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Blue light is scattered more than other wavelengths by the gases in the atmosphere, giving Earth a blue halo when seen from space onboard ISS at a height of 402–424 km.
Composition of Earth's atmosphere by volume. The lower pie represents the trace gases that together compose about 0.038% of the atmosphere (0.043% with CO2 at 2014 concentration). The numbers are from a variety of years (mainly 1987, with and methane from 2009) and do not represent any single source.

The atmosphere of Earth is the layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

The common name air (English pronunciation: /ɛər/) is given to the atmospheric gases used in breathing and photosynthesis. By volume, dry air contains 78.09% nitrogen, 20.95% oxygen,<ref name="NYT-20131003">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref> 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air content and atmospheric pressure vary at different layers, and air suitable for the survival of terrestrial plants and terrestrial animals is found only in Earth's troposphere and artificial atmospheres.

The atmosphere has a mass of about 5.15×10{{#invoke:Gapnum|main|18}} kg,<ref>Lide, David R. Handbook of Chemistry and Physics. Boca Raton, FL: CRC, 1996: 14-7</ref> three quarters of which is within about {{safesubst:#invoke:convert|convert}} of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at {{safesubst:#invoke:convert|convert}}, or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around {{safesubst:#invoke:convert|convert}}. Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.

The study of Earth's atmosphere and its processes is called atmospheric science (aerology). Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann.<ref>[1] Ultraviolet radiation in the solar system By Manuel Vázquez, Arnold Hanslmeier</ref>


Atmosphere of Earth sections
Intro  Composition   Structure of the atmosphere   Physical properties  Optical properties  Circulation  Evolution of Earth's atmosphere  Images from space  See also  References  External links  

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Earth's::convert    Earth::layer    About::altitude    Gases::above    Title::which    Layers::vapor

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Blue light is scattered more than other wavelengths by the gases in the atmosphere, giving Earth a blue halo when seen from space onboard ISS at a height of 402–424 km.
Composition of Earth's atmosphere by volume. The lower pie represents the trace gases that together compose about 0.038% of the atmosphere (0.043% with CO2 at 2014 concentration). The numbers are from a variety of years (mainly 1987, with and methane from 2009) and do not represent any single source.

The atmosphere of Earth is the layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).

The common name air (English pronunciation: /ɛər/) is given to the atmospheric gases used in breathing and photosynthesis. By volume, dry air contains 78.09% nitrogen, 20.95% oxygen,<ref name="NYT-20131003">{{#invoke:citation/CS1|citation |CitationClass=news }}</ref> 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air content and atmospheric pressure vary at different layers, and air suitable for the survival of terrestrial plants and terrestrial animals is found only in Earth's troposphere and artificial atmospheres.

The atmosphere has a mass of about 5.15×10{{#invoke:Gapnum|main|18}} kg,<ref>Lide, David R. Handbook of Chemistry and Physics. Boca Raton, FL: CRC, 1996: 14-7</ref> three quarters of which is within about {{safesubst:#invoke:convert|convert}} of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at {{safesubst:#invoke:convert|convert}}, or 1.57% of Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around {{safesubst:#invoke:convert|convert}}. Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.

The study of Earth's atmosphere and its processes is called atmospheric science (aerology). Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann.<ref>[1] Ultraviolet radiation in the solar system By Manuel Vázquez, Arnold Hanslmeier</ref>


Atmosphere of Earth sections
Intro  Composition   Structure of the atmosphere   Physical properties  Optical properties  Circulation  Evolution of Earth's atmosphere  Images from space  See also  References  External links  

PREVIOUS: IntroNEXT: Composition
<<>>