Earth & SkyGreek → English
Ergosphere
/ˈɜːrɡoʊsfɪər/noun
The region outside a rotating black hole's event horizon where spacetime is dragged around so strongly that nothing can remain still.
The Greek roots
ἔργον
érgon
work, deed
σφαῖρα
sphaîra
ball, sphere
Literally: “work sphere”
The story of the word
ἔργον, work, plus σφαῖρα. Roger Penrose showed in 1969 that an object split in two inside this shell could drop one half into the hole and fling the other out carrying more energy than the whole had going in, the surplus taken from the hole's spin. The name records exactly that: the region where work can be extracted from a black hole. Everything inside it is forced to rotate, including light.
- How it travelled
- Ancient Greek → scientific coinage → English
- First recorded
- 20th century
Same family
energyergonomicssurgeryatmospherehemisphere
In a sentence
Jets may be powered by magnetic fields threading the ergosphere.
Nothing in the ergosphere can hover, however hard it burns.