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{{redirect|Atmosphere|the unit of measure|Atmosphere (unit)}}

{{redirect|Atmosphere|the unit of measure|Atmosphere (unit)}}

The atmosphere does not end at a specific place. The higher above the Earth, the thinner the atmosphere. There is no clear [[border]] between the atmosphere and [[outer space]], though the [[Kármán line]] is sometimes treated as a border. Even higher, for some purposes the edge of the [[magnetosphere]] is treated as a border. 75% of the atmosphere is within {{convert|11|km|abbr=off}} of the Earth's [[surface]].

The atmosphere does not end at a specific place. The higher above the Earth, the thinner the atmosphere. There is no clear [[border]] between the atmosphere and [[outer space]], though the [[Kármán line]] is sometimes treated as a border. Even higher, for some purposes the edge of the [[magnetosphere]] is treated as a border. 75% of the atmosphere is within {{convert|11|km|abbr=off}} of the Earth's [[surface]].

== History of Earth's atmosphere ==

== History of Earth's atmosphere ==

The most important thing to remember about the [[Earth]] and other planets is that ''they do not come from the [[Sun]]''. They or their materials were picked up by the Sun's [[gravitation]] as it moved through space. The Sun is just composed of [[hydrogen]], with a little bit of [[helium]]. Nothing else. The material which makes up planets and their satellites is almost entirely heavier elements whose origin was in earlier [[Supernova|supernovae]] explosions. The planets do give off small quantities of hydrogen and helium: this comes from the decay of larger [[radioactive]] molecules whose origin is also ancient supernovae.

An important thing to remember about the [[Earth]] and other planets is that ''they do not come from the [[Sun]]''. They or their materials were picked up by the Sun's [[gravitation]] as it moved through space. The Sun is just composed of [[hydrogen]], with a little bit of [[helium]]. The material which makes up [[rocky planet]]<nowiki/>s and their satellites is almost entirely heavier elements whose origin was in earlier [[Supernova|supernovae]] explosions. The planets do give off small quantities of hydrogen and helium: this comes from the decay of larger [[radioactive]] molecules whose origin is also ancient supernovae.

Originally, the Earth's atmosphere had almost no free [[oxygen]].

Originally, the Earth's atmosphere had almost no free [[oxygen]].

File:Atmosphere gas proportions.svg|Composition of Earth's atmosphere by molecular count, excluding water vapor. Lower pie represents trace gases that together compose about 0.0434% of the atmosphere (0.0442% at August 2021 concentrations). Numbers are mainly from 2000, with {{CO2}} and methane from 2019, and do not represent any single source.

File:Atmosphere gas proportions.svg|Composition of Earth's atmosphere by molecular count, excluding water vapor. Lower pie represents trace gases that together compose about 0.0434% of the atmosphere (0.0442% at August 2021 concentrations). Numbers are mainly from 2000, with {{CO2}} and methane from 2019, and do not represent any single source.

File:Earth's atmosphere.svg|Earth's atmosphere. Lower four layers of the atmosphere in three dimensions as seen diagonally from above the exobase. Layers drawn to scale, objects within the layers are not to scale. Aurorae shown here at the bottom of the thermosphere can actually form at any altitude in this atmospheric layer.

File:Earth's atmosphere.svg|Earth's atmosphere. Lower four layers of the atmosphere in three dimensions as seen diagonally from above the exobase. Layers drawn to scale, objects within the layers are not to scale. Aurorae shown at the bottom of the thermosphere can form at any altitude within this layer.

File:ISS-46 Soyuz TMA-17M reentry.jpg|[[Afterglow]] of the [[troposphere]] (orange), the [[stratosphere]] (blue) and the mesosphere (dark) at which [[atmospheric entry]] begins, leaving smoke trails, such as in this case of a [[spacecraft]] reentry

File:ISS-46 Soyuz TMA-17M reentry.jpg|[[Afterglow]] of the [[troposphere]] (orange), the [[stratosphere]] (blue) and the mesosphere (dark) at which [[atmospheric entry]] begins, leaving smoke trails, such as in this case of a [[spacecraft]] reentry

File:ISS-47_Islands_In_The_Sky,_Indonesia.jpg|A picture of Earth's troposphere with its different [[cloud types]] of low to [[high altitude]]s casting shadows. Sunlight is reflected off the ocean, after it was filtered into a redish light by passing through much of the troposphere at sunset. The above lying [[stratosphere]] can be seen at the [[horizon]] as a band of its characteristic glow of [[Rayleigh scattering|blue scattered]] sunlight.

File:ISS-47_Islands_In_The_Sky,_Indonesia.jpg|A picture of Earth's troposphere, with different [[cloud types]] at low and [[high altitude]]s casting shadows. Sunlight, filtered into a reddish hue by passing through much of the troposphere at sunset, is reflected off the ocean. The above-lying [[stratosphere]] can be seen at the [[horizon]] as a band of its characteristic glow of [[Rayleigh scattering|blue scattered]] sunlight.

File:Atmospheric Temperature Trend.jpg|Temperature trends in two thick layers of the atmosphere as measured between January 1979 and December 2005 by [[microwave sounding unit]]s and [[advanced microwave sounding unit]]s on [[NOAA]] weather satellites. The instruments record microwaves emitted from oxygen molecules in the atmosphere. Source:

File:Atmospheric Temperature Trend.jpg|Temperature trends in two thick layers of the atmosphere as measured between January 1979 and December 2005 by [[microwave sounding unit]]s and [[advanced microwave sounding unit]]s on [[NOAA]] weather satellites. The instruments record microwaves emitted from oxygen molecules in the atmosphere. Source:

File:Atmosphere model.png|Temperature and mass density against altitude from the [[NRLMSISE-00]] [[International Standard Atmosphere|standard atmosphere]] model (the eight dotted lines in each "decade" are at the eight cubes 8, 27, 64, ..., 729)

File:Atmosphere model.png|Temperature and mass density against altitude from the [[NRLMSISE-00]] [[International Standard Atmosphere|standard atmosphere]] model (the eight dotted lines in each "decade" are at the eight cubes 8, 27, 64, ..., 729)

File:Atmospheric electromagnetic opacity.svg|Rough plot of Earth's atmospheric [[transmittance]] (or opacity) to various wavelengths of electromagnetic radiation, including [[visible light]]

File:Openstax Astronomy EM spectrum and atmosphere.jpg|Rough plot of Earth's atmospheric [[transmittance]] (or opacity) to various wavelengths of electromagnetic radiation, including [[visible light]]

File:SB DouglasPreserve SunAtmosphericEffects 2017 3 cropped.jpg|Distortive effect of [[atmospheric refraction]] upon the shape of the sun at the horizon

File:SB DouglasPreserve SunAtmosphericEffects 2017 3 cropped.jpg|Distortive effect of [[atmospheric refraction]] upon the shape of the sun at the horizon

== Other websites ==

== Other websites ==

*[http://www.ux1.eiu.edu/~cfjps/1400/atmos_struct.html The Atmosphere]

*[http://www.ux1.eiu.edu/~cfjps/1400/atmos_struct.html The Atmosphere]

[[Category:Atmosphere]]

[[Category:Atmosphere]]

[[Category:Earth]]

[[Category:Earth]]

[[Category:Meteorology]]

[[Category:Meteorology]]