Miscellany

Jai Ganesh · 2025-01-18 17:10:03

2326) Formula/Formulae

Gist

Other form: formulas.

A formula is generally a fixed pattern that is used to achieve consistent results. It might be made up of words, numbers, or ideas that work together to define a procedure to be followed for the desired outcome.

Formulas, the patterns we follow in life, are used everywhere. In math or science, a formula might express a numeric or chemical equation; in cooking, a recipe is a formula. Baby formula is made up of the nutrients necessary for maintaining healthy growth, and the right formula for a fuel mixture is critical for a racing car's best performance. Everyone has their favorite formula for success. J. Paul Getty once gave his as "rise early, work hard, strike oil."

Summary

A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name since it does not contain any words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulae can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than chemical names and structural formulae.

The simplest types of chemical formulae are called empirical formulae, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulae indicate the simple numbers of each type of atom in a molecule, with no information on structure. For example, the empirical formula for glucose is CH2O (twice as many hydrogen atoms as carbon and oxygen), while its molecular formula is C6H12O6 (12 hydrogen atoms, six carbon and oxygen atoms).

Sometimes a chemical formula is complicated by being written as a condensed formula (or condensed molecular formula, occasionally called a "semi-structural formula"), which conveys additional information about the particular ways in which the atoms are chemically bonded together, either in covalent bonds, ionic bonds, or various combinations of these types. This is possible if the relevant bonding is easy to show in one dimension. An example is the condensed molecular/chemical formula for ethanol, which is CH3−CH2−OH or CH3CH2OH. However, even a condensed chemical formula is necessarily limited in its ability to show complex bonding relationships between atoms, especially atoms that have bonds to four or more different substituents.

Since a chemical formula must be expressed as a single line of chemical element symbols, it often cannot be as informative as a true structural formula, which is a graphical representation of the spatial relationship between atoms in chemical compounds (see for example the figure for butane structural and chemical formulae, at right). For reasons of structural complexity, a single condensed chemical formula (or semi-structural formula) may correspond to different molecules, known as isomers. For example, glucose shares its molecular formula C6H12O6 with a number of other sugars, including fructose, galactose and mannose. Linear equivalent chemical names exist that can and do specify uniquely any complex structural formula (see chemical nomenclature), but such names must use many terms (words), rather than the simple element symbols, numbers, and simple typographical symbols that define a chemical formula.

Chemical formulae may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. While, as noted, chemical formulae do not have the full power of structural formulae to show chemical relationships between atoms, they are sufficient to keep track of numbers of atoms and numbers of electrical charges in chemical reactions, thus balancing chemical equations so that these equations can be used in chemical problems involving conservation of atoms, and conservation of electric charge.

Details

In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a chemical formula. The informal use of the term formula in science refers to the general construct of a relationship between given quantities.

The plural of formula can be either formulas (from the most common English plural noun form) or, under the influence of scientific Latin, formulae (from the original Latin).

In mathematics

In mathematics, a formula generally refers to an equation or inequality relating one mathematical expression to another, with the most important ones being mathematical theorems. For example, determining the volume of a sphere requires a significant amount of integral calculus or its geometrical analogue, the method of exhaustion. However, having done this once in terms of some parameter (the radius for example), mathematicians have produced a formula to describe the volume of a sphere in terms of its radius:

.

Having obtained this result, the volume of any sphere can be computed as long as its radius is known. Here, notice that the volume V and the radius r are expressed as single letters instead of words or phrases. This convention, while less important in a relatively simple formula, means that mathematicians can more quickly manipulate formulas which are larger and more complex. Mathematical formulas are often algebraic, analytical or in closed form.

In a general context, formulas often represent mathematical models of real world phenomena, and as such can be used to provide solutions (or approximate solutions) to real world problems, with some being more general than others. For example, the formula

is an expression of Newton's second law, and is applicable to a wide range of physical situations. Other formulas, such as the use of the equation of a sine curve to model the movement of the tides in a bay, may be created to solve a particular problem. In all cases, however, formulas form the basis for calculations.

Expressions are distinct from formulas in the sense that they don't usually contain relations like equality (=) or inequality (<). Expressions denote a mathematical object, where as formulas denote a statement about mathematical objects. This is analogous to natural language, where a noun phrase refers to an object, and a whole sentence refers to a fact. For example,

is an expression, while
is a formula.

However, in some areas mathematics, and in particular in computer algebra, formulas are viewed as expressions that can be evaluated to true or false, depending on the values that are given to the variables occurring in the expressions. For example

takes the value false if x is given a value less than 1, and the value true otherwise.

In mathematical logic

In mathematical logic, a formula (often referred to as a well-formed formula) is an entity constructed using the symbols and formation rules of a given logical language.[8] For example, in first-order logic,

is a formula, provided that f is a unary function symbol, P a unary predicate symbol, and Q a ternary predicate symbol.

Chemical formulas

In modern chemistry, a chemical formula is a way of expressing information about the proportions of atoms that constitute a particular chemical compound, using a single line of chemical element symbols, numbers, and sometimes other symbols, such as parentheses, brackets, and plus (+) and minus (−) signs. For example, H2O is the chemical formula for water, specifying that each molecule consists of two hydrogen (H) atoms and one oxygen (O) atom. Similarly, O−3 denotes an ozone molecule consisting of three oxygen atoms and a net negative charge.

The structural formula for butane. There are three common non-pictorial types of chemical formulas for this molecule:
* the empirical formula C2H5
* the molecular formula C4H10 and
* the condensed formula (or semi-structural formula) CH3CH2CH2CH3.

A chemical formula identifies each constituent element by its chemical symbol, and indicates the proportionate number of atoms of each element.

In empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound—as ratios to the key element. For molecular compounds, these ratio numbers can always be expressed as whole numbers. For example, the empirical formula of ethanol may be written C2H6O, because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of ionic compounds, however, cannot be written as empirical formulas which contains only the whole numbers. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio, with n ranging from over 4 to more than 6.5.

When the chemical compound of the formula consists of simple molecules, chemical formulas often employ ways to suggest the structure of the molecule. There are several types of these formulas, including molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the molecular formula for glucose is C6H12O6 rather than the glucose empirical formula, which is CH2O. Except for the very simple substances, molecular chemical formulas generally lack needed structural information, and might even be ambiguous in occasions.

A structural formula is a drawing that shows the location of each atom, and which atoms it binds to.

In computing

In computing, a formula typically describes a calculation, such as addition, to be performed on one or more variables. A formula is often implicitly provided in the form of a computer instruction such as.

Degrees Celsius = (5/9)*(Degrees Fahrenheit - 32)

In computer spreadsheet software, a formula indicating how to compute the value of a cell, say A3, could be written as
=A1+A2
where A1 and A2 refer to other cells (column A, row 1 or 2) within the spreadsheet. This is a shortcut for the "paper" form A3 = A1+A2, where A3 is, by convention, omitted because the result is always stored in the cell itself, making the stating of the name redundant.

Units

Formulas used in science almost always require a choice of units. Formulas are used to express relationships between various quantities, such as temperature, mass, or charge in physics; supply, profit, or demand in economics; or a wide range of other quantities in other disciplines.

An example of a formula used in science is Boltzmann's entropy formula. In statistical thermodynamics, it is a probability equation relating the entropy S of an ideal gas to the quantity W, which is the number of microstates corresponding to a given macrostate:

where k is the Boltzmann constant, equal to , and W is the number of microstates consistent with the given macrostate.

eyJidWNrZXQiOiJjb250ZW50Lmhzd3N0YXRpYy5jb20iLCJrZXkiOiJnaWZcL2Rpc3RhbmNlLWZvcm11bGEuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo4Mjh9LCJ0b0Zvcm1hdCI6ImF2aWYifX0=

Jai Ganesh · 2025-01-19 00:05:18

2327) Continent

Gist

A continent is one of Earth's seven main divisions of land. The continents are, from largest to smallest: Asia, Africa, North America, South America, Antarctica, Europe, and Australia. When geographers identify a continent, they usually include all the islands associated with it.

A continent is a large continuous mass of land conventionally regarded as a collective region. There are seven continents: Asia, Africa, North America, South America, Antarctica, Europe, and Australia (listed from largest to smallest in size). Sometimes Europe and Asia are considered one continent called Eurasia.

Summary

A Continent is one of the larger continuous masses of land, namely, Asia, Africa, North America, South America, Antarctica, Europe, and Australia, listed in order of size. (Europe and Asia are sometimes considered a single continent, Eurasia.)

There is great variation in the sizes of continents; Asia is more than five times as large as Australia. The largest island in the world, Greenland, is only about one-fourth the size of Australia. The continents differ sharply in their degree of compactness. Africa has the most regular coastline and, consequently, the lowest ratio of coastline to total area. Europe is the most irregular and indented and has by far the highest ratio of coastline to total area.

The continents are not distributed evenly over the surface of the globe. If a hemisphere map centred in northwestern Europe is drawn, most of the world’s land area can be seen to lie within that hemisphere. More than two-thirds of the Earth’s land surface lies north of the Equator, and all the continents except Antarctica are wedge shaped, wider in the north than they are in the south.

The distribution of the continental platforms and ocean basins on the surface of the globe and the distribution of the major landform features have long been among the most intriguing problems for scientific investigation and theorizing. Among the many hypotheses that have been offered as explanation are: (1) the tetrahedral (four-faced) theory, in which a cooling earth assumes the shape of a tetrahedron by spherical collapse; (2) the accretion theory, in which younger rocks attached to older shield areas became buckled to form the landforms; (3) the continental-drift theory, in which an ancient floating continent drifted apart; and (4) the convection-current theory, in which convection currents in the Earth’s interior dragged the crust to cause folding and mountain making.

Geological and seismological evidence accumulated in the 20th century indicates that the continental platforms do “float” on a crust of heavier material that forms a layer completely enveloping the Earth. Each continent has one of the so-called shield areas that formed 2 billion to 4 billion years ago and is the core of the continent to which the remainder (most of the continent) has been added. Even the rocks of the extremely old shield areas are older in the centre and younger toward the margins, indicating that this process of accumulation started early. In North America the whole northeast quarter of the continent, called the Canadian, or Laurentian, Shield, is characterized by the ancient rocks of what might be called the original continent. In Europe the shield area underlies the eastern Scandinavian peninsula and Finland. The Guiana Highlands of South America are the core of that continent. Much of eastern Siberia is underlain by the ancient rocks, as are western Australia and southern Africa.

Details

A continent is any of several large geographical regions. Continents are generally identified by convention rather than any strict criteria. A continent could be a single landmass or a part of a very large landmass, as in the case of Asia or Europe. Due to this, the number of continents varies; up to seven or as few as four geographical regions are commonly regarded as continents. Most English-speaking countries recognize seven regions as continents. In order from largest to smallest in area, these seven regions are Asia, Africa, North America, South America, Antarctica, Europe, and Australia. Different variations with fewer continents merge some of these regions; examples of this are merging Asia and Europe into Eurasia, North America and South America into America, and Africa, Asia, and Europe into Afro-Eurasia.

Oceanic islands are occasionally grouped with a nearby continent to divide all the world's land into geographical regions. Under this scheme, most of the island countries and territories in the Pacific Ocean are grouped together with the continent of Australia to form the geographical region of Oceania.

In geology, a continent is defined as "one of Earth's major landmasses, including both dry land and continental shelves". The geological continents correspond to seven large areas of continental crust that are found on the tectonic plates, but exclude small continental fragments such as Madagascar that are generally referred to as microcontinents. Continental crust is only known to exist on Earth.

The idea of continental drift gained recognition in the 20th century. It postulates that the current continents formed from the breaking up of a supercontinent (Pangaea) that formed hundreds of millions of years ago.

Etymology

From the 16th century the English noun continent was derived from the term continent land, meaning continuous or connected land[5] and translated from the Latin terra continens. The noun was used to mean "a connected or continuous tract of land" or mainland. It was not applied only to very large areas of land—in the 17th century, references were made to the continents (or mainlands) of the Isle of Man, Ireland and Wales and in 1745 to Sumatra. The word continent was used in translating Greek and Latin writings about the three "parts" of the world, although in the original languages no word of exactly the same meaning as continent was used.

While continent was used on the one hand for relatively small areas of continuous land, on the other hand geographers again raised Herodotus's query about why a single large landmass should be divided into separate continents. In the mid-17th century, Peter Heylin wrote in his Cosmographie that "A Continent is a great quantity of Land, not separated by any Sea from the rest of the World, as the whole Continent of Europe, Asia, Africa." In 1727, Ephraim Chambers wrote in his Cyclopædia, "The world is ordinarily divided into two grand continents: the Old and the New." And in his 1752 atlas, Emanuel Bowen defined a continent as "a large space of dry land comprehending many countries all joined together, without any separation by water. Thus Europe, Asia, and Africa is one great continent, as America is another."[8] However, the old idea of Europe, Asia and Africa as "parts" of the world ultimately persisted with these being regarded as separate continents.

Definitions and application

By convention, continents "are understood to be large, continuous, discrete masses of land, ideally separated by expanses of water". By this definition, all continents have to be an island of some metric. In modern schemes with five or more recognized continents, at least one pair of continents is joined by land in some fashion. The criterion "large" leads to arbitrary classification: Greenland, with a surface area of 2,166,086 square kilometres (836,330 sq mi), is only considered the world's largest island, while Australia, at 7,617,930 square kilometres (2,941,300 sq mi), is deemed the smallest continent.

Earth's major landmasses all have coasts on a single, continuous World Ocean, which is divided into several principal oceanic components by the continents and various geographic criteria.

The geological definition of a continent has four criteria: high elevation relative to the ocean floor; a wide range of igneous, metamorphic and sedimentary rocks rich in silica; a crust thicker than the surrounding oceanic crust; and well-defined limits around a large enough area.

Extent

The most restricted meaning of continent is that of a continuous area of land or mainland, with the coastline and any land boundaries forming the edge of the continent. In this sense, the term continental Europe (sometimes referred to in Britain as "the Continent") is used to refer to mainland Europe, excluding islands such as Great Britain, Iceland, Ireland, and Malta, while the term continent of Australia may refer to the mainland of Australia, excluding New Guinea, Tasmania, and other nearby islands. Similarly, the continental United States refers to "the 49 States (including Alaska but excluding Hawaii) located on the continent of North America, and the District of Columbia."

From the perspective of geology or physical geography, continent may be extended beyond the confines of continuous dry land to include the shallow, submerged adjacent area (the continental shelf) and the islands on the shelf (continental islands), as they are structurally part of the continent.

From this perspective, the edge of the continental shelf is the true edge of the continent, as shorelines vary with changes in sea level. In this sense the islands of Great Britain and Ireland are part of Europe, while Australia and the island of New Guinea together form a continent. Taken to its limit, this view could support the view that there are only three continents: Antarctica, Australia-New Guinea, and a single mega-continent which joins Afro-Eurasia and America via the contiguous continental shelf in and around the Bering Sea. The vast size of the latter compared to the first two might even lead some to say it is the only continent, the others being more comparable to Greenland or New Zealand.

As a cultural construct, the concept of a continent may go beyond the continental shelf to include oceanic islands and continental fragments. In this way, Iceland is considered a part of Europe, and Madagascar a part of Africa. Extrapolating the concept to its extreme, some geographers group the Australian continental landmass with other islands in the Pacific Ocean into Oceania, which is usually considered a region rather than a continent. This divides the entire land surface of Earth into continents, regions, or quasi-continents.

Separation

The criterion that each continent is a discrete landmass is commonly relaxed due to historical conventions and practical use. Of the seven most globally recognized continents, only Antarctica and Australia are completely separated from other continents by the ocean. Several continents are defined not as absolutely distinct bodies but as "more or less discrete masses of land". Africa and Asia are joined by the Isthmus of Suez, and North America and South America by the Isthmus of Panama. In both cases, there is no complete separation of these landmasses by water (disregarding the Suez Canal and the Panama Canal, which are both narrow and shallow, as well as human-made). Both of these isthmuses are very narrow compared to the bulk of the landmasses they unite.

North America and South America are treated as separate continents in the seven-continent model. However, they may also be viewed as a single continent known as America. This viewpoint was common in the United States until World War II, and remains prevalent in some Asian six-continent models. The single American continent model remains a common view in European countries like France, Greece, Hungary, Italy, Malta, Portugal, Spain, Latin American countries and some Asian countries.

The criterion of a discrete landmass is completely disregarded if the continuous landmass of Eurasia is classified as two separate continents (Asia and Europe). Physiographically, Europe and the Indian subcontinent are large peninsulas of the Eurasian landmass. However, Europe is considered a continent with its comparatively large land area of 10,180,000 square kilometres (3,930,000 sq mi), while the Indian subcontinent, with less than half that area, is considered a subcontinent. The alternative view—in geology and geography—that Eurasia is a single continent results in a six-continent view of the world. Some view the separation of Eurasia into Asia and Europe as a residue of Eurocentrism: "In physical, cultural and historical diversity, China and India are comparable to the entire European landmass, not to a single European country. [...]." However, for historical and cultural reasons, the view of Europe as a separate continent continues in almost all categorizations.

If continents are defined strictly as discrete landmasses, embracing all the contiguous land of a body, then Africa, Asia, and Europe form a single continent which may be referred to as Afro-Eurasia. Combined with the consolidation of the Americas, this would produce a four-continent model consisting of Afro-Eurasia, America, Antarctica, and Australia.

When sea levels were lower during the Pleistocene ice ages, greater areas of the continental shelf were exposed as dry land, forming land bridges between Tasmania and the Australian mainland. At those times, Australia and New Guinea were a single, continuous continent known as Sahul. Likewise, Afro-Eurasia and the Americas were joined by the Bering Land Bridge. Other islands, such as Great Britain, were joined to the mainlands of their continents. At that time, there were just three discrete landmasses in the world: Africa-Eurasia-America, Antarctica, and Australia-New Guinea (Sahul).

Number

There are several ways of distinguishing the continents:

* The seven-continent model is taught in most English-speaking countries, including Australia, Canada, the United Kingdom, and the United States, and also in Bangladesh, China, India, Indonesia, Pakistan, the Philippines, Sri Lanka, Suriname, parts of Europe and Africa.
* The six-continent combined-Eurasia model is mostly used in Russia and some parts of Eastern Europe.
* The six-continent combined-America model is taught in Greece and many Romance-speaking countries—including Latin America.
* The Olympic flag's five rings represent the five inhabited continents of the combined-America model but excludes the uninhabited Antarctica.

In the English-speaking countries, geographers often use the term Oceania to denote a geographical region which includes most of the island countries and territories in the Pacific Ocean, as well as the continent of Australia.

Eighth continent

Zealandia (a submerged continent) has been called the eighth continent.

Area and population

The following table provides areas given by the Encyclopædia Britannica for each continent in accordance with the seven-continent model, including Australasia along with Melanesia, Micronesia, and Polynesia as parts of Oceania. It also provides populations of continents according to 2021 estimates by the United Nations Statistics Division based on the United Nations geoscheme, which includes all of Egypt (including the Isthmus of Suez and the Sinai Peninsula) as a part of Africa, all of Armenia, Azerbaijan, Cyprus, Georgia, Indonesia, Kazakhstan, and Turkey (including East Thrace) as parts of Asia, all of Russia (including Siberia) as a part of Europe, all of Panama and the United States (including Hawaii) as parts of North America, and all of Chile (including Easter Island) as a part of South America.

Geological continents

Geologists use four key attributes to define a continent:

* Elevation – The landmass, whether dry or submerged beneath the ocean, should be elevated above the surrounding ocean crust.
* Geology – The landmass should contain different types of rock: igneous, metamorphic, and sedimentary.
* Crustal structure – The landmass should consist of the continental crust, which is thicker and has a lower seismic velocity than the oceanic crust.
* Limits and area – The landmass should have clearly defined boundaries and an area of more than one million square kilometres.

With the addition of Zealandia in 2017, Earth currently has seven recognized geological continents:

* Africa
* Antarctica
* Australia
* Eurasia
* North America
* South America
* Zealandia

Due to a seeming lack of Precambrian cratonic rocks, Zealandia's status as a geological continent has been disputed by some geologists. However, a study conducted in 2021 found that part of the submerged continent is indeed Precambrian, twice as old as geologists had previously thought, which is further evidence that supports the idea of Zealandia being a geological continent.

All seven geological continents are spatially isolated by geologic features.

Additional Information

A continent is one of Earth’s seven main divisions of land. The continents are, from largest to smallest: Asia, Africa, North America, South America, Antarctica, Europe, and Australia.

When geographers identify a continent, they usually include all the islands associated with it. Japan, for instance, is part of the continent of Asia. Greenland and all the islands in the Caribbean Sea are usually considered part of North America.

Together, the continents add up to about 148 million square kilometers (57 million square miles) of land. Continents make up most—but not all—of Earth’s land surface. A very small portion of the total land area is made up of islands that are not considered physical parts of continents. The ocean covers almost three-fourths of Earth. The area of the ocean is more than double the area of all the continents combined. All continents border at least one ocean. Asia, the largest continent, has the longest series of coastlines.

Coastlines, however, do not indicate the actual boundaries of the continents. Continents are defined by their continental shelves. A continental shelf is a gently sloping area that extends outward from the beach far into the ocean. A continental shelf is part of the ocean, but also part of the continent.

To geographers, continents are also culturally distinct. The continents of Europe and Asia, for example, are actually part of a single, enormous piece of land called Eurasia. But linguistically and ethnically, the areas of Asia and Europe are distinct. Because of this, most geographers divide Eurasia into Europe and Asia. An imaginary line, running from the northern Ural Mountains in Russia south to the Caspian and Black Seas, separates Europe, to the west, from Asia, to the east.

Building the Continents

Earth formed 4.6 billion years ago from a great, swirling cloud of dust and gas. The continuous smashing of space debris and the pull of gravity made Earth's core heat up. As the heat increased, some of Earth’s rocky materials melted and rose to the surface, where they cooled and formed a crust. Heavier material sank toward Earth’s center. Eventually, Earth came to have three main layers: the core, the mantle, and the crust.

The crust and the top portion of the mantle form a rigid shell around Earth that is broken up into huge sections called tectonic plates. The heat from inside Earth causes the plates to slide around on the molten mantle. Today, tectonic plates continue to slowly slide around the surface, just as they have been doing for hundreds of millions of years. Geologists believe the interaction of the plates, a process called plate tectonics, contributed to the creation of continents.

Studies of rocks found in ancient areas of North America have revealed the oldest known pieces of the continents began to form nearly four billion years ago, soon after Earth itself formed. At that time, a primitive ocean covered Earth. Only a small fraction of the crust was made up of continental material. Scientists theorize that this material built up along the boundaries of tectonic plates during a process called subduction. During subduction, plates collide, and the edge of one plate slides beneath the edge of another.

When heavy oceanic crust subducted toward the mantle, it melted in the mantle’s intense heat. Once melted, the rock became lighter. Called magma, it rose through the overlying plate and burst out as lava. When the lava cooled, it hardened into igneous rock.

Gradually, the igneous rock built up into small volcanic islands above the surface of the ocean. Over time, these islands grew bigger, partly as the result of more lava flows and partly from the buildup of material scraped off descending plates. When plates carrying islands subducted, the islands themselves did not descend into the mantle. Their material fused with that of islands on the neighboring plate. This made even larger landmasses—the first continents.

The building of volcanic islands and continental material through plate tectonics is a process that continues today. Continental crust is much lighter than oceanic crust. In subduction zones, where tectonic plates interact with each other, oceanic crust always subducts beneath continental crust. Oceanic crust is constantly being recycled in the mantle. For this reason, continental crust is much, much older than oceanic crust.

Wandering Continents

If you could visit Earth as it was millions of years ago, it would look very different. The continents have not always been where they are today. About 480 million years ago, most continents were scattered chunks of land lying along or south of the Equator. Millions of years of continuous tectonic activity changed their positions, and by 240 million years ago, almost all of the world’s land was joined in a single, huge continent. Geologists call this supercontinent Pangaea, which means “all lands” in Greek.

By about 200 million years ago, the forces that helped form Pangaea caused the supercontinent to begin to break apart. The pieces of Pangaea that began to move apart were the beginnings of the continents that we know today.

A giant landmass that would become Europe, Asia, and North America separated from another mass that would split up into other continents and regions. In time, Antarctica and Oceania, still joined together, broke away and drifted south. The small piece of land that would become the peninsula of India broke away and for millions of years moved north as a large island. It eventually collided with Asia. Gradually, the different landmasses moved to their present locations.

The positions of the continents are always changing. North America and Europe are moving away from each other at the rate of about 2.5 centimeters (one inch) per year. If you could visit the planet in the future, you might find that part of the United States' state of California had separated from North America and become an island. Africa might have split in two along the Great Rift Valley. It is even possible that another supercontinent may form someday.

Continental Features

The surface of the continents has changed many times because of mountain building, weathering, erosion, and build-up of sediment. Continuous, slow movement of tectonic plates also changes surface features.

The rocks that form the continents have been shaped and reshaped many times. Great mountain ranges have risen and then have been worn away. Ocean waters have flooded huge areas and then gradually dried up. Massive ice sheets have come and gone, sculpting the landscape in the process.

Today, all continents have great mountain ranges, vast plains, extensive plateaus, and complex river systems. The landmasses’s average elevation above sea level is about 838 meters (2,750 feet).

Although each is unique, all the continents share two basic features: old, geologically stable regions, and younger, somewhat more active regions. In the younger regions, the process of mountain building has happened recently and often continues to happen.

The power for mountain building, or orogeny, comes from plate tectonics. One way mountains form is through the collision of two tectonic plates. The impact creates wrinkles in the crust, just as a rug wrinkles when you push against one end of it. Such a collision created Asia’s Himalaya several million years ago. The plate carrying India slowly and forcefully shoved the landmass of India into Asia, which was riding on another plate. The collision continues today, causing the Himalaya to grow taller every year.

Recently formed mountains, called coastal ranges, rise near the western coasts of North America and South America. Older, more stable mountain ranges are found in the interior of continents. The Appalachians of North America and the Urals, on the border between Europe and Asia, are older mountain ranges that are not geologically active.

Even older than these ancient, eroded mountain ranges are flatter, more stable areas of the continents called cratons. A craton is an area of ancient crust that formed during Earth’s early history. Every continent has a craton. Microcontinents, like New Zealand, lack cratons.

Cratons have two forms: shields and platforms. Shields are bare rocks that may be the roots or cores of ancient mountain ranges that have completely eroded away. Platforms are cratons with sediment and sedimentary rock lying on top.

The Canadian Shield makes up about a quarter of North America. For hundreds of thousands of years, sheets of ice up to 3.2 kilometers (two miles) thick coated the Canadian Shield. The moving ice wore away material on top of ancient rock layers, exposing some of the oldest formations on Earth. When you stand on the oldest part of the Canadian Shield, you stand directly on rocks that formed more than 3.5 billion years ago.

North America

North America, the third-largest continent, extends from the tiny Aleutian Islands in the northwest to the Isthmus of Panama in the south. The continent includes the enormous island of Greenland in the northeast. In the far north, the continent stretches halfway around the world, from Greenland to the Aleutians. But at Panama’s narrowest part, the continent is just 50 kilometers (31 miles) across.

Young mountains—including the Rockies, North America’s largest chain—rise in the West. Some of Earth’s youngest mountains are found in the Cascade Range of the U.S. states of Washington, Oregon, and California. Some peaks there began to form only about one million years ago—a wink of an eye in Earth’s long history. North America’s older mountain ranges rise near the East Coast of the United States and Canada.

In between the mountain systems lie wide plains that contain deep, rich soil. Much of the soil was formed from material deposited during the most recent glacial period. This Ice Age reached its peak about 18,000 years ago. As glaciers retreated, streams of melted ice dropped sediment on the land, building layers of fertile soil in the plains region. Grain grown in this region, called the “breadbasket of North America,” feeds a large part of the world.

North America contains a variety of natural wonders. Landforms and all types of vegetation can be found within its boundaries. North America has deep canyons, such as Copper Canyon in the Mexican state of Chihuahua. Yellowstone National Park, in the U.S. state of Wyoming, has some of the world’s most active geysers. Canada’s Bay of Fundy has the greatest variation of tide levels in the world. The Great Lakes form the planet’s largest area of freshwater. In California, giant sequoias, the world’s most massive trees, grow more than 76 meters (250 feet) tall and nearly 31 meters (100 feet) around.

Greenland, off the east coast of Canada, is the world’s largest island. Despite its name, Greenland is mostly covered with ice. Its ice is a remnant of the great ice sheets that once blanketed much of the North American continent. Greenland is the only place besides Antarctica that still has an ice sheet.

From the freezing Arctic to the tropical jungles of Central America, North America enjoys more climate variation than any other continent. Almost every type of ecosystem is represented somewhere on the continent, from coral reefs in the Caribbean to Greenland’s ice sheet to the Great Plains in the U.S. and Canada.

Today, North America is home to the citizens of Canada, the United States, Greenland (an autonomous terrirory of Denmark), Mexico, Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, Panama, and the island countries and territories that dot the Caribbean Sea and the western North Atlantic.

Most of North America sits on the North American Plate. Parts of the Canadian province of British Columbia and the U.S. states of Washington, Oregon, and California sit on the tiny Juan de Fuca Plate. Parts of California and the Mexican state of Baja California sit on the enormous Pacific Plate. Parts of Baja California and the Mexican states of Baja California Sur, Sonora, Sinaloa, and Jalisco sit on the Cocos Plate. The Caribbean Plate carries most of the small islands of the Caribbean Sea (south of the island of Cuba) as well as Central America from Honduras to Panama. The Hawaiian Islands, in the middle of the Pacific Ocean on the Pacific Plate, are usually considered part of North America.

South America

South America is connected to North America by the narrow Isthmus of Panama. These two continents weren’t always connected; they came together only three million years ago. South America is the fourth-largest continent and extends from the sunny beaches of the Caribbean Sea to the frigid waters near the Antarctic Circle.

South America’s southernmost islands, called Tierra del Fuego, are less than 1,120 kilometers (700 miles) from Antarctica. These islands even host some Antarctic birds, such as penguins, albatrosses, and terns. Early Spanish explorers visiting the islands for the first time saw small fires dotting the land. These fires, made by Indigenous people, seemed to float on the water, which is probably how the islands got their name—Tierra del Fuego means "Land of Fire."

The Andes, Earth’s longest terrestrial mountain range, stretch the entire length of South America. Many active volcanoes dot the range. These volcanic areas are fueled by heat generated as a large oceanic plate, called the Nazca Plate, grinds beneath the plate carrying South America.

The central-southern area of South America has pampas, or plains. These rich areas are ideal for agriculture. The growing of wheat is a major industry in the pampas. Grazing animals, such as cattle and sheep, are also raised in the pampas region.

In northern South America, the Amazon River and its tributaries flow through the world’s largest tropical rainforest. In volume, the Amazon is the largest river in the world. More water flows from it than from the next six largest rivers combined.

South America is also home to the world’s highest waterfall, Angel Falls, in the country of Venezuela. Water flows more than 979 meters (3,212 feet)—almost one mile. The falls are so high that most of the water evaporates into mist or is blown away by wind before it reaches the ground.

South American rainforests contain an enormous wealth of animal and plant life. More than 15,000 species of plants and animals are found only in the Amazon Basin. Many Amazonian plant species are sources of food and medicine for the rest of the world. Scientists are trying to find ways to preserve this precious and fragile environment as people move into the Amazon Basin and clear land for settlements and agriculture.

Twelve independent countries make up South America: Brazil, Colombia, Argentina, Peru, Venezuela, Chile, Ecuador, Bolivia, Paraguay, Uruguay, Guyana, and Suriname. The territories of French Guiana, which is claimed by France, and the Falkland Islands, which are adminstered by the United Kingdom but claimed by Argentina, are also part of South America.

Almost all of South America sits on top of the South American Plate.

Europe

Europe, the sixth-largest continent, contains just seven percent of the world’s land. In total area, the continent of Europe is only slightly larger than the country of Canada. However, the population of Europe is more than twice that of South America. Europe has 46 countries and many of the world’s major cities, including London, the United Kingdom; Paris, France; Berlin, Germany; Rome, Italy; Madrid, Spain; and Moscow, Russia.

Most European countries have access to the ocean. The continent is bordered by the Arctic Ocean in the north, the Atlantic Ocean in the west, the Caspian Sea in the southeast, and the Mediterranean and Black Seas in the south. The nearness of these bodies of water and the navigation of many of Europe’s rivers played a major role in the continent’s history. Early Europeans learned the river systems of the Volga, Danube, Don, Rhine, and Po, and could successfully travel the length and width of the small continent for trade, communication, or conquest.

Navigation and exploration outside of Europe was an important part of the development of the continent’s economic, social, linguistic, and political legacy. European explorers were responsible for colonizing land on every continent except Antarctica. This colonization process had a drastic impact on the economic and political development of those continents, as well as Europe. Europe's colonial period ended in the violent transfer of wealth and land from Indigenous peoples in the Americas, and later Africa, Oceania, and Asia.

In the east, the Ural Mountains separate Europe from Asia. The nations of Russia and Kazakhstan straddle both continents. Another range, the Kjølen Mountains, extends along the northern part of the border between Sweden and Norway. To the south, the Alps form an arc stretching from Albania to Austria, then across Switzerland and northern Italy into France. As the youngest and steepest of Europe’s mountains, the Alps geologically resemble the Rockies of North America, another young range.

A large area of gently rolling plains extends from northern France eastward to the Urals. A climate of warm summers, cold winters, and plentiful rain helps make much of this European farmland very productive.

The climate of Western Europe, especially around the Mediterranean Sea, makes it one of the world’s leading tourism destinations.

Almost all of Europe sits on the massive Eurasian Plate.

Africa

Africa, the second-largest continent, covers an area more than three times that of the United States. From north to south, Africa stretches about 8,000 kilometers (5,000 miles). It is connected to Asia by the Isthmus of Suez in Egypt.

The Sahara, which covers much of North Africa, is the world’s largest hot desert. The world’s longest river, the Nile, flows more than 6,560 kilometers (4,100 miles) from its most remote headwaters in Lake Victoria to the Mediterranean Sea in the north. A series of falls and rapids along the southern part of the river makes navigation difficult. The Nile has played an important role in the history of Africa. In ancient Egyptian civilization, it was a source of life for food, water, and transportation.

The top half of Africa is mostly dry, hot desert. The middle area has savannas, or flat, grassy plains. This region is home to wild animals such as lions, giraffes, elephants, hyenas, cheetahs, and wildebeests. The central and southern areas of Africa are dominated by rainforests. Many of these forests thrive around Africa’s other great rivers, the Zambezi, the Congo, and the Niger. These rivers also served as the homes to Great Zimbabwe, the Kingdom of Kongo, and the Ghana Empire, respectively. However, trees are being cut down in Africa’s rainforests for many of the same reasons deforestation is taking place in the rainforests of South America and Asia: development for businesses, homes, and agriculture.

Much of Africa is a high plateau surrounded by narrow strips of coastal lowlands. Hilly uplands and mountains rise in some areas of the interior. Glaciers on Mount Kilimanjaro in Tanzania sit just kilometers from the tropical jungles below. Even though Kilimanjaro is not far from the Equator, snow covers its summit all year long.

In eastern Africa, a giant depression called the Great Rift Valley runs from the Red Sea to the country of Mozambique. (The rift valley actually starts in southwestern Asia.) The Great Rift Valley is a site of major tectonic activity, where the continent of Africa is splitting into two. Geologists have already named the two parts of the African Plate. The Nubian Plate will carry most of the continent, to the west of the rift; the Somali Plate will carry the far eastern part of the continent, including the so-called “Horn of Africa.” The Horn of Africa is a peninsula that resembles the upturned horn of a rhinoceros. The countries of Eritrea, Ethiopia, Djibouti, and Somalia sit on the Horn of Africa and the Somali Plate.

Africa is home to 54 countries but only 16 percent of the world’s total population. The area of central-eastern Africa is important to scientists who study evolution and the earliest origins of humanity. This area is thought to be the place where hominids began to evolve.

The entire continent of Africa sits on the African Plate.

Asia

Asia, the largest continent, stretches from the eastern Mediterranean Sea to the western Pacific Ocean. There are more than 40 countries in Asia. Some are among the most-populated countries in the world, including China, India, and Indonesia. Sixty percent of Earth’s population lives in Asia. More than a third of the world’s people live in China and India alone.

The continent of Asia includes many islands, some of them are countries unto themselves. The Philippines, Indonesia, Japan, and Taiwan are major island nations in Asia.

Most of Asia’s people live in cities or fertile farming areas near river valleys, plains, and coasts. The plateaus in Central Asia are largely unsuitable for farming and are thinly populated.

Asia accounts for almost a third of the world’s land. The continent has a wide range of climate regions, from polar in the Siberian Arctic to tropical in equatorial Indonesia. Parts of Central Asia, including the Gobi Desert in China and Mongolia, are dry year-round. Southeast Asia, on the other hand, depends on the annual monsoons, which bring rain and make agriculture possible.

Monsoon rains and snowmelt feed Asian rivers such as the Ganges, the Yellow, the Mekong, the Indus, and the Yangtze. The rich valley between the Tigris and Euphrates Rivers in western Asia is called the “Fertile Crescent” for its place in the development of agriculture and human civilization.

Asia is the most mountainous of all the continents. More than 50 of the highest peaks in the world are in Asia. Mount Everest, which reaches more than 8,700 meters (29,000 feet) high in the Himalaya range, is the highest point on Earth. These mountains have become major destination spots for adventurous travelers.

Plate tectonics continuously push the mountains higher. As the landmass of India pushes northward into the landmass of Eurasia, parts of the Himalaya rise at a rate of about 2.5 centimeters (one inch) every five years.

Asia contains, not only, Earth’s highest elevation, but also its lowest place on land: the shores of the Dead Sea in the countries of Israel and Jordan. The land there lies more than 390 meters (1,300 feet) below sea level.

Although the Eurasian Plate carries most of Asia, it is not the only one supporting major parts of the large continent. The Arabian Peninsula, in the continent’s southwest, is carried by the Arabian Plate. The Indian Plate supports the Indian peninsula, sometimes called the Indian subcontinent. The Australian Plate carries some islands in Indonesia. The North American Plate carries eastern Siberia and the northern islands of Japan.

Australia

In addition to being the smallest continent, Australia is the flattest and the second-driest, after Antarctica. The region including the continent of Australia is sometimes called Oceania, to include the thousands of tiny islands of the Central Pacific and South Pacific, most notably Melanesia, Micronesia, and Polynesia (including the U.S. state of Hawai‘i). However, the continent of Australia itself includes only the nation of Australia, the eastern portion of the island of New Guinea (the nation of Papua New Guinea) and the island nation of New Zealand.

Australia covers just less than 8.5 million square kilometers (about 3.5 million square miles). Its population is about 31 million. It is the most sparsely populated continent, after Antarctica.

A plateau in the middle of mainland Australia makes up most of the continent’s total area. Rainfall is light on the plateau, and not many people have settled there. The Great Dividing Range, a long mountain range, rises near the east coast and extends from the northern part of the territory of Queensland through the territories of New South Wales and Victoria. Mainland Australia is known for the Outback, a desert area in the interior. This area is so dry, hot, and barren that few people live there.

In addition to the hot plateaus and deserts in mainland Australia, the continent also features lush equatorial rainforests on the island of New Guinea, tropical beaches, and high mountain peaks and glaciers in New Zealand.

Most of Australia’s people live in cities along the southern and eastern coasts of the mainland. Major cities include Perth, Sydney, Brisbane, Melbourne, and Adelaide.

Biologists who study animals consider Australia a living laboratory. When the continent began to break away from Antarctica more than 60 million years ago, it carried a cargo of animals with it. Isolated from life on other continents, the animals developed into creatures unique to Australia, such as the koala (Phascolarctos cinereus), the platypus (Ornithorhynchus anatinus), and the Tasmanian devil (Sarcophilus harrisii).

The Great Barrier Reef, off mainland Australia’s northeast coast, is another living laboratory. The world’s largest coral reef ecosystem, it is home to thousands of species of fish, sponges, marine mammals, corals, and crustaceans. The reef itself is 1,920 kilometers (1,200 miles) of living coral communities. By some estimates, it is the world’s largest living organism.

Most of Australia sits on the Australian Plate. The southern part of the South Island of New Zealand sits on the Pacific Plate.

Antarctica

Antarctica is the windiest, driest, and iciest place on Earth—it is the world's largest desert. Antarctica is larger than Europe or Australia, but unlike those continents, it has no permanent human population. People who work there are scientific researchers and support staff, such as pilots and cooks.

The climate of Antarctica makes it impossible to support agriculture or a permanent civilization. Temperatures in Antarctica, much lower than Arctic temperatures, plunge lower than -73 degrees Celsius (-100 degrees Fahrenheit).

Scientific bases and laboratories have been established in Antarctica for studies in fields that include geology, oceanography, and meteorology. The freezing temperatures of Antarctica make it an excellent place to study the history of Earth’s atmosphere and climate. Ice cores from the massive Antarctic ice sheet have recorded changes in Earth’s temperature and atmospheric gases for thousands of years. Antarctica is also an ideal place for discovering meteorites, or stony objects that have impacted Earth from space. The dark meteorites, often made of metals like iron, stand out from the white landscape of most of the continent.

Antarctica is almost completely covered with ice, sometimes as thick as 3.2 kilometers (two miles). In winter, Antarctica’s surface area may double as pack ice builds up in the ocean around the continent.

Like all other continents, Antarctica has volcanic activity. The most active volcano is Mount Erebus, which is less than 1,392 kilometers (870 miles) from the South Pole. Its frequent eruptions are evidenced by hot, molten rock beneath the continent’s icy surface.

Antarctica does not have any countries. However, scientific groups from different countries inhabit the research stations. A multinational treaty negotiated in 1959 and reviewed in 1991 states that research in Antarctica can only be used for peaceful purposes. McMurdo Station, the largest community in Antarctica, is operated by the United States. Vostok Station, where the coldest temperature on Earth was recorded, is operated by Russia.

All of Antarctica sits on the Antarctic Plate.

Jai Ganesh · 2025-01-19 18:48:06

2328) Computer (Printing)

Gist

A printer is a device that accepts text and graphic output from a computer and transfers the information to paper, usually to standard-size, 8.5" by 11" sheets of paper. Printers vary in size, speed, sophistication and cost.

Summary

A printer is electronic device that accepts text files or images from a computer and transfers them to a medium such as paper or film. It can be connected directly to the computer or indirectly via a network. Printers are classified as impact printers (in which the print medium is physically struck) and non-impact printers. Most impact printers are dot-matrix printers, which have a number of pins on the print head that emerge to form a character. Non-impact printers fall into three main categories: laser printers use a laser beam to attract toner to an area of the paper; ink-jet printers spray a jet of liquid ink; and thermal printers transfer wax-based ink or use heated pins to directly imprint an image on specially treated paper. Important printer characteristics include resolution (in dots per inch), speed (in sheets of paper printed per minute), colour (full-colour or black-and-white), and cache memory (which affects the speed at which a file can be printed).

Details

What is a printer?

A printer is a device that accepts text and graphic output from a computer and transfers the information to paper, usually to standard-size, 8.5" by 11" sheets of paper. Printers vary in size, speed, sophistication and cost. In general, more expensive printers are used for more frequent printing or high-resolution color printing.

Personal computer printers can be distinguished as impact or non-impact printers. Early impact printers worked something like an automatic typewriter, with a key striking an inked impression on paper for each printed character. The dot matrix printer, an impact printer that strikes the paper a line at a time, was a popular low-cost option.

The best-known non-impact printers are the inkjet printer and the laser printer. The inkjet sprays ink from an ink cartridge at very close range to the paper as it rolls by, while the laser printer uses a laser beam reflected from a mirror to attract ink (called toner) to selected paper areas as a sheet rolls over a drum.

Different types of printers

There are many different printer manufacturers available today, including Canon, Epson, Hewlett-Packard, Xerox and Lexmark, among many others. There are also several types of printers to choose from, which we'll explore below.

* Inkjet printers recreate a digital image by spraying ink onto paper. These are the most common type of personal printer.
* Laser printers are used to create high-quality prints by passing a laser beam at a high speed over a negatively charged drum to define an image. Color laser printers are more often found in professional settings.
* 3D printers are a relatively new printer technology. 3D printing creates a physical object from a digital file. It works by adding layer upon layer of material until the print job is complete and the object is whole.
* Thermal printers produce an image on paper by passing paper with a thermochromic coating over a print head comprised of electrically heated elements and produces an image in the area where the heated coating turns black. A dye-sublimation printer is a form of thermal printing technology that uses heat to transfer dye onto materials.
* All-in-one printers are multifunction devices that combine printing with other technologies such as a copier, scanner and/or fax machine.
* LED printers are similar to laser printers but use a light-emitting diode array in the print head instead of a laser.
* Photo printers are similar to inkjet printers but are designed specifically to print high-quality photos, which require a lot of ink and special paper to ensure the ink doesn't smear.

Older printer types

There are a few first-generation printer types that are outdated and rarely used today:

* Dot matrix printer: Dot matrix printing is an older impact printer technology for text documents that strikes the paper one line at a time. Dot matrix printers offer very basic print quality.
* Line printer: A line printer prints a single line of text at a time. While an older form of printing, line printers are still in use today.

Features to look for in a printer

The four printer qualities of most interest to users are:

* Color: Most modern printers offer color printing. However, they can also be set to print in black and white. Color printers are more expensive to operate since they use two ink cartridges -- one color and one black ink -- or toners that need to be replaced after a certain number of pages are printed. Printing ink cartridges or toner cartridges are comprised of black, cyan, magenta and yellow ink. The ink can be mixed together, or it may come in separate monochrome solid ink printer cartridges, depending on the type of printer.
* Resolution: Printer resolution -- the sharpness of text and images on paper -- is usually measured in dots per inch (dpi). Most inexpensive printers provide sufficient resolution for most purposes at 600 dpi.
* Speed: If a user does a lot of printing, printing speed is an important feature. Inexpensive printers print only about 3 to 6 sheets per minute. However, faster printing speeds are an option with a more sophisticated, expensive printer.
* Memory: Most printers come with a small amount of memory -- typically 2-16 megabytes- that can be expanded by the user. Having more than the minimum amount of memory is helpful and faster when printing out pages with large images.

Printer I/O interfaces

The most common I/O interface for printers had been the parallel Centronics interface with a 36-pin plug.

Nowadays, however, printers and computers are likely to use a serial interface, especially a USB or FireWire with smaller and less cumbersome plugs.

Printer languages

Printer languages are commands from the computer to the printer to tell the printer how to format the document being printed. These commands manage font size, graphics, compression of data sent to the printer, color, etc. The two most popular printer languages are PostScript and Printer Control Language.

Postscript

Postscript is a printer language that uses English phrases and programmatic constructions to describe the appearance of a printed page to the printer. Adobe developed the printer language in 1985, and introduced new features such as outline fonts and vector graphics which can be printed with a plotter.

Printers now come from the factory with (or can be loaded with) Postscript support. Postscript is not restricted to printers. It can be used with any device that creates an image using dots such as screen displays, slide recorders and image-setters.

Printer Control Language (PCL)

PCL (Printer Control Language) is an escape code language used to send commands to the printer for printing documents. Escape code language has its name because the escape key begins the command sequence followed by a series of code numbers. HP originally devised PCL for dot matrix and inkjet printers.

Since its introduction, PCL has become an industry standard. Other manufacturers who sell HP clones have copied it. Some of these clones are very good, but there are small differences in the way they print a page compared to real HP printers.

In 1984, the original HP LaserJet printer was introduced using PCL, which helped change the appearance of low-cost printer documents from poor to exceptional quality.

Fonts

A font is a set of characters of a specific style and size within an overall typeface design. Printers use resident fonts and soft fonts to print documents.

Resident fonts

Resident fonts are built into the hardware of a printer. They are also called internal fonts or built-in fonts.

All printers come with one or more resident fonts. Additional fonts can be added by inserting a font cartridge into the printer or installing soft fonts on the hard drive. Resident fonts cannot be erased, unlike soft fonts.

Soft fonts

Soft fonts are installed onto the hard drive or flash drive and then sent to the computer's memory when a document is printed that uses the particular soft font. Soft fonts can be downloaded from the internet or purchased in stores.

Additional Information

In computing, a printer is a peripheral machine which makes a durable representation of graphics or text, usually on paper. While most output is human-readable, bar code printers are an example of an expanded use for printers. Different types of printers include 3D printers, inkjet printers, laser printers, and thermal printers.

History

The first computer printer designed was a mechanically driven apparatus by Charles Babbage for his difference engine in the 19th century; however, his mechanical printer design was not built until 2000.

The first patented printing mechanism for applying a marking medium to a recording medium or more particularly an electrostatic inking apparatus and a method for electrostatically depositing ink on controlled areas of a receiving medium, was in 1962 by C. R. Winston, Teletype Corporation, using continuous inkjet printing. The ink was a red stamp-pad ink manufactured by Phillips Process Company of Rochester, NY under the name Clear Print. This patent (US3060429) led to the Teletype Inktronic Printer product delivered to customers in late 1966.

The first compact, lightweight digital printer was the EP-101, invented by Japanese company Epson and released in 1968, according to Epson.

The first commercial printers generally used mechanisms from electric typewriters and Teletype machines. The demand for higher speed led to the development of new systems specifically for computer use. In the 1980s there were daisy wheel systems similar to typewriters, line printers that produced similar output but at much higher speed, and dot-matrix systems that could mix text and graphics but produced relatively low-quality output. The plotter was used for those requiring high-quality line art like blueprints.

The introduction of the low-cost laser printer in 1984, with the first HP LaserJet, and the addition of PostScript in next year's Apple LaserWriter set off a revolution in printing known as desktop publishing. Laser printers using PostScript mixed text and graphics, like dot-matrix printers, but at quality levels formerly available only from commercial typesetting systems. By 1990, most simple printing tasks like fliers and brochures were now created on personal computers and then laser printed; expensive offset printing systems were being dumped as scrap. The HP Deskjet of 1988 offered the same advantages as a laser printer in terms of flexibility, but produced somewhat lower-quality output (depending on the paper) from much less-expensive mechanisms. Inkjet systems rapidly displaced dot-matrix and daisy-wheel printers from the market. By the 2000s, high-quality printers of this sort had fallen under the $100 price point and became commonplace.

The rapid improvement of internet email through the 1990s and into the 2000s has largely displaced the need for printing as a means of moving documents, and a wide variety of reliable storage systems means that a "physical backup" is of little benefit today.

Starting around 2010, 3D printing became an area of intense interest, allowing the creation of physical objects with the same sort of effort as an early laser printer required to produce a brochure. As of the 2020s, 3D printing has become a widespread hobby due to the abundance of cheap 3D printer kits, with the most common process being Fused deposition modeling.

Types:

Personal printer

Personal printers are mainly designed to support individual users, and may be connected to only a single computer. These printers are designed for low-volume, short-turnaround print jobs, requiring minimal setup time to produce a hard copy of a given document. They are generally slow devices ranging from 6 to around 25 pages per minute (ppm), and the cost per page is relatively high. However, this is offset by the on-demand convenience. Some printers can print documents stored on memory cards or from digital cameras and scanners.

Networked printer

Networked or shared printers are "designed for high-volume, high-speed printing". They are usually shared by many users on a network and can print at speeds of 45 to around 100 ppm. The Xerox 9700 could achieve 120 ppm. An ID Card printer is used for printing plastic ID cards. These can now be customised with important features such as holographic overlays, HoloKotes and watermarks. This is either a direct to card printer (the more feasible option) or a retransfer printer.

Virtual printer

A virtual printer is a piece of computer software whose user interface and API resembles that of a printer driver, but which is not connected with a physical computer printer. A virtual printer can be used to create a file which is an image of the data which would be printed, for archival purposes or as input to another program, for example to create a PDF or to transmit to another system or user.

Barcode printer

A barcode printer is a computer peripheral for printing barcode labels or tags that can be attached to, or printed directly on, physical objects. Barcode printers are commonly used to label cartons before shipment, or to label retail items with UPCs or EANs.

3D printer

A 3D printer is a device for making a three-dimensional object from a 3D model or other electronic data source through additive processes in which successive layers of material (including plastics, metals, food, cement, wood, and other materials) are laid down under computer control. It is called a printer by analogy with an inkjet printer which produces a two-dimensional document by a similar process of depositing a layer of ink on paper.

ID card printer

A card printer is an electronic desktop printer with single card feeders which print and personalize plastic cards. In this respect they differ from, for example, label printers which have a continuous supply feed. Card dimensions are usually 85.60 × 53.98 mm, standardized under ISO/IEC 7810 as ID-1. This format is also used in EC-cards, telephone cards, credit cards, driver's licenses and health insurance cards. This is commonly known as the bank card format. Card printers are controlled by corresponding printer drivers or by means of a specific programming language. Generally card printers are designed with laminating, striping, and punching functions, and use desktop or web-based software. The hardware features of a card printer differentiate a card printer from the more traditional printers, as ID cards are usually made of PVC plastic and require laminating and punching. Different card printers can accept different card thickness and dimensions.

The principle is the same for practically all card printers: the plastic card is passed through a thermal print head at the same time as a color ribbon. The color from the ribbon is transferred onto the card through the heat given out from the print head. The standard performance for card printing is 300 dpi (300 dots per inch, equivalent to 11.8 dots per mm). There are different printing processes, which vary in their detail:

Thermal transfer

Mainly used to personalize pre-printed plastic cards in monochrome. The color is "transferred" from the (monochrome) color ribbon ;Dye sublimation:This process uses four panels of color according to the CMYK color ribbon. The card to be printed passes under the print head several times each time with the corresponding ribbon panel. Each color in turn is diffused (sublimated) directly onto the card. Thus it is possible to produce a high depth of color (up to 16 million shades) on the card. Afterwards a transparent overlay (O) also known as a topcoat (T) is placed over the card to protect it from mechanical wear and tear and to render the printed image UV resistant.

Reverse image technology

The standard for high-security card applications that use contact and contactless smart chip cards. The technology prints images onto the underside of a special film that fuses to the surface of a card through heat and pressure. Since this process transfers dyes and resins directly onto a smooth, flexible film, the print-head never comes in contact with the card surface itself. As such, card surface interruptions such as smart chips, ridges caused by internal RFID antennae and debris do not affect print quality. Even printing over the edge is possible.

Thermal rewrite print process

In contrast to the majority of other card printers, in the thermal rewrite process the card is not personalized through the use of a color ribbon, but by activating a thermal sensitive foil within the card itself. These cards can be repeatedly personalized, erased and rewritten. The most frequent use of these are in chip-based student identity cards, whose validity changes every semester.

Common printing problems

Many printing problems are caused by physical defects in the card material itself, such as deformation or warping of the card that is fed into the machine in the first place. Printing irregularities can also result from chip or antenna embedding that alters the thickness of the plastic and interferes with the printer's effectiveness. Other issues are often caused by operator errors, such as users attempting to feed non-compatible cards into the card printer, while other printing defects may result from environmental abnormalities such as dirt or contaminants on the card or in the printer. Reverse transfer printers are less vulnerable to common printing problems than direct-to-card printers, since with these printers the card does not come into direct contact with the printhead.

Variations

Broadly speaking there are three main types of card printers, differing mainly by the method used to print onto the card. They are:

Near to Edge

This term designates the cheapest type of printing by card printers. These printers print up to 5 mm from the edge of the card stock.

Direct to Card

Also known as "Edge to Edge Printing". The print-head comes in direct contact with the card. This printing type is the most popular nowadays, mostly due to cost factor. The majority of identification card printers today are of this type.

Reverse Transfer

Also known as "High Definition Printing" or "Over the Edge Printing". The print-head prints to a transfer film backwards (hence the reverse) and then the printed film is rolled onto the card with intense heat (hence the transfer). The term "over the edge" is due to the fact that when the printer prints onto the film it has a "bleed", and when rolled onto the card the bleed extends to completely over the edge of the card, leaving no border.
Different ID Card Printers use different encoding techniques to facilitate disparate business environments and to support security initiatives. Known encoding techniques are:

* Contact Smart Card

The Contact Smart Cards use RFID technology and require direct contact to a conductive plate to register admission or transfer of information. The transmission of commands, data, and card status held between the two physical contact points.

* Contactless Smart Card

Contactless Smart Cards exhibit integrated circuit that can store and process data while communicating with the terminal via Radio Frequency. Unlike Contact Smart Card, contact less cards feature intelligent re-writable microchip that can be transcribed through radio waves.

* HiD Proximity

HID's proximity technology allows fast, accurate reading while offering card or key tag read ranges from 4" to 24" inches (10 cm to 60.96 cm), dependent on the type of proximity reader being used. Since these cards and key tags do not require physical contact with the reader, they are virtually maintenance and wear-free.

ISO Magnetic Stripe

A magnetic stripe card is a type of card capable of storing data by modifying the magnetism of tiny iron-based magnetic particles on a band of magnetic material on the card. The magnetic stripe, sometimes called swipe card or magstripe, is read by physical contact and swiping past a magnetic reading head.

Software

There are basically two categories of card printer software: desktop-based, and web-based (online). The biggest difference between the two is whether or not a customer has a printer on their network that is capable of printing identification cards. If a business already owns an ID card printer, then a desktop-based badge maker is probably suitable for their needs. Typically, large organizations who have high employee turnover will have their own printer. A desktop-based badge maker is also required if a company needs their IDs make instantly. An example of this is the private construction site that has restricted access. However, if a company does not already have a local (or network) printer that has the features they need, then the web-based option is a perhaps a more affordable solution. The web-based solution is good for small businesses that do not anticipate a lot of rapid growth, or organizations who either can not afford a card printer, or do not have the resources to learn how to set up and use one. Generally speaking, desktop-based solutions involve software, a database (or spreadsheet) and can be installed on a single computer or network.

Other options

Alongside the basic function of printing cards, card printers can also read and encode magnetic stripes as well as contact and contact free RFID chip cards (smart cards). Thus card printers enable the encoding of plastic cards both visually and logically. Plastic cards can also be laminated after printing. Plastic cards are laminated after printing to achieve a considerable increase in durability and a greater degree of counterfeit prevention. Some card printers come with an option to print both sides at the same time, which cuts down the time taken to print and less margin of error. In such printers one side of id card is printed and then the card is flipped in the flip station and other side is printed.

Applications

Alongside the traditional uses in time attendance and access control (in particular with photo personalization), countless other applications have been found for plastic cards, e.g. for personalized customer and members' cards, for sports ticketing and in local public transport systems for the production of season tickets, for the production of school and college identity cards as well as for the production of national ID cards.

Jai Ganesh · 2025-01-20 00:25:47

2329) Osteoarthritis

Gist

Osteoarthritis is the most common type of arthritis (a condition that affects your joints). Healthcare providers sometimes refer to it as degenerative joint disease or OA. It happens when the cartilage that lines your joints is worn down over time and your bones rub against each other when you use your affected joints.

Usually, the ends of bones in your joints are capped in a layer of tough, smooth cartilage. Cartilage is like a two-in-one shock absorber and lubricant — it helps the bones in your joints move past each other smoothly and safely. If you have osteoarthritis, the cartilage in your affected joints wears away over time. Eventually, your bones rub against each other when you move your joints.

Osteoarthritis can affect any of your joints, but most commonly develops in your:

* Hands.
* Knees.
* Hips.
* Neck (cervical spine).
* Lower back (lumbar spine).

Summary

Osteoarthritis is a disorder of the joints characterized by progressive deterioration of the articular cartilage or of the entire joint, including the articular cartilage, the synovium (joint lining), the ligaments, and the subchondral bone (bone beneath the cartilage). Osteoarthritis is the most common joint disease, although estimates of incidence and prevalence vary across different regions of the world and among different populations. By some estimates nearly 10 percent of men and about 18 percent of women over age 60 are affected by the condition. Although its suffix indicates otherwise, osteoarthritis is not characterized by excessive joint inflammation as is the case with rheumatoid arthritis. The disease may be asymptomatic, especially in the early years of its onset. As it progresses, however, pain, stiffness, and a limitation in movement may develop. Common sites of discomfort are the vertebrae, knees, and hips—joints that bear much of the weight of the body.

The cause of osteoarthritis is not completely understood, but biomechanical forces that place stress on the joints (e.g., bearing weight, postural or orthopedic abnormalities, or injuries that cause chronic irritation of the bone) are thought to interact with biochemical and genetic factors to contribute to osteoarthritis. Early stages of the condition are characterized by changes in cartilage thickness, which in turn are associated with an imbalance between cartilage breakdown and repair. The cartilage eventually becomes softened and roughened. Over time the cartilage wears away, and the subchondral bone, deprived of its protective cover, attempts to regenerate the destroyed tissue, resulting in increased bone density at the site of damage and an uneven remodeling of the surface of the joint. Thick bony outgrowths called spurs sometimes develop. Articulation of the joint becomes difficult. These developments are compounded by a reduction in synovial fluid, which acts as a natural joint lubricant and shock absorber.

Depending on the site and severity of the disease, various treatments are employed. Individuals who experience moderate symptoms can be treated by a combination of the following: analgesic (pain-relieving) medications, periodic rest, weight reduction, corticosteroid injections, and physical therapy or exercise. Surgical procedures such as hip or knee replacement or joint debridement (the removal of unhealthy tissue) may be necessary to relieve more severe pain and improve joint function. Injections of a joint lubricant consisting of hyaluronic acid, a substance normally found in synovial fluid, can help relieve pain and joint stiffness in some persons with osteoarthritis.

Researchers have also been investigating the therapeutic potential of the purine nucleoside adenosine, a substance that is found naturally in cells and that has been developed into a drug for medical use. Studies in animals have shown that replenishing adenosine levels in diseased joints can aid cartilage regrowth.

Details

Osteoarthritis (OA) is a type of degenerative joint disease that results from breakdown of joint cartilage and underlying bone. It is believed to be the fourth leading cause of disability in the world, affecting 1 in 7 adults in the United States alone. The most common symptoms are joint pain and stiffness. Usually the symptoms progress slowly over years. Other symptoms may include joint swelling, decreased range of motion, and, when the back is affected, weakness or numbness of the arms and legs. The most commonly involved joints are the two near the ends of the fingers and the joint at the base of the thumbs, the knee and hip joints, and the joints of the neck and lower back. The symptoms can interfere with work and normal daily activities. Unlike some other types of arthritis, only the joints, not internal organs, are affected.

Causes include previous joint injury, abnormal joint or limb development, and inherited factors. Risk is greater in those who are overweight, have legs of different lengths, or have jobs that result in high levels of joint stress. Osteoarthritis is believed to be caused by mechanical stress on the joint and low grade inflammatory processes. It develops as cartilage is lost and the underlying bone becomes affected. As pain may make it difficult to exercise, muscle loss may occur. Diagnosis is typically based on signs and symptoms, with medical imaging and other tests used to support or rule out other problems. In contrast to rheumatoid arthritis, in osteoarthritis the joints do not become hot or red.

Treatment includes exercise, decreasing joint stress such as by rest or use of a cane, support groups, and pain medications. Weight loss may help in those who are overweight. Pain medications may include paracetamol (acetaminophen) as well as NSAIDs such as naproxen or ibuprofen. Long-term opioid use is not recommended due to lack of information on benefits as well as risks of addiction and other side effects. Joint replacement surgery may be an option if there is ongoing disability despite other treatments.[2] An artificial joint typically lasts 10 to 15 years.

Osteoarthritis is the most common form of arthritis, affecting about 237 million people or 3.3% of the world's population, as of 2015. It becomes more common as people age. Among those over 60 years old, about 10% of males and 18% of females are affected. Osteoarthritis is the cause of about 2% of years lived with disability.

Signs and symptoms

The main symptom is pain, causing loss of ability and often stiffness. The pain is typically made worse by prolonged activity and relieved by rest. Stiffness is most common in the morning, and typically lasts less than thirty minutes after beginning daily activities, but may return after periods of inactivity. Osteoarthritis can cause a crackling noise (called "crepitus") when the affected joint is moved, especially shoulder and knee joint. A person may also complain of joint locking and joint instability. These symptoms would affect their daily activities due to pain and stiffness. Some people report increased pain associated with cold temperature, high humidity, or a drop in barometric pressure, but studies have had mixed results.

Osteoarthritis commonly affects the hands, feet, spine, and the large weight-bearing joints, such as the hips and knees, although in theory, any joint in the body can be affected. As osteoarthritis progresses, movement patterns (such as gait), are typically affected. Osteoarthritis is the most common cause of a joint effusion of the knee.

In smaller joints, such as at the fingers, hard bony enlargements, called Heberden's nodes (on the distal interphalangeal joints) or Bouchard's nodes (on the proximal interphalangeal joints), may form, and though they are not necessarily painful, they do limit the movement of the fingers significantly. Osteoarthritis of the toes may be a factor causing formation of bunions, rendering them red or swollen.

Causes

Damage from mechanical stress with insufficient self repair by joints is believed to be the primary cause of osteoarthritis. Sources of this stress may include misalignments of bones caused by congenital or pathogenic causes; mechanical injury; excess body weight; loss of strength in the muscles supporting a joint; and impairment of peripheral nerves, leading to sudden or uncoordinated movements. The risk of osteoarthritis increases with aging, history of joint injury, or family history of osteoarthritis. However exercise, including running in the absence of injury, has not been found to increase the risk of knee osteoarthritis. Nor has cracking one's knuckles been found to play a role.

Primary

The development of osteoarthritis is correlated with a history of previous joint injury and with obesity, especially with respect to knees. Changes in gender hormone levels may play a role in the development of osteoarthritis, as it is more prevalent among post-menopausal women than among men of the same age. Conflicting evidence exists for the differences in hip and knee osteoarthritis in African Americans and Caucasians.

Occupational

Increased risk of developing knee and hip osteoarthritis was found among those who work with manual handling (e.g. lifting), have physically demanding work, walk at work, and have climbing tasks at work (e.g. climb stairs or ladders). With hip osteoarthritis, in particular, increased risk of development over time was found among those who work in bent or twisted positions. For knee osteoarthritis, in particular, increased risk was found among those who work in a kneeling or squatting position, experience heavy lifting in combination with a kneeling or squatting posture, and work standing up. Women and men have similar occupational risks for the development of osteoarthritis.

Secondary

This type of osteoarthritis is caused by other factors but the resulting pathology is the same as for primary osteoarthritis:

* Alkaptonuria
* Congenital disorders of joints
* Diabetes doubles the risk of having a joint replacement due to osteoarthritis and people with diabetes have joint replacements at a younger age than those without diabetes.
* Ehlers-Danlos syndrome
* Hemochromatosis and Wilson's disease
* Inflammatory diseases (such as Perthes' disease), (Lyme disease), and all chronic forms of arthritis (e.g., costochondritis, gout, and rheumatoid arthritis). In gout, uric acid crystals cause the cartilage to degenerate at a faster pace.
* Injury to joints or ligaments (such as the ACL) as a result of an accident or orthopedic operations.
* Ligamentous deterioration or instability may be a factor.
* Marfan syndrome
* Obesity
* Joint infection

Pathophysiology

While osteoarthritis is a degenerative joint disease that may cause gross cartilage loss and morphological damage to other joint tissues, more subtle biochemical changes occur in the earliest stages of osteoarthritis progression. The water content of healthy cartilage is finely balanced by compressive force driving water out and hydrostatic and osmotic pressure drawing water in. Collagen fibres exert the compressive force, whereas the Gibbs–Donnan effect and cartilage proteoglycans create osmotic pressure which tends to draw water in.

However, during onset of osteoarthritis, the collagen matrix becomes more disorganized and there is a decrease in proteoglycan content within cartilage. The breakdown of collagen fibers results in a net increase in water content. This increase occurs because whilst there is an overall loss of proteoglycans (and thus a decreased osmotic pull), it is outweighed by a loss of collagen.

Other structures within the joint can also be affected. The ligaments within the joint become thickened and fibrotic, and the menisci can become damaged and wear away. Menisci can be completely absent by the time a person undergoes a joint replacement. New bone outgrowths, called "spurs" or osteophytes, can form on the margins of the joints, possibly in an attempt to improve the congruence of the articular cartilage surfaces in the absence of the menisci. The subchondral bone volume increases and becomes less mineralized (hypo mineralization). All these changes can cause problems functioning. The pain in an osteoarthritic joint has been related to thickened synovium and to subchondral bone lesions.

Additional Information

Osteoarthritis is a degenerative joint disease, in which the tissues in the joint break down over time. It is the most common type of arthritis and is more common in older people.

People with osteoarthritis usually have joint pain and, after rest or inactivity, stiffness for a short period of time. The most commonly affected joints include the:

* Hands (ends of the fingers and at the base and ends of the thumbs).
* Knees.
* Hips.
* Neck.
* Lower back.

Osteoarthritis affects each person differently. For some people, osteoarthritis is relatively mild and does not affect day-to-day activities. For others, it causes significant pain and disability. Joint damage usually develops gradually over years, although it could worsen quickly in some people.

What happens in osteoarthritis?

Researchers do not know what triggers or starts the breakdown of the tissues in the joint. However, as osteoarthritis begins to develop, it can damage all the areas of the joint, including:

* Cartilage, the tissue that covers the ends where two bones meet to form a joint.
* Tendons and ligaments.
* Synovium, the lining of the joint.
* Bone.
* Meniscus in the knee.

As the damage of soft tissues in the joint progresses, pain, swelling, and loss of joint motion develops. If you have joint pain, you may be less active, and this can lead to muscle weakness, which may cause more stress on the joint. Over time, the joint may lose its normal shape. Also, small bone growths, called osteophytes or bone spurs, may grow on the edges of the joint. The shape of the bone may also change. Bits of bone or cartilage can also break off and float inside the joint space. This causes more damage. Researchers continue to study the cause of pain in people who have osteoarthritis.

Who Gets Osteoarthritis?

Anyone can get osteoarthritis; however, it is more common as people age. Women are more likely than men to have osteoarthritis, especially after age 50. For many women, it develops after menopause.

Younger people can also develop osteoarthritis, usually as the result of:

* Joint injury.
* Abnormal joint structure.
* Genetic defect in joint cartilage.

Symptoms of Osteoarthritis

The symptoms of osteoarthritis often begin slowly and usually begin with one or a few joints. The common symptoms of osteoarthritis include:

* Pain when using the joint, which may improve with rest. For some people, in the later stages of the disease, the pain may be worse at night. Pain can be localized or widespread.
* Joint stiffness, usually lasting less than 30 minutes, in the morning or after resting for a period of time.
* Joint changes that can limit joint movement.
* Swelling in and around the joint, especially after a lot of activity or use of that area.
* Changes in the ability to move the joint.
* Feeling that the joint is loose or unstable.

Osteoarthritis symptoms can affect joints differently. For example:

* Hands. Bony enlargements and shape changes in the finger joints can happen over time.
* Knees. When walking or moving, you may hear a grinding or scaping noise. Over time, muscle and ligament weakness can cause the knee to buckle.
* Hips. You might feel pain and stiffness in the hip joint or in the groin, inner thigh, or buttocks. Sometimes, the pain from arthritis in the hip can radiate (spread) to the knees. Over time, you may not be able to move your hip as far as you did in the past.
* Spine. You may feel stiffness and pain in the neck or lower back. As changes in the spine happen, some people develop spinal stenosis, which can lead to other symptoms.

As your symptoms worsen over time, activities that you could participate in become difficult to do, such as stepping up, getting on or off the toilet or in and out of a chair, gripping a pan, or walking across a parking lot.

Pain and other symptoms of osteoarthritis may lead you to feel tired, have problems sleeping, and feel depressed.

Cause of Osteoarthritis

Osteoarthritis happens when the cartilage and other tissues within the joint break down or have a change in their structure. This does not happen because of simple wear and tear on the joints. Instead, changes in the tissue can trigger the breakdown, which usually happens gradually over time.

Certain factors may make it more likely for you to develop the disease, including:

* Aging.
* Being overweight or obese.
* History of injury or surgery to a joint.
* Overuse from repetitive movements of the joint.
* Joints that do not form correctly.
* Family history of osteoarthritis.

Jai Ganesh · 2025-01-20 18:23:25

2330) Globe

Gist

A globe is a three-dimensional scale model of the Earth or other round body. Because it is spherical, or ball-shaped, it can represent surface features, directions, and distances more accurately than a flat map.

Summary

A globe is a three-dimensional scale model of the Earth or other round body. Because it is spherical, or ball-shaped, it can represent surface features, directions, and distances more accurately than a flat map. On the other hand, a globe may be less practical for travelers, since globes are much bulkier than flat maps and often carry less detailed information.

The oldest known globe was made more than 2,100 years ago by Crates of Mallus, a Greek philosopher and geographer who lived in what is today Turkey. The oldest globe that survives to this day was made by the German geographer Martin Behaim in 1492—just before Christopher Columbus sailed to the New World. This globe is more accurate than Crates', but still leaves out North America, South America, Australia, and Antarctica.

The Earth is not the only planet that has been mapped onto a globe. In the past few decades, spacecraft have made detailed maps of the surfaces of other planets and moons. Globes for some of them, such as the planet Mars and our own Moon, are available for purchase.

Even the night sky around the Earth, known as the celestial sphere, has been mapped onto a globe. Celestial globes represent stars and planets visible above certain parts of the Earth. Many constellations, such as the Big Dipper, are outlined into familiar shapes on celestial globes. Looking for patterns on celestial globes makes finding individual stars easier to spot.

Like most early terrestrial globes, most early celestial globes were made of metal. Metal globes are usually cast in two halves, or hemispheres. These halves are then welded together with hot metal, creating a seam, or raised line, in the middle of the sphere. It is nearly impossible to create seamless globes—globes that are made of a single piece of metal. Nevertheless, astronomers and metalsmiths in what is today India and Pakistan created such celestial globes in the 1500s.

An ancient type of globe is the armillary sphere. An armillary sphere has a mini-globe of Earth surrounded by rings representing movement of visible stars and planets. The rings are adjustable, so they reflect the stars and planets visible at different times of the year in different places on the globe. Before the invention of the telescope, armillary spheres were the most important tools astronomers had. In fact, celestial globes and armillary spheres have likely been used at least as long as terrestrial globes, if not longer.

Details

A globe is a spherical model of Earth, of some other celestial body, or of the celestial sphere. Globes serve purposes similar to maps, but, unlike maps, they do not distort the surface that they portray except to scale it down. A model globe of Earth is called a terrestrial globe. A model globe of the celestial sphere is called a celestial globe.

A globe shows details of its subject. A terrestrial globe shows landmasses and water bodies. It might show nations and major cities and the network of latitude and longitude lines. Some have raised relief to show mountains and other large landforms. A celestial globe shows notable stars, and may also show positions of other prominent astronomical objects. Typically, it will also divide the celestial sphere into constellations.

The word globe comes from the Latin word globus, meaning "sphere". Globes have a long history. The first known mention of a globe is from Strabo, describing the Globe of Crates from about 150 BC. The oldest surviving terrestrial globe is the Erdapfel, made by Martin Behaim in 1492. The oldest surviving celestial globe sits atop the Farnese Atlas, carved in the 2nd century Roman Empire.

Terrestrial and planetary

Flat maps are created using a map projection that inevitably introduces an increasing amount of distortion the larger the area that the map shows. A globe is the only representation of the Earth that does not distort either the shape or the size of large features – land masses, bodies of water, etc.

The Earth's circumference is quite close to 40 million metres. Many globes are made with a circumference of one metre, so they are models of the Earth at a scale of 1:40 million. In imperial units, many globes are made with a diameter of one foot (about 30 cm), yielding a circumference of 3.14 feet (about 96 cm) and a scale of 1:42 million. Globes are also made in many other sizes.

Some globes have surface texture showing topography or bathymetry. In these, elevations and depressions are purposely exaggerated, as they otherwise would be hardly visible. For example, one manufacturer produces a three dimensional raised relief globe with a 64 cm (25 in) diameter (equivalent to a 200 cm circumference, or approximately a scale of 1:20 million) showing the highest mountains as over 2.5 cm (1 in) tall, which is about 57 times higher than the correct scale of Mount Everest.

Most modern globes are also imprinted with parallels and meridians, so that one can tell the approximate coordinates of a specific location. Globes may also show the boundaries of countries and their names.

Many terrestrial globes have one celestial feature marked on them: a diagram called the analemma, which shows the apparent motion of the Sun in the sky during a year.

Globes generally show north at the top, but many globes allow the axis to be swiveled so that southern portions can be viewed conveniently. This capability also permits exploring the Earth from different orientations to help counter the north-up bias caused by conventional map presentation.

Celestial

Celestial globes show the apparent positions of the stars in the sky. They omit the Sun, Moon and planets because the positions of these bodies vary relative to those of the stars, but the ecliptic, along which the Sun moves, is indicated. In their most basic form celestial globes represent the stars as if the viewer were looking down upon the sky as a globe that surrounds the earth.

History

The sphericity of the Earth was established by Greek astronomy in the 3rd century BC, and the earliest terrestrial globe appeared from that period. The earliest known example is the one constructed by Crates of Mallus in Cilicia (now Çukurova in modern-day Turkey), in the mid-2nd century BC.

No terrestrial globes from Antiquity have survived. An example of a surviving celestial globe is part of a Hellenistic sculpture, called the Farnese Atlas, surviving in a 2nd-century AD Roman copy in the Naples Archaeological Museum, Italy.

Early terrestrial globes depicting the entirety of the Old World were constructed in the Islamic world. During the Middle Ages in Christian Europe, while there are writings alluding to the idea that the earth was spherical, no known attempts at making a globe took place before the fifteenth century. The earliest extant terrestrial globe was made in 1492 by Martin Behaim (1459–1537) with help from the painter Georg Glockendon. Behaim was a German mapmaker, navigator, and merchant. Working in Nuremberg, Germany, he called his globe the "Nürnberg Terrestrial Globe." It is now known as the Erdapfel. Before constructing the globe, Behaim had traveled extensively. He sojourned in Lisbon from 1480, developing commercial interests and mingling with explorers and scientists. He began to construct his globe after his return to Nürnberg in 1490.

China made many mapping advancements such as sophisticated land surveys and the invention of the magnetic compass. However, no record of terrestrial globes in China exists until a globe was introduced by the Persian astronomer, Jamal ad-Din, in 1276.

Another early globe, the Hunt–Lenox Globe, ca. 1510, is thought to be the source of the phrase Hic Sunt Dracones, or "Here be dragons". A similar grapefruit-sized globe made from two halves of an ostrich egg was found in 2012 and is believed to date from 1504. It may be the oldest globe to show the New World. Stefaan Missine, who analyzed the globe for the Washington Map Society journal Portolan, said it was "part of an important European collection for decades." After a year of research in which he consulted many experts, Missine concluded the Hunt–Lenox Globe was a copper cast of the egg globe.

A facsimile globe showing America was made by Martin Waldseemüller in 1507. Another "remarkably modern-looking" terrestrial globe of the Earth was constructed by Taqi al-Din at the Constantinople observatory of Taqi ad-Din during the 1570s.

The world's first seamless celestial globe was built by Mughal scientists under the patronage of Jahangir.

Globus IMP, electro-mechanical devices including five-inch globes have been used in Soviet and Russian spacecraft from 1961 to 2002 as navigation instruments. In 2001, the TMA version of the Soyuz spacecraft replaced this instrument with a digital map.

Manufacture

Traditionally, globes were manufactured by gluing a printed paper map onto a sphere, often made from wood.

The most common type has long, thin gores (strips) of paper that narrow to a point at the poles, small disks cover over the inevitable irregularities at these points. The more gores there are, the less stretching and crumpling is required to make the paper map fit the sphere. This method of globe making was illustrated in 1802 in an engraving in The English Encyclopedia by George Kearsley.

Modern globes are often made from thermoplastic. Flat, plastic disks are printed with a distorted map of one of the Earth's hemispheres. This is placed in a machine which molds the disk into a hemispherical shape. The hemisphere is united with its opposite counterpart to form a complete globe.

Usually a globe is mounted so that its rotation axis is 23.5° (0.41 rad) from vertical, which is the angle the Earth's rotation axis deviates from perpendicular to the plane of its orbit. This mounting makes it easy to visualize how seasons change.

In the 1800s small pocket globes (less than 3 inches) were status symbols for gentlemen and educational toys for rich children.

Examples

Sorted in decreasing sizes:

* The Unisphere in Flushing Meadows, New York, at the Billie Jean King USTA Tennis Center, at 37 m (120 ft) in diameter, is the world's largest geographical globe. This corresponds to a scale of about 1:350 000. (There are larger spherical structures, such as the Cinesphere in Toronto, Ontario, Canada, but this does not have geographical or astronomical markings.)
* Wyld's Great Globe, located in London's Leicester Square from 1851-1862, was a hollow globe 60 feet 4 inches (18.39 m) in diameter designed by mapmaker James Wyld. Visitors could climb stairs to view a plaster of Paris model of the Earth's surface, complete with mountains and rivers to scale.
* Eartha, the world's largest rotating globe with a diameter of 12 m (41 ft), located at the DeLorme headquarters in Yarmouth, Maine. This corresponds to a scale of about 1:1.1 million. Eartha was constructed in 1998.
* The P-I Globe, a 13.5-ton 30-foot (9.1 m) neon globe with rotating "It's in the P-I" words and an 18-foot eagle, was made in 1948 for the Seattle Post-Intelligencer's headquarters. It was moved to the newspaper's new location in 1986.
* The Great Globe at Swanage is a stone sphere that stands at Durlston Castle within Durlston Country Park, England. Measuring 10 feet (3.0 m) in diameter and weighing 40 tons, this intricately carved globe showcases the continents, oceans, and specific regions of the world. Crafted from Portland stone, it spans about 3 meters (10 ft) in diameter.

Additional Information

A globe is the most common general-use model of spherical Earth. It is a sphere or ball that bears a map of the Earth on its surface and is mounted on an axle that permits rotation. The ancient Greeks, who knew the Earth to be a sphere, were the first to use globes to represent the surface of the Earth. Crates of Mallus is said to have made one in about 150 bce. The earliest surviving terrestrial globe was made in Nürnberg in 1492 by Martin Behaim, who almost undoubtedly influenced Christopher Columbus to attempt to sail west to the Orient. In ancient times, “celestial globes” were used to represent the constellations; the earliest surviving one is the marble Farnese globe, a celestial globe dating from about 25 ce.

Today’s globe, typically hollow, may be made of almost any light, strong material, such as cardboard, plastic, or metal. Some are translucent. They may also be inflatable. Terrestrial globes are usually mounted with the axis tilted 23.5° from the vertical, to help simulate the inclination of the Earth relative to the plane in which it orbits the Sun. Terrestrial globes may be physical, showing natural features such as deserts and mountain ranges (sometimes molded in relief), or political, showing countries, cities, etc. While most globes emphasize the surface of the land, a globe may also show the bottom of the sea. Globes also can be made to depict the surfaces of spherical bodies other than the Earth, for example, the Moon. Celestial globes are also still in use.

Jai Ganesh · Yesterday 00:11:49

2331) North Pole

Gist

North Pole, the northern end of Earth's axis, lying in the Arctic Ocean, about 450 miles (725 km) north of Greenland.

Summary

North Pole, the northern end of Earth’s axis, lying in the Arctic Ocean, about 450 miles (725 km) north of Greenland. This geographic North Pole does not coincide with the magnetic North Pole—to which magnetic compasses point and which in the early 21st century lay north of the Queen Elizabeth Islands of extreme northern Canada at approximately 82°15′ N 112°30′ W (it is steadily migrating northwest)—or with the geomagnetic North Pole, the northern end of Earth’s geomagnetic field (about 79°30′ N 71°30′ W). The geographic pole, located at a point where the ocean depth is about 13,400 feet (4,080 metres) deep and covered with drifting pack ice, experiences six months of complete sunlight and six months of total darkness each year.

The American explorer Robert E. Peary claimed to have reached the pole by dog sledge in April 1909, and another American explorer, Richard E. Byrd, claimed to have reached it by airplane on May 9, 1926; the claims of both men were later questioned. Three days after Byrd’s attempt, on May 12, the pole was definitely reached by an international team of Roald Amundsen, Lincoln Ellsworth, and Umberto Nobile, who traversed the polar region in a dirigible. The first ships to visit the pole were the U.S. nuclear submarines Nautilus (1958) and Skate (1959), the latter surfacing through the ice, and the Soviet icebreaker Arktika was the first surface ship to reach it (1977). Other notable surface expeditions include the first confirmed to reach the pole (1968; via snowmobile), the first to traverse the polar region (1969; Alaska to Svalbard, via dog sled), and the first to travel to the pole and back without resupply (1986; also via dog sled); the last expedition also included the first woman to reach the pole, American Ann Bancroft. After reaching the South Pole on January 11, 1986, the British explorer Robert Swan led an expedition to the North Pole, reaching his destination on May 14, 1989 and thereby becoming the first person to walk to both poles.

Details

The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's axis of rotation meets its surface. It is called the True North Pole to distinguish from the Magnetic North Pole.

The North Pole is by definition the northernmost point on the Earth, lying antipodally to the South Pole. It defines geodetic latitude 90° North, as well as the direction of true north. At the North Pole all directions point south; all lines of longitude converge there, so its longitude can be defined as any degree value. No time zone has been assigned to the North Pole, so any time can be used as the local time. Along tight latitude circles, counterclockwise is east and clockwise is west. The North Pole is at the center of the Northern Hemisphere. The nearest land is usually said to be Kaffeklubben Island, off the northern coast of Greenland about 700 km (430 mi) away, though some perhaps semi-permanent gravel banks lie slightly closer. The nearest permanently inhabited place is Alert on Ellesmere Island, Canada, which is located 817 km (508 mi) from the Pole.

While the South Pole lies on a continental land mass, the North Pole is located in the middle of the Arctic Ocean amid waters that are almost permanently covered with constantly shifting sea ice. The sea depth at the North Pole has been measured at 4,261 m (13,980 ft) by the Russian Mir submersible in 2007 and at 4,087 m (13,409 ft) by USS Nautilus in 1958. This makes it impractical to construct a permanent station at the North Pole (unlike the South Pole). However, the Soviet Union, and later Russia, constructed a number of manned drifting stations on a generally annual basis since 1937, some of which have passed over or very close to the Pole. Since 2002, a group of Russians have also annually established a private base, Barneo, close to the Pole. This operates for a few weeks during early spring. Studies in the 2000s predicted that the North Pole may become seasonally ice-free because of Arctic ice shrinkage, with timescales varying from 2016 to the late 21st century or later.

Attempts to reach the North Pole began in the late 19th century, with the record for "Farthest North" being surpassed on numerous occasions. The first undisputed expedition to reach the North Pole was that of the airship Norge, which overflew the area in 1926 with 16 men on board, including expedition leader Roald Amundsen. Three prior expeditions – led by Frederick Cook (1908, land), Robert Peary (1909, land) and Richard E. Byrd (1926, aerial) – were once also accepted as having reached the Pole. However, in each case later analysis of expedition data has cast doubt upon the accuracy of their claims.

The first verified individuals to reach the North Pole on the ground was in 1948 by a 24-man Soviet party, part of Aleksandr Kuznetsov's Sever-2 expedition to the Arctic, who flew part-way to the Pole first before making the final trek to the Pole on foot. The first complete land expedition to reach the North Pole was in 1968 by Ralph Plaisted, Walt Pederson, Gerry Pitzl and Jean-Luc Bombardier, using snowmobiles and with air support.

Precise definition

The Earth's axis of rotation – and hence the position of the North Pole – was commonly believed to be fixed (relative to the surface of the Earth) until, in the 18th century, the mathematician Leonhard Euler predicted that the axis might "wobble" slightly. Around the beginning of the 20th century astronomers noticed a small apparent "variation of latitude", as determined for a fixed point on Earth from the observation of stars. Part of this variation could be attributed to a wandering of the Pole across the Earth's surface, by a range of a few metres. The wandering has several periodic components and an irregular component. The component with a period of about 435 days is identified with the eight-month wandering predicted by Euler and is now called the Chandler wobble after its discoverer. The exact point of intersection of the Earth's axis and the Earth's surface, at any given moment, is called the "instantaneous pole", but because of the "wobble" this cannot be used as a definition of a fixed North Pole (or South Pole) when metre-scale precision is required.

It is desirable to tie the system of Earth coordinates (latitude, longitude, and elevations or orography) to fixed landforms. However, given plate tectonics and isostasy, there is no system in which all geographic features are fixed. Yet the International Earth Rotation and Reference Systems Service and the International Astronomical Union have defined a framework called the International Terrestrial Reference System.

Exploration:

Pre-1900

As early as the 16th century, many prominent people correctly believed that the North Pole was in a sea, which in the 19th century was called the Polynya or Open Polar Sea. It was therefore hoped that passage could be found through ice floes at favorable times of the year. Several expeditions set out to find the way, generally with whaling ships, already commonly used in the cold northern latitudes.

One of the earliest expeditions to set out with the explicit intention of reaching the North Pole was that of British naval officer William Edward Parry, who in 1827 reached latitude 82°45′ North. In 1871, the Polaris expedition, a US attempt on the Pole led by Charles Francis Hall, ended in disaster. Another British Royal Navy attempt to get to the pole, part of the British Arctic Expedition, by Commander Albert H. Markham reached a then-record 83°20'26" North in May 1876 before turning back. An 1879–1881 expedition commanded by US naval officer George W. De Long ended tragically when their ship, the USS Jeannette, was crushed by ice. Over half the crew, including De Long, were lost.

In April 1895, the Norwegian explorers Fridtjof Nansen and Hjalmar Johansen struck out for the Pole on skis after leaving Nansen's icebound ship Fram. The pair reached latitude 86°14′ North before they abandoned the attempt and turned southwards, eventually reaching Franz Josef Land.

In 1897, Swedish engineer Salomon August Andrée and two companions tried to reach the North Pole in the hydrogen balloon Örnen ("Eagle"), but came down 300 km (190 mi) north of Kvitøya, the northeasternmost part of the Svalbard archipelago. They trekked to Kvitøya but died there three months after their crash. In 1930 the remains of this expedition were found by the Norwegian Bratvaag Expedition.

The Italian explorer Luigi Amedeo, Duke of the Abruzzi and Captain Umberto Cagni of the Italian Royal Navy (Regia Marina) sailed the converted whaler Stella Polare ("Pole Star") from Norway in 1899. On 11 March 1900, Cagni led a party over the ice and reached latitude 86° 34’ on 25 April, setting a new record by beating Nansen's result of 1895 by 35 to 40 km (22 to 25 mi). Cagni barely managed to return to the camp, remaining there until 23 June. On 16 August, the Stella Polare left Rudolf Island heading south and the expedition returned to Norway.

1900–1940

The US explorer Frederick Cook claimed to have reached the North Pole on 21 April 1908 with two Inuit men, Ahwelah and Etukishook, but he was unable to produce convincing proof and his claim is not widely accepted.

The conquest of the North Pole was for many years credited to US Navy engineer Robert Peary, who claimed to have reached the Pole on 6 April 1909, accompanied by Matthew Henson and four Inuit men, Ootah, Seeglo, Egingwah, and Ooqueah. However, Peary's claim remains highly disputed and controversial. Those who accompanied Peary on the final stage of the journey were not trained in navigation, and thus could not independently confirm his navigational work, which some claim to have been particularly sloppy as he approached the Pole.

The distances and speeds that Peary claimed to have achieved once the last support party turned back seem incredible to many people, almost three times that which he had accomplished up to that point. Peary's account of a journey to the Pole and back while traveling along the direct line – the only strategy that is consistent with the time constraints that he was facing – is contradicted by Henson's account of tortuous detours to avoid pressure ridges and open leads.

The British explorer Wally Herbert, initially a supporter of Peary, researched Peary's records in 1989 and found that there were significant discrepancies in the explorer's navigational records. He concluded that Peary had not reached the Pole. Support for Peary came again in 2005, however, when British explorer Tom Avery and four companions recreated the outward portion of Peary's journey with replica wooden sleds and Canadian Eskimo Dog teams, reaching the North Pole in 36 days, 22 hours – nearly five hours faster than Peary. However, Avery's fastest 5-day march was 90 nautical miles (170 km), significantly short of the 135 nautical miles (250 km) claimed by Peary. Avery writes on his web site that "The admiration and respect which I hold for Robert Peary, Matthew Henson and the four Inuit men who ventured North in 1909, has grown enormously since we set out from Cape Columbia. Having now seen for myself how he travelled across the pack ice, I am more convinced than ever that Peary did indeed discover the North Pole."

The first claimed flight over the Pole was made on 9 May 1926 by US naval officer Richard E. Byrd and pilot Floyd Bennett in a Fokker tri-motor aircraft. Although verified at the time by a committee of the National Geographic Society, this claim has since been undermined by the 1996 revelation that Byrd's long-hidden diary's solar sextant data (which the NGS never checked) consistently contradict his June 1926 report's parallel data by over 100 mi (160 km). The secret report's alleged en-route solar sextant data were inadvertently so impossibly overprecise that he excised all these alleged raw solar observations out of the version of the report finally sent to geographical societies five months later (while the original version was hidden for 70 years), a realization first published in 2000 by the University of Cambridge after scrupulous refereeing.

The first consistent, verified, and scientifically convincing attainment of the Pole was on 12 May 1926, by Norwegian explorer Roald Amundsen and his US sponsor Lincoln Ellsworth from the airship Norge. Norge, though Norwegian-owned, was designed and piloted by the Italian Umberto Nobile. The flight started from Svalbard in Norway, and crossed the Arctic Ocean to Alaska. Nobile, with several scientists and crew from the Norge, overflew the Pole a second time on 24 May 1928, in the airship Italia. The Italia crashed on its return from the Pole, with the loss of half the crew.

Another transpolar flight [ru] was accomplished in a Tupolev ANT-25 airplane with a crew of Valery Chkalov, Georgy Baydukov and Alexander Belyakov, who flew over the North Pole on 19 June 1937, during their direct flight from the Soviet Union to the USA without any stopover.

Ice station

In May 1937 the world's first North Pole ice station, North Pole-1, was established by Soviet scientists 20 kilometres (13 mi) from the North Pole after the ever first landing of four heavy and one light aircraft onto the ice at the North Pole. The expedition members — oceanographer Pyotr Shirshov, meteorologist Yevgeny Fyodorov, radio operator Ernst Krenkel, and the leader Ivan Papanin — conducted scientific research at the station for the next nine months. By 19 February 1938, when the group was picked up by the ice breakers Taimyr and Murman, their station had drifted 2850 km to the eastern coast of Greenland.

1940–2000

In May 1945 an RAF Lancaster of the Aries expedition became the first Commonwealth aircraft to overfly the North Geographic and North Magnetic Poles. The plane was piloted by David Cecil McKinley of the Royal Air Force. It carried an 11-man crew, with Kenneth C. Maclure of the Royal Canadian Air Force in charge of all scientific observations. In 2006, Maclure was honoured with a spot in Canada's Aviation Hall of Fame.

Discounting Peary's disputed claim, the first men to set foot at the North Pole were a Soviet party including geophysicists Mikhail Ostrekin and Pavel Senko, oceanographers Mikhail Somov and Pavel Gordienko, and other scientists and flight crew (24 people in total) of Aleksandr Kuznetsov's Sever-2 expedition (March–May 1948). It was organized by the Chief Directorate of the Northern Sea Route. The party flew on three planes (pilots Ivan Cherevichnyy, Vitaly Maslennikov and Ilya Kotov) from Kotelny Island to the North Pole and landed there at 4:44pm (Moscow Time, UTC+04:00) on 23 April 1948. They established a temporary camp and for the next two days conducted scientific observations. On 26 April the expedition flew back to the continent.

Next year, on 9 May 1949 two other Soviet scientists (Vitali Volovich and Andrei Medvedev) became the first people to parachute onto the North Pole. They jumped from a Douglas C-47 Skytrain, registered CCCP H-369.

On 3 May 1952, U.S. Air Force Lieutenant Colonel Joseph O. Fletcher and Lieutenant William Pershing Benedict, along with scientist Albert P. Crary, landed a modified Douglas C-47 Skytrain at the North Pole. Some Western sources considered this to be the first landing at the Pole until the Soviet landings became widely known.

The United States Navy submarine USS Nautilus (SSN-571) crossed the North Pole on 3 August 1958. On 17 March 1959 USS Skate (SSN-578) surfaced at the Pole, breaking through the ice above it, becoming the first naval vessel to do so.

The first confirmed surface conquest of the North Pole was accomplished by Ralph Plaisted, Walt Pederson, Gerry Pitzl and Jean Luc Bombardier, who traveled over the ice by snowmobile and arrived on 19 April 1968. The United States Air Force independently confirmed their position.

On 6 April 1969 Wally Herbert and companions Allan Gill, Roy Koerner and Kenneth Hedges of the British Trans-Arctic Expedition became the first men to reach the North Pole on foot (albeit with the aid of dog teams and airdrops). They continued on to complete the first surface crossing of the Arctic Ocean – and by its longest axis, Barrow, Alaska, to Svalbard – a feat that has never been repeated. Because of suggestions (later proven false) of Plaisted's use of air transport, some sources classify Herbert's expedition as the first confirmed to reach the North Pole over the ice surface by any means. In the 1980s Plaisted's pilots Weldy Phipps and Ken Lee signed affidavits asserting that no such airlift was provided. It is also said that Herbert was the first person to reach the pole of inaccessibility.

On 17 August 1977 the Soviet nuclear-powered icebreaker Arktika completed the first surface vessel journey to the North Pole.

In 1982 Ranulph Fiennes and Charles R. Burton became the first people to cross the Arctic Ocean in a single season. They departed from Cape Crozier, Ellesmere Island, on 17 February 1982 and arrived at the geographic North Pole on 10 April 1982. They travelled on foot and snowmobile. From the Pole, they travelled towards Svalbard but, due to the unstable nature of the ice, ended their crossing at the ice edge after drifting south on an ice floe for 99 days. They were eventually able to walk to their expedition ship MV Benjamin Bowring and boarded it on 4 August 1982 at position 80:31N 00:59W. As a result of this journey, which formed a section of the three-year Transglobe Expedition 1979–1982, Fiennes and Burton became the first people to complete a circumnavigation of the world via both North and South Poles, by surface travel alone. This achievement remains unchallenged to this day. The expedition crew included a Jack Russell Terrier named Bothie who became the first dog to visit both poles.

In 1985 Sir Edmund Hillary (the first man to stand on the summit of Mount Everest) and Neil Armstrong (the first man to stand on the moon) landed at the North Pole in a small twin-engined ski plane. Hillary thus became the first man to stand at both poles and on the summit of Everest.

In 1986 Will Steger, with seven teammates, became the first to be confirmed as reaching the Pole by dogsled and without resupply.

USS Gurnard (SSN-662) operated in the Arctic Ocean under the polar ice cap from September to November 1984 in company with one of her sister ships, the attack submarine USS Pintado (SSN-672). On 12 November 1984 Gurnard and Pintado became the third pair of submarines to surface together at the North Pole. In March 1990, Gurnard deployed to the Arctic region during exercise Ice Ex '90 and completed only the fourth winter submerged transit of the Bering and Seas. Gurnard surfaced at the North Pole on 18 April, in the company of the USS Seahorse (SSN-669).

On 6 May 1986 USS Archerfish (SSN 678), USS Ray (SSN 653) and USS Hawkbill (SSN-666) surfaced at the North Pole, the first tri-submarine surfacing at the North Pole.

On 21 April 1987 Shinji Kazama of Japan became the first person to reach the North Pole on a motorcycle.

On 18 May 1987 USS Billfish (SSN 676), USS Sea Devil (SSN 664) and HMS Superb (S 109) surfaced at the North Pole, the first international surfacing at the North Pole.

In 1988 a team of 13 (9 Soviets, 4 Canadians) skied across the arctic from Siberia to northern Canada. One of the Canadians, Richard Weber, became the first person to reach the Pole from both sides of the Arctic Ocean.

On April 16, 1990, a German-Swiss expedition led by a team of the University of Giessen reached the Geographic North Pole for studies on pollution of pack ice, snow and air. Samples taken were analyzed in cooperation with the Geological Survey of Canada and the Alfred Wegener Institute for Polar and Marine Research. Further stops for sample collections were on multi-year sea ice at 86°N, at Cape Columbia and Ward Hunt Island.

On 4 May 1990 Børge Ousland and Erling Kagge became the first explorers ever to reach the North Pole unsupported, after a 58-day ski trek from Ellesmere Island in Canada, a distance of 800 km.

On 7 September 1991 the German research vessel Polarstern and the Swedish icebreaker Oden reached the North Pole as the first conventional powered vessels. Both scientific parties and crew took oceanographic and geological samples and had a common tug of war and a football game on an ice floe. Polarstern again reached the pole exactly 10 years later, with the Healy.

In 1998, 1999, and 2000, Lada Niva Marshs (special very large wheeled versions made by BRONTO, Lada/Vaz's experimental product division) were driven to the North Pole. The 1998 expedition was dropped by parachute and completed the track to the North Pole. The 2000 expedition departed from a Russian research base around 114 km from the Pole and claimed an average speed of 20–15 km/h in an average temperature of −30 °C.

21st century

Commercial airliner flights on the polar routes may pass within viewing distance of the North Pole. For example, a flight from Chicago to Beijing may come close as latitude 89° N, though because of prevailing winds return journeys go over the Bering Strait. In recent years journeys to the North Pole by air (landing by helicopter or on a runway prepared on the ice) or by icebreaker have become relatively routine, and are even available to small groups of tourists through adventure holiday companies. Parachute jumps have frequently been made onto the North Pole in recent years. The temporary seasonal Russian camp of Barneo has been established by air a short distance from the Pole annually since 2002, and caters for scientific researchers as well as tourist parties. Trips from the camp to the Pole itself may be arranged overland or by helicopter.

The first attempt at underwater exploration of the North Pole was made on 22 April 1998 by Russian firefighter and diver Andrei Rozhkov with the support of the Diving Club of Moscow State University, but ended in fatality. The next attempted dive at the North Pole was organized the next year by the same diving club, and ended in success on 24 April 1999. The divers were Michael Wolff (Austria), Brett Cormick (UK), and Bob Wass (USA).

In 2005 the United States Navy submarine USS Charlotte (SSN-766) surfaced through 155 cm (61 in) of ice at the North Pole and spent 18 hours there.

In July 2007 British endurance swimmer Lewis Gordon Pugh completed a 1 km (0.62 mi) swim at the North Pole. His feat, undertaken to highlight the effects of global warming, took place in clear water that had opened up between the ice floes.[51] His later attempt to paddle a kayak to the North Pole in late 2008, following the erroneous prediction of clear water to the Pole, was stymied when his expedition found itself stuck in thick ice after only three days. The expedition was then abandoned.

By September 2007 the North Pole had been visited 66 times by different surface ships: 54 times by Soviet and Russian icebreakers, 4 times by Swedish Oden, 3 times by German Polarstern, 3 times by USCGC Healy and USCGC Polar Sea, and once by CCGS Louis S. St-Laurent and by Swedish Vidar Viking.

2007 descent to the North Pole seabed

On 2 August 2007 a Russian scientific expedition Arktika 2007 made the first ever manned descent to the ocean floor at the North Pole, to a depth of 4.3 km (2.7 mi), as part of the research programme in support of Russia's 2001 extended continental shelf claim to a large swathe of the Arctic Ocean floor. The descent took place in two MIR submersibles and was led by Soviet and Russian polar explorer Artur Chilingarov. In a symbolic act of visitation, the Russian flag was placed on the ocean floor exactly at the Pole.

The expedition was the latest in a series of efforts intended to give Russia a dominant influence in the Arctic according to The New York Times.

MLAE 2009 Expedition

In 2009 the Russian Marine Live-Ice Automobile Expedition (MLAE-2009) with Vasily Elagin as a leader and a team of Afanasy Makovnev, Vladimir Obikhod, Alexey Shkrabkin, Sergey Larin, Alexey Ushakov and Nikolay Nikulshin reached the North Pole on two custom-built 6 x 6 low-pressure-tire ATVs. The vehicles, Yemelya-1 and Yemelya-2, were designed by Vasily Elagin, a Russian mountain climber, explorer and engineer. They reached the North Pole on 26 April 2009, 17:30 (Moscow time). The expedition was partly supported by Russian State Aviation. The Russian Book of Records recognized it as the first successful vehicle trip from land to the Geographical North Pole.

MLAE 2013 Expedition

On 1 March 2013 the Russian Marine Live-Ice Automobile Expedition (MLAE 2013) with Vasily Elagin as a leader, and a team of Afanasy Makovnev, Vladimir Obikhod, Alexey Shkrabkin, Andrey Vankov, Sergey Isayev and Nikolay Kozlov on two custom-built 6 x 6 low-pressure-tire ATVs—Yemelya-3 and Yemelya-4—started from Golomyanny Island (the Severnaya Zemlya Archipelago) to the North Pole across drifting ice of the Arctic Ocean. The vehicles reached the Pole on 6 April and then continued to the Canadian coast. The coast was reached on 30 April 2013 (83°08N, 075°59W Ward Hunt Island), and on 5 May 2013 the expedition finished in Resolute Bay, NU. The way between the Russian borderland (Machtovyi Island of the Severnaya Zemlya Archipelago, 80°15N, 097°27E) and the Canadian coast (Ward Hunt Island, 83°08N, 075°59W) took 55 days; it was ~2300 km across drifting ice and about 4000 km in total. The expedition was totally self-dependent and used no external supplies. The expedition was supported by the Russian Geographical Society.

Day and night

The sun at the North Pole is continuously above the horizon during the summer and continuously below the horizon during the winter. Sunrise is just before the March equinox (around 20 March); the Sun then takes three months to reach its highest point of near 23½° elevation at the summer solstice (around 21 June), after which time it begins to sink, reaching sunset just after the September equinox (around 23 September). When the Sun is visible in the polar sky, it appears to move in a horizontal circle above the horizon. This circle gradually rises from near the horizon just after the vernal equinox to its maximum elevation (in degrees) above the horizon at summer solstice and then sinks back toward the horizon before sinking below it at the autumnal equinox. Hence the North and South Poles experience the slowest rates of sunrise and sunset on Earth.

The twilight period that occurs before sunrise and after sunset has three different definitions:

* a civil twilight period of about two weeks;
* a nautical twilight period of about five weeks; and
* an astronomical twilight period of about seven weeks.

These effects are caused by a combination of the Earth's axial tilt and its revolution around the Sun. The direction of the Earth's axial tilt, as well as its angle relative to the plane of the Earth's orbit around the Sun, remains very nearly constant over the course of a year (both change very slowly over long time periods). At northern midsummer the North Pole is facing towards the Sun to its maximum extent. As the year progresses and the Earth moves around the Sun, the North Pole gradually turns away from the Sun until at midwinter it is facing away from the Sun to its maximum extent. A similar sequence is observed at the South Pole, with a six-month time difference.

Since longitude is undefined at the north pole, the exact time is a matter of convention. Polar expeditions use whatever time is most convenient, such as Greenwich Mean Time or the time zone of their origin.

Jai Ganesh · Yesterday 16:56:33

2332) Veggie Burger

Gist

Commercially available veggie burgers may contain: Vegetable protein (derived from beans, soy, peas or other source) Other vegetables such as carrots, squash, mushrooms, peppers, beets, water chestnuts or onions.

A veggie burger is a food that looks like a hamburger but that is made with vegetables instead of meat.

Details

A veggie burger or meatless burger is a hamburger made with a patty that does not contain meat, or the patty of such a hamburger. The patty may be made from ingredients like beans (especially soybeans and tofu), nuts, grains, seeds, or fungi such as mushrooms or mycoprotein.

The essence of the veggie burger patty has existed in various Eurasian cuisines for millennia, including in the form of grilled or fried meatless discs, or as koftas, a commonplace item in Indian cuisine. These may be made of entirely vegetarian ingredients such as legumes or other plant-derived proteins.

Preparation

Whilst commercial brands of veggie burger are widespread, hundreds of recipes exist for veggie burgers online and in cookbooks, aimed at the home cook and based on cereal grains, nuts, seeds, breadcrumbs, beans, textured soya protein, with starchy flours or flaxseed meal to stabilize the mix. Recipes offer a variety of flavors and textures, often containing herbs and spices and ingredients, like tamari or nutritional yeast, to increase the umami taste. Desirable characteristics include mouthfeel, a seared surface, crunch, chewiness, spiciness and resistance to crumbling. Like a meat burger, they can be pan fried, grilled, barbecued or oven cooked. Some are designed to be eaten in a toasted bun or brioche, with similar accompaniments to a traditional meat burger, such as tomato slices, onion rings, dill pickled cucumber, mayonnaise, mustard and ketchup. Others are stand-alone patties that are eaten with other vegetables, salad or a dipping sauce. Home produced veggie burgers can be frozen and stored, just like commercial varieties.

Commercial brands

Products include dried mixes to which water is added before cooking, or ready-made burgers, often found in the store chiller or freezer compartments. Some popular brands of veggie burger include the Boca Burger, the Gardenburger, Morningstar Farms, and Quorn. In the 2010s, realistic meat-like burgers were developed, led by the companies Beyond Meat and Impossible Foods.

Origin

There have been numerous claims of invention of the veggie burger. The dish, by name, may have been created in London in 1982 by Gregory Sams, who called it the 'VegeBurger'. Sams and his brother Craig had run a natural food restaurant in Paddington since the 1960s; a Carrefour hypermarket in Southampton sold 2000 packets in three weeks after its launch. An earlier reference can be heard in the 7 June 1948 episode of the American radio drama series Let George Do It called "The Mister Mirch Case" where a character refers to "vegeburgers" as a burger made of nuts and legumes.

Using the name Gardenburger, an early veggie burger was developed by Paul Wenner around 1980 or 1981 in Wenner's vegetarian restaurant, The Gardenhouse, in Gresham, Oregon.

Restaurants

Some fast food companies have been offering vegetarian foods increasingly since the beginning of the 21st century.

India

In India where vegetarianism is widespread, McDonald's, Burger King, Wendy's and KFC serve veggie burgers. In 2012, McDonald's opened its first vegetarian-only restaurant in India. A popular type of burger is the Vada pav, also known as the Bombay burger. It originated in or near the city of Mumbai and consists of a fritter (vada), cooked with potatoes mixed with green chilis and various spices, enclosed in a bread roll (pav).

United States

Burger King (BK) introduced a veggie burger in 2002, the first to be made available nationally in the U.S. They have also sold veggie burgers in their Australian franchise, Hungry Jack's. In 2019, BK rolled out the Impossible Whopper as a veggie burger that realistically imitates their signature beef-based Whopper hamburger.

Veggie burgers have been sold in certain Subways and Harvey's, as well as many chain restaurants, such as Red Robin, Chili's, Denny's, Friendly's, Culvers, Johnny Rockets, and Hard Rock Cafe. Occasionally the veggie burger option will appear at the bottom of a menu as a possible substitution for beef or turkey burgers, rather than as an individual menu item.

McDonald's

Different kinds of veggie burgers, including the vegetarian McVeggie, the vegan McVegan, and the McPlant, are also served permanently in McDonald's restaurants in:

* India (McVeggie, consisting of a fried, breaded patty of ground vegetables, with lettuce and ketchup, in a wholewheat, sesame or focaccia bun)
* Bahrain
* Cheung Chau, Hong Kong (McVeggie, in Cheung Chau Bun Festival)
* Egypt (McFalafel, consisting of a falafel patty with tomato, lettuce and tahini sauce)
* Finland (McVegan)
* Germany since February 2010, McDonald's Germany, its fourth-biggest global market, is serving veggie burgers in all its restaurants.
* Greece (McVeggie, consisting of a breaded and fried vegetable patty with tomato, iceberg lettuce and ketchup, in a sesame bun)
* Malaysia
* The Netherlands (Groentenburger=Vegetable Burger)
* Portugal (McVeggie, since November 2016)
* New Zealand (McVeggie, since December 2019)
* Sweden (McVegan)
* Switzerland (Vegi Mac)
* United Arab Emirates
* United Kingdom (McPlant)

Manufacturing process

Manufacturing often follows certain steps. One commercial recipe runs as follows.

The grains and vegetables used in the patties are first washed and thoroughly cleaned to help ensure the removal of dirt, bacteria, chemical residues, and other materials that may be on the raw products. This process can either be done by hand or through the use of machinery such as high-pressure sprayers. With the use of a conveyor belt, the food is moved along under a high-pressure sprayer to remove the debris listed above. Another method that may be used by companies is the use of a hollow drum which circulates the food while water is sprayed onto it to remove the debris.

Next, a steam-heated mixer is used to cook the grain and remove any extra debris and excess water. The mixer typically has oils within it (such as safflower oil). As the oil simmers, the grains are gradually added in and the blades are used to mix the grains around. The steam created in the mixer allows the grains to cook resulting in a puree.

Next the vegetables are cut up into smaller pieces to allow more surface area for cooking purposes. This can be done by hand or through the use of machines in factories.

The vegetables are then added to the grain mixture in the steam-heated mixture. The exact ratio of grains to vegetables is unique to each company, resulting in different textures and tastes that are produced.

As the vegetables are being cooked in the mixer, their natural sugars release, resulting in caramelization. The sweet flavors thus created from this caramelization are mixed uniformly in the mixer. The technique used for the creation of this caramelization mixture is called mirepoix. This technique is very important to the production of veggie burgers, as it adds both texture and flavor to the patty.

Dry ingredients, such as oats, can be added to the manufacturing process.

The mirepoix mixture is then placed into another mixing tub, where dry ingredients such as oats, walnuts, potato flakes, and more are added. The mixture is then folded together to make a uniform mix. The moisture from the vegetables causes the mixture to become sticky, thus clumping together like cookie dough. This is important, as it allows the veggie burger to stick together to form the patty.

The mixture is now put into an automatic patty-making machine or press. The press then punches out the patties into a disc shape onto a conveyor belt underneath. A constant spray of water may also be used to prevent any of the mixture from sticking to machinery parts. Once on the conveyor tray, the patties move along to be put onto baking trays.

Patties are first inspected to make sure they are the correct shape, size, and texture to ensure a high-quality product. The trays are then put into a heated convection oven at a designated temperature and time.

Once out of the oven, the patties are quickly frozen with techniques such as individual quick freezing and cryogenic freezing. These quick-freezing methods freeze the patties within 30 minutes to lock in nutrients and preserve texture by the formation of a number of small ice crystals.

The frozen patties are again placed on a conveyor belt that takes them to a vacuum-packaging machine. The machine seals the patties into measured plastic sleeves and draws out any excess air. The packages are then loaded into printed cardboard boxes with the aid of another machine or done manually. The flaps on the box are then sealed closed and the product is kept in temperature-controlled storage before, during, and after delivery to grocery stores.

Purpose of ingredients:

Grains

Grains are primarily used in the manufacturing of veggie burgers to act as a meat substitute. The grains, such as rice and wheat, provide carbohydrates and protein components and to provide bulk to the patty. They also provide texture to the burger, which can change depending on the type of grain used. This texture and look is important as they wish to make the patty look like a beef patty.

Vegetables

Vegetables, such as corn, carrots, and mushrooms, provide texture and taste. Additionally, they provide moisture when heated. This allows the disc shape without breaking apart easily. The vegetables also provide nutrients with the addition of some vitamins and minerals.

Dry ingredients

Adding dry ingredients, such as oats, flours, nuts, or breadcrumbs, can absorb excess moisture and liquid, which results in the patty sticking together tightly. This could turn the moist veggie patties into a sticky consistency, which also helps the patties shape easily. Dry ingredients provide proteins and fiber, which add nutritional value to the veggie patty. Dry ingredients, such as walnuts and almonds, are also rich in energy, vitamins and minerals.

Stabilizers

Tapioca starch and vegetable gum are two common ingredients used as stabilizers in veggie burger. Tapioca starch is often used as a thickening agent due to its cheaper price. It gets sticky once it is wet, which helps to hold the burger patty tightly together.[34] Vegetable gum also helps to hold everything together in the patty.

Oils

Oils, such as safflower, coconut, and olive oil, can lubricate the grain mix, and allow further cooking processing when the wheat is added. This facilitates the Maillard reaction and brings out the flavors of the veggie burger. Oils can also prevent the ingredients from sticking to the mixing machine, thus allowing them to be mixed well and heated together.

Salt

Salt is typically used for flavor, and may also be used as a preservative in veggie burgers. With the use of salt, the water activity of the food is reduced. This helps prevent the growth of micro-organisms and prolongs the shelf life of the food.

Naming

In October 2020, the EU rejected an amendment proposed by the Committee on Agriculture and Rural Development which, if passed, would have resulted in companies being forced to call veggie burgers by the term "veggie discs".

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Jai Ganesh · Yesterday 20:44:34

2333) South Pole

Gist

South Pole is the southern end of the Earth’s axis, lying in Antarctica, about 300 miles (480 km) south of the Ross Ice Shelf. This geographic South Pole does not coincide with the magnetic South Pole, from which magnetic compasses point and which lies on the Adélie Coast (at about 66°00′ S, 139°06′ E; the magnetic pole moves about 8 miles [13 km] to the northwest each year). Nor does it coincide with the geomagnetic South Pole, the southern end of the Earth’s geomagnetic field (this pole also moves; during the early 1990s it was located about 79°13′ S, 108°44′ E). The geographic pole, at an elevation of some 9,300 feet (2,830 metres; the elevation also changes constantly) above sea level, has six months of complete daylight and six months of total darkness each year. Ice thickness is 8,850 feet (2,700 metres). First reached by the Norwegian explorer Roald Amundsen on December 14, 1911, the pole was reached the following year by the British explorer Robert F. Scott and in 1929 by the American explorer Richard E. Byrd. After reaching the South Pole on January 11, 1986, the British explorer Robert Swan led an expedition to the North Pole, reaching his destination on May 14, 1989 and thereby becoming the first person to walk to both poles. The South Pole is the site of a U.S. station and landing strip (Amundsen-Scott); owing to the movement of the polar ice cap, a new location of the exact rotational pole is marked periodically by station personnel.

Summary

The South Pole is the southern end of Earth’s axis. The axis is an imaginary line through the center of Earth around which the planet rotates. The South Pole is located in Antarctica.

Geographic and Magnetic Poles

In the geographic system of latitude and longitude, the South Pole is at 90° south. All the lines of longitude run between it and the North Pole.

This geographic South Pole is not the same as the magnetic South Pole. Compasses point away from the magnetic South Pole, toward the magnetic North Pole. Although the geographic poles are fixed, the magnetic poles move slowly over time. The magnetic South Pole is now on the Adélie Coast, in the part of eastern Antarctica that is across the ocean from Australia.

A Year at the Pole

The geographic South Pole does not experience seasons, days, or nights like most other places on Earth. At the pole, six months of darkness, or winter, follow six months of daylight, or summer. The Sun rises on about September 21. It appears to move in a circle until it sets on about March 22. For the other half of the year, the South Pole is dark. This phenomenon happens because, as Earth revolves around the Sun, Earth’s axis stays tilted at the same angle. During its six months of summer, the South Pole points toward the Sun. During its six months of winter, it points away from the Sun.

Exploration and Study

Antarctica is a difficult place to explore. The first efforts to do so and to reach the South Pole began in the early 1900s. Ernest Henry Shackleton, an Irish-born British explorer, almost reached the South Pole in 1909. The first people to succeed were the Norwegian explorer Roald Amundsen and his four companions. They reached the pole on December 14, 1911. The British explorer Robert F. Scott had hoped to beat Amundsen to the pole, but he did not arrive until January 17, 1912. Scott and his men died on their return trip. U.S. explorer Richard E. Byrd made the first flight over the South Pole on November 29, 1929.

In 1957–58 British explorer Vivian Fuchs led the first crossing of Antarctica by way of the pole. The group set out in tracked vehicles in November 1957. After making it to the South Pole, the group reached the opposite coast in March 1958.

In late 1956 a U.S. Navy team began building a station at the South Pole. The facility—called the Amundsen-Scott South Pole Station—was improved in the 1970s and early 2000s.

Scientists now live there year-round.

Details

The South Pole is the southernmost point on Earth. It is the precise point of the southern intersection of Earth's axis and Earth's surface.

From the South Pole, all directions are north. Its latitude is 90 degrees south, and all lines of longitude meet there (as well as at the North Pole).

The South Pole is located on Antarctica, one of Earth's seven continents. Although land at the South Pole is only about a hundred meters above sea level, the ice sheet above it is roughly 2,700-meters (9,000-feet) thick. This elevation makes the South Pole much colder than the North Pole, which sits in the middle of the Arctic Ocean. In fact, the warmest temperature ever recorded at the South Pole was a freezing -12.3 degrees Celsius (9.9 degrees Fahrenheit).

The South Pole is close to the coldest place on Earth. The coldest temperature recorded at the South Pole, -82.8 degrees Celsius (-117.0 degrees Fahrenheit), is still warmer than the coldest temperature ever recorded, -89.2 degrees Celsius (-128.6 degrees Fahrenheit). That temperature was recorded at the Russian Vostok Research Station, about 1,300 kilometers (808 miles) away.

Because Earth rotates on a tilted axis as it revolves around the sun, sunlight is experienced in extremes at the poles. In fact, the South Pole experiences only one sunrise (at the September equinox) and one sunset (at the March equinox) every year. From the South Pole, the sun is always above the horizon in the summer and below the horizon in the winter. This means the region experiences up to 24 hours of sunlight in the summer and 24 hours of darkness in the winter.

Due to plate tectonics, the exact location of the South Pole is constantly moving. Plate tectonics is the process of large slabs of Earth's crust moving slowly around the planet, bumping into and pulling apart from one another.

Over billions of years, Earth's continents have shifted together and drifted apart. Millions of years ago, land that today is the east coast of South America was at the South Pole. Today, the ice sheet above the South Pole drifts about 10 meters (33 feet) every year.

Amundsen–Scott South Pole Station

Compared to the North Pole, the South Pole is relatively easy to travel to and study. The North Pole is in the middle of the Arctic Ocean, while the South Pole is on a stable piece of land.

The United States has had scientists working at Amundsen–Scott South Pole Station since 1956. Between 50 and 200 scientists and support staff live at the this research station at any given time. The station itself does not sit on the ground or ice sheet. It is able to adjust its elevation, to prevent it from being buried in snow, which accumulates at a rate of about 20 centimeters (eight inches) every year, and does not melt.

In the winter, the Amundsen–Scott South Pole Station is completely self-sufficient. The dark sky, freezing temperatures, and gale-force winds prevent most supplies from being flown or trekked in. All food, medical supplies, and other material must be secured before the long Antarctic winter. The station's energy is provided by three enormous generators that run on jet fuel.

In winter, stores of food are supplemented by the Amundsen–Scott South Pole Station's greenhouse. Vegetables in the greenhouse are grown with hydroponics, in a nutrient solution instead of soil.

Some of the earliest discoveries made at South Pole research stations helped support the theory of continental drift, the idea that continents drift apart and shift together. Rock samples collected near the South Pole and throughout Antarctica match samples dated to the same time period collected at tropical latitudes. Geologists conclude that the samples formed at the same time and the same place, and were torn apart over millions of years, as the planet split into different continents.

Today, the Amundsen–Scott South Pole Station is host to a wide variety of research. The relatively undisturbed ice sheet maintains a pristine record of snowfalls, air quality, and weather patterns. Ice cores provide data for glaciologists, climatologists, and meteorologists, as well as scientists tracking patterns in climate change.

The South Pole has low temperatures and humidity and high elevation, making it an outstanding place to study astronomy and astrophysics. The South Pole Telescope studies low-frequency radiation, such as microwaves and radio waves. The South Pole Telescope is one of the instruments designed measure the cosmic microwave background (CMB)–faint, diffuse radiation left over from the Big Bang.

Astrophysicists also search for tiny particles called neutrinos at the South Pole. Neutrinos interact very, very weakly with all other matter. Neutrino detectors therefore must be very large to detect a measurable number of the particles. The Amundsen–Scott South Pole Station's IceCube Neutrino Detector has more than 80 "strings" of sensors reaching as deep as 2,450 meters (8,038 feet) beneath the ice. It is the largest neutrino detector in the world.

Ecosystems at the South Pole

Although the Antarctic coast is teeming with marine life, few biologists conduct research at the Amundsen–Scott South Pole Station. The habitat is far too harsh for most organisms to survive.

In fact, the South Pole sits in the middle of the largest, coldest, driest, and windiest desert on Earth. More temperate parts of this desert (called either East Antarctica or Maudlandia) support native flora such as moss and lichen, and organisms such as mites and midges. The South Pole itself has no native plant or animal life at all. Sometimes, however, seabirds such as skuas can be spotted if they are blown off-course.

Exploration

The early 20th century's "Race to the Pole" stands as a symbol of the harrowing nature of polar exploration.

European and American explorers had attempted to reach the South Pole since British Capt. Robert Falcon Scott's expedition of 1904. Scott, along with fellow Antarctic explorers Ernest Shackleton and Edward Wilson, came within 660 kilometers (410 miles) of the pole, but turned back due to weather and inadequate supplies.

Shackleton and Scott were determined to reach the pole. Scott worked with scientists, intent on using the best techniques to gather data and collect samples.

Shackleton also conducted scientific surveys, although his expeditions were more narrowly focused on reaching the South Pole. He came within 160 kilometers (100 miles) of the pole in 1907, but again had to turn back due to weather.

Scott gathered public support and public funding for his 1910 Terra Nova expedition. He secured provisions and scientific equipment. In addition to the sailors and scientists on his team, the Terra Nova expedition also included tourists—guests who helped finance the voyage in exchange for taking part in it.

On the way to Antarctica, the Terra Nova expedition stopped in Australia to take on final supplies. Here, Scott received a surprising telegram from Norwegian explorer Roald Amundsen: "Beg leave to inform you Fram [Amundsen's ship] proceeding Antarctic."

Amundsen was apparently racing for the pole, ahead of Scott, but had kept all preparation secret. His initial ambition, to be the first to reach the North Pole, had been thwarted by American explorers Frederick Cook and Robert Peary, both of whom claimed to reach the North Pole first. (Both claims are now disputed, and Amundsen's flight over the North Pole is generally recognized as the first verified journey there.)

The Terra Nova and Fram expeditions arrived in Antarctica about the same time, in the middle of the Antarctic summer (January). They set up base camps about 640 kilometers (400 miles) apart. As they proceeded south, both expeditions established resupply depots with supplies for their return journey. While Scott's team stuck to a route forged by Shackleton years earlier, Amundsen took a new route.

Scott proceeded with scientific and expeditionary equipment hauled by dogs, ponies, and motor sledges. The motorized equipment soon broke down, and the ponies could not adapt to the harsh Antarctic climate. Even the sled dogs became weary. All the ponies died, and most members of the expedition turned back. Only four men from the Terra Nova expedition (including Scott's friend Wilson) proceeded with Scott to the pole.

Amundsen traveled by dogsled, with a team of explorers, skiers, and mushers. The foresight and navigation paid off: Amundsen reached the pole in December 1911. He called the camp Polheim, and the entire Fram expedition successfully returned to their resupply depots, ship, and Norway.

More than a month later, Scott reached the South Pole, only to be met by Amundsen's camp—he had left a tent, equipment, and supplies for Scott, as well as a note for the King of Norway to be delivered if the Fram expedition failed to make it back.

Disheartened, Scott's team slowly headed back north. They faced colder temperatures and harsher weather than Amundsen's team. They had fewer supplies. Suffering from hunger, hypothermia, and frostbite, all members of Scott's South Pole expedition died fewer than 18 kilometers (11 miles) from a resupply depot.

American explorer Richard E. Byrd became the first person to fly over the South Pole, in 1926, and the Amundsen–Scott South Pole Station was established 30 years later.

However, the next overland expedition to the South Pole was not made until 1958, more than 40 years after Amundsen and Scott's deadly race. The 1958 expedition was led by legendary New Zealand mountaineer Sir Edmund Hillary, who had become the first person to scale Mount Everest in 1953.

Transportation to the South Pole

Almost all scientists and support personnel, as well as supplies, are flown in to the South Pole. Hardy military aircraft usually fly from McMurdo Station, an American facility on the Antarctic coast and the most populated area on the continent. The extreme and unpredictable weather around the pole can often delay flights.

In 2009, the U.S. completed construction of the South Pole Traverse. Also called the McMurdo-South Pole Highway, this stretch of unpaved road runs more than 1,600 kilometers (995 miles) over the Antarctic ice sheet, from McMurdo Station to the Amundsen–Scott South Pole Station. It takes about 40 days for supplies to reach the pole from McMurdo, but the route is far more reliable and inexpensive than air flights. The highway can also supply much heavier equipment (such as that needed by the South Pole's astrophysics laboratories) than aircraft.

Resources and Territorial Claims

The entire continent of Antarctica has no official political boundaries. Seven countries made defined claims to Antarctic territory prior to the Antarctic Treaty of 1959, which does not legally recognize any claims.

Additional Information

The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the point in the Southern Hemisphere where the Earth's axis of rotation meets its surface. It is called the True South Pole to distinguish from the Magnetic South Pole.

The South Pole is by definition the southernmost point on the Earth, lying antipodally to the North Pole. It defines geodetic latitude 90° South, as well as the direction of true south. At the South Pole all directions point North; all lines of longitude converge there, so its longitude can be defined as any degree value. No time zone has been assigned to the South Pole, so any time can be used as the local time. Along tight latitude circles, clockwise is east and counterclockwise is west. The South Pole is at the center of the Southern Hemisphere. Situated on the continent of Antarctica, it is the site of the United States Amundsen–Scott South Pole Station, which was established in 1956 and has been permanently staffed since that year.

Geography

For most purposes, the Geographic South Pole is defined as the southern point of the two points where Earth's axis of rotation intersects its surface (the other being the Geographic North Pole). However, Earth's axis of rotation is actually subject to very small "wobbles" (polar motion), so this definition is not adequate for very precise work.

The geographic coordinates of the South Pole are usually given simply as 90°S, since its longitude is geometrically undefined and irrelevant. When a longitude is desired, it may be given as 0°. At the South Pole, all directions face north. For this reason, directions at the Pole are given relative to "grid north", which points northward along the prime meridian. Along tight latitude circles, clockwise is east, and counterclockwise is west, opposite to the North Pole.

The Geographic South Pole is presently located on the continent of Antarctica, although this has not been the case for all of Earth's history because of continental drift. It sits atop a featureless, barren, windswept and icy plateau at an altitude of 2,835 m (9,301 ft) above sea level, and is located about 1,300 km (810 mi) from the nearest open sea at the Bay of Whales. The ice is estimated to be about 2,700 m (8,900 ft) thick at the Pole, so the land surface under the ice sheet is actually near sea level.

The polar ice sheet is moving at a rate of roughly 10 m (33 ft) per year in a direction between 37° and 40° west of grid north, down towards the Weddell Sea. Therefore, the position of the station and other artificial features relative to the geographic pole gradually shift over time.

The Geographic South Pole is marked by a stake in the ice alongside a small sign; these are repositioned each year in a ceremony on New Year's Day to compensate for the movement of the ice. The sign records the respective dates that Roald Amundsen and Robert F. Scott reached the Pole, followed by a short quotation from each man, and gives the elevation as "9,301 FT.". A new marker stake is designed and fabricated each year by staff at the site.

Ceremonial South Pole

The Ceremonial South Pole is an area set aside for photo opportunities at the South Pole Station. It is located some meters from the Geographic South Pole, and consists of a metallic sphere on a short barber pole, surrounded by the flags of the original Antarctic Treaty signatory states.

Historic monuments:

Amundsen's Tent

The tent was erected by the Norwegian expedition led by Roald Amundsen on its arrival on 14 December 1911. It is currently buried beneath the snow and ice in the vicinity of the Pole. It has been designated a Historic Site or Monument (HSM 80), following a proposal by Norway to the Antarctic Treaty Consultative Meeting. The precise location of the tent is unknown, but based on calculations of the rate of movement of the ice and the accumulation of snow, it is believed, as of 2010, to lie between 1.8 and 2.5 km (1.1 and 1.5 miles) from the Pole at a depth of 17 m (56 ft) below the present surface.

Argentine Flagpole

A flagpole erected at the South Geographical Pole in December 1965 by the First Argentine Overland Polar Expedition has been designated a Historic Site or Monument (HSM 1) following a proposal by Argentina to the Antarctic Treaty Consultative Meeting.

Exploration:

Pre-1900

In 1820, several expeditions claimed to have been the first to have sighted Antarctica, with the first being the Russian expedition led by Fabian Gottlieb von Bellingshausen and Mikhail Lazarev. The first landing was probably just over a year later when English-born American captain John Davis, a sealer, set foot on the ice.

The basic geography of the Antarctic coastline was not understood until the mid-to-late 19th century. American naval officer Charles Wilkes claimed (correctly) that Antarctica was a new continent, basing the claim on his exploration in 1839–40, while James Clark Ross, in his expedition of 1839–1843, hoped that he might be able to sail all the way to the South Pole; He was unsuccessful.

1900–1950

British explorer Robert Falcon Scott on the Discovery Expedition of 1901–1904 was the first to attempt to find a route from the Antarctic coastline to the South Pole. Scott, accompanied by Ernest Shackleton and Edward Wilson, set out with the aim of travelling as far south as possible, and on 31 December 1902, reached 82°16′ S. Shackleton later returned to Antarctica as leader of the British Antarctic Expedition (Nimrod Expedition) in a bid to reach the Pole. On 9 January 1909, with three companions, he reached 88°23' S – 112 miles (180 km) from the Pole – before being forced to turn back.

The first men to reach the Geographic South Pole were the Norwegian Roald Amundsen and his party on 14 December 1911. Amundsen named his camp Polheim and the entire plateau surrounding the Pole King Haakon VII Vidde in honour of King Haakon VII of Norway. Robert Falcon Scott returned to Antarctica with his second expedition, the Terra Nova Expedition, initially unaware of Amundsen's secretive expedition. Scott and four other men reached the South Pole on 17 January 1912, thirty-four days after Amundsen. On the return trip, Scott and his four companions all died of starvation and extreme cold.

In 1914 Ernest Shackleton's Imperial Trans-Antarctic Expedition set out with the goal of crossing Antarctica via the South Pole, but his ship, the Endurance, was frozen in pack ice and sank 11 months later. The overland journey was never made.

US Admiral Richard Evelyn Byrd, with the assistance of his first pilot Bernt Balchen, became the first person to fly over the South Pole on 29 November 1929.

1950–present

It was not until 31 October 1956 that humans once again set foot at the South Pole, when a party led by Admiral George J. Dufek of the US Navy landed there in an R4D-5L Skytrain (C-47 Skytrain) aircraft. The US Amundsen–Scott South Pole Station was established by air over 1956–1957 for the International Geophysical Year and has been continuously staffed since then by research and support personnel.

After Amundsen and Scott, the next people to reach the South Pole overland (albeit with some air support) were Edmund Hillary (4 January 1958) and Vivian Fuchs (19 January 1958) and their respective parties, during the Commonwealth Trans-Antarctic Expedition. There have been many subsequent expeditions to arrive at the South Pole by surface transportation, including those by Havola, Crary, and Fiennes. The first group of women to reach the pole were Pam Young, Jean Pearson, Lois Jones, Eileen McSaveney, Kay Lindsay, and Terry Tickhill in 1969. In 1978–79, Michele Eileen Raney became the first woman to winter at the South Pole.

Subsequent to the establishment, in 1987, of the logistic support base at Patriot Hills Base Camp, the South Pole became more accessible to non-government expeditions.

In the summer of 1988-1989, Chilean glaciologist Alejo Contreras Steading reached the South Pole on foot; before that, he had arrived in 1980 by other means.

On 30 December 1989, Arved Fuchs and Reinhold Messner were the first to traverse Antarctica via the South Pole without animal or motorized help, using only skis and the help of wind. Two women, Victoria E. Murden and Shirley Metz, reached the pole by land on 17 January 1989.

The fastest unsupported journey to the Geographic South Pole from the ocean is 24 days and one hour from Hercules Inlet and was set in 2011 by Norwegian adventurer Christian Eide, who beat the previous solo record set in 2009 by American Todd Carmichael of 39 days and seven hours, and the previous group record also set in 2009 of 33 days and 23 hours.

The fastest solo, unsupported and unassisted trek to the south pole by a female was performed by Hannah McKeand from the UK in 2006. She made the journey in 39 days 9 hours 33 minutes. She started on 19 November 2006 and finished on 28 December 2006.

In the 2011–12 summer, separate expeditions by Norwegian Aleksander Gamme and Australians James Castrission and Justin Jones jointly claimed the first unsupported trek without dogs or kites from the Antarctic coast to the South Pole and back. The two expeditions started from Hercules Inlet a day apart, with Gamme starting first, but completing according to plan the last few kilometers together. As Gamme traveled alone he thus simultaneously became the first to complete the task solo.

On 28 December 2018, Captain Lou Rudd became the first Briton to cross the Antarctic unassisted via the south pole, and the second person to make the journey in 56 days.[30] On 10 January 2020, Mollie Hughes became the youngest person to ski to the pole, aged

Climate and day and night

During winter (May through August), the South Pole receives no sunlight at all, and is completely dark apart from moonlight. In summer (October through February), the sun is continuously above the horizon and appears to move in a counter-clockwise circle. However, it is always relatively low in the sky, reaching a maximum of approximately 23.5° around the December solstice because of the approximately 23.5° tilt of the earth's axis. Much of the sunlight that does reach the surface is reflected by the white snow. This lack of warmth from the sun, combined with the high altitude (about 2,800 metres (9,200 ft)), means that the South Pole has one of the coldest climates on Earth (though it is not quite the coldest; that record goes to the region in the vicinity of the Vostok Station, also in Antarctica, which lies at a higher elevation).

The South Pole is at an altitude of 9,200 feet (2,800 m) but feels like 11,000 feet (3,400 m). Centripetal force from the spin of the planet throws the atmosphere toward the equator. The South Pole is colder than the North Pole primarily because of the elevation difference and for being in the middle of a continent. The North Pole is a few feet from sea level in the middle of an ocean.

In midsummer, as the sun reaches its maximum elevation of about 23.5 degrees, high temperatures at the South Pole in January average at −25.9 °C (−15 °F). As the six-month "day" wears on and the sun gets lower, temperatures drop as well: they reach −55 °C (−67 °F) around sunset (late March) and sunrise (late September). In midwinter, the average temperature remains steady at around −60 °C (−76 °F). The highest temperature ever recorded at the Amundsen–Scott South Pole Station was −12.3 °C (9.9 °F) on Christmas Day, 2011, and the lowest was −82.8 °C (−117.0 °F) on 23 June 1982 (for comparison, the lowest temperature directly recorded anywhere on earth was −89.2 °C (−128.6 °F) at Vostok Station on 21 July 1983, though −93.2 °C (−135.8 °F) was measured indirectly by satellite in East Antarctica between Dome A and Dome F in August 2010). Mean annual temperature at the South Pole is –49.5 °C (–57.1 °F).

The South Pole has an ice cap climate (Köppen climate classification EF). It resembles a desert, receiving very little precipitation. Air humidity is near zero. However, high winds can cause the blowing of snowfall, and the accumulation of snow amounts to about 7 cm (2.8 in) per year. The former dome seen in pictures of the Amundsen–Scott station is partially buried due to snow storms, and the entrance to the dome had to be regularly bulldozed to uncover it. More recent buildings are raised on stilts so that the snow does not build up against their sides.

Time

In most places on Earth, local time is determined by longitude, such that the time of day is more-or-less synchronised to the perceived position of the Sun in the sky (for example, at midday the Sun is roughly perceived to be at its highest). This line of reasoning fails at the South Pole, where the Sun is seen to rise and set only once per year with solar elevation varying only with day of the year, not time of day. There is no a priori reason for placing the South Pole in any particular time zone, but as a matter of practical convenience the Amundsen–Scott South Pole Station keeps New Zealand Time (UTC+12/UTC+13). This is because the US flies its resupply missions ("Operation Deep Freeze") out of McMurdo Station, which is supplied from Christchurch, New Zealand.

Flora and fauna

Due to its exceptionally harsh climate, there are no native resident plants or animals at the South Pole. Off-course south polar skuas and snow petrels are occasionally seen there.

In 2000 it was reported that microbes had been detected living in the South Pole ice. Scientists published in the journal Gondwana Research that evidence had been found of dinosaurs with feathers to protect the animals from the extreme cold. The fossils had been found over 100 years ago in Koonwarra, Australia, but in sediment which had accumulated under a lake which had been near to the South Pole millions of years ago.

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Jai Ganesh · Today 00:04:01

2333) Matter

Gist

In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume.

Matter is anything that takes up space and can be weighed. In other words, matter has volume and mass.

Summary

Matter is material substance that constitutes the observable universe and, together with energy, forms the basis of all objective phenomena.

At the most fundamental level, matter is composed of elementary particles known as quarks and leptons (the class of elementary particles that includes electrons). Quarks combine into protons and neutrons and, along with electrons, form atoms of the elements of the periodic table, such as hydrogen, oxygen, and iron. Atoms may combine further into molecules such as the water molecule, H2O. Large groups of atoms or molecules in turn form the bulk matter of everyday life.

Depending on temperature and other conditions, matter may appear in any of several states. At ordinary temperatures, for instance, gold is a solid, water is a liquid, and nitrogen is a gas, as defined by certain characteristics: solids hold their shape, liquids take on the shape of the container that holds them, and gases fill an entire container. These states can be further categorized into subgroups. Solids, for example, may be divided into those with crystalline or amorphous structures or into metallic, ionic, covalent, or molecular solids, on the basis of the kinds of bonds that hold together the constituent atoms. Less-clearly defined states of matter include plasmas, which are ionized gases at very high temperatures; foams, which combine aspects of liquids and solids; and clusters, which are assemblies of small numbers of atoms or molecules that display both atomic-level and bulklike properties.

However, all matter of any type shares the fundamental property of inertia, which—as formulated within Isaac Newton’s three laws of motion—prevents a material body from responding instantaneously to attempts to change its state of rest or motion. The mass of a body is a measure of this resistance to change; it is enormously harder to set in motion a massive ocean liner than it is to push a bicycle. Another universal property is gravitational mass, whereby every physical entity in the universe acts so as to attract every other one, as first stated by Newton and later refined into a new conceptual form by Albert Einstein.

Although basic ideas about matter trace back to Newton and even earlier to Aristotle’s natural philosophy, further understanding of matter, along with new puzzles, began emerging in the early 20th century. Einstein’s theory of special relativity (1905) shows that matter (as mass) and energy can be converted into each other according to the famous equation E = mc2, where E is energy, m is mass, and c is the speed of light. This transformation occurs, for instance, during nuclear fission, in which the nucleus of a heavy element such as uranium splits into two fragments of smaller total mass, with the mass difference released as energy. Einstein’s theory of gravitation, also known as his theory of general relativity (1916), takes as a central postulate the experimentally observed equivalence of inertial mass and gravitational mass and shows how gravity arises from the distortions that matter introduces into the surrounding space-time continuum.

The concept of matter is further complicated by quantum mechanics, whose roots go back to Max Planck’s explanation in 1900 of the properties of electromagnetic radiation emitted by a hot body. In the quantum view, elementary particles behave both like tiny balls and like waves that spread out in space—a seeming paradox that has yet to be fully resolved. Additional complexity in the meaning of matter comes from astronomical observations that began in the 1930s and that show that a large fraction of the universe consists of “dark matter.” This invisible material does not affect light and can be detected only through its gravitational effects. Its detailed nature has yet to be determined.

On the other hand, through the contemporary search for a unified field theory, which would place three of the four types of interactions between elementary particles (the strong force, the weak force, and the electromagnetic force, excluding only gravity) within a single conceptual framework, physicists may be on the verge of explaining the origin of mass. Although a fully satisfactory grand unified theory (GUT) has yet to be derived, one component, the electroweak theory of Sheldon Glashow, Abdus Salam, and Steven Weinberg (who shared the 1979 Nobel Prize for Physics for this work) predicted that an elementary subatomic particle known as the Higgs boson imparts mass to all known elementary particles. After years of experiments using the most powerful particle accelerators available, scientists finally announced in 2012 the discovery of the Higgs boson.

Details

In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which are made up of interacting subatomic particles, and in everyday as well as scientific usage, matter generally includes atoms and anything made up of them, and any particles (or combination of particles) that act as if they have both rest mass and volume. However it does not include massless particles such as photons, or other energy phenomena or waves such as light or heat. Matter exists in various states (also known as phases). These include classical everyday phases such as solid, liquid, and gas – for example water exists as ice, liquid water, and gaseous steam – but other states are possible, including plasma, Bose–Einstein condensates, fermionic condensates, and quark–gluon plasma.

Usually atoms can be imagined as a nucleus of protons and neutrons, and a surrounding "cloud" of orbiting electrons which "take up space". However, this is only somewhat correct because subatomic particles and their properties are governed by their quantum nature, which means they do not act as everyday objects appear to act – they can act like waves as well as particles, and they do not have well-defined sizes or positions. In the Standard Model of particle physics, matter is not a fundamental concept because the elementary constituents of atoms are quantum entities which do not have an inherent "size" or "volume" in any everyday sense of the word. Due to the exclusion principle and other fundamental interactions, some "point particles" known as fermions (quarks, leptons), and many composites and atoms, are effectively forced to keep a distance from other particles under everyday conditions; this creates the property of matter which appears to us as matter taking up space.

For much of the history of the natural sciences, people have contemplated the exact nature of matter. The idea that matter was built of discrete building blocks, the so-called particulate theory of matter, appeared in both ancient Greece and ancient India. Early philosophers who proposed the particulate theory of matter include the ancient Indian philosopher Kanada (c. 6th–century BCE or after), pre-Socratic Greek philosopher Leucippus (~490 BCE), and pre-Socratic Greek philosopher Democritus (~470–380 BCE).

Related concepts:

Comparison with mass

Matter should not be confused with mass, as the two are not the same in modern physics. Matter is a general term describing any 'physical substance'. By contrast, mass is not a substance but rather an extensive property of matter and other substances or systems; various types of mass are defined within physics – including but not limited to rest mass, inertial mass, relativistic mass, and mass–energy.

While there are different views on what should be considered matter, the mass of a substance has exact scientific definitions. Another difference is that matter has an "opposite" called antimatter, but mass has no opposite—there is no such thing as "anti-mass" or negative mass, so far as is known, although scientists do discuss the concept. Antimatter has the same (i.e. positive) mass property as its normal matter counterpart.

Different fields of science use the term matter in different, and sometimes incompatible, ways. Some of these ways are based on loose historical meanings from a time when there was no reason to distinguish mass from simply a quantity of matter. As such, there is no single universally agreed scientific meaning of the word "matter". Scientifically, the term "mass" is well-defined, but "matter" can be defined in several ways. Sometimes in the field of physics "matter" is simply equated with particles that exhibit rest mass (i.e., that cannot travel at the speed of light), such as quarks and leptons. However, in both physics and chemistry, matter exhibits both wave-like and particle-like properties, the so-called wave–particle duality.

Relation with chemical substance

A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be combined without reacting, they may form a chemical mixture. If a mixture is separated to isolate one chemical substance to a desired degree, the resulting substance is said to be chemically pure.

Chemical substances can exist in several different physical states or phases (e.g. solids, liquids, gases, or plasma) without changing their chemical composition. Substances transition between these phases of matter in response to changes in temperature or pressure. Some chemical substances can be combined or converted into new substances by means of chemical reactions. Chemicals that do not possess this ability are said to be inert.

Pure water is an example of a chemical substance, with a constant composition of two hydrogen atoms bonded to a single oxygen atom (i.e. H2O). The atomic ratio of hydrogen to oxygen is always 2:1 in every molecule of water. Pure water will tend to boil near 100 °C (212 °F), an example of one of the characteristic properties that define it. Other notable chemical substances include diamond (a form of the element carbon), table salt (NaCl; an ionic compound), and refined sugar (C12H22O11; an organic compound).

Definition:

Based on atoms

A definition of "matter" based on its physical and chemical structure is: matter is made up of atoms. Such atomic matter is also sometimes termed ordinary matter. As an example, deoxyribonucleic acid molecules (DNA) are matter under this definition because they are made of atoms. This definition can be extended to include charged atoms and molecules, so as to include plasmas (gases of ions) and electrolytes (ionic solutions), which are not obviously included in the atoms definition. Alternatively, one can adopt the protons, neutrons, and electrons definition.

Based on protons, neutrons and electrons

A definition of "matter" more fine-scale than the atoms and molecules definition is: matter is made up of what atoms and molecules are made of, meaning anything made of positively charged protons, neutral neutrons, and negatively charged electrons. This definition goes beyond atoms and molecules, however, to include substances made from these building blocks that are not simply atoms or molecules, for example electron beams in an old cathode ray tube television, or white dwarf matter—typically, carbon and oxygen nuclei in a sea of degenerate electrons. At a microscopic level, the constituent "particles" of matter such as protons, neutrons, and electrons obey the laws of quantum mechanics and exhibit wave–particle duality. At an even deeper level, protons and neutrons are made up of quarks and the force fields (gluons) that bind them together, leading to the next definition.

Based on quarks and leptons

As seen in the above discussion, many early definitions of what can be called "ordinary matter" were based upon its structure or "building blocks". On the scale of elementary particles, a definition that follows this tradition can be stated as: "ordinary matter is everything that is composed of quarks and leptons", or "ordinary matter is everything that is composed of any elementary fermions except antiquarks and antileptons". The connection between these formulations follows.

Leptons (the most famous being the electron), and quarks (of which baryons, such as protons and neutrons, are made) combine to form atoms, which in turn form molecules. Because atoms and molecules are said to be matter, it is natural to phrase the definition as: "ordinary matter is anything that is made of the same things that atoms and molecules are made of". (However, notice that one also can make from these building blocks matter that is not atoms or molecules.) Then, because electrons are leptons, and protons and neutrons are made of quarks, this definition in turn leads to the definition of matter as being "quarks and leptons", which are two of the four types of elementary fermions (the other two being antiquarks and antileptons, which can be considered antimatter as described later). Carithers and Grannis state: "Ordinary matter is composed entirely of first-generation particles, namely the [up] and [down] quarks, plus the electron and its neutrino." (Higher generations particles quickly decay into first-generation particles, and thus are not commonly encountered.)

This definition of ordinary matter is more subtle than it first appears. All the particles that make up ordinary matter (leptons and quarks) are elementary fermions, while all the force carriers are elementary bosons. The W and Z bosons that mediate the weak force are not made of quarks or leptons, and so are not ordinary matter, even if they have mass. In other words, mass is not something that is exclusive to ordinary matter.

The quark–lepton definition of ordinary matter, however, identifies not only the elementary building blocks of matter, but also includes composites made from the constituents (atoms and molecules, for example). Such composites contain an interaction energy that holds the constituents together, and may constitute the bulk of the mass of the composite. As an example, to a great extent, the mass of an atom is simply the sum of the masses of its constituent protons, neutrons and electrons. However, digging deeper, the protons and neutrons are made up of quarks bound together by gluon fields (see dynamics of quantum chromodynamics) and these gluon fields contribute significantly to the mass of hadrons. In other words, most of what composes the "mass" of ordinary matter is due to the binding energy of quarks within protons and neutrons. For example, the sum of the mass of the three quarks in a nucleon is approximately 12.5 MeV/c^2, which is low compared to the mass of a nucleon (approximately 938 MeV/c^2). The bottom line is that most of the mass of everyday objects comes from the interaction energy of its elementary components.

The Standard Model groups matter particles into three generations, where each generation consists of two quarks and two leptons. The first generation is the up and down quarks, the electron and the electron neutrino; the second includes the charm and strange quarks, the muon and the muon neutrino; the third generation consists of the top and bottom quarks and the tau and tau neutrino. The most natural explanation for this would be that quarks and leptons of higher generations are excited states of the first generations. If this turns out to be the case, it would imply that quarks and leptons are composite particles, rather than elementary particles.

This quark–lepton definition of matter also leads to what can be described as "conservation of (net) matter" laws—discussed later below. Alternatively, one could return to the mass–volume–space concept of matter, leading to the next definition, in which antimatter becomes included as a subclass of matter.

Based on elementary fermions (mass, volume, and space)

A common or traditional definition of matter is "anything that has mass and volume (occupies space)". For example, a car would be said to be made of matter, as it has mass and volume (occupies space).

The observation that matter occupies space goes back to antiquity. However, an explanation for why matter occupies space is recent, and is argued to be a result of the phenomenon described in the Pauli exclusion principle, which applies to fermions. Two particular examples where the exclusion principle clearly relates matter to the occupation of space are white dwarf stars and neutron stars, discussed further below.

Thus, matter can be defined as everything composed of elementary fermions. Although we do not encounter them in everyday life, antiquarks (such as the antiproton) and antileptons (such as the positron) are the antiparticles of the quark and the lepton, are elementary fermions as well, and have essentially the same properties as quarks and leptons, including the applicability of the Pauli exclusion principle which can be said to prevent two particles from being in the same place at the same time (in the same state), i.e. makes each particle "take up space". This particular definition leads to matter being defined to include anything made of these antimatter particles as well as the ordinary quark and lepton, and thus also anything made of mesons, which are unstable particles made up of a quark and an antiquark.

In general relativity and cosmology

In the context of relativity, mass is not an additive quantity, in the sense that one cannot add the rest masses of particles in a system to get the total rest mass of the system. In relativity, usually a more general view is that it is not the sum of rest masses, but the energy–momentum tensor that quantifies the amount of matter. This tensor gives the rest mass for the entire system. Matter, therefore, is sometimes considered as anything that contributes to the energy–momentum of a system, that is, anything that is not purely gravity. This view is commonly held in fields that deal with general relativity such as cosmology. In this view, light and other massless particles and fields are all part of matter.

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