The Earth from the Air: Yann Arthus-Bertrand

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About 3.4 billion years ago, nitrogen formed the major part of the then stable "second atmosphere". The influence of life has to be taken into account rather soon in the history of the atmosphere because hints of early life-forms appear as early as 3.5 billion years ago. [52] How Earth at that time maintained a climate warm enough for liquid water and life, if the early Sun put out 30% lower solar radiance than today, is a puzzle known as the " faint young Sun paradox".

Air is the invisible mixture of gases that surrounds Earth. Air contains important substances, such as oxygen and nitrogen, that most species need to survive. Human beings ( Homo sapiens), of course, are one of those species. Sometimes, the word " atmosphere" is used instead of the word "air." Because of its temperature, the atmosphere emits infrared radiation. For example, on clear nights Earth's surface cools down faster than on cloudy nights. This is because clouds (H 2O) are strong absorbers and emitters of infrared radiation. This is also why it becomes colder at night at higher elevations. The combined absorption spectra of the gases in the atmosphere leave "windows" of low opacity, allowing the transmission of only certain bands of light. The optical window runs from around 300nm ( ultraviolet-C) up into the range humans can see, the visible spectrum (commonly called light), at roughly 400–700nm and continues to the infrared to around 1100nm. There are also infrared and radio windows that transmit some infrared and radio waves at longer wavelengths. For example, the radio window runs from about one centimetre to about eleven-metre waves. All living or once-living materials contain carbon. These materials are organic. Plants and other autotrophs depend on carbon dioxide to create nutrients in a process called photosynthesis. These nutrients contain carbon. Animals and other organisms that consume autotrophs obtain carbon. Fossil fuels, the remains of ancient plants and animals, contain very high amounts of carbon. The troposphere is the lowest layer of Earth's atmosphere. It extends from Earth's surface to an average height of about 12km (7.5mi; 39,000ft), although this altitude varies from about 9km (5.6mi; 30,000ft) at the geographic poles to 17km (11mi; 56,000ft) at the Equator, [21] with some variation due to weather. The troposphere is bounded above by the tropopause, a boundary marked in most places by a temperature inversion (i.e. a layer of relatively warm air above a colder one), and in others by a zone that is isothermal with height. [29] [30]a b Anne Marie Helmenstine, PhD (June 16, 2018). "The 4 Most Abundant Gases in Earth's Atmosphere". The average atmospheric pressure at sea level is defined by the International Standard Atmosphere as 101325 pascals (760.00 Torr; 14.6959 psi; 760.00 mmHg). This is sometimes referred to as a unit of standard atmospheres (atm). Total atmospheric mass is 5.1480×10 18 kg (1.135×10 19 lb), [40] about 2.5% less than would be inferred from the average sea level pressure and Earth's area of 51007.2 megahectares, this portion being displaced by Earth's mountainous terrain. Atmospheric pressure is the total weight of the air above unit area at the point where the pressure is measured. Thus air pressure varies with location and weather. Earth and the rest of the solar system formed about 4.6 billion years ago from a huge, spinning cloud of gas and dust. Earth's early atmosphere consisted of gases in the solar nebula, primarily hydrogen. The atmosphere changed significantly over time, affected by many factors such as volcanism, life, and weathering. Recently, human activity has also contributed to atmospheric changes, such as global warming, ozone depletion and acid deposition.

Vázquez, M.; Hanslmeier, A. (2006). "Historical Introduction". Ultraviolet Radiation in the Solar System. Astrophysics and Space Science Library. Vol.331. Springer Science & Business Media. p.17. Bibcode: 2005ASSL..331.....V. doi: 10.1007/1-4020-3730-9_1. ISBN 978-1-4020-3730-6.In addition to Earth’s revolution and rotation periods, we experience light and darkness due to Earth’s axis not being straight up-and-down. Earth’s axis of rotation is tilted 23.5°. This tilt influences temperature changes and other weather patterns from season to season.

is below 100km (62mi; 330,000ft), the Kármán line. By international convention, this marks the beginning of space where human travelers are considered astronauts. Air Composition". The Engineering ToolBox . Retrieved 2017-07-04. The composition of air is unchanged until elevation of approximately 10.000 m Main article: Troposphere A picture of Earth's troposphere with its different cloud types of low to high altitudes 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 blue scattered sunlight. Detlev Möller: Luft: Chemie, Physik, Biologie, Reinhaltung, Recht. Walter de Gruyter, 2003, ISBN 3-11-016431-0, S. 173. (View in Google Books).David C. Catling and Kevin J. Zahnle, The Planetary Air Leak, Scientific American, May 2009, p. 26 (accessed 25 July 2012) Water vapor in the air is sometimes visible as clouds. Water enters the atmosphere through the water cycle. The water cycle also brings molecules in the air into oceans, lakes, and rivers. Within the five principal layers above, which are largely determined by temperature, several secondary layers may be distinguished by other properties: a b Haynes, H. M., ed. (2016–2017), CRC Handbook of Chemistry and Physics (97thed.), CRC Press, p.14-3, ISBN 978-1-4987-5428-6 , which cites Allen's Astrophysical Quantities but includes only ten of its largest constituents. homosphere – AMS Glossary". Amsglossary.allenpress.com. Archived from the original on 14 September 2010 . Retrieved 2010-10-16.