Outer Space

Jai Ganesh · 2023-12-01 20:30:39

Outer Space

Gist

Outer space is the part of space that is very far away from Earth.

Summary

Outer space (often called space) consists of the relatively empty regions of the universe outside the atmospheres of celestial bodies. Outer space is used to distinguish it from airspace and terrestrial locations. There is no clear boundary between Earth's atmosphere and space, as the density of the atmosphere gradually decreases as the altitude increases.

For practical purposes, the Fédération Aéronautique Internationale has established the Kármán line, at an altitude of 100 kilometers (62 mi), as a working definition for the boundary between aeronautics and astronautics. This line was chosen because, as Theodore von Kármán calculated, a vehicle traveling above that altitude would have to move faster than orbital velocity to derive sufficient aerodynamic lift from the atmosphere to support itself. The United States designates people who travel above an altitude of 50 miles (80 km) as astronauts. During re-entry, roughly 120 kilometers (75 mi) marks the boundary where atmospheric drag becomes noticeable, depending on the ballistic coefficient of the vehicle.

Contrary to popular understanding, outer space is not completely empty, that is, it is not a perfect vacuum. Rather, it contains a low density of particles, predominantly hydrogen plasma, as well as electromagnetic radiation. Hypothetically, it also contains dark matter and dark energy.

Details

Outer space, commonly referred to simply as space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty; it is a near-perfect vacuum containing a low density of particles, predominantly a plasma of hydrogen and helium as well as electromagnetic radiation, magnetic fields, neutrinos, dust, and cosmic rays. The baseline temperature of outer space, as set by the background radiation from the Big Bang, is 2.7 kelvins (−270 °C; −455 °F).

The plasma between galaxies is thought to account for about half of the baryonic (ordinary) matter in the universe, having a number density of less than one hydrogen atom per cubic metre and a kinetic temperature of millions of kelvins. Local concentrations of matter have condensed into stars and galaxies. Intergalactic space takes up most of the volume of the universe, but even galaxies and star systems consist almost entirely of empty space. Most of the remaining mass-energy in the observable universe is made up of an unknown form, dubbed dark matter and dark energy.

Outer space does not begin at a definite altitude above Earth's surface. The Kármán line, an altitude of 100 km (62 mi) above sea level, is conventionally used as the start of outer space in space treaties and for aerospace records keeping. Certain portions of the upper stratosphere and the mesosphere are sometimes referred to as "near space". The framework for international space law was established by the Outer Space Treaty, which entered into force on 10 October 1967. This treaty precludes any claims of national sovereignty and permits all states to freely explore outer space. Despite the drafting of UN resolutions for the peaceful uses of outer space, anti-satellite weapons have been tested in Earth orbit.

Humans began the physical exploration of space during the 20th century with the advent of high-altitude balloon flights. This was followed by crewed rocket flights and, then, crewed Earth orbit, first achieved by Yuri Gagarin of the Soviet Union in 1961. The economic cost of putting objects, including humans, into space is very high, limiting human spaceflight to low Earth orbit and the Moon. On the other hand, uncrewed spacecraft have reached all of the known planets in the Solar System. Outer space represents a challenging environment for human exploration because of the hazards of vacuum and radiation. Microgravity has a negative effect on human physiology that causes both muscle atrophy and bone loss.

Interplanetary space

Interplanetary space is defined by the solar wind, a continuous stream of charged particles emanating from the Sun that creates a very tenuous atmosphere (the heliosphere) for billions of kilometers into space. This wind has a particle density of 5–10 protons/{cm}^3 and is moving at a velocity of 350–400 km/s (780,000–890,000 mph). Interplanetary space extends out to the heliopause where the influence of the galactic environment starts to dominate over the magnetic field and particle flux from the Sun. The distance and strength of the heliopause varies depending on the activity level of the solar wind. The heliopause in turn deflects away low-energy galactic cosmic rays, with this modulation effect peaking during solar maximum.

The volume of interplanetary space is a nearly total vacuum, with a mean free path of about one astronomical unit at the orbital distance of the Earth. This space is not completely empty, and is sparsely filled with cosmic rays, which include ionized atomic nuclei and various subatomic particles. There is also gas, plasma and dust, small meteors, and several dozen types of organic molecules discovered to date by microwave spectroscopy. A cloud of interplanetary dust is visible at night as a faint band called the zodiacal light.

Interplanetary space contains the magnetic field generated by the Sun. There are magnetospheres generated by planets such as Jupiter, Saturn, Mercury and the Earth that have their own magnetic fields. These are shaped by the influence of the solar wind into the approximation of a teardrop shape, with the long tail extending outward behind the planet. These magnetic fields can trap particles from the solar wind and other sources, creating belts of charged particles such as the Van Allen radiation belts. Planets without magnetic fields, such as Mars, have their atmospheres gradually eroded by the solar wind.

Interstellar space

Bow shock formed by the magnetosphere of the young star LL Orionis (center) as it collides with the Orion Nebula flow
Interstellar space is the physical space lying beyond the bubbles of plasma, known as astrospheres, formed by stellar winds originating from individual stars. The contents of interstellar space are called the interstellar medium, and the boundary between an astrosphere and interstellar space is known as an astropause. The Solar System's astrosphere and astropause are known as the heliosphere and heliopause, respectively.

Approximately 70% of the mass of the interstellar medium consists of lone hydrogen atoms; most of the remainder consists of helium atoms. This is enriched with trace amounts of heavier atoms formed through stellar nucleosynthesis. These atoms are ejected into the interstellar medium by stellar winds or when evolved stars begin to shed their outer envelopes such as during the formation of a planetary nebula. The cataclysmic explosion of a supernova propagates shock waves of stellar ejecta outward, distributing it throughout the interstellar medium, including the heavy elements previously formed within the star's core. The density of matter in the interstellar medium can vary considerably: the average is around 106 particles per m^3, but cold molecular clouds can hold {10}^8–{10}^{12} per m^3.

A number of molecules exist in interstellar space, as tiny as 0.1 μm dust particles. The tally of molecules discovered through radio astronomy is steadily increasing at the rate of about four new species per year. Large regions of higher density matter known as molecular clouds allow chemical reactions to occur, including the formation of organic polyatomic species. Much of this chemistry is driven by collisions. Energetic cosmic rays penetrate the cold, dense clouds and ionize hydrogen and helium, resulting, for example, in the trihydrogen cation. An ionized helium atom can then split relatively abundant carbon monoxide to produce ionized carbon, which in turn can lead to organic chemical reactions.

The local interstellar medium is a region of space within 100 pc of the Sun, which is of interest both for its proximity and for its interaction with the Solar System. This volume nearly coincides with a region of space known as the Local Bubble, which is characterized by a lack of dense, cold clouds. It forms a cavity in the Orion Arm of the Milky Way galaxy, with dense molecular clouds lying along the borders, such as those in the constellations of Ophiuchus and Taurus. (The actual distance to the border of this cavity varies from 60 to 250 pc or more.) This volume contains about {10}^{4}-{10}^{5} stars and the local interstellar gas counterbalances the astrospheres that surround these stars, with the volume of each sphere varying depending on the local density of the interstellar medium. The Local Bubble contains dozens of warm interstellar clouds with temperatures of up to 7,000 K and radii of 0.5–5 pc.

When stars are moving at sufficiently high peculiar velocities, their astrospheres can generate bow shocks as they collide with the interstellar medium. For decades it was assumed that the Sun had a bow shock. In 2012, data from Interstellar Boundary Explorer (IBEX) and NASA's Voyager probes showed that the Sun's bow shock does not exist. Instead, these authors argue that a subsonic bow wave defines the transition from the solar wind flow to the interstellar medium. A bow shock is a third boundary characteristic of an astrosphere, laying outside the termination shock and the astropause.

Intergalactic space

Intergalactic space is the physical space between galaxies. Studies of the large-scale distribution of galaxies show that the universe has a foam-like structure, with groups and clusters of galaxies lying along filaments that occupy about a tenth of the total space. The remainder forms huge voids that are mostly empty of galaxies. Typically, a void spans a distance of 7–30 megaparsecs.

Surrounding and stretching between galaxies, there is a rarefied plasma[122] that is organized in a galactic filamentary structure. This material is called the intergalactic medium (IGM). The density of the IGM is 5–200 times the average density of the universe. It consists mostly of ionized hydrogen; i.e. a plasma consisting of equal numbers of electrons and protons. As gas falls into the intergalactic medium from the voids, it heats up to temperatures of {10}^{5} K to {10}^{7} K, which is high enough so that collisions between atoms have enough energy to cause the bound electrons to escape from the hydrogen nuclei; this is why the IGM is ionized. At these temperatures, it is called the warm–hot intergalactic medium (WHIM). (Although the plasma is very hot by terrestrial standards, {10}^{5} K is often called "warm" in astrophysics.) Computer simulations and observations indicate that up to half of the atomic matter in the universe might exist in this warm–hot, rarefied state. When gas falls from the filamentary structures of the WHIM into the galaxy clusters at the intersections of the cosmic filaments, it can heat up even more, reaching temperatures of {10}^{8} K and above in the so-called intracluster medium (ICM).

Application

The absence of air makes outer space an ideal location for astronomy at all wavelengths of the electromagnetic spectrum. This is evidenced by the spectacular pictures sent back by the Hubble Space Telescope, allowing light from more than 13 billion years ago—almost to the time of the Big Bang—to be observed. Not every location in space is ideal for a telescope. The interplanetary zodiacal dust emits a diffuse near-infrared radiation that can mask the emission of faint sources such as extrasolar planets. Moving an infrared telescope out past the dust increases its effectiveness. Likewise, a site like the Daedalus crater on the far side of the Moon could shield a radio telescope from the radio frequency interference that hampers Earth-based observations.

Uncrewed spacecraft in Earth orbit are an essential technology of modern civilization. They allow direct monitoring of weather conditions, relay long-range communications like television, provide a means of precise navigation, and allow remote sensing of the Earth. The latter role serves a wide variety of purposes, including tracking soil moisture for agriculture, prediction of water outflow from seasonal snow packs, detection of diseases in plants and trees, and surveillance of military activities.

The deep vacuum of space could make it an attractive environment for certain industrial processes, such as those requiring ultraclean surfaces. Like asteroid mining, space manufacturing would require a large financial investment with little prospect of immediate return. An important factor in the total expense is the high cost of placing mass into Earth orbit: $9,000–$29,000 per kg, according to a 2006 estimate (allowing for inflation since then). The cost of access to space has declined since 2013. Partially reusable rockets such as the Falcon 9 have lowered access to space below 3500 dollars per kilogram. With these new rockets the cost to send materials into space remains prohibitively high for many industries. Proposed concepts for addressing this issue include, fully reusable launch systems, non-rocket spacelaunch, momentum exchange tethers, and space elevators.

Interstellar travel for a human crew remains at present only a theoretical possibility. The distances to the nearest stars mean it would require new technological developments and the ability to safely sustain crews for journeys lasting several decades. For example, the Daedalus Project study, which proposed a spacecraft powered by the fusion of deuterium and helium-3, would require 36 years to reach the "nearby" Alpha Centauri system. Other proposed interstellar propulsion systems include light sails, ramjets, and beam-powered propulsion. More advanced propulsion systems could use antimatter as a fuel, potentially reaching relativistic velocities.

In addition to astronomy and space travel, the ultracold temperature of outer space can be used as a renewable cooling technology for various applications on Earth through passive daytime radiative cooling, which enhances longwave infrared (LWIR) thermal radiation heat transfer on the Earth's surface through the infrared window into outer space to lower ambient temperatures. It became possible with the discovery to suppress solar heating with photonic metamaterials.

Additional Information

For all intents and purposes, outer space is basically what lies beyond the Earth’s atmosphere. For example, the Sun, planets, stars, and galaxies - all these things are in outer space.

If there’s an outer space, then it stands to reason that there must also be an inner space. This is defined as being the area between the Earth’s surface and the edge of the Earth’s atmosphere.

However, the Earth’s atmosphere doesn’t suddenly stop once it reaches a certain point. As you might imagine, it surrounds the Earth but gradually dissipates with distance. The reality is that the Earth’s atmosphere extends as far as nearly 400,000 miles (over 600,000 kilometers) out into space.

That’s roughly 50 times the Earth’s diameter and well past the Moon. That said, the atmosphere is so incredibly tenuous at that distance that it wasn’t detected until the end of the 20th century. The Solar and Heliospheric Observatory (SOHO) satellite was the first to detect it, but it was only when scientists re-analyzed the data that the discovery was made.

So does this mean that the Moon, the International Space Station, and thousands of satellites all orbit the Earth in inner space, and not outer space? If we were to stick to the definition of “inner space” then yes, but there’s a broader definition of space we need to consider.

Irene · 2024-04-23 19:35:33

Hi Jai Ganesh, i am sure you did a reliable research. But i have a question what created the big bang? And how did humans get to earth? Thanks

Jai Ganesh · 2024-04-23 22:49:23

Big Bang : The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. It was first proposed in 1927 by Roman Catholic priest and physicist Georges Lemaître. Various cosmological models of the Big Bang explain the evolution of the observable universe from the earliest known periods through its subsequent large-scale form. These models offer a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure. The overall uniformity of the universe, known as the flatness problem, is explained through cosmic inflation: a sudden and very rapid expansion of space during the earliest moments. However, physics currently lacks a widely accepted theory of quantum gravity that can successfully model the earliest conditions of the Big Bang.

Crucially, these models are compatible with the Hubble–Lemaître law—the observation that the farther away a galaxy is, the faster it is moving away from Earth. Extrapolating this cosmic expansion backwards in time using the known laws of physics, the models describe an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning (typically named "the Big Bang singularity"). In 1964 the CMB was discovered, which convinced many cosmologists that the competing steady-state model of cosmic evolution was falsified, since the Big Bang models predict a uniform background radiation caused by high temperatures and densities in the distant past. A wide range of empirical evidence strongly favors the Big Bang event, which is now essentially universally accepted. Detailed measurements of the expansion rate of the universe place the Big Bang singularity at an estimated 13.787±0.020 billion years ago, which is considered the age of the universe.

There remain aspects of the observed universe that are not yet adequately explained by the Big Bang models. After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later atoms. The unequal abundances of matter and antimatter that allowed this to occur is an unexplained effect known as baryon asymmetry. These primordial elements—mostly hydrogen, with some helium and lithium—later coalesced through gravity, forming early stars and galaxies. Astronomers observe the gravitational effects of an unknown dark matter surrounding galaxies. Most of the gravitational potential in the universe seems to be in this form, and the Big Bang models and various observations indicate that this excess gravitational potential is not created by baryonic matter, such as normal atoms. Measurements of the redshifts of supernovae indicate that the expansion of the universe is accelerating, an observation attributed to an unexplained phenomenon known as dark energy.

Second part:

Humans have been present in space either, in the common sense, through their direct presence and activity like human spaceflight, or through mediation of their presence and activity like with uncrewed spaceflight, making "telepresence" possible. Human presence in space, particularly through mediation, can take many physical forms from space debris, uncrewed spacecraft, artificial satellites, space observatories, crewed spacecraft, art in space, to human outposts in outer space such as space stations. While human presence in space, particularly its continuation and permanence can be a goal in itself, human presence can have a range of purposes and modes from space exploration, commercial use of space to space settlement or even colonization and militarisation of space. Human presence in space is realized and sustained through the advancement and application of space sciences, particularly astronautics in the form of spaceflight and space infrastructure.

Humans have achieved some mediated presence throughout the Solar System, but the most extensive presence has been in orbit around Earth. Humans have sustained direct presence in orbit around Earth since the year 2000 through continuously crewing the ISS, and with few interruptions through crewing the space station Mir since the later 1980s. The increasing and extensive human presence in orbital space around Earth, beside its benefits, has also produced a threat to it by carrying with it space debris, potentially cascading into the so-called Kessler syndrome. This has raised the need for regulation and mitigation of such to secure a sustainable access to outer space.

Securing the access to space and human presence in space has been pursued and allowed by the establishment of space law and space industry, creating a space infrastructure. But sustainability has remained a challenging goal, with the United Nations seeing the need to advance long-term sustainability of outer space activities in space science and application, and the United States having it as a crucial goal of its contemporary space policy and space program.

Irene · 2024-04-23 23:05:57

Jai Genesh, thanks.

Irene · 2024-04-23 23:09:53

Jai Genesh, so do you belive the big bang theory?

Jai Ganesh · 2024-04-24 00:10:50

I am neutral.

KerimF · 2024-04-24 02:09:52

I wonder what kind of difference believing (or not believing) the big bang theory, for example, may do in a human life.
But, in general, a wise human pretends believing what most people around him are supposed to believe in order to be on the safe side.

Irene · 2024-04-24 03:48:10

KerimF, what do you mean?

KerimF · 2024-04-24 08:11:15

I mean, see what happened to Galileo for example. He chose to live hard days for presenting openly his discoveries which were not supposed to be heard by the world's multitudes of his time.

Jai Ganesh · 2024-04-24 16:46:31

Introduction

Through space exploration humans have learned a great deal about the planets, stars, and other objects in space. More than 5,000 spacecraft have been launched into space to gather information since 1957. They include spacecraft with humans on board, space probes, and satellites. The Soviet Union (now Russia) and the United States were originally the main countries exploring space. Many other countries are now involved.

Astronauts

Astronauts (called cosmonauts in Russia and taikonauts in China) go through a thorough training program. They study math and science in classrooms. They learn to operate their spacecraft by using computer-controlled simulators. These devices present astronauts with conditions that they will later experience during actual flight. Astronauts also must improve their physical fitness. They make special trips in airplanes to get used to the feeling of weightlessness.

Humans cannot survive in outer space on their own. The environment is not the same as it is on Earth. Astronauts therefore travel in space in tightly sealed compartments. They bring their own supply of oxygen with them. Once in space, astronauts may conduct scientific experiments. They also may make repairs to their spacecraft or other equipment in space. They wear heavy space suits for work outside the spacecraft.

The Race into Space

In the 1900s scientists developed rockets that could travel fast enough to escape the pull of the force called gravity. Gravity is a force on Earth that pulls objects toward the center of the planet. The development of powerful rockets allowed the Soviet Union to launch the first artificial satellite on October 4, 1957. It was called Sputnik 1, and it orbited around Earth. On November 3, 1957, the Soviet Union sent a dog into orbit. On April 12, 1961, the Russian cosmonaut Yury Gagarin became the first human to circle Earth in space. In 1963 Valentina Tereshkova became the first woman in space.

The National Aeronautics and Space Administration (NASA) took charge of the U.S. effort. The first U.S. satellite was launched on January 31, 1958. On May 5, 1961, astronaut Alan B. Shepard, Jr., became the first American to enter space. Shepard flew for only 15 minutes and did not complete an orbit around Earth. On February 20, 1962, John H. Glenn, Jr., completed three orbits around Earth. On July 20, 1969, astronaut Neil Armstrong became the first human to walk on the Moon.

Space Stations

Space stations are spacecraft that stay in orbit for a long period of time. Scientists can spend days or even months at a station doing experiments. The Soviet Union began launching space stations in 1971, and the United States followed in 1973. But these stations did not stay in space long. The Soviet station Mir stayed in orbit much longer, from 1986 to 2001.

In the 1990s the United States and 15 other countries agreed to build and operate a large space station together. The new project was called the International Space Station (ISS). Assembly of the ISS began in 1998. The first crew began to live in the station in November 2000.

Space Shuttles

In 1981 the United States launched the first reusable spacecraft, called a space shuttle. The main section had wings and was called the orbiter. Attached to the orbiter were rockets, fuel tanks, and oxygen tanks. These boosted the craft through the thickest part of Earth’s atmosphere. When their fuel was used up, the boosters fell into the ocean, where they could be recovered. At the end of a mission, the orbiter returned to Earth and landed like an airplane.

The first shuttle missions were successful. Astronaut Sally Ride became the first U.S. woman in space on June 18, 1983. But in January 1986 the shuttle Challenger exploded 73 seconds after liftoff. All seven crew members were killed. NASA stopped the shuttle program to study the cause of the explosion.

The United States returned to space in September 1988 with the launching of the shuttle Discovery. In 1990 Discovery put the Hubble Space Telescope into orbit around Earth. This telescope sends clear images of space back to Earth. But then in February 2003 the shuttle Columbia broke apart as it was returning to Earth. The seven crew members on board were killed. The shuttle program did not resume until 2005.

NASA ended the shuttle program in 2011. Later missions to space were expected to use Russian spacecraft or new spacecraft built by U.S. companies.

Space Probes

Space probes are vehicles that carry scientific equipment but no passengers. Some make one-way voyages into deep space. Probes are controlled from Earth by radio. They send back their findings the same way.

In the late 1950s the Soviet Union and the United States launched their first deep-space probes. Probes eventually landed on the planets Mars and Venus and flew past the planets Jupiter, Saturn, Uranus, and Neptune. They collected information on the planets’ atmospheres, moons, and ring systems. In the early 2000s scientists sent several new probes to explore Mars and other planets and objects in space.

Math Is Fun Forum

#1 2023-12-01 20:30:39

Outer Space

#2 2024-04-23 19:35:33

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#3 2024-04-23 22:49:23

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#5 2024-04-23 23:09:53

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#6 2024-04-24 00:10:50

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