exosphere
[ ek-soh-sfeer ]
/ ˈɛk soʊˌsfɪər /
noun
the highest region of the atmosphere, where the air density is so low that a fast-moving air molecule is more than 50 percent likely to escape from the atmosphere instead of hitting other molecules.
OTHER WORDS FROM exosphere
ex·o·spher·i·cal [ek-suh-sfer-i-kuh l, -sfeer-] /ˌɛk səˈsfɛr ɪ kəl, -ˈsfɪər-/, ex·o·spher·ic, adjectiveWords nearby exosphere
exorcize,
exordium,
exoserosis,
exoskeleton,
exosmosis,
exosphere,
exospore,
exosporium,
exostosis,
exostosis cartilaginea,
exoteric
Example sentences from the Web for exosphere
The atoms of the exosphere were lonely, uncrowded, isolated particles.
First on the Moon |Jeff SuttonHis instruments told him they were breaching the exosphere, where molecular matter had almost ceased to exist.
First on the Moon |Jeff SuttonIn the shed on the left is Orion, which is a two-stage rocket for deep penetration into the exosphere.
The Scarlet Lake Mystery |Harold Leland Goodwin
British Dictionary definitions for exosphere
exosphere
/ (ˈɛksəʊˌsfɪə) /
noun
the outermost layer of the earth's atmosphere. It extends from about 400 km above the earth's surface
Scientific definitions for exosphere
exosphere
[ ĕk′sō-sfîr′ ]
The outermost region of the Earth's atmosphere, beginning at an altitude of approximately 550 km to 700 km (341 to 434 mi) and merging with the interplanetary medium at around 10,000 km (6,200 mi). The exosphere consists chiefly of ionized hydrogen, which creates the geocorona by reflecting far-ultraviolet light from the Sun. On the remote edges of the exosphere, hydrogen atoms are so sparse that each cubic centimeter might contain only one atom; furthermore, the pressure and gravity are weak enough that atoms in the exosphere can escape entirely and drift into space. Artificial satellites generally orbit in this region. See also mesosphere stratosphere thermosphere troposphere. See illustration at atmosphere.