Outer space

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This article is about the space between celestial bodies. For the general concept, see Space. For other uses, see Outer space (disambiguation).

The boundary between space and Earth, at an altitude of 100 km, roughly where the yellow line of airglow is visible.

Outer space (or simply space) is the expanse beyond celestial bodies and their atmospheres. It contains ultra-low levels of particle densities, constituting a near-perfect vacuum[1] of predominantly hydrogen and helium plasma, permeated by electromagnetic radiation, cosmic rays, neutrinos, magnetic fields and dust. The baseline temperature of outer space, as set by the background radiation from the Big Bang, is 2.7 kelvins (−270 °C; −455 °F).[2]

The

kelvins.[3] 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.[4][5][6][7]

Outer space does not begin at a definite altitude above Earth's surface. The Kármán line, an altitude of 100 km (62 mi) above

UN resolutions for the peaceful uses of outer space, anti-satellite weapons
have been tested in Earth orbit.

The concept that the space between the Earth and the Moon must be a vacuum was first proposed in the 17th century after scientists discovered that

Microgravity has a negative effect on human physiology that causes both muscle atrophy and bone loss
.

Terminology

The use of the short version space,as meaning 'the region beyond Earth's sky', predates the use of full term "outer space", with the earliest recorded use in an epic poem by John Milton called Paradise Lost, published in 1667.[10][11]

The term outward space existed in a poem from 1842 by the English poet Lady

Emmeline Stuart-Wortley called "The Maiden of Moscow",[12] but in astronomy the term outer space found its application for the first time in 1845 by Alexander von Humboldt.[13] The term was eventually popularized through the writings of H. G. Wells after 1901.[14]

"Spaceborne" denotes existing in outer space, especially if carried by a spacecraft;[15][16] similarly, "space-based" means based in outer space or using space technology.[citation needed]

Formation and state

Main article: Big Bang
A model of the expanding universe opening up from the viewer's left, facing the viewer in a 3/4 pose.
Timeline of the expansion of the universe, where space, including hypothetical non-observable portions of the universe, is represented at each time by the circular sections. On the left, the dramatic expansion occurs in the inflationary epoch; and at the center, the expansion accelerates (artist's concept; neither time nor size are to scale).

The size of the whole universe is unknown, and it might be infinite in extent.[17] According to the Big Bang theory, the very early universe was an extremely hot and dense state about 13.8 billion years ago[18] which rapidly expanded. About 380,000 years later the universe had cooled sufficiently to allow protons and electrons to combine and form hydrogen—the so-called recombination epoch. When this happened, matter and energy became decoupled, allowing photons to travel freely through the continually expanding space.[19] Matter that remained following the initial expansion has since undergone gravitational collapse to create stars, galaxies and other astronomical objects, leaving behind a deep vacuum that forms what is now called outer space.[20] As light has a finite velocity, this theory constrains the size of the directly observable universe.[19]

The present day

spatial geometry of the observable universe is "flat", meaning that photons on parallel paths at one point remain parallel as they travel through space to the limit of the observable universe, except for local gravity.[21] The flat universe, combined with the measured mass density of the universe and the accelerating expansion of the universe, indicates that space has a non-zero vacuum energy, which is called dark energy.[22]

Estimates put the average energy density of the present day universe at the equivalent of 5.9 protons per cubic meter, including dark energy, dark matter, and baryonic matter (ordinary matter composed of atoms). The atoms account for only 4.6% of the total energy density, or a density of one proton per four cubic meters.[23] The density of the universe is clearly not uniform; it ranges from relatively high density in galaxies—including very high density in structures within galaxies, such as planets, stars, and black holes—to conditions in vast voids that have much lower density, at least in terms of visible matter.[24] Unlike matter and dark matter, dark energy seems not to be concentrated in galaxies: although dark energy may account for a majority of the mass-energy in the universe, dark energy's influence is 5 orders of magnitude smaller than the influence of gravity from matter and dark matter within the Milky Way.[25]

Environment

Main articles: Space environment, Space weather, and Space weathering
The black background is outer space as seen from Earth's surface at night. The interplanetary dust cloud is illuminated and visible as zodiacal light, with its parts the false dawn,[26] gegenschein and the rest of its band, which is visually crossed by the Milky Way

Outer space is the closest known approximation to a

hydrogen atoms per cubic meter.[27] By comparison, the air humans breathe contains about 1025 molecules per cubic meter.[28][29] The low density of matter in outer space means that electromagnetic radiation can travel great distances without being scattered: the mean free path of a photon in intergalactic space is about 1023 km, or 10 billion light years.[30] In spite of this, extinction, which is the absorption and scattering of photons by dust and gas, is an important factor in galactic and intergalactic astronomy.[31]

Stars, planets, and moons retain their atmospheres by gravitational attraction. Atmospheres have no clearly delineated upper boundary: the density of atmospheric gas gradually decreases with distance from the object until it becomes indistinguishable from outer space.[32] The Earth's atmospheric pressure drops to about 0.032 Pa at 100 kilometres (62 miles) of altitude,[33] compared to 100,000 Pa for the International Union of Pure and Applied Chemistry (IUPAC) definition of standard pressure. Above this altitude, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the Sun and the dynamic pressure of the solar wind. The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather.[34]

The temperature of outer space is measured in terms of the

solar corona reaches temperatures over 1.2–2.6 million K.[41]

Magnetic fields have been detected in the space around just about every class of celestial object. Star formation in spiral galaxies can generate small-scale

radio lobes. Non-thermal radio sources have been detected even among the most distant, high-z sources, indicating the presence of magnetic fields.[42]

Outside a protective atmosphere and magnetic field, there are few obstacles to the passage through space of energetic

Don Pettit, space has a burned/metallic odor that clings to their suits and equipment, similar to the scent of an arc welding torch.[46][47]

Human access

Effect on biology and human bodies

Main articles: Effect of spaceflight on the human body, Bioastronautics, Uncontrolled decompression, and Weightlessness
See also: Astrobiology, Astrobotany, Plants in space, and Animals in space
The lower half shows a blue planet with patchy white clouds. The upper half has a man in a white spacesuit and maneuvering unit against a black background.
Because of the hazards of a vacuum, astronauts must wear a pressurized space suit while outside their spacecraft.

Despite the harsh environment, several life forms have been found that can withstand extreme space conditions for extended periods. Species of lichen carried on the ESA BIOPAN facility survived exposure for ten days in 2007.[48] Seeds of Arabidopsis thaliana and Nicotiana tabacum germinated after being exposed to space for 1.5 years.[49] A strain of Bacillus subtilis has survived 559 days when exposed to low Earth orbit or a simulated Martian environment.[50] The lithopanspermia hypothesis suggests that rocks ejected into outer space from life-harboring planets may successfully transport life forms to another habitable world. A conjecture is that just such a scenario occurred early in the history of the Solar System, with potentially microorganism-bearing rocks being exchanged between Venus, Earth, and Mars.[51]

Vacuum

The lack of pressure in space is the most immediate dangerous characteristic of space to humans. Pressure decreases above Earth, reaching a level at an altitude of around 19.14 km (11.89 mi) that matches the

Harry G. Armstrong.[citation needed
]

At or above the Armstrong line, fluids in the throat and lungs boil away. More specifically, exposed bodily liquids such as saliva, tears, and liquids in the lungs boil away. Hence, at this altitude, human survival requires a pressure suit, or a pressurized capsule.[52]

Out in space, sudden exposure of an unprotected human to very low

hypoxia.[55]

As a consequence of rapid decompression, oxygen dissolved in the blood empties into the lungs to try to equalize the partial pressure gradient. Once the deoxygenated blood arrives at the brain, humans lose consciousness after a few seconds and die of hypoxia within minutes.[56] Blood and other body fluids boil when the pressure drops below 6.3 kPa, and this condition is called ebullism.[57] The steam may bloat the body to twice its normal size and slow circulation, but tissues are elastic and porous enough to prevent rupture. Ebullism is slowed by the pressure containment of blood vessels, so some blood remains liquid.[58][59] Swelling and ebullism can be reduced by containment in a pressure suit. The Crew Altitude Protection Suit (CAPS), a fitted elastic garment designed in the 1960s for astronauts, prevents ebullism at pressures as low as 2 kPa.[60] Supplemental oxygen is needed at 8 km (5 mi) to provide enough oxygen for breathing and to prevent water loss, while above 20 km (12 mi) pressure suits are essential to prevent ebullism.[61] Most space suits use around 30–39 kPa of pure oxygen, about the same as the partial pressure of oxygen at the Earth's surface. This pressure is high enough to prevent ebullism, but evaporation of nitrogen dissolved in the blood could still cause decompression sickness and gas embolisms if not managed.[62]

Weightlessness

Main article: Weightlessness § Health effects

cardiovascular system, decreased production of red blood cells, balance disorders, and a weakening of the immune system. Lesser symptoms include loss of body mass, nasal congestion, sleep disturbance, and puffiness of the face.[64]

Radiation

During long-duration space travel, radiation can pose an

gastrointestinal tract.[65] On a round-trip Mars mission lasting three years, a large fraction of the cells in an astronaut's body would be traversed and potentially damaged by high energy nuclei.[66] The energy of such particles is significantly diminished by the shielding provided by the walls of a spacecraft and can be further diminished by water containers and other barriers. The impact of the cosmic rays upon the shielding produces additional radiation that can affect the crew. Further research is needed to assess the radiation hazards and determine suitable countermeasures.[67]

Boundary

For the furthest reaches of space, see observable universe.
Illustration of Earth's atmosphere gradual transition into outer space

There is no clear boundary between Earth's atmosphere and space, as the density of the atmosphere gradually decreases as the altitude increases. There are several standard boundary designations, namely:

In 2009, scientists reported detailed measurements with a Supra-Thermal Ion Imager (an instrument that measures the direction and speed of ions), which allowed them to establish a boundary at 118 km (73.3 mi) above Earth. The boundary represents the midpoint of a gradual transition over tens of kilometers from the relatively gentle winds of the Earth's atmosphere to the more violent flows of charged particles in space, which can reach speeds well over 268 m/s (880 ft/s).[71][72]

There is no internationally recognized legal altitude limit on national airspace, although the Kármán line is the most frequently used for this purpose. Objections have been made about setting this limit too high, as it could inhibit space activities due to concerns about airspace violations.[73]

Legal status

Main article: Space law
Conventional anti-satellite weapons such as the SM-3 missile remain legal under space law, even though they create hazardous space debris

The

common heritage of mankind has been used, though not without opposition, to enforce the right to access and shared use of outer space for all nations equally, particularly non-spacefaring nations.[74] It prohibits the development of nuclear weapons in outer space. The treaty was passed by the United Nations General Assembly in 1963 and signed in 1967 by the USSR, the United States of America and the United Kingdom. As of 2017, 105 state parties have either ratified or acceded to the treaty. An additional 25 states signed the treaty, without ratifying it.[75][76]

Since 1958, outer space has been the subject of multiple United Nations resolutions. Of these, more than 50 have been concerning the international co-operation in the peaceful uses of outer space and preventing an arms race in space.[77] Four additional space law treaties have been negotiated and drafted by the UN's Committee on the Peaceful Uses of Outer Space. Still, there remains no legal prohibition against deploying conventional weapons in space, and anti-satellite weapon have been successfully tested by the US, USSR, China,[78] and in 2019, India.[79] The 1979 Moon Treaty turned the jurisdiction of all heavenly bodies (including the orbits around such bodies) over to the international community. The treaty has not been ratified by any nation that currently practices human spaceflight.[80]

In 1976, eight equatorial states (

Bogotá Declaration, they claimed control of the segment of the geosynchronous orbital path corresponding to each country.[81] These claims are not internationally accepted.[82]

An increasing issue of international space law and regulation has been the dangers of the growing number of space debris.[83]

Earth orbit

Main articles: Geocentric orbit and Orbital decay

A spacecraft enters orbit when its centripetal acceleration due to gravity is less than or equal to the centrifugal acceleration due to the horizontal component of its velocity. For a low Earth orbit, this velocity is about 7,800 m/s (28,100 km/h; 17,400 mph);[84] by contrast, the fastest piloted airplane speed ever achieved (excluding speeds achieved by deorbiting spacecraft) was 2,200 m/s (7,900 km/h; 4,900 mph) in 1967 by the North American X-15.[85]

To achieve an orbit, a

MJ/kg, which is six times the energy needed merely to climb to the corresponding altitude.[86] Spacecraft with a perigee below about 2,000 km (1,200 mi) are subject to drag from the Earth's atmosphere,[87] which decreases the orbital altitude. The rate of orbital decay depends on the satellite's cross-sectional area and mass, as well as variations in the air density of the upper atmosphere. Below about 300 km (190 mi), decay becomes more rapid with lifetimes measured in days. Once a satellite descends to 180 km (110 mi), it has only hours before it vaporizes in the atmosphere.[88] The escape velocity required to pull free of Earth's gravitational field altogether and move into interplanetary space is about 11,200 m/s (40,300 km/h; 25,100 mph).[89]

Regions

See also: Location of Earth

Regions near the Earth

Space in proximity to the Earth is physically similar to the remainder of interplanetary space, but it remains a critical region for various Earth–orbiting satellites and has been subject to extensive studies. The frequency of spacecraft traversing this area has led to it being divided into multiple zones.

Near-Earth space is the region of space extending from

space pollution, mainly in the form of space debris, threatening any space activity in this region.[90] Some of this debris re-enters Earth's atmosphere periodically.[91] Although it meets the definition of outer space, the atmospheric density inside low-Earth orbital space, the first few hundred kilometers above the Kármán line, is still sufficient to produce significant drag on satellites.[88]

artificial satellites[92]

Geospace is a region of space that includes Earth's upper atmosphere and magnetosphere.[93] The Van Allen radiation belts lie within the geospace. The outer boundary of geospace is the magnetopause, which forms an interface between the Earth's magnetosphere and the solar wind. The inner boundary is the ionosphere.[94][95]

The variable space-weather conditions of geospace are affected by the behavior of the Sun and the solar wind; the subject of geospace is interlinked with

magnetotail that sometimes extends out to more than 100–200 Earth radii.[97][98] For roughly four days of each month, the lunar surface is shielded from the solar wind as the Moon passes through the magnetotail.[99]

Geospace is populated by electrically charged particles at very low densities, the motions of which are controlled by the

aurorae seen at high latitudes in an oval surrounding the geomagnetic poles.[101]

Earth and the Moon as seen from cislunar space on the 2022 Artemis 1 mission

xGeo space is a concept used by the US to refer to space of high Earth orbits, ranging from beyond geosynchronous orbit (GEO) at approximately 35,786 km (22,236 mi),[102] out to the L2 Earth-Moon Lagrange point at 448,900 km (278,934 mi). This is located beyond the orbit of the Moon and therefore includes cislunar space.[103] Translunar space is the region of lunar transfer orbits, between the Moon and Earth.[104] Cislunar space is a region outside of Earth that includes lunar orbits, the Moon's orbital space around Earth and the Lagrange points.[105]

The region where a body's

Near-Earth Objects (NEOs), such as horseshoe librators and Earth trojans, with some NEOs at times becoming temporary satellites and quasi-moons to Earth.[citation needed
]

Deep space is defined by the United States government as region of space beyond low-Earth orbit, including cislunar space.

Moon's orbital distance.[113]

Near-Earth space showing the low-Earth (blue), medium Earth (green), and high Earth (red) orbits. The last extends beyond the radius of geosynchronous orbits

Interplanetary space

Main article: Interplanetary medium
At lower left, a white coma stands out against a black background. Nebulous material streams away to the top and left, slowly fading with distance.
The sparse plasma (blue) and dust (white) in the tail of comet Hale–Bopp are being shaped by pressure from solar radiation and the solar wind, respectively.

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

astropause) where the influence of the galactic environment starts to dominate over the magnetic field and particle flux from the Sun.[115] The distance and strength of the heliopause varies depending on the activity level of the solar wind.[116] The heliopause in turn deflects away low-energy galactic cosmic rays, with this modulation effect peaking during solar maximum.[117]

The volume of interplanetary space is a nearly total vacuum, with a mean free path of about one

meteors, and several dozen types of organic molecules discovered to date by microwave spectroscopy.[119] A cloud of interplanetary dust is visible at night as a faint band called the zodiacal light.[120]

Interplanetary space contains the magnetic field generated by the Sun.[114] 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.[121]

Interstellar space

Main article: Interstellar medium
"Interstellar space" redirects here. For the album, see Interstellar Space.
Patchy orange and blue nebulosity against a black background, with a curved orange arc wrapping around a star at the center.
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 outside the bubbles of plasma, known as

heliopause
.

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

molecular clouds can hold 108–1012 per m3.[36][124]

A number of molecules exist in interstellar space, as tiny as 0.1 μm dust particles.[127] 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.[128]

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 104–105 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.[129]

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.[130][131] A bow shock is a third boundary characteristic of an astrosphere, laying outside the termination shock and the astropause.[131]

Intergalactic space

Main articles: Warm–hot intergalactic medium, Intracluster medium, and Intergalactic dust
cosmic voids
of the intergalactic medium

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

cosmic voids that are mostly empty of galaxies. Typically, a void spans a distance of 7–30 megaparsecs.[132]

Surrounding and stretching between galaxies, there is a

intergalactic medium (IGM). The density of these filaments of intergalactic medium is about one atom per cubic meter,[135] 5–200 times the average density of the universe,[136] because of the cosmic voids. The IGM consists mostly of ionized hydrogen; i.e. a plasma consisting of equal numbers of electrons and protons.[citation needed
]

As gas falls into the intergalactic medium from the voids, it heats up to temperatures of 105 K to 107 K,[3] 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, 105 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.[136][137][138] 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 108 K and above in the so-called intracluster medium (ICM).[139]

Overview of different scales of space as
Observable Universe of the Universe

History of discovery

In 350 BCE, Greek philosopher Aristotle suggested that nature abhors a vacuum, a principle that became known as the horror vacui. This concept built upon a 5th-century BCE ontological argument by the Greek philosopher Parmenides, who denied the possible existence of a void in space.[140] Based on this idea that a vacuum could not exist, in the West it was widely held for many centuries that space could not be empty.[141] As late as the 17th century, the French philosopher René Descartes argued that the entirety of space must be filled.[142]

In

ancient China, the 2nd-century astronomer Zhang Heng became convinced that space must be infinite, extending well beyond the mechanism that supported the Sun and the stars. The surviving books of the Hsüan Yeh school said that the heavens were boundless, "empty and void of substance". Likewise, the "sun, moon, and the company of stars float in the empty space, moving or standing still".[143]

The Italian scientist

air pressure is lower.[144] In 1648, his brother-in-law, Florin Périer, repeated the experiment on the Puy de Dôme mountain in central France and found that the column was shorter by three inches. This decrease in pressure was further demonstrated by carrying a half-full balloon up a mountain and watching it gradually expand, then contract upon descent.[145]

A glass display case holds a mechanical device with a lever arm, plus two metal hemispheres attached to draw ropes.
The original Magdeburg hemispheres (left) used to demonstrate Otto von Guericke's vacuum pump (right)

In 1650, German scientist Otto von Guericke constructed the first vacuum pump: a device that would further refute the principle of horror vacui. He correctly noted that the atmosphere of the Earth surrounds the planet like a shell, with the density gradually declining with altitude. He concluded that there must be a vacuum between the Earth and the Moon.[146]

In the 15th century, German theologian

William Gilbert arrived at a similar conclusion, arguing that the stars are visible to us only because they are surrounded by a thin aether or a void.[149] This concept of an aether originated with ancient Greek philosophers, including Aristotle, who conceived of it as the medium through which the heavenly bodies move.[150]

The concept of a universe filled with a luminiferous aether retained support among some scientists until the early 20th century. This form of aether was viewed as the medium through which light could propagate.[151] In 1887, the Michelson–Morley experiment tried to detect the Earth's motion through this medium by looking for changes in the speed of light depending on the direction of the planet's motion. The null result indicated something was wrong with the concept. The idea of the luminiferous aether was then abandoned. It was replaced by Albert Einstein's theory of special relativity, which holds that the speed of light in a vacuum is a fixed constant, independent of the observer's motion or frame of reference.[152][153]

The first professional astronomer to support the concept of an infinite universe was the Englishman

Henrietta Leavitt.[157] This established that the Andromeda galaxy, and by extension all galaxies, lay well outside the Milky Way.[158]

The modern concept of outer space is based on the

"Big Bang" cosmology, first proposed in 1931 by the Belgian physicist Georges Lemaître.[159] This theory holds that the universe originated from a very dense form that has since undergone continuous expansion.[160]

The earliest known estimate of the temperature of outer space was by the Swiss physicist Charles É. Guillaume in 1896. Using the estimated radiation of the background stars, he concluded that space must be heated to a temperature of 5–6 K. British physicist Arthur Eddington made a similar calculation to derive a temperature of 3.18 K in 1926. German physicist Erich Regener used the total measured energy of cosmic rays to estimate an intergalactic temperature of 2.8 K in 1933.[161] American physicists Ralph Alpher and Robert Herman predicted 5 K for the temperature of space in 1948, based on the gradual decrease in background energy following the then-new Big Bang theory.[161]

Exploration

Main articles: Space exploration and Human presence in space
See also: Astronautics, Spaceflight, and Human spaceflight
first image of Earth taken by a person.[162]
South is up.

For most of human history, space was explored by observations made from the Earth's surface—initially with the unaided eye and then with the telescope. Before reliable rocket technology, the closest that humans had come to reaching outer space was through balloon flights. In 1935, the American Explorer II crewed balloon flight reached an altitude of 22 km (14 mi).[163] This was greatly exceeded in 1942 when the third launch of the German A-4 rocket climbed to an altitude of about 80 km (50 mi). In 1957, the uncrewed satellite Sputnik 1 was launched by a Russian R-7 rocket, achieving Earth orbit at an altitude of 215–939 kilometres (134–583 mi).[164] This was followed by the first human spaceflight in 1961, when Yuri Gagarin was sent into orbit on Vostok 1. The first humans to escape low Earth orbit were Frank Borman, Jim Lovell and William Anders in 1968 on board the American Apollo 8, which achieved lunar orbit[165] and reached a maximum distance of 377,349 km (234,474 mi) from the Earth.[166]

The first spacecraft to reach escape velocity was the Soviet

interstellar space.[170]

Application

See also:
Space habitation
interstellar space is visible, as well as in the foreground, above Earth, the airglow of the ionosphere just below and beyond the so-defined edge of space the Kármán line in the thermosphere

Outer space has become an important element of global society. It provides multiple applications that are beneficial to the economy and scientific research.

The placing of

stratospheric balloons or high-altitude platform stations, which have other benefits.[173]

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.[174] 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.[175] 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.[176]

The deep vacuum of space could make it an attractive environment for certain industrial processes, such as those requiring ultraclean surfaces.

space elevators.[180]

light sails, ramjets, and beam-powered propulsion. More advanced propulsion systems could use antimatter as a fuel, potentially reaching relativistic velocities.[181]

In addition to astronomy and space travel, the ultracold temperature of outer space can be used as a

Earth's surface through the infrared window into outer space to lower ambient temperatures.[184][185] It became possible with the discovery to suppress solar heating with photonic metamaterials.[186]

See also

References

Citations

  1. ISBN 978-0-444-59874-5
    .
  2. ^ Chuss, David T. (June 26, 2008), Cosmic Background Explorer, NASA Goddard Space Flight Center, archived from the original on May 9, 2013, retrieved 2013-04-27.
  3. ^
    Bibcode:2010AAS...21631808G
    .
  4. ^ Freedman & Kaufmann 2005, pp. 573, 599–601.
  5. S2CID 123199266
    .
  6. ^ "Dark Energy, Dark Matter", NASA Science, archived from the original on June 2, 2013, retrieved May 31, 2013, It turns out that roughly 68% of the Universe is dark energy. Dark matter makes up about 27%.
  7. ^ Freedman & Kaufmann 2005, pp. 650–653.
  8. ^ a b O'Leary 2009, p. 84.
  9. ^ a b "Where does space begin?", Aerospace Engineering, archived from the original on 2015-11-17, retrieved 2015-11-10.
  10. ^ Harper, Douglas (November 2001), Space, The Online Etymology Dictionary, archived from the original on 2009-02-24, retrieved 2009-06-19.
  11. JSTOR 24461820
    .
  12. ^ Stuart Wortley 1841, p. 410.
  13. ^ Von Humboldt 1845, p. 39.
  14. ^ Harper, Douglas, "Outer", Online Etymology Dictionary, archived from the original on 2010-03-12, retrieved 2008-03-24.
  15. ^ "Definition of SPACEBORNE", Merriam-Webster, 2022-05-17, retrieved 2022-05-18.
  16. ^ "Spaceborne definition and meaning", Collins English Dictionary, 2022-05-17, retrieved 2022-05-18.
  17. ^ Liddle 2015, pp. 33.
  18. S2CID 218716838
    .
  19. ^
    PMID 19708526
    .
  20. ^ Silk 2000, pp. 105–308.
  21. ^ WMAP – Shape of the universe, NASA, December 21, 2012, archived from the original on June 1, 2012, retrieved June 4, 2013.
  22. ^ Sparke & Gallagher 2007, pp. 329–330.
  23. ^ Wollack, Edward J. (June 24, 2011), What is the Universe Made Of?, NASA, archived from the original on July 26, 2016, retrieved 2011-10-14.
  24. doi:10.1086/113647
    .
  25. S2CID 118961123
  26. ^ "False Dawn", www.eso.org, retrieved 14 February 2017.
  27. atomic mass unit
    is 1.66 × 10−24 g, for roughly 40 atoms per cubic meter.
  28. ^ Borowitz & Beiser 1971.
  29. ^ Tyson, Patrick (January 2012), The Kinetic Atmosphere: Molecular Numbers (PDF), archived from the original (PDF) on 7 December 2013, retrieved 13 September 2013.
  30. ^ Davies 1977, p. 93.
  31. Bibcode:2004ASPC..309...33F
    .
  32. ^ Chamberlain 1978, p. 2.
  33. ^ Squire, Tom (September 27, 2000), "U.S. Standard Atmosphere, 1976", Thermal Protection Systems Expert and Material Properties Database, NASA, archived from the original on October 15, 2011, retrieved 2011-10-23.
  34. doi:10.2151/jmsj.85b.193
    .
  35. doi:10.1086/144984
    .
  36. ^ a b Prialnik 2000, pp. 195–196.
  37. ^ Spitzer 1978, p. 28–30.
  38. doi:10.3389/fphy.2014.00030
    .
  39. S2CID 119217397
    .
  40. ^ ALMA reveals ghostly shape of 'coldest place in the universe', National Radio Astronomy Observatory, October 24, 2013, retrieved 2020-10-07.
  41. doi:10.1086/166015
    .
  42. ISBN 978-1-4419-7317-7, archived
    from the original on 2017-09-20.
  43. S2CID 119237295
    .
  44. ^ Lang 1999, p. 462.
  45. ^ Lide 1993, p. 11-217.
  46. ^ What Does Space Smell Like?, Live Science, July 20, 2012, archived from the original on February 28, 2014, retrieved February 19, 2014.
  47. ^ Lizzie Schiffman (July 17, 2013), What Does Space Smell Like, Popular Science, archived from the original on February 24, 2014, retrieved February 19, 2014.
  48. PMID 21545267
    .
  49. PMID 22680697, archived
    (PDF) from the original on 2014-12-13, retrieved 2013-05-19.
  50. PMID 22680695
    .
  51. Bibcode:2010LPICo1538.5272N
    .
  52. ^ Piantadosi 2003, pp. 188–189.
  53. PMID 29493973
    , retrieved 2022-12-18.
  54. ^ Krebs, Matthew B.; Pilmanis, Andrew A. (November 1996), Human pulmonary tolerance to dynamic over-pressure (PDF), United States Air Force Armstrong Laboratory, archived from the original on 2012-11-30, retrieved 2011-12-23.
  55. ^ Busby, D. E. (July 1967), A prospective look at medical problems from hazards of space operations (PDF), Clinical Space Medicine, NASA, NASA-CR-856, retrieved 2022-12-20.
  56. PMID 6404482
    .
  57. S2CID 43248662, archived from the original
    (PDF) on 2012-04-26, retrieved 2011-12-16.
  58. ^ Billings 1973, pp. 1–34.
  59. ^ Landis, Geoffrey A. (August 7, 2007), Human Exposure to Vacuum, www.geoffreylandis.com, archived from the original on July 21, 2009, retrieved 2009-06-19.
  60. PMID 4872696
    .
  61. ^ Ellery 2000, p. 68.
  62. ^ Davis, Johnson & Stepanek 2008, pp. 270–271.
  63. ^ Kanas & Manzey 2008, pp. 15–48.
  64. PMID 19509005
    .
  65. ^ Kennedy, Ann R., Radiation Effects, National Space Biological Research Institute, archived from the original on 2012-01-03, retrieved 2011-12-16.
  66. PMID 11537306
  67. PMID 14593437
    .
  68. ^ Wong & Fergusson 2010, p. 16.
  69. ^ FAA Commercial Space Astronaut Wings Program (PDF), Federal Aviation Administration, July 20, 2021, retrieved 2022-12-18.
  70. ^ Petty, John Ira (February 13, 2003), "Entry", Human Spaceflight, NASA, archived from the original on October 27, 2011, retrieved 2011-12-16.
  71. ^ Thompson, Andrea (April 9, 2009), Edge of Space Found, space.com, archived from the original on July 14, 2009, retrieved 2009-06-19.
  72. doi:10.1029/2008JA013757
    .
  73. doi:10.1016/j.actaastro.2018.07.003
    .
  74. ^ Durrani, Haris (19 July 2019), "Is Spaceflight Colonialism?", The Nation, retrieved 6 October 2020.
  75. ^ Status of International Agreements relating to activities in outer space as of 1 January 2017 (PDF), United Nations Office for Outer Space Affairs/ Committee on the Peaceful Uses of Outer Space, March 23, 2017, archived from the original (PDF) on March 22, 2018, retrieved 2018-03-22.
  76. ^ Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies, United Nations Office for Outer Space Affairs, January 1, 2008, archived from the original on April 27, 2011, retrieved 2009-12-30.
  77. ^ Index of Online General Assembly Resolutions Relating to Outer Space, United Nations Office for Outer Space Affairs, 2011, archived from the original on 2010-01-15, retrieved 2009-12-30.
  78. ^ Wong & Fergusson 2010, p. 4.
  79. ^ Solanki, Lalit (2019-03-27), "India Enters the Elite Club: Successfully Shot Down Low Orbit Satellite", The Mirk, retrieved 2019-03-28.
  80. ^ Columbus launch puts space law to the test, European Science Foundation, November 5, 2007, archived from the original on December 15, 2008, retrieved 2009-12-30.
  81. ^ Representatives of the States traversed by the Equator (December 3, 1976), "Declaration of the first meeting of equatorial countries", Space Law, Bogota, Republic of Colombia: JAXA, archived from the original on November 24, 2011, retrieved 2011-10-14.
  82. ^ Gangale, Thomas (2006), "Who Owns the Geostationary Orbit?", Annals of Air and Space Law, 31, archived from the original on 2011-09-27, retrieved 2011-10-14.
  83. ^ "ESIL Reflection – Clearing up the Space Junk – On the Flaws and Potential of International Space Law to Tackle the Space Debris Problem – European Society of International Law". European Society of International Law. 2023-03-09. Retrieved 2024-04-24.
  84. ^ Hill, James V. H. (April 1999), "Getting to Low Earth Orbit", Space Future, archived from the original on 2012-03-19, retrieved 2012-03-18.
  85. ^ Shiner, Linda (November 1, 2007), X-15 Walkaround, Air & Space Magazine, retrieved 2009-06-19.
  86. ^ Dimotakis, P.; et al. (October 1999), 100 lbs to Low Earth Orbit (LEO): Small-Payload Launch Options, The Mitre Corporation, pp. 1–39, archived from the original on 2017-08-29, retrieved 2012-01-21.
  87. ^ Ghosh 2000, pp. 47–48.
  88. ^ a b Kennewell, John; McDonald, Andrew (2011), Satellite Lifetimes and Solar Activity, Commonwealth of Australia Bureau of Weather, Space Weather Branch, archived from the original on 2011-12-28, retrieved 2011-12-31.
  89. ^ Williams, David R. (November 17, 2010), "Earth Fact Sheet", Lunar & Planetary Science, NASA, archived from the original on October 30, 2010, retrieved 2012-05-10.
  90. ^ a b "42 USC 18302: Definitions", uscode.house.gov (in Kinyarwanda), December 15, 2022, retrieved December 17, 2022.
  91. Bibcode:1999STIN...9941786P, archived from the original
    (PDF) on 2000-09-01, retrieved 2012-05-05.
  92. ^ "ARES | Orbital Debris Program Office | Photo Gallery".
  93. ^ Schrijver & Siscoe 2010, p. 363, 379.
  94. ^ Kintner, Paul; GMDT Committee and Staff (September 2002), Report of the Living With a Star Geospace Mission Definition Team (PDF), NASA, archived (PDF) from the original on 2012-11-02, retrieved 2012-04-15.
  95. ^ Schrijver & Siscoe 2010, p. 379.
  96. ^ Fichtner & Liu 2011, pp. 341–345.
  97. ^ Koskinen 2010, pp. 32, 42.
  98. JSTOR 24975910
  99. ^ Mendillo 2000, p. 275.
  100. ^ Goodman 2006, p. 244.
  101. ^ "Geomagnetic Storms" (PDF), OECD/IFP Futures Project on "Future Global Shocks", CENTRA Technology, Inc., pp. 1–69, January 14, 2011, archived (PDF) from the original on March 14, 2012, retrieved 2012-04-07.
  102. ^ Howell, Elizabeth (April 24, 2015), "What Is a Geosynchronous Orbit?", Space.com, retrieved 8 December 2022.
  103. ^ Hitchens, Theresa (2022-04-21), "To infinity and beyond: New Space Force unit to monitor 'xGEO' beyond Earth's orbit", Breaking Defense, retrieved 2022-12-17.
  104. ^ "Why We Explore", NASA, June 13, 2013, retrieved December 17, 2022.
  105. ^ Strickland, John K. (October 1, 2012), The cislunar gateway with no gate, The Space Review, archived from the original on February 7, 2016, retrieved 2016-02-10.
  106. ISBN 978-0-87590-851-9, archived from the original
    (PDF) on April 26, 2012, retrieved 2011-12-31.. This work lists a Hill sphere radius of 234.9 times the mean radius of Earth, or 234.9 × 6,371 km = 1.5 million km.
  107. ^ Barbieri 2006, p. 253.
  108. ^ "51 U.S.C 10101 -National and Commercial Space Programs, Subtitle I-General, Chapter 101-Definitions", United States Code, Office of Law Revision Council, U. S. House of Representatives, retrieved January 5, 2023.
  109. ^ Dickson 2010, p. 57.
  110. ^ Williamson 2006, p. 97.
  111. ^ "Definition of 'deep space'", Collins English Dictionary, retrieved 2018-01-15.
  112. ^ ITU-R Radio Regulations, Article 1, Terms and definitions, Section VIII, Technical terms relating to space, paragraph 1.177. (PDF), International Telecommunication Union, retrieved 2018-02-05.
  113. ^ The semi-major axis of the Moon's orbit is 384,400 km, which is 19.2% of two million km, or about one-fifth.
    Williams, David R. (December 20, 2021). "Moon Fact Sheet". NASA. Retrieved 2023-09-23.
  114. ^ a b Papagiannis 1972, pp. 12–149.
  115. ^ Abby Cessna (July 5, 2009), "Interplanetary space", Universe Today, archived from the original on March 19, 2015.
  116. ^ Phillips, Tony (2009-09-29), Cosmic Rays Hit Space Age High, NASA, archived from the original on 2009-10-14, retrieved 2009-10-20.
  117. Bibcode:2017nova.pres.2992K
    , retrieved 2019-01-31.
  118. EurekAlert!
    , retrieved 12 March 2019.
  119. Bibcode:2004IAUS..213..275F
    .
  120. ISBN 978-3-642-75363-3
    .
  121. S2CID 121800711
    .
  122. ^ Jia-Rui Cook (September 12, 2013), "How do we know when Voyager reaches interstellar space?", JPL News, 2013-278, archived from the original on September 15, 2013.
  123. ^ Cooper, Keith (2023-01-17). "Interstellar space: What is it and where does it begin?". Space.com. Retrieved 2024-01-30.
  124. ^
    S2CID 16232084
    .
  125. S2CID 91378510
    .
  126. doi:10.1086/169509
    .
  127. ^ Rauchfuss 2008, pp. 72–81.
  128. PMID 16894148
    .
  129. Bibcode:2006ASPC..352...79R
    .
  130. S2CID 206540880
    .
  131. ^ a b Fox, Karen C. (May 10, 2012), NASA – IBEX Reveals a Missing Boundary at the Edge of the Solar System, NASA, archived from the original on May 12, 2012, retrieved 2012-05-14.
  132. ^ Wszolek 2013, p. 67.
  133. doi:10.1093/mnras/257.1.135
    .
  134. ^ Wadsley, James W.; et al. (August 20, 2002), "The Universe in Hot Gas", Astronomy Picture of the Day, NASA, archived from the original on June 9, 2009, retrieved 2009-06-19.
  135. ^ "Intergalactic medium". Harvard & Smithsonian. 2022-06-16. Retrieved 2024-04-16.
  136. ^
    S2CID 17524108
    .
  137. S2CID 17801881
    .
  138. S2CID 119247429
    .
  139. S2CID 17196808
    .
  140. ^ Grant 1981, p. 10.
  141. ^ Porter, Park & Daston 2006, p. 27.
  142. ^ Eckert 2006, p. 5.
  143. ^ Needham & Ronan 1985, pp. 82–87.
  144. ^ Holton & Brush 2001, pp. 267–268.
  145. ^ Cajori 1917, pp. 64–66.
  146. ^ Genz 2001, pp. 127–128.
  147. ^ Tassoul & Tassoul 2004, p. 22.
  148. ^ Gatti 2002, pp. 99–104.
  149. ^ Kelly 1965, pp. 97–107.
  150. ^ Olenick, Apostol & Goodstein 1986, p. 356.
  151. ^ Hariharan 2003, p. 2.
  152. ^ Olenick, Apostol & Goodstein 1986, pp. 357–365.
  153. ^ Thagard 1992, pp. 206–209.
  154. ^ Maor 1991, p. 195.
  155. ^ Webb 1999, pp. 71–73.
  156. doi:10.1086/132128
    .
  157. ^ Cepheid Variable Stars & Distance Determination, CSIRO Australia, October 25, 2004, archived from the original on August 30, 2011, retrieved 2011-09-12.
  158. ^ Tyson & Goldsmith 2004, pp. 114–115.
  159. S2CID 4089233
    .
  160. ^ Big Bang Cosmology, NASA, retrieved 2024-04-24.
  161. ^ a b Assis, A. K. T.; et al. (July 1995), "History of the 2.7 K Temperature Prior to Penzias and Wilson", Apeiron, 2 (3): 79–87.
  162. ^ Woods, W. David; O'Brien, Frank (2006), "Day 1: The Green Team and Separation", Apollo 8 Flight Journal, NASA, archived from the original on September 23, 2008, retrieved October 29, 2008. TIMETAG 003:42:55.
  163. S2CID 120710485
    .
  164. ^ O'Leary 2009, pp. 209–224.
  165. ^ Harrison 2002, pp. 60–63.
  166. ^ Orloff 2001.
  167. ^ Hardesty, Eisman & Krushchev 2008, pp. 89–90.
  168. ^ Collins 2007, p. 86.
  169. ^ Harris 2008, pp. 7, 68–69.
  170. ^ Wall, Mike (September 12, 2013), "Voyager 1 Has Left Solar System", Web, Space.com, archived from the original on 14 September 2013, retrieved 13 September 2013.
  171. ^ Razani 2012, pp. 97–99.
  172. ^ "Space Foundation Releases The Space Report 2023 Q2, Showing Annual Growth of Global Space Economy to $546B". Space Foundation. 2023-07-25. Retrieved 2024-04-24.
  173. ^ Bisset, Victoria (2023-02-04). "In a world of drones and satellites, why use a spy balloon anyway?". Washington Post. Retrieved 2024-04-24.
  174. ^ Harrington, J.D.; et al. (12 December 2012), NASA's Hubble Provides First Census of Galaxies Near Cosmic Dawn, 12-428, archived from the original on 22 March 2015. {{citation}}: Unknown parameter |agency= ignored (help)
  175. Bibcode:2001ESABu.105...60L
    .
  176. ISBN 978-92-9092-806-5
    .
  177. ^ Chapmann, Glenn (May 22–27, 1991), "Space: the Ideal Place to Manufacture Microchips", in Blackledge, R.; Radfield, C.; Seida, S. (eds.), Proceedings of the 10th International Space Development Conference (PDF), San Antonio, Texas, pp. 25–33, archived from the original (PDF) on 2011-07-06, retrieved 2010-01-12.{{citation}}: CS1 maint: location missing publisher (link)
  178. S2CID 119111392
    .
  179. doi:10.2514/1.16244
    .
  180. ^ Bolonkin 2010, p. xv.
  181. Bibcode:1990QJRAS..31..377C
    .
  182. S2CID 248972097
    – via Elsevier Science Direct, Radiative cooling does not consume external energy but rather harvests coldness from outer space as a new renewable energy source.
  183. S2CID 232147880
    – via ACS Publications, Daytime radiative cooling has attracted considerable attention recently due to its tremendous potential for passively exploiting the coldness of the universe as clean and renewable energy.
  184. doi:10.1016/j.energy.2018.03.084
    – via Elsevier Science Direct, An alternative, third geoengineering approach would be enhanced cooling by thermal radiation from the Earth's surface into space.
  185. PMID 33446648
    , One possibly alternative approach is passive radiative cooling—a sky-facing surface on the Earth spontaneously cools by radiating heat to the ultracold outer space through the atmosphere's longwave infrared (LWIR) transparency window (λ ~ 8–13 μm).
  186. S2CID 249695930
    – via Royal Society of Chemistry.

Sources

External links
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