Earth & SkyGreek → English
Exosphere
/ˈɛksoʊˌsfɪr/noun
The outermost layer of the atmosphere, where gas thins into space.
The Greek roots
ἔξω
éxō
outside, beyond
σφαῖρα
sphaîra
ball, sphere
Literally: “outer sphere”
The story of the word
Up there the air is so sparse that a hydrogen atom can travel hundreds of kilometres without meeting another one, and a fast enough atom simply leaves; Earth loses a few kilograms of hydrogen a second this way. The name was coined in the mid-twentieth century on the pattern already set by stratosphere and ionosphere. σφαῖρα in Greek was a ball for throwing, the word Homer uses when Nausicaa and her maids play on the beach and wake Odysseus.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 20th century
Same family
exodusexoskeletonatmospherestratosphere
In a sentence
Satellites in low orbit still scrape the top of the exosphere and lose height every year.