"By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases."
It is the study of atmospheric conditions, including temperature, pressure, and chemical composition, on celestial bodies like planets, moons, and asteroids.
"The atmosphere of Earth creates pressure, absorbs most meteoroids and ultraviolet solar radiation, warms the surface through heat retention (greenhouse effect), allowing life and liquid water to exist on the Earth's surface, and reduces temperature extremes between day and night."
"Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere."
"Air composition, temperature, and atmospheric pressure vary with altitude."
"Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in Earth's troposphere."
"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."
"The atmosphere has a mass of about 5.15×10^18 kg."
"Three quarters of the atmosphere's mass is within about 11 km (6.8 mi; 36,000 ft) of the surface."
"The atmosphere becomes thinner with increasing altitude, with no definite boundary between the atmosphere and outer space."
"The Kármán line, at 100 km (62 mi) 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 120 km (75 mi)."
"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."
"Atmospheric science includes multiple subfields, such as climatology and atmospheric physics."
"The study of historic atmosphere is called paleoclimatology."
"The atmosphere [...] reduces temperature extremes between day and night (the diurnal temperature variation)."
"The atmosphere of Earth creates [...] absorbs most meteoroids and ultraviolet solar radiation."
"The atmosphere of Earth creates [...] allowing life and liquid water to exist on the Earth's surface."