Changes

Solid [[particulate]]s, including [[ash]], [[dust]], [[volcanic ash]], etc. are small parts of atmosphere. They are important in making [[cloud]]s and [[fog]].

Solid [[particulate]]s, including [[ash]], [[dust]], [[volcanic ash]], etc. are small parts of atmosphere. They are important in making [[cloud]]s and [[fog]].

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. 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 ==

Originally, the Earth's atmosphere had almost no free [[oxygen]]. The first atmosphere consisted of gases in the solar nebula, primarily [[hydrogen]]. There might be simple [[hydride]]s such as those now found in the [[gas giant]]s ([[Jupiter]] and [[Saturn]]): water vapor, [[methane]] and [[ammonia]].<ref name=Zahnle>{{Cite journal |last1=Zahnle |first1=K. |last2=Schaefer |first2=L. |last3=Fegley |first3=B. |doi=10.1101/cshperspect.a004895 |title=Earth's Earliest Atmospheres |journal=Cold Spring Harbor Perspectives in Biology |volume=2 |issue=10 |pages=a004895 |year=2010 |pmid=20573713 |pmc=2944365}}</ref> The atmosphere gradually changed to mostly carbon dioxide and nitrogen. The lighter gases, like hydrogen and [[helium]], cannot be held by the Earth's [[gravity]], and would escape. For a long time (say 2 billion years or more), the atmosphere was dominated by carbon dioxide.

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

 

#The first atmosphere consisted of gases in the [[solar nebula]], mainly [[hydrogen]]. There might also have been simple [[hydride]]s such as those now found in the [[gas giant]]s ([[Jupiter]] and [[Saturn]]): [[water vapor]], [[methane]] and [[ammonia]].<ref name=Zahnle>{{Cite journal |last1=Zahnle |first1=K. |last2=Schaefer |first2=L. |last3=Fegley |first3=B. |doi=10.1101/cshperspect.a004895 |title=Earth's Earliest Atmospheres |journal=Cold Spring Harbor Perspectives in Biology |volume=2 |issue=10 |pages=a004895 |year=2010 |pmid=20573713 |pmc=2944365}}</ref>  

In the [[Great Oxygenation Event]] the atmosphere changed to the kind we have now, with oxygen replacing the carbon dioxide. Our atmosphere is still mostly nitrogen, but most living organisms interact more with oxygen than with nitrogen. Oxygenation began with [[cyanobacteria]] making free oxygen by [[photosynthesis]]. Most organisms today need oxygen for their [[respiration]]: only a few [[anaerobic organism]]<nowiki/>s can grow without oxygen.<ref>Heinrich D. Holland: ''The oxygenation of the atmosphere and oceans.'' In: ''Phil. Trans. R. Soc.'' B, vol. 361, 2006, p. 903–915 http://rstb.royalsocietypublishing.org/content/361/1470/903.full.pdf</ref><ref>Knoll, Andrew H. 2004. ''Life on a young planet: the first three billion years of evolution on Earth''. Princeton, N.J. {{ISBN|0-691-12029-3}}</ref>

#The atmosphere gradually changed to mostly [[carbon dioxide]] and [[nitrogen]]. The lighter gases, like hydrogen and [[helium]], cannot be held by the Earth's [[gravity]], and would escape. For a long time (say two billion years or more), the atmosphere was dominated by carbon dioxide.

 

#In the [[Great Oxygenation Event]] the atmosphere changed to the kind we have now, with oxygen replacing the carbon dioxide. Our atmosphere is still mostly nitrogen, but most living organisms interact more with oxygen than with nitrogen. Oxygenation began with [[cyanobacteria]] making free oxygen by [[photosynthesis]]. Most organisms today need oxygen for their [[respiration]]: only a few [[anaerobic organism]]<nowiki/>s can grow without oxygen.<ref>Heinrich D. Holland: ''The oxygenation of the atmosphere and oceans.'' In: ''Phil. Trans. R. Soc.'' B, vol. 361, 2006, p. 903–915 http://rstb.royalsocietypublishing.org/content/361/1470/903.full.pdf</ref><ref>Knoll, Andrew H. 2004. ''Life on a young planet: the first three billion years of evolution on Earth''. Princeton, N.J. {{ISBN|0-691-12029-3}}</ref>

== Temperature and the atmospheric layers ==

== Temperature and the atmospheric layers ==

[[File:Profil temperature atmosphere.png|thumb|Temperature at various altitudes]]

[[File:Profil temperature atmosphere.png|thumb|Temperature at various altitudes]]

Some parts of the atmosphere are hot or cold, depending on [[height]]. Starting from the surface and climbing straight up, the air gets colder in the troposphere, but then it becomes hotter, higher in the stratosphere. These changes of [[temperature]] are divided into layers. These are like layers of an onion. The difference between the layers is the way the temperature changes.

Some parts of the atmosphere are hot or cold, depending on [[height]]. Starting from the surface and climbing straight up, the air gets colder in the troposphere, but then it becomes hotter, higher in the stratosphere. These changes of [[temperature]] are divided into layers. These are like layers of an onion. The difference between the layers is the way the temperature changes.

== Related pages ==

== Related pages ==

* [[Template:Life timeline|Life timeline]]

* [[Template:Life timeline|Life timeline]]