Concept
Atmosphere
Overview
An atmosphere is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. The name originates from Ancient Greek ἀτμός (atmós) 'vapour, steam' and σφαῖρα (sphaîra) 'sphere'. An object acquires most of its atmosphere during its primordial epoch, either by accretion of matter or by outgassing of volatiles. The chemical interaction of the atmosphere with the solid surface can change its fundamental composition, as can photochemical interaction with the Sun. A planet retains an atmosphere for longer durations when the gravity is high and the temperature is low. The solar wind works to strip away a planet's outer atmosphere, although this process is slowed by a magnetosphere. The further a body is from the Sun, the lower the rate of atmospheric stripping.
Aside from Mercury, all Solar System planets have substantial atmospheres, as does the dwarf planet Pluto and the moon Titan. The high gravity and low temperature of Jupiter and the other gas giant planets allow them to retain massive atmospheres of mostly hydrogen and helium. Lower mass terrestrial planets orbit closer to the Sun, and so mainly retain higher molar mass atmospheres made of carbon, nitrogen, and oxygen, with trace amounts of inert gas. Atmospheres have been detected around exoplanets such as HD 209458 b and Kepler-7b.
A stellar atmosphere is the outer region of a star, which includes the layers above the opaque photosphere; stars of low temperature might have outer atmospheres containing compound molecules. Other objects with atmospheres are brown dwarfs and active comets.
Overview adapted from Wikipedia (CC BY-SA 4.0; see the article history for authors).
Possible passages
Found by search and not yet checked by a person; they may only mention the idea in passing.
So the air never draws off an electric atmosphere from any body, but in proportion to the non-electrics mix'd with it: it rather keeps such an atmosphere confin'd, which from the mutual repulsion of its particles, tends to dissipation, and would immediately dissipate _in vacuo_.--And thus the experiment of the feather inclosed in a glass vessel hermetically sealed, but moving on the approach of the rubbed tube, is…
Benjamin Franklin, Experiments and Observations on Electricity Made at Philadelphia in America
Names Atmosphere several times; states what Atmosphere is.
At all such positions the particular constitutions of the atmosphere are subject to variation, and thus become alternately more intense or more relaxed in their respective qualities. In this manner, by certain positions of the Moon, the flux and reflux of the sea are caused: and, when the Luminaries may be in angles, a change of the wind is produced, according to the direction of the Moon’s…
Ptolemy, Ptolemy's Tetrabiblos
Names Atmosphere several times; states what Atmosphere is.
That the dense gases thus continually being generated will form the entire mass of the solar atmosphere, is not probable. If anything is to be inferred, either from the Nebular Hypothesis, or from the analogies supplied by the planets, it must be concluded that the outermost part of the solar atmosphere consists of what are called permanent gases--gases that are not condensible into fluid even at low temperatures.
Herbert Spencer, Illustrations of Universal Progress
Names Atmosphere several times; states what Atmosphere is.
Related ideas
- Force
- Gas
- Neptune
- Moon
- Molecule
- Mercury (planet)
- Diffusion
- Solar System
- Uranus
- Comet
- Climate
- Earth
- Evolution
- Extraterrestrial life
Place in the tradition
Part of Philosophy of science.