of professional and amateur races, which are held mostly in continental Europe, the United States, and Asia. The recreational use of the bicycle is widespread in Europe and the United States. Use of the bicycle as a mode of transportation is particularly important in non-Western nations and in flatter countries, some of which, like the Netherlands, have a widespread system of bicycle paths.

Early history of the sport

Cycling as a sport officially began on May 31, 1868, with a 1,200-metre (1,312-yard) race between the fountains and the entrance of Saint-Cloud Park (near Paris). The winner was James Moore, an 18-year-old expatriate Englishman from Paris. On November 7, 1869, the first city-to-city race was held between Paris and Rouen; again Moore was the winner, having covered the 135 km (84 miles) in 10 hours 25 minutes, including time spent walking his bicycle up the steeper hills. While road racing became common within a few years in continental Europe, in England the deteriorated conditions of the roads made them unsuitable, and therefore the sport there focused on the track or time trials.

In the United States the first recorded race was held on May 24, 1878, in Boston, two years after the start of professional baseball and 13 years before basketball was invented. Almost all of the early American racing was on tracks, in long races sometimes employing pacers who rode ahead of contestants at a fast speed and then dropped away. By the 1890s there were about 100 dirt, cement, or wooden tracks around the country, mainly in big cities. More than 600 professionals traveled on this national circuit, which ranged from Boston to San Francisco, with competitions in such cities as St. Louis, Salt Lake City, Denver, and Los Angeles. The sport received an enormous publicity boost on June 30, 1899, when one of these riders, Charles M. Murphy, rode on a wooden track behind a Long Island Rail Road train and covered a mile in 57.8 seconds, earning the nickname of Mile-a-Minute Murphy.

A particularly grueling form of racing flourished in the United States in the 1890s: the six-day race, 142 hours (since the races usually started at midnight and ended, six days later, at 10 PM) of nonstop competition with prizes up to $10,000 and an international field of riders. This form of racing was transformed with the change from one-man teams to two-man teams in 1899, and six-day races retained their popularity well into the 1930s. While no longer held in the United States, these races continue to attract large crowds in Belgium, Italy, France, and Germany.

Modern sport racing

The development of racing as a popular sport in Europe began in the 1890s with the improvement in road conditions and the introduction of some of the one-day classics that continue to this day (for example, the Paris-Roubaix race). After France and Belgium, races were introduced in Italy, Spain, and the Netherlands. In 1903 the 21-day-long Tour de France was inaugurated and has continued every year since except during World Wars I and II. Ranking just behind this premier race are the grand three-week tours of Italy (the Giro d’Italia) and Spain (the Vuelta a España). Usually, the Giro is held in May and June, the Tour de France in July, the Vuelta in September, and the World Championships in October. Prizes in these races are substantial, amounting to $2.5 million in the Tour de France alone.

European road racing was under the sponsorship of bicycle manufacturers until the late 1920s, when national and regional teams were introduced. Trade sponsors returned after World War II but with the waning of bicycle manufacturers, teams began turning to various sponsors, including automobile manufacturers, insurance companies, and banks. The professional road-racing season now begins in January with races in Australia and Malaysia, continues from February through October in Europe and the United States, and closes, again in Asia, in November and December. For most riders, the season includes about 120 days of competition spread over eight months.

With the waning of six-day races during the Depression in the United States, American interest in cycling began to fade until the 1980s. American riders dominated the Olympic Games in Los Angeles in 1984, and in 1986 Greg LeMond won the first of his three Tours de France, rekindling American interest. In England, racing declined in popularity after the turn of the 20th century, with the advent of the automobile; despite the occasional Briton who makes a career as a professional on the Continent and a sporadic series of races, such as the Milk Race and the Prutour, both now defunct, the sport remains marginal. Hindering the growth of the sport in England is the public clamour that arises whenever a road is closed for a bicycle race. In Asia and Australia, however, there is no such resistance, and the roads are usually lined with spectators for such races as the Tour Down Under in Australia, the Tour of Langkawi in Malaysia, and the Japan Cup. These races attract many professional teams from Europe and the United States. Many other Asian countries have races also, mainly for amateur teams from the region.

Road and track races for men were held at the first modern Olympic Games in 1896; women entered Olympic competition in road races in 1984 and track races in 1988. Mountain biking, a cross-country race over rough terrain, became an Olympic event for men and women at the 1996 Games in Atlanta. The Atlanta Games also marked the first Olympics at which professionals were allowed to enter the road race and time trial competitions.

Competition

The sport is governed overall by the Union Cycliste Internationale (UCI), which is based in Switzerland, and by each country’s cycling federation. Amateur races are held for both men and women in local, regional, and national competition by age group, ranging upward in age from competitors 12 to 13 years old. In the World Championships, amateurs are no longer differentiated from professionals among men, but the sport is divided into those under 23, called espoirs (hopefuls), and those over that age. Categories of competition during the season include time trials, which can be an individual or team event; one-day, or classic, races in which distances can vary between 200 and 280 km (124 to 175 miles) for professionals and 140 to 200 km (87 to 124 miles) for amateurs; and multiday, or stage, races, basically a series of classic races run on successive days. The winner of a stage race is the rider with lowest aggregate time for all stages. Also popular, especially in Britain and the United States, are criterium races, which are run over a relatively short distance of 4 to 5 km (2.5 to 3 miles) for a succession of laps totaling up to 100 km (62 miles).

Track racing events include the sprint, the pursuit, the one-kilometre time trial, the points race, and the keirin, or motor-paced race. Keirin is especially popular in Japan because betting on the outcome is legal there, much like a horse or dog race. Some European track stars ride on the keirin circuit in Japan, both for the experience and for the salary. Cyclo-cross, or cross-country racing, established in the mid-1920s, covers rough terrain that may require racers to dismount and walk or run with their bicycles. Mountain biking, over rough terrain, but usually downhill rather than on the flat, is increasingly popular. One difference between cyclo-cross and mountain-bike racing is that cyclo-cross riders are allowed to ride up to three bicycles during a race, whereas in mountain-bike competition the cyclist must carry all the tools necessary to fix the bicycle, as only one bicycle may be used during a race. One other recent form of racing is bicycle motocross (BMX) racing, which can be traced to motocross racing. Racers (children and adults) ride on dirt tracks which feature a large number of jumps and turns. BMX racing is very popular in the United States, Europe, and Australia. In 2008 BMX racing made its Olympic debut at the Beijing Games in the form of a men’s individual race and a women’s individual race.

Doping

The use of performance-enhancing drugs is considered to be widespread in cycling, especially after the scandal that shook the Tour de France in 1998 and resulted in the expulsion of one of the leading teams (the Festina team). To circumvent the medications prohibited by the UCI, many professional teams and individual riders employ doctors to administer drugs that are difficult to detect, such as erythropoietin (EPO), a hormone that acts to increase the level of red blood cells and thus the flow of oxygen to muscles. The UCI periodically checks riders for the level of red cells in their blood, with a limit of 50 percent (55 percent for riders from high-altitude regions); anything above that is regarded as an indication of the use of EPO and carries a two-year suspension. Stimulants and antifatigue drugs such as amphetamines are detectable and therefore outmoded performance-enhancing drugs.

Recreation

Cycling as recreation became organized shortly after racing did. In its early days, cycling brought the sexes together in an unchaperoned way, particularly after the 1880s when cycling became more accessible owing to the invention of the Rover Safety bicycle. Public cries of alarm at the prospect of moral chaos arose from this and from the evolution of women’s cycling attire, which grew progressively less enveloping and restrictive.

In modern times, recreational cycling has been a cornerstone in fitness campaigns, especially in the United States, where more than 65 million people are believed to ride regularly, including more than 6 million who use bicycles to commute. Bicycle and touring clubs abound in Europe, especially in France, Belgium, Italy, and England. Touring by bicycle (cyclotourism) is also on the increase worldwide. Bicycle paths have been created on the streets of many cities and in national as well as municipal parks, and in the United States more than 10,000 miles (16,000 km) of abandoned railroad corridors have been turned into bicycle paths.

Transportation

Since its invention, the bicycle has always been an inexpensive and democratic form of transportation. The advent of the automobile slowed the growth of cycling as a means of conveyance in some Western societies, whereas in China and Southeast Asia the bicycle has remained a very popular form of transportation. In Africa and several central European nations many people travel by bicycle. In the 1990s citizens and city planners in industrialized nations began to question the role of the automobile in urban life; some observers blamed the problem of suburban sprawl in countries such as the United States directly on the rise of automobile-based planning and designs. International groups such as Critical Mass formed to encourage traffic laws and city design more conducive to cycling.

Jai Ganesh · 2023-06-26 00:51:08

1820) Shadow

Gist

A shadow is a dark shape on a surface that is made when something stands between a light and the surface. Shadow is darkness in a place caused by something preventing light from reaching it.

Summary

A shadow is a dark shape that appears on a surface when someone or something moves between the surface and a source of light. A shadow is an area of darkness created when a source of light is blocked.

Details

A shadow is a dark area where light from a light source is blocked by an object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or a reverse projection of the object blocking the light.

Point and non-point light sources

Umbra, penumbra and antumbra.

A point source of light casts only a simple shadow, called an "umbra". For a non-point or "extended" source of light, the shadow is divided into the umbra, penumbra, and antumbra. The wider the light source, the more blurred the shadow becomes. If two penumbras overlap, the shadows appear to attract and merge. This is known as the shadow blister effect.

The outlines of the shadow zones can be found by tracing the rays of light emitted by the outermost regions of the extended light source. The umbra region does not receive any direct light from any part of the light source and is the darkest. A viewer located in the umbra region cannot directly see any part of the light source.

By contrast, the penumbra is illuminated by some parts of the light source, giving it an intermediate level of light intensity. A viewer located in the penumbra region will see the light source, but it is partially blocked by the object casting the shadow.

If there is more than one light source, there will be several shadows, with the overlapping parts darker, and various combinations of brightnesses or even colors. The more diffuse the lighting is, the softer and more indistinct the shadow outlines become until they disappear. The lighting of an overcast sky produces few visible shadows.

The absence of diffusing atmospheric effects in the vacuum of outer space produces shadows that are stark and sharply delineated by high-contrast boundaries between light and dark.

For a person or object touching the surface where the shadow is projected (e.g. a person standing on the ground, or a pole in the ground) the shadows converge at the point of contact.

A shadow shows, apart from distortion, the same image as the silhouette when looking at the object from the sun-side, hence the mirror image of the silhouette seen from the other side.

Astronomy

The names umbra, penumbra and antumbra are often used for the shadows cast by astronomical objects, though they are sometimes used to describe levels of darkness, such as in sunspots. An astronomical object casts human-visible shadows when its apparent magnitude is equal or lower than -4. The only astronomical objects able to project visible shadows onto Earth are the Sun, the Moon, and in the right conditions, Venus or Jupiter. Night is caused by the hemisphere of a planet facing its orbital star blocking its sunlight.

A shadow cast by the Earth onto the Moon is a lunar eclipse. Conversely, a shadow cast by the Moon onto the Earth is a solar eclipse.

Daytime variation

The sun casts shadows that change dramatically through the day. The length of a shadow cast on the ground is proportional to the cotangent of the sun's elevation angle—its angle θ relative to the horizon. Near sunrise and sunset, when θ = 0° and cot(θ) = ∞, shadows can be extremely long. If the sun passes directly overhead (only possible in locations between the Tropics of Cancer and Capricorn), then θ = 90°, cot(θ) = 0, and shadows are cast directly underneath objects.

Such variations have long aided travellers during their travels, especially in barren regions such as the Arabian Desert.

Propagation speed

The farther the distance from the object blocking the light to the surface of projection, the larger the silhouette (they are considered proportional). Also, if the object is moving, the shadow cast by the object will project an image with dimensions (length) expanding proportionally faster than the object's own rate of movement. The increase of size and movement is also true if the distance between the object of interference and the light source are closer. This, however, does not mean the shadow may move faster than light, even when projected at vast distances, such as light years. The loss of light, which projects the shadow, will move towards the surface of projection at light speed.

Although the edge of a shadow appears to "move" along a wall, in actuality the increase of a shadow's length is part of a new projection that propagates at the speed of light from the object of interference. Since there is no actual communication between points in a shadow (except for reflection or interference of light, at the speed of light), a shadow that projects over a surface of large distances (light years) cannot convey information between those distances with the shadow's edge.

Lotus clour

Visual artists are usually very aware of colored light emitted or reflected from several sources, which can generate complex multicolored shadows. Chiaroscuro, sfumato, and silhouette are examples of artistic techniques which make deliberate use of shadow effects.

During the daytime, a shadow cast by an opaque object illuminated by sunlight has a bluish tinge. This happens because of Rayleigh scattering, the same property that causes the sky to appear blue. The opaque object is able to block the light of the sun, but not the ambient light of the sky which is blue as the atmosphere molecules scatter blue light more effectively. As a result, the shadow appears bluish.

Dimension

A shadow occupies a three-dimensional volume of space, but this is usually not visible until it projects onto a reflective surface. A light fog, mist, or dust cloud can reveal the 3D presence of volumetric patterns in light and shadow.

Fog shadows may look odd to viewers who are not used to seeing shadows in three dimensions. A thin fog is just dense enough to be illuminated by the light that passes through the gaps in a structure or in a tree. As a result, the path of an object's shadow through the fog becomes visible as a darkened volume. In a sense, these shadow lanes are the inverse of crepuscular rays caused by beams of light, they're caused by the shadows of solid objects.

Theatrical fog and strong beams of light are sometimes used by lighting designers and visual artists who seek to highlight three-dimensional aspects of their work.

Inversion

Oftentimes shadows of chain-linked fences and other such objects become inverted (light and dark areas are swapped) as they get farther from the object. A chain-link fence shadow will start with light diamonds and shadow outlines when it is touching the fence, but it will gradually blur. Eventually, if the fence is tall enough, the light pattern will go to shadow diamonds and light outlines.

Photography

In photography, which is essentially recording patterns of light, shade, and color, "highlights" and "shadows" are the brightest and darkest parts, respectively, of a scene or image. Photographic exposure must be adjusted (unless special effects are wanted) to allow the film or sensor, which has limited dynamic range, to record detail in the highlights without them being washed out, and in the shadows without their becoming undifferentiated black areas.

On satellite imagery and aerial photographs, taken vertically, tall buildings can be recognized as such by their long shadows (if the photographs are not taken in the tropics around noon), while these also show more of the shape of these buildings.

Analogous concepts

Shadow as a term is often used for any occlusion or blockage, not just those with respect to light. For example, a rain shadow is a dry area, which with respect to the prevailing wind direction, is beyond a mountain range; the elevated terrain impedes rainclouds from entering the dry zone. An acoustic shadow occurs when a direct sound has been blocked or diverted around a given area.

Cultural aspects

Shadows often appear in mythical or cultural contexts. Sometimes in a malevolent light, other times not. An unattended shade was thought by some cultures to be similar to that of a ghost. The name for the fear of shadows is "sciophobia" or "sciaphobia".

Chhaya is the Hindu goddess of shadows.

In heraldry, when a charge is supposedly shown "in the shadow" (the appearance is of the charge merely being outlined in a neutral tint rather than being of one or more tinctures different from the field on which it is placed), it is technically described as "umbrated". Supposedly, only a limited number of specific charges can be so depicted.

Shadows are often linked with darkness and evil; in common folklore, like shadows who come to life, are often evil beings trying to control the people they reflect. The film Upside-Down Magic features an antagonistic shadow spirit who possesses people.

Ancient Egyptians surmised that a shadow, which they called šwt (shut), contains something of the person it represents because it is always present. Through this association, statues of people and deities were sometimes referred to as shadows.

In a commentary to The Egyptian Book of the Dead (BD), Egyptologist Ogden Goelet, Jr. discusses the forms of the shadow: "In many BD papyri and tombs the deceased is depicted emerging from the tomb by day in shadow form, a thin, black, featureless silhouette of a person. The person in this form is, as we would put it, a mere shadow of his former existence, yet nonetheless still existing. Another form the shadow assumes in the BD, especially in connection with gods, is an ostrich-feather sun-shade, an object which would create a shadow.

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Jai Ganesh · 2023-06-27 00:11:42

1821) Waterfall

Summary

A waterfall is any point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf.

Waterfalls can be formed in several ways, but the most common method of formation is that a river courses over a top layer of resistant bedrock before falling on to softer rock, which erodes faster, leading to an increasingly high fall. Waterfalls have been studied for their impact on species living in and around them.

Humans have had a distinct relationship with waterfalls for years, travelling to see them, exploring and naming them. They can present formidable barriers to navigation along rivers. Waterfalls are religious sites in many cultures. Since the 18th century they have received increased attention as tourist destinations, sources of hydropower, and—particularly since the mid-20th century—as subjects of research.

Definition and terminology

A waterfall is generally defined as a point in a river where water flows over a steep drop that is close to or directly vertical. In 2000 Mabin specified that "The horizontal distance between the positions of the lip and plunge pool should be no more than c 25% of the waterfall height." There are various types and methods to classify waterfalls. Some scholars have included rapids as a subsection. What actually constitutes a waterfall continues to be debated.

Waterfalls are sometimes interchangeably referred to as "cascades" and "cataracts", though some sources specify a cataract as being a larger and more powerful waterfall and a cascade as being smaller. A plunge pool is a type of stream pool formed at the bottom of a waterfall. A waterfall may also be referred to as a "foss" or "force".

Details

A waterfall is a river or other body of water's steep fall over a rocky ledge into a plunge pool below. Waterfalls are also called cascades.

The process of erosion, the wearing away of earth, plays an important part in the formation of waterfalls. Waterfalls themselves also contribute to erosion.

Often, waterfalls form as streams flow from soft rock to hard rock. This happens both laterally (as a stream flows across the earth) and vertically (as the stream drops in a waterfall). In both cases, the soft rock erodes, leaving a hard ledge over which the stream falls.

A fall line is the imaginary line along which parallel rivers plunge as they flow from uplands to lowlands. Many waterfalls in an area help geologists and hydrologists determine a region's fall line and underlying rock structure.

As a stream flows, it carries sediment. The sediment can be microscopic silt, pebbles, or even boulders. Sediment can erode stream beds made of soft rock, such as sandstone or limestone. Eventually, the stream's channel cuts so deep into the stream bed that only a harder rock, such as granite, remains. Waterfalls develop as these granite formations form cliffs and ledges.

A stream's velocity increases as it nears a waterfall, increasing the amount of erosion taking place. The movement of water at the top of a waterfall can erode rocks to be very flat and smooth. Rushing water and sediment topple over the waterfall, eroding the plunge pool at the base. The crashing flow of the water may also create powerful whirlpools that erode the rock of the plunge pool beneath them.

The resulting erosion at the base of a waterfall can be very dramatic, and cause the waterfall to "recede." The area behind the waterfall is worn away, creating a hollow, cave-like structure called a "rock shelter." Eventually, the rocky ledge (called the outcropping) may tumble down, sending boulders into the stream bed and plunge pool below. This causes the waterfall to "recede" many meters upstream. The waterfall erosion process starts again, breaking down the boulders of the former outcropping.

Erosion is just one process that can form waterfalls. A waterfall may form across a fault, or crack in the Earth’s surface. An earthquake, landslide, glacier, or volcano may also disrupt stream beds and help create waterfalls.

Classifying Waterfalls

There is not a standard way to classify waterfalls. Some scientists classify waterfalls based on the average volume of water in the waterfall. A Class 10 waterfall using this scale is Inga Falls, Democratic Republic of Congo, where the Congo River twists in a series of rapids. The estimated volume of water discharged from Inga Falls is 25,768 cubic meters per second (910,000 cubic feet per second).

Another popular way of classifying waterfalls is by width. One of the widest waterfalls is Khone Phapheng Falls, Laos. At the Khone Phapheng Falls, the Mekong River flows through a succession of relatively shallow rapids. The width of the Khone Phapheng Falls is about 10,783 meters (35,376 feet).

Waterfalls are also classified by height. Angel Falls, the world’s tallest waterfall, plummets 979 meters (3,212 feet) into a remote canyon in a rain forest in Venezuela. The water, from the Gauja River, often does not reach the bottom. The fall is so long, and so steep, that air pressure is stronger often than the water pressure of the falls. The water is turned to mist before it reaches the small tributary below.

Types of Waterfalls

One of the most popular, if least scientific, ways to classify waterfalls is by type. A waterfall's type is simply the way the descends. Most waterfalls fit more than one category.

A block waterfall descends from a wide stream. Niagara Falls, in the United States and Canada, is a block waterfall on the Niagara River.

A cascade is a waterfall that descends over a series of rock steps. Monkey Falls, in the Indira Gandhi Wildlife Sanctuary and National Park in Tamil Nadu, India, is a gently sloping cascade. The waterfall is safe enough for children to play in the water.

A cataract is a powerful, even dangerous, waterfall. Among the widest and wildest of cataracts are the thundering waters of the Iguazu River on the border between Brazil and Argentina.

A chute is a waterfall in which the stream passage is very narrow, forcing water through at unusually high pressure. Three Chute Falls is named for the three "chutes" through which the Tenaya Creek falls in Yosemite National Park, California, U.S.

Fan waterfalls are named for their shape. Water spreads out horizontally as it descends. Virgin Falls is a striking fan waterfall on Tofino Creek, on Vancouver Island, British Columbia, Canada.

Frozen waterfalls are just what they sound like. For at least part of the year, the waterfall freezes. Mountaineers often climb frozen waterfalls as a challenging test of their skill. The Fang is a single pillar of ice in Vail, Colorado, U.S., that vertically plunges more than 30 meters (100 feet).

Horsetail waterfalls maintain contact with the hard rock that underlies them. Reichenbach Falls, a fall on the Reichenbach Stream in Switzerland, is a horsetail waterfall where legendary detective Sherlock Holmes allegedly fell to his doom.

Multi-step waterfalls are a series of connected waterfalls, each with their own plunge pool. The breathtaking "falling lakes" of Plitvice Lakes National Park, Croatia, are a series of multi-step waterfalls.

Plunge waterfalls, unlike horsetail falls, lose contact with the hard rock. The tallest waterfall in Japan, Hannoki Falls, is a plunge waterfall that stands 497 meters (1,640 feet). Hannoki Falls is seasonally fed by snowmelt from the Tateyama Mountains.

Punchbowl waterfalls are characterized by wide pools at their base. Wailua Falls is a punchbowl waterfall on the island of Kauai, Hawai'i, U.S. Although the plunge pool is tranquil and popular for swimming, the area around Wailua Falls itself is dangerous.

The water flowing over segmented waterfalls separate as distinct streams. Huge outcroppings of hard rock separate the streams of Nigretta Falls, a segmented waterfall in Victoria, Australia, before they meet in a large plunge pool.

Case Study: Niagara Falls

The Niagara River has two falls, one in the U.S. state of New York and one in the province of Ontario, Canada. Each waterfall is less than 60 meters (200 feet) tall, but together they are more than a kilometer (0.62 miles) wide.

Niagara and many other falls with large volumes of water are used to generate hydroelectric power. A tremendous volume of water flows over Niagara Falls, as much as 5,525 cubic meters (195,000 cubic feet) per second. Power stations upstream from the falls convert hydroelectric energy into electricity for residential and commercial use.

The U.S. and Canadian governments manage the Niagara River so carefully that it is possible for either country to "turn off" the falls. This is done at night, so as not to disturb the tourism industry, and the falls are never actually turned off, just slowed down. Water is diverted to canals and reservoirs, and the decreased flow allows engineers to check for erosion and other damage on the falls. U.S. and Canadian authorities also work together to ensure Niagara Falls doesn’t freeze in the winter, which would threaten power production.

Because waterfalls are barriers to navigation, canals are sometimes built to get around them. Niagara Falls prevents passage between Lake Erie and Lake Ontario on the Niagara River. In the 19th century, the Welland Canal was built to make passage between the two Great Lakes possible.

Additional Information

Waterfall is an area where flowing river water drops abruptly and nearly vertically. Waterfalls represent major interruptions in river flow. Under most circumstances, rivers tend to smooth out irregularities in their flow by processes of erosion and deposition. In time, the long profile of a river (the graph of its gradient) takes the form of a smooth curve, steepest toward the source, gentlest toward the mouth. Waterfalls interrupt this curve, and their presence is a measure of the progress of erosion. A waterfall may also be termed a falls or sometimes a cataract, the latter designation being most common when large volumes of water are involved. Waterfalls of small height and lesser steepness are called cascades; this term is often applied to a series of small falls along a river. Still gentler reaches of rivers that nonetheless exhibit turbulent flow and white water in response to a local increase in channel gradient are called rapids.

The highest waterfall in the world is Angel Falls in Venezuela (807 m [2,650 feet]). Arguably the largest waterfall is the Chutes de Khone (Khone Falls) on the Mekong River in Laos: the volume of water passing over it has been estimated at 11,600 cubic m (410,000 cubic feet) per second, although its height is only 70 m (230 feet).

There are several conditions that give rise to waterfalls. One of the most common reasons for a waterfall’s existence is difference in rock type. Rivers cross many lithological boundaries, and, if a river passes from a resistant rock bed to a softer one, it is likely to erode the soft rock more quickly and steepen its gradient at the junction between the rock types. This situation can occur as a river cuts and exhumes a junction between different rock beds. The riverbed of Niagara Falls, which forms part of the boundary between the United States and Canada, has a blocky dolomite cap overlying a series of weaker shales and sandstones.

A related cause of waterfalls is the presence of bars of hard rock in the riverbed. A series of cataracts has been created on the Nile where the river has worn its bed sufficiently to uncover the hard crystalline basement rock.

Other waterfalls are caused less by the character of rock formations and more by the structure or shape of the land. Uplifted plateau basalts, for example, may provide a resistant platform at the edge of which rivers produce waterfalls, as occurs on the Antrim basalts in Northern Ireland. On a much larger scale, the morphology of the southern half of Africa, a high plateau surrounded by a steep scarp slope, creates waterfalls and rapids on most of the area’s major rivers. These include the Livingstone Falls on the Congo River and the Augrabies Falls on the Orange River. In general, the occurrence of waterfalls increases in mountainous terrain as slopes get steeper.

Erosion and geology are not the only factors that create waterfalls. Tectonic movement along a fault may bring hard and soft rocks together and encourage the establishment of a waterfall. A drop in sea level promotes increased downcutting and the retreat upstream of a knickpoint (sharp change of gradient indicating the change of a river’s base-level). Depending on the change of sea level, river flow, and geology (among other factors), falls or rapids may develop at the knickpoint. Many waterfalls have been created by glaciation where valleys have been over-deepened by ice and tributary valleys have been left high up on steep valley sides. In the glacially gouged Yosemite Valley in California, the Yosemite Upper Falls tumble 436 m (1,430 feet) from such a hanging valley.

Within a river’s time scale, a waterfall is a temporary feature that is eventually worn away. The rapidity of erosion depends on the height of a given waterfall, its volume of flow, the type and structure of rocks involved, and other factors. In some cases the site of the waterfall migrates upstream by headward erosion of the cliff or scarp, while in others erosion may tend to act downward, to bevel the entire reach of the river containing the falls. With the passage of time, by either or both of these means, the inescapable tendency of rivers is to eliminate any waterfall that may have formed. The energy of rivers is directed toward the achievement of a relatively smooth, concave upward, longitudinal profile.

Even in the absence of entrained rock debris, which serve as an erosive tool of rivers, the energy available for erosion at the base of a waterfall is great. One of the characteristic features associated with waterfalls of any great magnitude, with respect to volume of flow as well as to height, is the presence of a plunge pool, a basin that is scoured out of the river channel beneath the falling water. In some instances the depth of a plunge pool may nearly equal the height of the cliff causing the falls. Plunge pools eventually cause the collapse of the cliff face and the retreat of the waterfall. Retreat of waterfalls is a pronounced feature in some places. At Niagara, for example, the falls have retreated 11 km (7 miles) from the face of the escarpment where they began. Today much of Niagara’s water is diverted for hydroelectric power generation, but it has been estimated that with normal flow the rate of retreat would be about 1 m (3 feet) per year.

Jai Ganesh · 2023-06-28 00:10:44

1822) Driving

Gist

The ability to drive a car, the activity of driving, or the way someone drives.

Details

Driving is the controlled operation and movement of a vehicle, including cars, motorcycles, trucks, and buses. Permission to drive on public highways is granted based on a set of conditions being met and drivers are required to follow the established road and traffic laws in the location they are driving. The word driving, has etymology dating back to the 15th century and has developed as what driving has encompassed has changed from working animals in the 15th to automobiles in the 1800s. Driving skills have also developed since the 15th century with physical, mental and safety skills being required to drive. This evolution of the skills required to drive have been accompanied by the introduction of driving laws which relate to not only the driver but the driveability of a car.

The term "driver" originated in the 15th century, referring to the occupation of driving working animals like pack or draft horses. It later applied to electric railway drivers in 1889 and motor-car drivers in 1896. The world's first long-distance road trip by automobile occurred in 1888 when Bertha Benz drove a Benz Patent-Motorwagen from Mannheim to Pforzheim, Germany. Driving requires both physical and mental skills, as well as an understanding of the rules of the road.

In many countries, drivers must pass practical and theoretical driving tests to obtain a driving license. Physical skills required for driving include proper hand placement, gear shifting, pedal operation, steering, braking, and operation of ancillary devices. Mental skills involve hazard awareness, decision-making, evasive maneuvering, and understanding vehicle dynamics. Distractions, altered states of consciousness, and certain medical conditions can impair a driver's mental skills.

Safety concerns in driving include poor road conditions, low visibility, texting while driving, speeding, impaired driving, sleep-deprived driving, and reckless driving. Laws regarding driving, driver licensing, and vehicle registration vary between jurisdictions. Most countries have laws against driving under the influence of alcohol or other drugs. Some countries impose annual renewals or point systems for driver's licenses to maintain road safety.

The World Health Organization estimates that 1.35 million people are killed each year in road traffic; it is the leading cause of death for people age 15 to 29.

Etymology

The origin of the term driver, as recorded from the 15th century, refers to the occupation of driving working animals, especially pack horses or draft horses. The verb ' to drive ' in origin means "to force to move, to impel by physical force". It is first recorded of electric railway drivers in 1889 and of a motor-car driver in 1896. Early alternatives were motorneer,[2] motor-man, motor-driver or motorist. French favors "conducteur" (the English equivalent, "conductor", being used—from the 1830s—not of the driver but of the person in charge of passengers and collecting fares), while German influenced areas adopted Fahrer (used of coach-drivers in the 18th century, but shortened about 1900 from the compound Kraftwagen Fahrer), and the verbs führen, lenken, steuern—all with a meaning "steer, guide, navigate"—translating to conduire.

Introduction of the automobile

In 1899, an automobile was driven to the summit of Mount Washington, New Hampshire, for the first time
The world's first long-distance road trip by automobile was in August 1888 when Bertha Benz, wife of Benz Patent-Motorwagen inventor Karl Benz, drove 66 mi (106 km) Mannheim to Pforzheim, Germany, and returned, in the third experimental Benz motor car, which had a maximum speed of 10 mph (16 km/h), with her two teenage sons Richard and Eugen but without the consent and knowledge of her husband. She had said she wanted to visit her mother, but also intended to generate publicity for her husband's invention, which had only been taken on short test drives before.

In 1899, F. O. Stanley and his wife, Flora, drove their Stanley Steamer automobile, sometimes called a locomobile, to the summit of Mount Washington in New Hampshire in the United States to generate publicity for their automobile. The 7.6-mile (12.2 km) journey took over two hours (not counting time to add more water); the descent was accomplished by putting the engine in low gear and much braking.

Driving skills

Driving in traffic is more than just knowing how to operate the mechanisms which control the vehicle; it requires knowing how to apply the rules of the road (which ensures safe and efficient sharing with other users). An effective driver also has an intuitive understanding of the basics of vehicle handling and can drive responsibly.

Although direct operation of a bicycle and a mounted animal are commonly referred to as riding, such operators are legally considered drivers and are required to obey the rules of the road. Driving over a long distance is referred to as a road trip.

In some countries, a basic both practical and theoretical knowledge of the rules of the road is assessed with a driving test(s) and those who pass are issued with a driving license.

Physical skill

A driver must have physical skills to be able to control direction, acceleration, and deceleration. For motor vehicles, the detailed tasks include:

* Proper hand placement and seating position
* Starting the vehicle's engine with the starting system
* Setting the transmission to the correct gear
* Depressing the pedals with one's feet to accelerate, slow and stop the vehicle and
* If the vehicle is equipped with a manual transmission, to modulate the clutch
* Steering the vehicle's direction with the steering wheel
* Applying brake pressure to slow or stop the vehicle
* Operating other important ancillary devices such as the indicators, headlights, parking brake and windshield wipers
* Speed and Skid control

Mental skill

Avoiding or successfully handling an emergency driving situation can involve the following skills:

* Observing the environment for road signs, driving conditions, and hazards
* Awareness of surroundings, especially in heavy and city traffic
* Making good and quick decisions based on factors such as road and traffic conditions
* Evasive maneuvering
* Understanding vehicle dynamics
* Left- and right-hand traffic

Driver with two cell phones

Distractions can compromise a driver's mental skills, as can any altered state of consciousness. One study on the subject of mobile phones and driving safety concluded that, after controlling for driving difficulty and time on task, drivers talking on a phone exhibited greater impairment than drivers who were suffering from alcohol intoxication. In the US "During daylight hours, approximately 481,000 drivers are using cell phones while driving according to the publication on the National Highway Traffic Safety Association. Another survey indicated that music could adversely affect a driver's concentration."

Seizure disorders and Alzheimer's disease are among the leading medical causes of mental impairment among drivers in the United States and Europe. Whether or not physicians should be allowed, or even required, to report such conditions to state authorities, remains highly controversial.

Safety

Safety issues in driving include:

* Driving in poor road conditions and low visibility
* Texting while driving
* Speeding
* Drug–impaired driving and driving under the influence
* Distracted driving
* Sleep-deprived driving
* Reckless driving and street racing

Age

There is a high rate of injury and death caused by motor vehicle accidents that involve teenage drivers. There is evidence that the less teenagers drive, the risk of injury drops. There is a lack of evidence as to whether educational interventions to promote active transport and share information about the risks, cost, and stresses involved with driving are effective at reducing or delaying car driving in the teenage years.

Driveability

Driveability of a vehicle means the smooth delivery of power, as demanded by the driver. Typical causes of driveability degradation are rough idling, misfiring, surging, hesitation, or insufficient power.

Driving laws

Drivers are subject to the laws of the jurisdiction in which they are driving.

International conventions

Geneva convention requires drivers to be 18 years old.

Vienna convention requires additional skills for drivers.

Local driving laws

The rules of the road, driver licensing and vehicle registration schemes vary considerably between jurisdictions, as do laws imposing criminal responsibility for negligent driving, vehicle safety inspections and compulsory insurance. Most countries also have differing laws against driving while under the influence of alcohol or other drugs. Aggressive driving and road rage have become problems for drivers in some areas.

Some countries require annual renewal of the driver's license. This may require getting through another driving test or vision screening test to get recertified. Also, some countries use a points system for the driver's license. Both techniques (annual renewal with tests, points system) may or may not improve road safety compared to when the driver is not continuously or annually evaluated.

Ownership and insurance

Car ownership does not require a driver's license at all. As such, even with a withdrawn driver's license, former drivers are still legally allowed to possess a car and thus have access to it. In the USA, between 1993 and 1997 13.8% of all drivers involved in fatal crashes had no driver's license.

In some countries (such as the UK), the car itself needs have a certificate that proves the vehicle is safe and roadworthy. Also, it needs to have a minimum of third party insurance.

Driving training

Motorists are almost universally required to take lessons with an approved instructor and to pass a driving test before being granted a license. Almost all countries allow all adults with good vision and health to apply to take a driving test and, if successful, to drive on public roads.

In many countries, even after passing one's driving test, new motorists are initially subject to special restrictions. For example, in Australia, novice drivers are required to carry "P" ("provisional") plates;, in New Zealand it is called restricted (R) both are subject to alcohol limits and other restrictions for the first two years of driving. Many U.S. states now issue graduated drivers' licenses to novice minors. Typically, newly licensed minors may not drive or operate a motorized vehicle at night or with a passenger other than family members. The duration of the restriction varies from six months to until the driver is 18 years old. This is due to the mental aptitude of a young or inexperienced driver not being fully developed.

A few countries banned women driving in the past. In Oman, women were not allowed to drive until 1970. In Saudi Arabia, women were not issued driving licenses until 2018. Saudi women had periodically staged driving protests against these restrictions and in September 2017, the Saudi government agreed to lift the ban, which went into effect in June 2018.

Jai Ganesh · 2023-06-29 00:07:54

1823) Drawing

Summary

Drawing is the art or technique of producing images on a surface, usually paper, by means of marks, usually of ink, graphite, chalk, charcoal, or crayon.

Drawing as formal artistic creation might be defined as the primarily linear rendition of objects in the visible world, as well as of concepts, thoughts, attitudes, emotions, and fantasies given visual form, of symbols and even of abstract forms. This definition, however, applies to all graphic arts and techniques that are characterized by an emphasis on form or shape rather than mass and colour, as in painting. Drawing as such differs from graphic printing processes in that a direct relationship exists between production and result. Drawing, in short, is the end product of a successive effort applied directly to the carrier. Whereas a drawing may form the basis for reproduction or copying, it is nonetheless unique by its very nature.

Although not every artwork has been preceded by a drawing in the form of a preliminary sketch, drawing is in effect the basis of all visual arts. Often the drawing is absorbed by the completed work or destroyed in the course of completion. Thus, the usefulness of a ground plan drawing of a building that is to be erected decreases as the building goes up. Similarly, points and lines marked on a raw stone block represent auxiliary drawings for the sculpture that will be hewn out of the material. Essentially, every painting is built up of lines and pre-sketched in its main contours; only as the work proceeds is it consolidated into coloured surfaces. As shown by an increasing number of findings and investigations, drawings form the material basis of mural, panel, and book paintings. Such preliminary sketches may merely indicate the main contours or may predetermine the final execution down to exact details. They may also be mere probing sketches. Long before the appearance of actual small-scale drawing, this procedure was much used for monumental murals. With sinopia—the preliminary sketch found on a layer of its own on the wall underneath the fresco, or painting on freshly spread, moist plaster—one reaches the point at which a work that merely served as technical preparation becomes a formal drawing expressing an artistic intention.

Not until the late 14th century, however, did drawing come into its own—no longer necessarily subordinate, conceptually or materially, to another art form. Autonomous, or independent, drawings, as the name implies, are themselves the ultimate aim of an artistic effort; therefore, they are usually characterized by a pictorial structure and by precise execution down to details.

Formally, drawing offers the widest possible scope for the expression of artistic intentions. Bodies, space, depth, substantiality, and even motion can be made visible through drawing. Furthermore, because of the immediacy of its statement, drawing expresses the draftsperson’s personality spontaneously in the flow of the line; it is, in fact, the most personal of all artistic statements. It is thus plausible that the esteem in which drawing was held should have developed parallel to the value placed on individual artistic talent. Ever since the Renaissance, drawing has gradually been losing its anonymous and utilitarian status in the eyes of artists and the public, and its documents have been increasingly valued and collected.

Details

Drawing is a visual art that uses an instrument to mark paper or another two-dimensional surface. The instrument might be pencils, crayons, pens with inks, brushes with paints or combinations of these, and in more modern times, computer styluses with graphics tablets.

A drawing instrument releases a small amount of material onto a surface, leaving a visible mark. The most common support for drawing is paper, although other materials, such as cardboard, vellum, wood, plastic, leather, canvas, and board, have been used. Temporary drawings may be made on a blackboard or whiteboard. Drawing has been a popular and fundamental means of public expression throughout human history. It is one of the simplest and most efficient means of communicating ideas. The wide availability of drawing instruments makes drawing one of the most common artistic activities.

In addition to its more artistic forms, drawing is frequently used in commercial illustration, animation, architecture, engineering, and technical drawing. A quick, freehand drawing, usually not intended as a finished work, is sometimes called a sketch. An artist who practices or works in technical drawing may be called a drafter, draftsman, or draughtsman.

Overview

Drawing is one of the oldest forms of human expression within the visual arts. It is generally concerned with the marking of lines and areas of tone onto paper/other material, where the accurate representation of the visual world is expressed upon a plane surface. Traditional drawings were monochrome, or at least had little colour, while modern colored-pencil drawings may approach or cross a boundary between drawing and painting. In Western terminology, drawing is distinct from painting, even though similar media often are employed in both tasks. Dry media, normally associated with drawing, such as chalk, may be used in pastel paintings. Drawing may be done with a liquid medium, applied with brushes or pens. Similar supports likewise can serve both: painting generally involves the application of liquid paint onto prepared canvas or panels, but sometimes an underdrawing is drawn first on that same support.

Drawing is often exploratory, with considerable emphasis on observation, problem-solving and composition. Drawing is also regularly used in preparation for a painting, further obfuscating their distinction. Drawings created for these purposes are called studies.

There are several categories of drawing, including figure drawing, cartooning, doodling, and freehand. There are also many drawing methods, such as line drawing, stippling, shading, the surrealist method of entopic graphomania (in which dots are made at the sites of impurities in a blank sheet of paper, and lines are then made between the dots), and tracing (drawing on a translucent paper, such as tracing paper, around the outline of preexisting shapes that show through the paper).

A quick, unrefined drawing may be called a sketch.

In fields outside art, technical drawings or plans of buildings, machinery, circuitry and other things are often called "drawings" even when they have been transferred to another medium by printing.

History

In communication

Drawing is one of the oldest forms of human expression, with evidence for its existence preceding that of written communication. It is believed that drawing was used as a specialised form of communication before the invention of the written language, demonstrated by the production of cave and rock paintings around 30,000 years ago (Art of the Upper Paleolithic). These drawings, known as pictograms, depicted objects and abstract concepts. The sketches and paintings produced by Neolithic times were eventually stylised and simplified in to symbol systems (proto-writing) and eventually into early writing systems.

In manuscripts

Before the widespread availability of paper in Europe, monks in European monasteries used drawings, either as underdrawings for illuminated manuscripts on vellum or parchment, or as the final image. Drawing has also been used extensively in the field of science, as a method of discovery, understanding and explanation.

In science

Drawing diagrams of observations is an important part of scientific study.

In 1609, astronomer Galileo Galilei explained the changing phases of Venus and also the sunspots through his observational telescopic drawings. In 1924, geophysicist Alfred Wegener used illustrations to visually demonstrate the origin of the continents.

As artistic expression

Drawing is used to express one's creativity, and therefore has been prominent in the world of art. Throughout much of history, drawing was regarded as the foundation for artistic practice. Initially, artists used and reused wooden tablets for the production of their drawings. Following the widespread availability of paper in the 14th century, the use of drawing in the arts increased. At this point, drawing was commonly used as a tool for thought and investigation, acting as a study medium whilst artists were preparing for their final pieces of work. The Renaissance brought about a great sophistication in drawing techniques, enabling artists to represent things more realistically than before, and revealing an interest in geometry and philosophy.

The invention of the first widely available form of photography led to a shift in the hierarchy of the arts. Photography offered an alternative to drawing as a method for accurately representing visual phenomena, and traditional drawing practice was given less emphasis as an essential skill for artists, particularly so in Western society.

Notable artists and draftsmen

Drawing became significant as an art form around the late 15th century, with artists and master engravers such as Albrecht Dürer and Martin Schongauer (c. 1448-1491), the first Northern engraver known by name. Schongauer came from Alsace, and was born into a family of goldsmiths. Albrecht Dürer, a master of the next generation, was also the son of a goldsmith.

Old Master Drawings often reflect the history of the country in which they were produced, and the fundamental characteristics of a nation at that time. In 17th-century Holland, a Protestant country, there were almost no religious artworks, and, with no King or court, most art was bought privately. Drawings of landscapes or genre scenes were often viewed not as sketches but as highly finished works of art. Italian drawings, however, show the influence of Catholicism and the Church, which played a major role in artistic patronage. The same is often true of French drawings, although in the 17th century the disciplines of French Classicism meant drawings were less Baroque than the more free Italian counterparts, which conveyed a greater sense of movement.

In the 20th century Modernism encouraged "imaginative originality" and some artists' approach to drawing became less literal, more abstract. World-renowned artists such as Pablo Picasso, Andy Warhol and Jean-Michel Basquiat helped challenge the status quo, with drawing being very much at the centre of their practice, and often re-interpreting traditional technique.

Basquiat's drawings were produced in many different mediums, most commonly ink, pencil, felt-tip or marker, and oil-stick, and he drew on any surface that came to hand, such as doors, clothing, refrigerators, walls and baseball helmets.

The centuries have produced a canon of notable artists and draftsmen, each with their own distinct language of drawing, including:

14th, 15th and 16th: Leonardo da Vinci • Albrecht Dürer • Hans Holbein the Younger • Michelangelo • Pisanello • Raphael
17th: Claude • Jacques de Gheyn II • Guercino • Nicolas Poussin • Rembrandt • Peter Paul Rubens • Pieter Saenredam
18th: François Boucher • Jean-Honoré Fragonard • Giovanni Battista Tiepolo • Antoine Watteau
19th: Aubrey Beardsley • Paul Cézanne • Jacques-Louis David • Honoré Daumier • Edgar Degas • Théodore Géricault • Francisco Goya • Jean-Auguste-Dominique Ingres • Pierre-Paul Prud'hon • Odilon Redon • John Ruskin • Georges Seurat • Henri de Toulouse-Lautrec • Vincent van Gogh
20th: Max Beckmann • Jean Dubuffet • M. C. Escher • Arshile Gorky • George Grosz • Paul Klee • Oskar Kokoschka • Käthe Kollwitz • Alfred Kubin • André Masson • Alphonse Mucha • Jules Pascin • Pablo Picasso • Egon Schiele • Jean-Michel Basquiat • Andy Warhol

Materials

The medium is the means by which ink, pigment or color are delivered onto the drawing surface. Most drawing media are either dry (e.g. graphite, charcoal, pastels, Conté, silverpoint), or use a fluid solvent or carrier (marker, pen and ink). Watercolor pencils can be used dry like ordinary pencils, then moistened with a wet brush to get various painterly effects. Very rarely, artists have drawn with (usually decoded) invisible ink. Metalpoint drawing usually employs either of two metals: silver or lead. More rarely used are gold, platinum, copper, brass, bronze, and tinpoint.

Paper comes in a variety of different sizes and qualities, ranging from newspaper grade up to high quality and relatively expensive paper sold as individual sheets. Papers vary in texture, hue, acidity, and strength when wet. Smooth paper is good for rendering fine detail, but a more "toothy" paper holds the drawing material better. Thus a coarser material is useful for producing deeper contrast.

Newsprint and typing paper may be useful for practice and rough sketches. Tracing paper is used to experiment over a half-finished drawing, and to transfer a design from one sheet to another. Cartridge paper is the basic type of drawing paper sold in pads. Bristol board and even heavier acid-free boards, frequently with smooth finishes, are used for drawing fine detail and do not distort when wet media (ink, washes) are applied. Vellum is extremely smooth and suitable for very fine detail. Coldpressed watercolor paper may be favored for ink drawing due to its texture.

Acid-free, archival quality paper keeps its color and texture far longer than wood pulp based paper such as newsprint, which turns yellow and becomes brittle much sooner.

The basic tools are a drawing board or table, pencil sharpener and eraser, and for ink drawing, blotting paper. Other tools used are circle compass, ruler, and set square. Fixative is used to prevent pencil and crayon marks from smudging. Drafting tape is used to secure paper to drawing surface, and also to mask an area to keep it free of accidental marks, such as sprayed or spattered materials and washes. An easel or slanted table is used to keep the drawing surface in a suitable position, which is generally more horizontal than the position used in painting.

Technique

Almost all draftsmen use their hands and fingers to apply the media, with the exception of some handicapped individuals who draw with their mouth or feet.

Prior to working on an image, the artist typically explores how various media work. They may try different drawing implements on practice sheets to determine value and texture, and how to apply the implement to produce various effects.

The artist's choice of drawing strokes affects the appearance of the image. Pen and ink drawings often use hatching – groups of parallel lines. Cross-hatching uses hatching in two or more different directions to create a darker tone. Broken hatching, or lines with intermittent breaks, form lighter tones – and controlling the density of the breaks achieves a gradation of tone. Stippling uses dots to produce tone, texture and shade. Different textures can be achieved depending on the method used to build tone.

Drawings in dry media often use similar techniques, though pencils and drawing sticks can achieve continuous variations in tone. Typically a drawing is filled in based on which hand the artist favors. A right-handed artist draws from left to right to avoid smearing the image. Erasers can remove unwanted lines, lighten tones, and clean up stray marks. In a sketch or outline drawing, lines drawn often follow the contour of the subject, creating depth by looking like shadows cast from a light in the artist's position.

Sometimes the artist leaves a section of the image untouched while filling in the remainder. The shape of the area to preserve can be painted with masking fluid or cut out of a frisket and applied to the drawing surface, protecting the surface from stray marks until the mask is removed.

Another method to preserve a section of the image is to apply a spray-on fixative to the surface. This holds loose material more firmly to the sheet and prevents it from smearing. However the fixative spray typically uses chemicals that can harm the respiratory system, so it should be employed in a well-ventilated area such as outdoors.

Another technique is subtractive drawing in which the drawing surface is covered with graphite or charcoal and then erased to make the image.

Tone

Shading is the technique of varying the tonal values on the paper to represent the shade of the material as well as the placement of the shadows. Careful attention to reflected light, shadows and highlights can result in a very realistic rendition of the image.

Blending uses an implement to soften or spread the original drawing strokes. Blending is most easily done with a medium that does not immediately fix itself, such as graphite, chalk, or charcoal, although freshly applied ink can be smudged, wet or dry, for some effects. For shading and blending, the artist can use a blending stump, tissue, a kneaded eraser, a fingertip, or any combination of them. A piece of chamois is useful for creating smooth textures, and for removing material to lighten the tone. Continuous tone can be achieved with graphite on a smooth surface without blending, but the technique is laborious, involving small circular or oval strokes with a somewhat blunt point.

Shading techniques that also introduce texture to the drawing include hatching and stippling. A number of other methods produce texture. In addition to the choice of paper, drawing material and technique affect texture. Texture can be made to appear more realistic when it is drawn next to a contrasting texture; a coarse texture is more obvious when placed next to a smoothly blended area. A similar effect can be achieved by drawing different tones close together. A light edge next to a dark background stands out to the eye, and almost appears to float above the surface.

Form and proportion

Measuring the dimensions of a subject while blocking in the drawing is an important step in producing a realistic rendition of the subject. Tools such as a compass can be used to measure the angles of different sides. These angles can be reproduced on the drawing surface and then rechecked to make sure they are accurate. Another form of measurement is to compare the relative sizes of different parts of the subject with each other. A finger placed at a point along the drawing implement can be used to compare that dimension with other parts of the image. A ruler can be used both as a straightedge and a device to compute proportions.

Variation of proportion with age

When attempting to draw a complicated shape such as a human figure, it is helpful at first to represent the form with a set of primitive volumes. Almost any form can be represented by some combination of the cube, sphere, cylinder, and cone. Once these basic volumes have been assembled into a likeness, then the drawing can be refined into a more accurate and polished form. The lines of the primitive volumes are removed and replaced by the final likeness. Drawing the underlying construction is a fundamental skill for representational art, and is taught in many books and schools. Its correct application resolves most uncertainties about smaller details, and makes the final image look consistent.

A more refined art of figure drawing relies upon the artist possessing a deep understanding of anatomy and the human proportions. A trained artist is familiar with the skeleton structure, joint location, muscle placement, tendon movement, and how the different parts work together during movement. This allows the artist to render more natural poses that do not appear artificially stiff. The artist is also familiar with how the proportions vary depending on the age of the subject, particularly when drawing a portrait.

Perspective

Linear perspective is a method of portraying objects on a flat surface so that the dimensions shrink with distance. Each set of parallel, straight edges of any object, whether a building or a table, follows lines that eventually converge at a vanishing point. Typically this convergence point is somewhere along the horizon, as buildings are built level with the flat surface. When multiple structures are aligned with each other, such as buildings along a street, the horizontal tops and bottoms of the structures typically converge at a vanishing point.

When both the fronts and sides of a building are drawn, then the parallel lines forming a side converge at a second point along the horizon (which may be off the drawing paper.) This is a two-point perspective. Converging the vertical lines to a third point above or below the horizon then produces a three-point perspective.

Depth can also be portrayed by several techniques in addition to the perspective approach above. Objects of similar size should appear ever smaller the further they are from the viewer. Thus the back wheel of a cart appears slightly smaller than the front wheel. Depth can be portrayed through the use of texture. As the texture of an object gets further away it becomes more compressed and busy, taking on an entirely different character than if it was close. Depth can also be portrayed by reducing the contrast in more distant objects, and by making their colors less saturated. This reproduces the effect of atmospheric haze, and cause the eye to focus primarily on objects drawn in the foreground.

Artistry

The composition of the image is an important element in producing an interesting work of artistic merit. The artist plans element placement in the art to communicate ideas and feelings with the viewer. The composition can determine the focus of the art, and result in a harmonious whole that is aesthetically appealing and stimulating.

The illumination of the subject is also a key element in creating an artistic piece, and the interplay of light and shadow is a valuable method in the artist's toolbox. The placement of the light sources can make a considerable difference in the type of message that is being presented. Multiple light sources can wash out any wrinkles in a person's face, for instance, and give a more youthful appearance. In contrast, a single light source, such as harsh daylight, can serve to highlight any texture or interesting features.

When drawing an object or figure, the skilled artist pays attention to both the area within the silhouette and what lies outside. The exterior is termed the negative space, and can be as important in the representation as the figure. Objects placed in the background of the figure should appear properly placed wherever they can be viewed.

A study is a draft drawing that is made in preparation for a planned final image. Studies can be used to determine the appearances of specific parts of the completed image, or for experimenting with the best approach for accomplishing the end goal. However a well-crafted study can be a piece of art in its own right, and many hours of careful work can go into completing a study.

Process

Individuals display differences in their ability to produce visually accurate drawings. A visually accurate drawing is described as being "recognized as a particular object at a particular time and in a particular space, rendered with little addition of visual detail that can not be seen in the object represented or with little deletion of visual detail”.

Investigative studies have aimed to explain the reasons why some individuals draw better than others. One study posited four key abilities in the drawing process: motor skills required for mark-making, the drawer's own perception of their drawing, perception of objects being drawn, and the ability to make good representational decisions. Following this hypothesis, several studies have sought to conclude which of these processes are most significant in affecting the accuracy of drawings.

Motor control

Motor control is an important physical component in the 'Production Phase' of the drawing process. It has been suggested that motor control plays a role in drawing ability, though its effects are not significant.

Perception

It has been suggested that an individual's ability to perceive an object they are drawing is the most important stage in the drawing process. This suggestion is supported by the discovery of a robust relationship between perception and drawing ability.

This evidence acted as the basis of Betty Edwards' how-to-draw book, 'Drawing on the Right Side of the Brain'. Edwards aimed to teach her readers how to draw, based on the development of the reader's perceptual abilities.

Furthermore, the influential artist and art critic John Ruskin emphasised the importance of perception in the drawing process in his book 'The Elements of Drawing'. He stated that "For I am nearly convinced, that once we see keenly enough, there is very little difficult in drawing what we see".

Visual memory

This has also been shown to influence one's ability to create visually accurate drawings. Short-term memory plays an important part in drawing as one's gaze shifts between the object they are drawing and the drawing itself.

Decision-making

Some studies comparing artists to non-artists have found that artists spend more time thinking strategically while drawing. In particular, artists spend more time on 'metacognitive' activities such as considering different hypothetical plans for how they might progress with a drawing.

Jai Ganesh · 2023-06-30 00:11:16

1824) Weightlifting

Gist

The sport or activity of lifting heavy metal objects.

Summary

Weightlifting is a sport in which barbells are lifted competitively or as an exercise.

History

Weightlifting has a lengthy history. For many prehistoric tribes, the traditional test of manhood was the lifting of a special rock. Such manhood stones, some with the name of the first lifter incised, exist in Greece and in Scottish castles. The competitive lifting of stones still persists locally in Germany, Switzerland, the highlands of Montenegro, and the Basque region of Spain. In many such events the consecutive number of lifts within a given time period is used to declare a winner.

The origins of modern weightlifting competition are to be found in the 18th- and 19th-century strong men, such as Eugene Sandow and Arthur Saxon of Germany, George Hackenschmidt of Russia, and Louis Apollon of France, who performed in circuses and theatres. By 1891 there was international competition in London. The revived Olympic Games of 1896 included weightlifting events, as did the Games of 1900 and 1904, but thereafter these events were suspended until 1920. In that year, at the suggestion of the International Olympic Committee, the International Weightlifting Federation (Fédération Haltérophile Internationale; FHI) was formed to regularize events and supervise international competition. By 1928 the one- and two-hand lifts of earlier Games had given way to only two-hand lifts: the snatch, the clean and jerk, and the clean and press (described below). The press was abandoned in 1972.

In the Games before World War II, the leading weightlifters were French, German, and Egyptian. After the war American weightlifters were dominant until 1953. Thereafter Soviet and Bulgarian weightlifters held a virtual monopoly on world records and championships. By the late 1990s the leading countries competing in weightlifting were Turkey, Greece, and China. World championships were held in 1922–23 and from 1937, except during the war years, and European championships were held from 1924 through 1936. A weightlifting competition for women was added to the Olympic Games in 2000.

Equipment

The weight used in modern competitive lifting is the barbell, a steel bar or rod to which cast-iron or steel disk weights are attached at each end on a revolving sleeve. The range of weights added is 25, 20, 15, 10, 5, 2.5, and 1.25 kg (55, 44, 33, 22, 11, 5.5, and 2.75 pounds).

Lifts

From 1928 to 1968 the three international lifts were the snatch, the clean and jerk, and the press (or clean and press). In all lifts the barbell rests on the floor initially. Lifts are performed on a wooden platform 4 metres (13.1 feet) square. If a lifter steps off the platform during a lift, the lift is not allowed.

In the snatch the barbell is lifted from the floor to arm’s length overhead in a single, continuous, explosive movement, with the lifter being permitted to move his feet or to squat under the barbell as he lifts it before recovering to an erect position. The clean and jerk is a two-part lift. After lifting the barbell to the shoulders, the lifter jerks it overhead to arm’s length, with no restrictions on the time necessary to complete the lift or on leg movements. In both lifts, the lifter must complete the lift with feet in line, body erect, arms and legs extended, and the barbell in control overhead. The lifter must either hold the weight overhead for two seconds or wait for the referee’s signal before lowering the barbell back to the floor.

The press was also a two-part lift. As in the clean and jerk, the barbell was brought to the lifter’s shoulders, the same foot motion being allowed. Then the lifter had to stand erect until the referee signaled for the completion of the lift, which was achieved by pressing the barbell upward in a steady continuous movement to arm’s length overhead but without any assistance by moving the legs.

Weight categories

Men’s competitions are divided into eight body-weight categories (upper limits given): 56 kg (123 pounds), 62 kg (137 pounds), 69 kg (152 pounds), 77 kg (170 pounds), 85 kg (187 pounds), 94 kg (207 pounds), 105 kg (231 pounds), and more than 105 kg.

For women there are seven weight divisions: 48 kg (106 pounds), 53 kg (117 pounds), 58 kg (128 pounds), 63 kg (139 pounds), 69 kg (152 pounds), 75 kg (165 pounds), and more than 75 kg.

Details

Weightlifting or weight lifting generally refers to physical exercises and sports in which people lift weights, often in the form of dumbbells or barbells. People engage in weightlifting for a variety of different reasons. These can include: developing physical strength; promoting health and fitness; competing in weightlifting sports; and developing a muscular and aesthetic physique.

Olympic weightlifting is a specific type of weightlifting sport practiced at the Olympic Games, commonly referred to simply as "weightlifting". Other weightlifting sports include powerlifting, kettlebell lifting, and para powerlifting—the weightlifting sport practiced at the Paralympic Games. Different weightlifting sports may be distinguished by the different ways of lifting a weight, and/or the objects lifted. Weightlifting events are key elements of strength athletics.

Weight training is weightlifting to develop physical strength and/or a muscular physique. It is a common part of strength conditioning for athletes in many sports. When the primary goal is to develop an all-round muscular physique, this is bodybuilding. People who train with weights utilize both free weights (such as barbells, dumbbells, and kettlebells), and weight machines to train all parts of their bodies. A place and equipment for weight training is provided at gyms and leisure centres.

According to an article in The New York Times, lifting weights can prevent some disabilities, increase metabolism, and lower body fat. Using free weights, compared to machines, improves not only strength but muscle function as well. Lifting weights can also improve self-confidence and make people feel better about themselves.

Weightlifting sports

Competitive weight lifting is believed to pre-date written history. There are records in many civilizations of feats of strength performed by great heroes, perhaps mythological, such as Heracles, Goliath, Orm Storolfsson and Milo of Croton. In Ancient China and Greece, men lifted stones to prove their strength and manhood. There is a tradition in Scotland of weight lifting competitions in Scottish Highland Gatherings, which have been annual events since the 1820s;and these contests are forerunners of modern strength athletics.

When in 1896 the modern international Olympic Games began, weight lifting was an event at the first Games; and since 1920 weightlifting has been a regular part of the Olympics. By 1932 the Olympic competition comprised three lifts, all of which are different ways of lifting a weighted barbell from ground to overhead: namely the snatch, the clean and jerk, and the clean and press. The snatch is a wide-grip lift, in which the barbell is lifted overhead in one motion. The clean and jerk and the clean and press are combination lifts in which the weight is first taken from the ground to the front of the shoulders (the clean), and then from the shoulders to overhead (the first using a jerk, the second an overhead press). After 1972 the clean and press was discontinued due to difficulties in judging proper form. Today, the snatch and the clean and jerk are together known as the "olympic lifts"; and the sport of weightlifting as practiced at the Olympics can be called "olympic weightlifting" or "olympic-style weightlifting" to distinguish it from other weightlifting sports (wherever it is practiced). Its international governing body is the International Weightlifting Federation, which was founded in 1905.

The 1950s and 1960s saw the sport of powerlifting developing, originating in competitions where athletes competed in different lifting events to those at the Olympics. These different lifts were sometimes called "odd lifts". Previously, the weightlifting governing bodies in the United Kingdom and the United States had recognized various "odd lifts" for competition and record purposes. Eventually these competitions became standardized to three specific lifts: the squat, bench press, and deadlift; and this form of weightlifting sport was given its distinct name of powerlifting, with the International Powerlifting Federation being formed in 1972 to regulate and promote the sport.

In 1964 weightlifting debuted in the Paralympic Games, in the form of the bench press; and since the 1992 Games has been called powerlfiting, specifically Para powerlifting or Paralympic powerlifting.

Weightlifting for strength, health, and appearance

Bodybuilder Lukáš Osladil posing onstage with a variation of the Most Muscular pose, having eliminated most body fat
Strength training is also recorded as far back as ancient Greek and ancient Persian times. Weightlifting is used as an end to achieve different goals. For example, in weight training, a type of exercise using weights to increase muscle strength, and in bodybuilding, a form of body modification for aesthetic reasons. Strength training, bodybuilding, and working out to achieve a general level of physical fitness have all historically been closely associated with weightlifting. Weightlifting is very beneficial for health in countless ways. Weightlifting induces the production of collagen proteins which helps build structure and strength of tendons and ligaments. It also is optimal for promoting and improving joint stability. Weightlifting can also increase metabolism and increases resting metabolic rate. This means the body can burn calories faster and the body uses those calories to increase and build muscle mass. However, it is possible to engage in a training regimen for any of these purpose using exercises or equipment other than weights. Conversely, because the goal of bodybuilding is often to generate a particular appearance, a person who engages in weightlifting only to increase strength, or for competitive purposes, may not achieve the physical appearance sought in bodybuilding. Weight training aims to build muscle by prompting two different types of hypertrophy: sarcoplasmic and myofibrillar. Sarcoplasmic hypertrophy leads to larger muscles and so is favored by bodybuilders more than myofibrillar hypertrophy, which builds athletic strength. Sarcoplasmic hypertrophy is triggered by increasing repetitions, whereas myofibrillar hypertrophy is triggered by lifting heavier weight. In either case, there is an increase in both size and strength of the muscles (compared to what happens if that same individual does not lift weights at all), however, the emphasis is different.

Notably, weightlifting purely to develop physical strength can lead to the development of a very different body type than weightlifting for bodybuilding, with powerlifters and Olympic weightlifters tending to have endo-mesomorphic bodies, and bodybuilders tending to be more mesomorphic. The two main methods of weight lifting to build strength and muscle mass are hypertrophy and overload. Training for muscle size is usually done by achieving hypertrophy which is training with a lighter weight at higher volume or more repetitions. Muscle size increases due to metabolic fibers that result in visible muscle mass growth. Training muscles to build strength is typically achieved by the overload method. Overload involves training with increasing weight at each set. It can also mean increasing volume of repetitions at the same weight for each set. Both overload methods are optimal for building muscle mass and strength, however, lifting heavy weights at a lower volume or less repetitions is very optimal for building strength.

It has historically been observed that weightlifting both for health and for appearance is substantially more common among men than among women. A primary reason for this dichotomy has been a desire among women to avoid developing an appearance that is perceived as physically masculine, with a consequent focus on aerobic exercises over weightlifting activities. Another factor that has been suggested is that women who are interested in lifting weights tend to be uncomfortable in spaces dominated by men, which has been observed to cause women who do want to lift weights to take weights from the weight room to another part of the gym to work out, therefore using smaller weights and for shorter times. The prevelance of males in weightlifting is reinforced by marketing that depicts weightlifting as a primarily male activity.

Additional Information

Weightlifting (often known as Olympic weightlifting) is a sport in which athletes compete in lifting a barbell loaded with weight plates from the ground to overhead, with the aim of successfully lifting the heaviest weights. Athletes compete in two specific ways of lifting the barbell overhead. The snatch is a wide-grip lift, in which the weighted barbell is lifted overhead in one motion. The clean and jerk is a combination lift, in which the weight is first taken from the ground to the front of the shoulders (the clean), and then from the shoulders to over the head (the jerk).

Each weightlifter gets three attempts at both the snatch and the clean and jerk, with the snatch attempted first. An athlete's score is the combined total of the highest successfully-lifted weight in kilograms for each lift. Athletes compete in various weight classes, which are different for each gender and have changed over time.

Weightlifting is an Olympic sport, and has been contested in every Summer Olympic Games since 1920. While the sport is officially named "weightlifting", the terms "Olympic weightlifting" and "Olympic-style weightlifting" are often used to distinguish it from the other sports and events that involve the lifting of weights, such as powerlifting, weight training, and strongman events. Similarly, the snatch and the clean and jerk are known as the "Olympic lifts".

While other strength sports test limit strength, Olympic-style weightlifting also tests aspects of human ballistic limits (explosive strength): the olympic lifts are executed faster, and with more mobility and a greater range of motion during their execution, than other barbell lifts. The Olympic lifts, and their component lifts (e.g., cleans, squats) and their variations (e.g., power snatch, power clean) are used by elite athletes in other sports to train for both explosive and functional strength.

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Jai Ganesh · 2023-07-01 00:13:53

1825) Dam

Gist

A dam is a wall built across a river that stops the river's flow and collects the water, especially to make a reservoir (an artificial lake) that provides water for an area.

Summary

A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aquaculture, and navigability. Hydropower is often used in conjunction with dams to generate electricity. A dam can also be used to collect or store water which can be evenly distributed between locations. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions.

The word dam can be traced back to Middle English, and before that, from Middle Dutch, as seen in the names of many old cities, such as Amsterdam and Rotterdam.

Ancient dams were built in Mesopotamia and the Middle East for water control. The earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC. Egyptians also built dams, such as Sadd-el-Kafara Dam for flood control. In modern-day India, Dholavira had an intricate water-management system with 16 reservoirs and dams. The Great Dam of Marib in Yemen, built between 1750 and 1700 BC, was an engineering wonder, and Eflatun Pinar, a Hittite dam and spring temple in Turkey, dates to the 15th and 13th centuries BC. The Kallanai Dam in South India, built in the 2nd century AD, is one of the oldest water regulating structures still in use.

Roman engineers built dams with advanced techniques and materials, such as hydraulic mortar and Roman concrete, which allowed for larger structures. They introduced reservoir dams, arch-gravity dams, arch dams, buttress dams, and multiple arch buttress dams. In Iran, bridge dams were used for hydropower and water-raising mechanisms.

During the Middle Ages, dams were built in the Netherlands to regulate water levels and prevent sea intrusion. In the 19th century, large-scale arch dams were constructed around the British Empire, marking advances in dam engineering techniques. The era of large dams began with the construction of the Aswan Low Dam in Egypt in 1902. The Hoover Dam, a massive concrete arch-gravity dam, was built between 1931 and 1936 on the Colorado River. By 1997, there were an estimated 800,000 dams worldwide, with some 40,000 of them over 15 meters high.

Details

A dam is a structure built across a stream, a river, or an estuary to retain water. Dams are built to provide water for human consumption, for irrigating arid and semiarid lands, or for use in industrial processes. They are used to increase the amount of water available for generating hydroelectric power, to reduce peak discharge of floodwater created by large storms or heavy snowmelt, or to increase the depth of water in a river in order to improve navigation and allow barges and ships to travel more easily. Dams can also provide a lake for recreational activities such as swimming, boating, and fishing. Many dams are built for more than one purpose; for example, water in a single reservoir can be used for fishing, to generate hydroelectric power, and to support an irrigation system. Water-control structures of this type are often designated multipurpose dams.

Auxiliary works that can help a dam function properly include spillways, movable gates, and valves that control the release of surplus water downstream from the dam. Dams can also include intake structures that deliver water to a power station or to canals, tunnels, or pipelines designed to convey the water stored by the dam to far-distant places. Other auxiliary works are systems for evacuating or flushing out silt that accumulates in the reservoir, locks for permitting the passage of ships through or around the dam site, and fish ladders (graduated steps) and other devices to assist fish seeking to swim past or around a dam.

A dam can be a central structure in a multipurpose scheme designed to conserve water resources on a regional basis. Multipurpose dams can hold special importance in developing countries, where a single dam may bring significant benefits related to hydroelectric power production, agricultural development, and industrial growth. However, dams have become a focus of environmental concern because of their impact on migrating fish and riparian ecosystems. In addition, large reservoirs can inundate vast tracts of land that are home to many people, and this has fostered opposition to dam projects by groups who question whether the benefits of proposed projects are worth the costs.

In terms of engineering, dams fall into several distinct classes defined by structural type and by building material. The decision as to which type of dam to build largely depends on the foundation conditions in the valley, the construction materials available, the accessibility of the site to transportation networks, and the experiences of the engineers, financiers, and promoters responsible for the project. In modern dam engineering, the choice of materials is usually between concrete, earthfill, and rockfill. Although in the past a number of dams were built of jointed masonry, this practice is now largely obsolete and has been supplanted by concrete. Concrete is used to build massive gravity dams, thin arch dams, and buttress dams. The development of roller-compacted concrete allowed high-quality concrete to be placed with the type of equipment originally developed to move, distribute, and consolidate earthfill. Earthfill and rockfill dams are usually grouped together as embankment dams because they constitute huge mounds of earth and rock that are assembled into imposing man-made embankments.

Additional Information

A dam is a structure built across a stream or river to hold water back. Dams can be used to store water, control flooding, and generate electricity.

A dam is a structure built across a river or stream to hold back water. People have used different materials to build dams over the centuries. Ancient dam builders used natural materials such as rocks or clay. Modern-day dam builders often use concrete.

Manmade dams create artificial lakes called reservoirs. Reservoirs can be used to store water for farming, industry, and household use. They also can be used for fishing, boating, and other leisure activities. People have used dams for many centuries to help prevent flooding.

The ancient Mesopotamians may have been some of the first humans to build dams. The oldest known dam is the Jawa Dam, located in present-day Jordan. It was built in the fourth century B.C.E. Dams provided farmers with a steady source of water to irrigate crops. This allowed ancient Mesopotamians to feed a growing population.

The Romans were master-dam builders too. They used dams to divert water for drinking, bathing, and irrigation. One of the oldest dams still in use is the Cornalvo Dam in Spain. The ancient Romans built it in the first or second century C.E.

The force of flowing water creates mechanical power. People have harnessed this power for centuries with the use of dams. Small dams powered paddle wheels in pre-industrial Europe and America. These were used to help saw logs or grind corn and other grains.

During the Industrial Revolution, engineers began to build bigger dams. These industrial-sized dams could hold back more water to power the big machinery of factories and mines. They also could turn giant turbines to generate electricity.

The early 1900s ushered in an era of “big dam” building in America as demands for electricity increased. During the Great Depression, President Franklin D. Roosevelt put Americans back to work building massive dam projects. The most famous of these is the Hoover Dam.

The Hoover Dam sits on the border between Nevada and Arizona. It was completed in 1936. The Hoover Dam is regarded as an engineering marvel. It was the tallest dam ever built at the time—222 meters (727 feet). The dam helped to control the flow of water on the Colorado River by creating Lake Mead, one of the largest reservoirs in the United States. Lake Mead provides drinking water for the city of Las Vegas.

Dams have long been viewed as a symbol of human ingenuity. However, ecologists who study rivers and lakes have uncovered some environmental downsides to dam construction. Dams change the way rivers function, and in some cases, this can harm local fish populations.

Flooding landscapes to create reservoirs can have consequences for biodiversity as well. Brazilian biologist Raffaello Di Ponzio studies the impact of big dam projects on the plants and animals of the Amazon Rainforest. More than 200 hydroelectric dams have been proposed in Brazil. While these dams could help satisfy growing South American energy demands, they would also flood more than 10 million hectares (25 million acres) of the Amazon Rainforest.

Jai Ganesh · 2023-07-02 00:19:05

1826) Brick

Gist

A brick is a hardened rectangular block of mud, clay etc., used for building.

Summary

The brick, first produced in a sun-dried form at least 6,000 years ago and the forerunner of a wide range of structural clay products used today, is a small building unit in the form of a rectangular block, formed from clay or shale or mixtures and burned (fired) in a kiln, or oven, to produce strength, hardness, and heat resistance. The original concept of ancient brickmakers was that the unit should not be larger than what one man could easily handle; today, brick size varies from country to country, and every nation’s brickmaking industry produces a range of sizes that may run into the hundreds. The majority of bricks for most construction purposes have dimensions of approximately 5.5 × 9.5 × 20 centimetres (21/4 × 33/4 × 8 inches).

Details

A brick is a type of construction material used to build walls, pavements and other elements in masonry construction. Properly, the term brick denotes a unit primarily composed of clay, but is now also used informally to denote units made of other materials or other chemically cured construction blocks. Bricks can be joined using mortar, adhesives or by interlocking. Bricks are usually produced at brickworks in numerous classes, types, materials, and sizes which vary with region, and are produced in bulk quantities.

Block is a similar term referring to a rectangular building unit composed of clay or concrete, but is usually larger than a brick. Lightweight bricks (also called lightweight blocks) are made from expanded clay aggregate.

Fired bricks are one of the longest-lasting and strongest building materials, sometimes referred to as artificial stone, and have been used since circa 4000 BC. Air-dried bricks, also known as mud-bricks, have a history older than fired bricks, and have an additional ingredient of a mechanical binder such as straw.

Bricks are laid in courses and numerous patterns known as bonds, collectively known as brickwork, and may be laid in various kinds of mortar to hold the bricks together to make a durable structure.

History:

Middle East and South Asia

The ancient Jetavanaramaya stupa of Anuradhapura in Sri Lanka is one of the largest brick structures in the world.
The earliest bricks were dried mud-bricks, meaning that they were formed from clay-bearing earth or mud and dried (usually in the sun) until they were strong enough for use. The oldest discovered bricks, originally made from shaped mud and dating before 7500 BC, were found at Tell Aswad, in the upper Tigris region and in southeast Anatolia close to Diyarbakir.

Mud-brick construction was used at Çatalhöyük, from c. 7,400 BC.

Mud-brick structures, dating to c. 7,200 BC have been located in Jericho, Jordan Valley. These structures were made up of the first bricks with dimension 400x150x100 mm.

Between 5000 and 4500 BC, Mesopotamia had discovered fired brick. The standard brick sizes in Mesopotamia followed a general rule: the width of the dried or burned brick would be twice its thickness, and its length would be double its width.

The South Asian inhabitants of Mehrgarh also constructed, air-dried mud-brick structures, between 7000 and 3300 BC. and later the ancient Indus Valley cities of Mohenjo-daro, Harappa, and Mehrgarh. Ceramic, or fired brick was used as early as 3000 BC in early Indus Valley cities like Kalibangan.

In the middle of the third millennium BC, there was a rise in monumental baked brick architecture in Indus cities. Examples included the Great Bath at Mohenjo-daro, the fire altars of Kaalibangan, and the granary of Harappa. There was a uniformity to the brick sizes throughout the Indus Valley region, conforming to the 1:2:4, thickness, width, and length ratio. As the Indus civilization began its decline at the start of the second millennium BC, Harappans migrated east, spreading their knowledge of brickmaking technology. This led to the rise of cities like Pataliputra, Kausambi, and Ujjain, where there was an enormous demand for kiln-made bricks.

By 604 BC, bricks were the construction materials for architectural wonders such as the Hanging Gardens of Babylon, where glazed fired bricks were put into practice.

China

The earliest fired bricks appeared in Neolithic China around 4400 BC at Chengtoushan, a walled settlement of the Daxi culture. These bricks were made of red clay, fired on all sides to above 600 °C, and used as flooring for houses. By the Qujialing period (3300 BC), fired bricks were being used to pave roads and as building foundations at Chengtoushan.

According to Lukas Nickel, the use of ceramic pieces for protecting and decorating floors and walls dates back at various cultural sites to 3000-2000 BC and perhaps even before, but these elements should be rather qualified as tiles. For the longest time builders relied on wood, mud and rammed earth, while fired brick and mud-brick played no structural role in architecture. Proper brick construction, for erecting walls and vaults, finally emerges in the third century BC, when baked bricks of regular shape began to be employed for vaulting underground tombs. Hollow brick tomb chambers rose in popularity as builders were forced to adapt due to a lack of readily available wood or stone. The oldest extant brick building above ground is possibly Songyue Pagoda, dated to 523 AD.

By the end of the third century BCE in China, both hollow and small bricks were available for use in building walls and ceilings. Small fired bricks were first mass-produced during the construction of the tomb of China's first Emperor, Qin Shi Huangdi. The floors of the three pits of the terracotta army were paved with an estimated 230,000 small bricks, with the majority measuring 28x14x7 cm, following a 4:2:1 ratio. Up until the Middle Ages, buildings in Central Asia were typically built with unbaked bricks. It was only starting in the ninth century CE when buildings were entirely constructed using fired bricks.

The carpenter's manual Yingzao Fashi, published in 1103 at the time of the Song dynasty described the brick making process and glazing techniques then in use. Using the 17th-century encyclopaedic text Tiangong Kaiwu, historian Timothy Brook outlined the brick production process of Ming Dynasty China:

...the kilnmaster had to make sure that the temperature inside the kiln stayed at a level that caused the clay to shimmer with the colour of molten gold or silver. He also had to know when to quench the kiln with water so as to produce the surface glaze. To anonymous labourers fell the less skilled stages of brick production: mixing clay and water, driving oxen over the mixture to trample it into a thick paste, scooping the paste into standardised wooden frames (to produce a brick roughly 42 cm long, 20 cm wide, and 10 cm thick), smoothing the surfaces with a wire-strung bow, removing them from the frames, printing the fronts and backs with stamps that indicated where the bricks came from and who made them, loading the kilns with fuel (likelier wood than coal), stacking the bricks in the kiln, removing them to cool while the kilns were still hot, and bundling them into pallets for transportation. It was hot, filthy work.

Europe

Early civilisations around the Mediterranean, including the Ancient Greeks and Romans, adopted the use of fired bricks. By the early first century CE, standardised fired bricks were being heavily produced in Rome. The Roman legions operated mobile kilns, and built large brick structures throughout the Roman Empire, stamping the bricks with the seal of the legion. The Romans used brick for walls, arches, forts, aqueducts, etc. Notable mentions of Roman brick structures are the Herculaneum gate of Pompeii and the baths of Caracalla.

During the Early Middle Ages the use of bricks in construction became popular in Northern Europe, after being introduced there from Northwestern Italy. An independent style of brick architecture, known as brick Gothic (similar to Gothic architecture) flourished in places that lacked indigenous sources of rocks. Examples of this architectural style can be found in modern-day Denmark, Germany, Poland, and Kaliningrad (former East Prussia).

This style evolved into the Brick Renaissance as the stylistic changes associated with the Italian Renaissance spread to northern Europe, leading to the adoption of Renaissance elements into brick building. Identifiable attributes included a low-pitched hipped or flat roof, symmetrical facade, round arch entrances and windows, columns and pilasters, and more.

A clear distinction between the two styles only developed at the transition to Baroque architecture. In Lübeck, for example, Brick Renaissance is clearly recognisable in buildings equipped with terracotta reliefs by the artist Statius von Düren, who was also active at Schwerin (Schwerin Castle) and Wismar (Fürstenhof).

Long-distance bulk transport of bricks and other construction equipment remained prohibitively expensive until the development of modern transportation infrastructure, with the construction of canal, roads, and railways.

Industrial era

In the National Museum of Roman Art in Mérida, Spain (designed by Rafael Moneo and built in the 1980s) the coating of hard-fired clay bricks forms a compression-resistant element together with the fill of non-reinforced concrete.
Production of bricks increased massively with the onset of the Industrial Revolution and the rise in factory building in England. For reasons of speed and economy, bricks were increasingly preferred as building material to stone, even in areas where the stone was readily available. It was at this time in London that bright red brick was chosen for construction to make the buildings more visible in the heavy fog and to help prevent traffic accidents.

The transition from the traditional method of production known as hand-moulding to a mechanised form of mass-production slowly took place during the first half of the nineteenth century. Possibly the first successful brick-making machine was patented by Henry Clayton, employed at the Atlas Works in Middlesex, England, in 1855, and was capable of producing up to 25,000 bricks daily with minimal supervision. His mechanical apparatus soon achieved widespread attention after it was adopted for use by the South Eastern Railway Company for brick-making at their factory near Folkestone. The Bradley & Craven Ltd 'Stiff-Plastic Brickmaking Machine' was patented in 1853, apparently predating Clayton. Bradley & Craven went on to be a dominant manufacturer of brickmaking machinery. Predating both Clayton and Bradley & Craven Ltd. however was the brick making machine patented by Richard A. Ver Valen of Haverstraw, New York, in 1852.

At the end of the 19th century, the Hudson River region of New York State would become the world's largest brick manufacturing region, with 130 brickyards lining the shores of the Hudson River from Mechanicsville to Haverstraw and employing 8,000 people. At its peak, about 1 billion bricks were produced a year, with many being sent to New York City for use in its construction industry.

The demand for high office building construction at the turn of the 20th century led to a much greater use of cast and wrought iron, and later, steel and concrete. The use of brick for skyscraper construction severely limited the size of the building – the Monadnock Building, built in 1896 in Chicago, required exceptionally thick walls to maintain the structural integrity of its 17 storeys.

Following pioneering work in the 1950s at the Swiss Federal Institute of Technology and the Building Research Establishment in Watford, UK, the use of improved masonry for the construction of tall structures up to 18 storeys high was made viable. However, the use of brick has largely remained restricted to small to medium-sized buildings, as steel and concrete remain superior materials for high-rise construction.

Bricks are often made of shale because it easily splits into thin layers.

Uses

Bricks are a versatile building material, able to participate in a wide variety of applications, including:

* Structural walls, exterior and interior walls
* Bearing and non-bearing sound proof partitions
* The fireproofing of structural-steel members in the form of firewalls, party walls, enclosures and fire towers
* Foundations for stucco
* Chimneys and fireplaces
* Porches and terraces
* Outdoor steps, brick walks and paved floors
* Swimming pools

In the United States, bricks have been used for both buildings and pavement. Examples of brick use in buildings can be seen in colonial era buildings and other notable structures around the country. Bricks have been used in paving roads and sidewalks especially during the late 19th century and early 20th century. The introduction of asphalt and concrete reduced the use of brick for paving, but they are still sometimes installed as a method of traffic calming or as a decorative surface in pedestrian precincts. For example, in the early 1900s, most of the streets in the city of Grand Rapids, Michigan, were paved with bricks. Today, there are only about 20 blocks of brick-paved streets remaining (totalling less than 0.5 percent of all the streets in the city limits). Much like in Grand Rapids, municipalities across the United States began replacing brick streets with inexpensive asphalt concrete by the mid-20th century.

In Northwest Europe, bricks have been used in construction for centuries. Until recently, almost all houses were built almost entirely from bricks. Although many houses are now built using a mixture of concrete blocks and other materials, many houses are skinned with a layer of bricks on the outside for aesthetic appeal.

Bricks in the metallurgy and glass industries are often used for lining furnaces, in particular refractory bricks such as silica, magnesia, chamotte and neutral (chromomagnesite) refractory bricks. This type of brick must have good thermal shock resistance, refractoriness under load, high melting point, and satisfactory porosity. There is a large refractory brick industry, especially in the United Kingdom, Japan, the United States, Belgium and the Netherlands.

Engineering bricks are used where strength, low water porosity or acid (flue gas) resistance are needed.

In the UK a red brick university is one founded in the late 19th or early 20th century. The term is used to refer to such institutions collectively to distinguish them from the older Oxbridge institutions, and refers to the use of bricks, as opposed to stone, in their buildings.

Colombian architect Rogelio Salmona was noted for his extensive use of red bricks in his buildings and for using natural shapes like spirals, radial geometry and curves in his designs.

Limitations

Starting in the 20th century, the use of brickwork declined in some areas due to concerns about earthquakes. Earthquakes such as the San Francisco earthquake of 1906 and the 1933 Long Beach earthquake revealed the weaknesses of unreinforced brick masonry in earthquake-prone areas. During seismic events, the mortar cracks and crumbles, so that the bricks are no longer held together. Brick masonry with steel reinforcement, which helps hold the masonry together during earthquakes, has been used to replace unreinforced bricks in many buildings. Retrofitting older unreinforced masonry structures has been mandated in many jurisdictions. However, similar to steel corrosion in reinforced concrete, rebar rusting will compromise the structural integrity of reinforced brick and ultimately limit the expected lifetime, so there is a trade-off between earthquake safety and longevity to a certain extent.

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Jai Ganesh · 2023-07-03 00:16:09

1827) Shopping

Gist

Shopping is the activity of buying things from shops.

Summary

Shopping is the activity of visiting places where goods are sold in order to look at and buy things (such as food, clothing, etc.).

British : the things that are bought at a shop or store.

Details

Shopping is an activity in which a customer browses the available goods or services presented by one or more retailers with the potential intent to purchase a suitable selection of them. A typology of shopper types has been developed by scholars which identifies one group of shoppers as recreational shoppers, that is, those who enjoy shopping and view it as a leisure activity.

Online shopping has become a major disruptor in the retail industry as consumers can now search for product information and place product orders across different regions. Online retailers deliver their products directly to the consumers' home, offices, or wherever they want. The B2C (business to consumer) process has made it easy for consumers to select any product online from a retailer's website and to have it delivered relatively quickly. Using online shopping methods, consumers do not need to consume energy by physically visiting physical stores. This way they save time and the cost of traveling. A retailer or a shop is a business that presents a selection of goods and offers to trade or sell them to customers for money or other goods.

Shoppers' shopping experiences may vary. They are based on a variety of factors including how the customer is treated, convenience, the type of goods being purchased, and mood.

History:

Antiquity

In antiquity, marketplaces and fairs were established to facilitate the exchange of goods and services. People would shop for goods at a regular market in nearby towns. However, the transient nature of stalls and stall-holders meant the consumers needed to make careful inspection of goods prior to purchase. In ancient Greece, the agora served as a marketplace where merchants kept stalls or shops to sell their goods.

Ancient Rome utilized a similar marketplace known as the forum. Rome had two forums; the Forum Romanum and Trajan's Forum. Trajan's Market at Trajan's forum, built around 100-110CE, was a vast expanse, comprising multiple buildings with tabernae that served as retail shops, situated on four levels. The Roman forum was arguably the earliest example of a permanent retail shopfront. In the Roman world, the central market primarily served the local peasantry. Those who lived on the great estates were sufficiently attractive for merchants to call directly at their farm-gates, obviating their need to attend local markets.

Shopping lists are known to have been used by Romans. One such list was discovered near Hadrian's wall dated back to 75–125 CE and written for a soldier.

Middle Ages

Archaeological evidence suggests that the British engaged in minimal shopping in the early Middle Ages. Instead, they provided for their basic needs through subsistence farming practices and a system of localised personal exchanges. However, by the late Middle Ages, consumers turned to markets for the purchase of fresh produce, meat and fish and the periodic fairs where non-perishables and luxury goods could be obtained. Women were responsible for everyday household purchases, but most of their purchasing was of a mundane nature. For the main part, shopping was seen as a chore rather than a pleasure.

Relatively few permanent shops were to be found outside the most populous cities. Instead customers walked into the tradesman's workshops where they discussed purchasing options directly with tradesmen. Itinerant vendors such as costermongers, hucksters and peddlers operated alongside markets, providing the convenience of home delivery to households, and especially to geographically isolated communities.

In the more populous European cities, a small number of shops were beginning to emerge by the 13th century. Specialist retailers such as mercers and haberdashers were known to exist in London, while grocers sold "miscellaneous small wares as well as spices and medicines." However, these shops were primitive. As late as the 16th century, London's shops were described as little more than "rude booths."

The Medieval shopper's experience was very different from that of the contemporary shopper. Interiors were dark and shoppers had relatively few opportunities to inspect the merchandise prior to consumption. Glazed windows in retail environments, were virtually unknown during the medieval period. Goods were rarely out on display; instead retailers kept the merchandise at the rear of the store and would only bring out items on request. The service counter was virtually unknown and instead, many stores had openings onto the street from which they served customers.

In Britain, medieval attitudes to retailing and shopping were negative. Retailers were no better than hucksters, because they simply resold goods, by buying cheaper and selling dearer, without adding value of national accounts. Added to this were concerns about the self-interest of retailers and some of their more unethical practices. Attitudes to spending on luxury goods also attracted criticism, since it involved importing goods which did little to stimulate national accounts, and interfered with the growth of worthy local manufacturers.

Shopping for pleasure

The modern phenomenon of shopping for pleasure is closely linked to the emergence of a middle class in the 17th and 18th-century Europe. As standards of living improved in the 17th century, consumers from a broad range of social backgrounds began to purchase goods that were in excess of basic necessities. An emergent middle class or bourgeosie stimulated demand for luxury goods and began to purchase a wider range of luxury goods and imported goods, including: Indian cotton and calico; silk, tea and porcelain from China, spices from India and South-East Asia and tobacco, sugar, rum and coffee from the New World. The act of shopping came to be seen as a pleasurable pass-time or form of entertainment.

By the 17th-century, produce markets gradually gave way to shops and shopping centres; which changed the consumer's shopping experience. The New Exchange, opened in 1609 by Robert Cecil in the Strand was one such example of a planned shopping centre. Shops started to become important as places for Londoners to meet and socialise and became popular destinations alongside the theatre. Restoration London also saw the growth of luxury buildings as advertisements for social position with speculative architects like Nicholas Barbon and Lionel Cranfield.

Much pamphleteering of the time was devoted to justifying conspicuous consumption and private vice for luxury goods for the greater public good. This then scandalous line of thought caused great controversy with the publication of Bernard Mandeville's influential work Fable of the Bees in 1714, in which he argued that a country's prosperity ultimately lay in the self-interest of the consumer.

These trends gathered momentum in the 18th century, as rising prosperity and social mobility increased the number of people with disposable income for consumption. Important shifts included the marketing of goods for individuals as opposed to items for the household, and the new status of goods as status symbols, related to changes in fashion and desired for aesthetic appeal, as opposed to just their utility. The pottery inventor and entrepreneur, Josiah Wedgewood, pioneered the use of marketing techniques to influence and manipulate the direction of the prevailing tastes. One of his preferred sales techniques was to stage expansive showcases of wares in this private residences or in a rented hall, to which he invited the upper classes.

As the 18th-century progressed, a wide variety of goods and manufactures were steadily made available for the urban middle and upper classes. This growth in consumption led to the rise of 'shopping' - a proliferation of retail shops selling particular goods and the acceptance of shopping as a cultural activity in its own right. Specific streets and districts became devoted to retail, including the Strand and Piccadilly in London.

The rise of window shopping as a recreational activity accompanied the use of glass windows in retail shop-fronts. By the late eighteenth century, grand shopping arcades began to emerge across Britain, Europe and in the Antipodes in what became known as the "arcade era." Typically, these arcades had a roof constructed of glass to allow for natural light and to reduce the need for candles or electric lighting. Inside the arcade, individual stores were fitted with long glass exterior windows which allowed the emerging middle-classes to window shop and indulge in fantasies, even when they may not have been able to afford the high retail prices.

Designed to attract the genteel middle class, retailers sold luxury goods at relatively high prices. However, prices were never a deterrent, as these new arcades came to be the place to shop and to be seen. Arcades offered shoppers the promise of an enclosed space away from the chaos of daily street life; a place shoppers could socialise and spend their leisure time. As thousands of glass covered arcades spread across Europe, they became grander and more ornately decorated. By the mid nineteenth century, promenading in these arcades became a popular pass-time for the emerging middle classes.

In Europe, the Palais-Royal, which opened in 1784, became one of the earliest examples of the new style of shopping arcade, frequented by both the aristocracy and the middle classes. It developed a reputation as being a site of sophisticated conversation, revolving around the salons, cafés, and bookshops, but also became a place frequented by off-duty soldiers and was a favourite haunt of prostitutes, many of whom rented apartments in the building. In London, one of the first to use display windows in shops was retailer, Francis Place, who experimented with this new retailing method at his tailoring establishment in Charing Cross, where he fitted the shop-front with large plate glass windows. Although this was condemned by many, he defended his practice in his memoirs, claiming that he:

sold from the window more goods...than paid journeymen's wages and the expenses of housekeeping.

Retailers designed attractive shop fronts to entice patronage, using bright lights, advertisements and attractively arranged goods. The goods on offer were in a constant state of change, due to the frenetic change in fashions. A foreign visitor commented that London was "a world of gold and silver plate, then pearls and gems shedding their dazzling lustre, home manufactures of the most exquisite taste, an ocean of rings, watches, chains, bracelets, perfumes, ready-dresses, ribbons, lace, bonnets, and fruits from all the zones of the habitable world".

Evolution of stores: from arcades to department stores

In the second half of the 19th-century, shops transitioned from 'single-function' shops selling one type of good, to the department store where a large variety of goods were sold. As economic growth, fueled by the Industrial Revolution at the turn of the 19th-century, steadily expanded, the affluent bourgeois middle-class grew in size and wealth. This urbanized social group was the catalyst for the emergence of the retail revolution of the period.

The term, "department store" originated in the United States. In 19th century England, these stores were known as emporia or warehouse shops. A number of major department stores opened across the US, Britain and Europe from the mid nineteenth century including; Harrod's of London in 1834; Kendall's in Manchester in 1836; Selfridges of London in 1909; Macy's of New York in 1858; Bloomingdale's in 1861; Sak's in 1867; J.C. Penney in 1902; Le Bon Marché of France in 1852 and Galeries Lafayette of France in 1905.

The first reliably dated department store to be established, was Harding, Howell & Co, which opened in 1796 on Pall Mall, London. This venture was described as being a public retail establishment offering a wide range of consumer goods in different departments. This pioneering shop was closed down in 1820 when the business partnership was dissolved. Department stores were established on a large scale from the 1840s and 50s, in France, the United Kingdom and the US. French retailer, Le Bon Marche, is an example of a department store that has survived into current times Originally founded in 1838 as a lace and haberdashery store, it was revamped mid-century and opened as a department store in 1852.

Many of the early department stores were more than just a retail emporium; rather they were venues where shoppers could spend their leisure time and be entertained. Some department stores offered reading rooms, art galleries and concerts. Most department stores had tea-rooms or dining rooms and offered treatment areas where ladies could indulge in a manicure. The fashion show, which originated in the US in around 1907, became a staple feature event for many department stores and celebrity appearances were also used to great effect. Themed events featured wares from foreign shores, exposing shoppers to the exotic cultures of the Orient and Middle-East.

Shopping venues:

Shopping hubs

A larger commercial zone can be found in many cities, more formally called a central business district, but more commonly called "downtown" in the United States, or the "high street" in Britain, and souks in Arabic speaking areas.

Shopping hubs, or shopping centers, are collections of stores; that is a grouping of several businesses in a compact geographic area. It consists of a collection of retail, entertainment and service stores designed to serve products and services to the surrounding region.

Typical examples include shopping malls, town squares, flea markets and bazaars.

Traditionally, shopping hubs were called bazaars or marketplaces; an assortment of stalls lining streets selling a large variety of goods.

The modern shopping centre is now different from its antecedents, the stores are commonly in individual buildings or compressed into one large structure (usually called Mall in the USA).

The first modern shopping mall in the US was The Country Club Plaza in Kansas City which opened in 1922, from there the first enclosed mall was designed by Victor Gruen and opened in 1956 as Southdale Centre in Edina, Minnesota, a suburb of Minneapolis.

Malls peaked in America in the 1980s-1990s when many larger malls (more than 37,000 sq m in size) were built, attracting consumers from within a 32 km radius with their luxurious department stores.

Different types of malls can be found around the world. Superregional malls are very large malls that contain at least five department stores and 300 shops. This type of mall attracts consumers from a broad radius (up to a 160-km). A regional mall can contain at least two department stores or "anchor stores". One of the biggest malls in the world is the one near Miami, called "Sawgrass Mills Mall": it has 2,370,610 square feet (220,237 sq meters) of retail selling space, with over 329 retail outlets and name brand discounters.

The smaller malls are often called open-air strip centres or mini-marts and are typically attached to a grocery store or supermarket.

The smaller malls are less likely to include the same features of a large mall such as an indoor concourse, but are beginning to evolve to become enclosed to comply with all weather and customer preferences.

Stores

Stores are divided into multiple categories of stores which sell a selected set of goods or services. Usually they are tiered by target demographics based on the disposable income of the shopper. They can be tiered from cheap to pricey.

Some shops sell secondhand goods. Often the public can also sell goods to such shops. In other cases, especially in the case of a nonprofit shop, the public donates goods to these shops, commonly known as thrift stores in the United States, charity shops in the United Kingdom, or op shops in Australia and New Zealand. In give-away shops goods can be taken for free. In antique shops, the public can find goods that are older and harder to find. Sometimes people are broke and borrow money from a pawn shop using an item of value as collateral. College students are known to resell books back through college textbook bookstores. Old used items are often distributed through surplus stores.

Various types of retail stores that specialize in the selling of goods related to a theme include bookstores, boutiques, candy shops, liquor stores, gift shops, hardware stores, hobby stores, pet stores, pharmacies, gender shops and supermarkets.

Other stores such as big-box stores, hypermarkets, convenience stores, department stores, general stores, dollar stores sell a wider variety of products not horizontally related to each other.

Home shopping

Home mail delivery systems and modern technology (such as television, telephones, and the Internet), in combination with electronic commerce, allow consumers to shop from home. There are three main types of home shopping: mail or telephone ordering from catalogs; telephone ordering in response to advertisements in print and electronic media (such as periodicals, TV and radio); and online shopping. Online shopping has completely redefined the way people make their buying decisions; the Internet provides access to a lot of information about a particular product, which can be looked at, evaluated, and comparison-priced at any given time. Online shopping allows the buyer to save the time and expense, which would have been spent traveling to the store or mall. According to technology and research firm Forrester, mobile purchases or mcommerce will account for 49% of ecommerce, or $252 billion in sales, by 2020.

Neighborhood shopping

Convenience stores are common in North America, and are often called "bodegas" in Spanish-speaking communities or "dépanneurs" in French-speaking ones. Sometimes peddlers and ice cream trucks pass through neighborhoods offering goods and services. Also, garage sales are a common form of second hand resale.

Neighbourhood shopping areas and retailers give value to a community by providing various social and community services (like a library), and a social place to meet. Neighbourhood retailing differs from other types of retailers such as destination retailers because of the difference in offered products and services, location and popularity. Neighbourhood retailers include stores such as; Food shops/marts, dairies, Pharmacies, Dry cleaners, Hairdressers/barbers, Bottle shops, Cafés and take-away shops . Destination retailers include stores such as; Gift shops, Antique shops, Pet groomers, Engravers, Tattoo parlour, Bicycle shops, Herbal dispensary clinics, Art galleries, Office Supplies and framers. The neighbourhood retailers sell essential goods and services to the residential area they are located in. There can be many groups of neighbourhood retailers in different areas of a region or city, but destination retailers are often part of shopping malls where the numbers of consumers is higher than that of a neighbourhood retail area. The destination retailers are becoming more prevalent as they can provide a community with more than the essentials, they offer an experience, and a wider scope of goods and services.

Party shopping

The party plan is a method of marketing products by hosting a social event, using the event to display and demonstrate the product or products to those gathered, and then to take orders for the products before the gathering ends.

Shopping frenzies are periods of time where a burst of spending occurs, typically near holidays in the United States, with Christmas shopping being the biggest shopping spending season, starting as early as October and continuing until after Christmas.

Some religions regard such spending seasons as being against their faith and dismiss the practice. Many contest the over-commercialization and the response by stores that downplay the shopping season often cited in the War on Christmas.

The National Retail Federation (NRF) also highlights the importance of back-to-school shopping for retailers which comes second behind holiday shopping, when buyers often buy clothing and school supplies for their children. In 2017, Americans spent over $83 billion on back-to-school and back-to-college shopping, according to the NRF annual survey.

Seasonal shopping consists of buying the appropriate clothing for the particular season. In winter people bundle up in warm layers and coats to keep warm, while in summer people wear less clothing to stay cooler in the heat. Seasonal shopping now revolves a lot around holiday sales and buying more for less. Stores need to get rid of all of their previous seasonal clothing to make room for the new trends of the upcoming season. The end-of-season sales usually last a few weeks with prices lowering further towards the closing of the sale. During sales items can be discounted from 10% up to as much as 50%, with the biggest reduction sales occurring at the end of the season. Holiday shopping periods are extending their sales further and further with holidays such as Black Friday becoming a month-long event stretching promotions across November . These days shopping doesn't stop once the mall closes, as people have more access to stores and their sales than ever before with the help of the internet and apps. Today many people research their purchases online to find the cheapest and best deal with one third of all shopping searches on Google happen between 10:00 pm and 4:00 am. Shoppers are now spending more time consulting different sources before making a final purchasing decision. Shoppers once used an average of five sources for information before making a purchase, but numbers have risen to as high as 12 sources in 2014.

Spree shopping

Spree shopping, or ‘going on a shopping spree’, is an individual period of intense and indulgent shopping involving many purchases, which differs from both normal shopping and compulsive shopping in its scope and purpose. One study reportedly showed that the pleasure centers of the brain were stimulated during a shopping spree similarly to the stimulation experienced during sexual activity. A shopping spree may be "especially problematic for those whose immediate release of tension is followed by subsequent feelings of guilt, sadness, anger, or despair over what turned out to be an unwanted purchase".

Pricing and negotiation

Historically, prices were established through a system of barter or negotiation. The first retailer to adopt fixed prices is thought to be the retailers operating out of the Palais-Royal complex in the 18th-century. These retailers adopted a system of high price maintenance in order to cultivate images of luxury. For their upper class clientele, fixed prices spared them from hassle of bartering.

The pricing technique used by most retailers is cost-plus pricing. This involves adding a markup amount (or percentage) to the retailers' cost. Another common technique is manufacturers suggested list pricing. This simply involves charging the amount suggested by the manufacturer and usually printed on the product by the manufacturer.

In retail settings, psychological pricing or odd-number pricing are both widely used. Psychological pricing which refers to a range of tactics, designed to have a positive psychological impact. For example, price tags using the terminal digit "9" (e.g., 9.99, 19.99, or 199.99) can be used to signal price points and bring an item in at just under the consumer's reservation price. However, in Chinese societies, prices are generally either a round number or sometimes some lucky number. This creates price points.

In a fixed-price system, consumers may still use bargaining or haggling; a negotiation about the price. Economists see this as determining how the transaction's total economic surplus will be divided between consumers and producers. Neither party has a clear advantage because the threat of no sale exists, in which case the surplus would vanish for both.

When shopping online, it can be more difficult to negotiate price given that you are not directly interacting with a sales person. Some consumers use price comparison services to locate the best price and/or to make a decision about who or where to buy from to save money.

"Window shopping"

"Window shopping" is a term referring to the browsing of goods by a consumer with or without the intent to purchase. Window shopping is often practised by a particular segment, known as the recreation-conscious or hedonistic shopper. Recreational shopping is characterised by the consumer's engagement in the purchase process, and recreational shoppers are those consumers who see the act of shopping as a form of enjoyment. Other consumers use window shopping as part of their planning activity for a later purchase.

Showrooming, the practice of examining merchandise in a traditional retail store without purchasing it, but then shopping online to find a lower price for the same item, has become an increasingly prevalent problem for traditional retailers as a result of online competitors, so much so that some have begun to take measures to combat it.

Utility cycling

In countries like Denmark, the Netherlands and Germany the high levels of utility cycling also includes shopping trips e.g. 9% of all shopping trips in Germany are by bicycle.

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Jai Ganesh · 2023-07-04 00:12:44

1828) Lateral Thinking

Gist

Lateral thinking is a manner of solving problems using an indirect and creative approach via reasoning that is not immediately obvious. It involves ideas that may not be obtainable using only traditional step-by-step logic.

Summary:

What is lateral thinking?

It essentially means being able to think creatively or "outside the box" in order to solve a problem.

Usually, logical thinking is used to solve problems in a direct, straightforward way (also known as vertical thinking). Lateral thinking however, looks at things from a sideways perspective (also known as horizontal thinking), in order to find answers that aren't immediately apparent.

The term was first coined by psychologist Edward de Bono. These skills are often required in creative careers like marketing or advertising.

If you study graphic or art and design at school, there's a good chance that you will have developed some of these skills already, which can be useful in your future career.

Examples of lateral thinking interview questions

These questions are particularly popular with job interviewers. Not only do they test your ability to think creatively, but they can also reveal your problem solving skills as well. If you're someone who enjoys playing puzzles or working out brain teasers, then you may already be good at answering these types of interview questions.

This type of interview question can sometimes be difficult to identify. If you're ever asked a question in an interview that seems a bit odd, or perhaps doesn't make sense upon first hearing, there's a chance it could be a lateral thinking question. The University of Kent has a great resource that provides a list of these types of questions. Here are some examples of lateral thinking based questions:

Name an ancient invention still in use in most parts of the world today that allows people to see through walls. Answer: The window.

An Australian woman was born in 1948 but only celebrated her 16th birthday quite recently. Why? Answer: She was born on February the 29th.

Or you may simply be asked: Can you give us an example of a difficult situation where you had to think laterally to get out of it?

This question is actually more difficult that it might seem. A good place to start could be to think of a time when you did something creative and came across a problem, then explain how you resolved it by using some sideways thinking.

How to improve your lateral thinking skills

Improving these skills can be challenging as lateral thinking comes more naturally to some people than others.

However, like everything else, practice makes perfect, and setting yourself lateral thinking examples can help.

Because this type of skill is "situational" and displays a thought process rather than something physical (like IT skills for example), it can be tough to come up with ways of boosting your ability.

Here are some exercises you could try:

Mind mapping

Mind maps can be a great way of solving a problem when logical thinking just doesn't help. Because mind maps are visual aids, they require your brain to adjust its thought processes, which can often help you find answers unexpectedly. Mind maps give you the opportunity to put all your ideas down on paper and then take a step back to gather your thoughts.

Using your senses

We all have five senses – sight, touch, hearing, smell and taste – yet we very rarely use all of them to solve problems. Typically, you use our visual senses to work things out but making use of our other senses can sometimes have useful results.

For example, when faced with a problem, why not speak your thoughts aloud and record them on your mobile phone? When you listen back, you may find something that you would have missed otherwise.

Reverse thinking

Reverse thinking involves analysing what people normally do in a situation and then doing the opposite. If you find yourself only getting so far into a problem and them becoming stuck, you might want to start at the end and work backwards. For example, look at the problem and then describe what you'd ideally like the solution to be. From there, you can begin working backwards to find the starting point to your solution.

What careers use lateral thinking?

Lateral thinking is a useful skill whatever job you end up doing, but there are some career paths where it can really come in handy. Here are some examples of lateral thinking career choices:

Advertising

People who work in advertising use this type of thinking to persuade us to buy products. If it's often those adverts that make us think or a little different that we remember the most.

Marketing

Marketers often have to come up with novel or creative ways to promote products and services. Although there are some rules in marketing, it's often the campaigns that bend the rules slightly that are successful.

Media

Working in the media, you may have to use these thinking skills to deliver a message in a creative way. Whether you're a journalist, filmmaker or press release writer, some sideways thinking can come in handy.

Hopefully all those examples of lateral thinking have helped you to understand what it's all about and why it could be useful in your career. Now it's time to check out those other employability skills you need to make it in the world of work.

Details

Lateral thinking is a manner of solving problems using an indirect and creative approach via reasoning that is not immediately obvious. It involves ideas that may not be obtainable using only traditional step-by-step logic. The term was first used in 1967 by Maltese psychologist Edward de Bono in his book The Use of Lateral Thinking. De Bono cites the Judgment of Solomon as an example of lateral thinking, where King Solomon resolves a dispute over the parentage of a child by calling for the child to be cut in half, and making his judgment according to the reactions that this order receives. Edward de Bono also links lateral thinking with humour, arguing it entails a switch-over from a familiar pattern to a new, unexpected one. It is this moment of surprise, generating laughter and new insight, which facilitates the ability to see a different thought pattern which initially was not obvious. According to de Bono, lateral thinking deliberately distances itself from the standard perception of creativity as "vertical" logic, the classic method for problem solving.

Critics have characterized lateral thinking as a pseudo-scientific concept, arguing de Bono's core ideas have never been rigorously tested or corroborated.

Methods

Lateral thinking has to be distinguished from critical thinking. Critical thinking is primarily concerned with judging the true value of statements and seeking errors whereas lateral thinking focuses more on the "movement value" of statements and ideas. A person uses lateral thinking to move from one known idea to new ideas. Edward de Bono defines four types of thinking tools:

* idea-generating tools intended to break current thinking patterns—routine patterns, the status quo
* focus tools intended to broaden where to search for new ideas
* harvest tools intended to ensure more value is received from idea generating output
* treatment tools that promote consideration of real-world constraints, resources, and support

Random entry idea generation

The thinker chooses an object at random, or a noun from a dictionary and associates it with the area they are thinking about. De Bono exemplifies this through the randomly-chosen word, "nose", being applied to an office photocopier, leading to the idea that the copier could produce a lavender smell when it was low on paper.

Provocation idea generation

A provocation is a statement that we know is wrong or impossible but used to create new ideas. De Bono gives an example of considering river pollution and setting up the provocation, "the factory is downstream of itself", causing a factory to be forced to take its water input from a point downstream of its output, an idea which later became law in some countries. Provocations can be set up by the use of any of the provocation techniques—wishful thinking, exaggeration, reversal, escape, distortion, or arising. The thinker creates a list of provocations and then uses the most outlandish ones to move their thinking forward to new ideas.

Movement techniques

The purpose of movement techniques is to produce as many alternatives as possible in order to encourage new ways of thinking about both problems and solutions. The production of alternatives tends to produce many possible solutions to problems that seemed to only have one possible solution. One can move from a provocation to a new idea through the following methods: extract a principle, focus on the difference, moment to moment, positive aspects or special circumstances.

Challenge

A tool which is designed to ask the question, "Why?", in a non-threatening way: why something exists or why it is done the way it is. The result is a very clear understanding of "Why?", which naturally leads to new ideas. The goal is to be able to challenge anything at all, not those that are problematic. For example, one could challenge the handles on coffee cups: The reason for the handle seems to be that the cup is often too hot to hold directly; perhaps coffee cups could be made with insulated finger grips, or there could be separate coffee-cup holders similar to beer holders, or coffee shouldn't be so hot in the first place.

Concept formation

Ideas carry out concepts. This tool systematically expands the range and number of concepts in order to end up with a very broad range of ideas to consider.

Disproving

Based on the idea that the majority is always wrong (as suggested by Henrik Ibsen and by John Kenneth Galbraith), take anything that is obvious and generally accepted as "goes without saying", question it, take an opposite view, and try to convincingly disprove it. This technique is similar to de Bono's "Black Hat" of Six Thinking Hats, which looks at identifying reasons to be cautious and conservative.

Fractionation

The purpose of fractionation is to create alternative perceptions of problems and solutions by taking the commonplace view of the situation and break it into multiple alternative situations in order to break away from the fixed view and see the situation from different angles, thus being able to generate multiple possible solutions that can be synthesized into more comprehensive answers.

When something creates a problem, the performance or the status quo of the situation drops. Problem-solving deals with finding out what caused the problem and then figuring out ways to fix the problem. The objective is to get the situation to where it should be. For example, a production line has an established run rate of 1000 items per hour. Suddenly, the run rate drops to 800 items per hour. Ideas as to why this happened and solutions to repair the production line must be thought of, such as giving the worker a pay raise. A study on engineering students' abilities to answer very open-ended questions suggests that students showing more lateral thinking were able to solve the problems much quicker and more accurately.

Lateral problem "solving"

Lateral thinking will often produce solutions whereby the problem appears as "obvious" in hindsight. That lateral thinking will often lead to problems that you never knew you had, or it will solve simple problems that have a huge potential. For example, if a production line produced 1000 books per hour, lateral thinking may suggest that a drop in output to 800 would lead to higher quality, and more motivated workers. Students have shown lateral thinking in their application of a variety of individual, unique concepts in order to solve complex problems.

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