the.com/exosphere
Earth's last gasp before space, where air is too thin to even bother being air.
means The outermost layer of Earth's atmosphere, where the air is so sparse that gas molecules can travel hundreds of kilometers without colliding before drifting off into space.
from From Greek 'exo-' (outside, beyond) joined to 'sphaira' (ball, globe) — the same 'sphere' that rolls through 'atmosphere' and 'hemisphere.' A modern scientific coinage, built the way scientists love to build words: snap a familiar Greek root onto a tidy Greek shape and you've named the edge of everything.
- top edge
- Stretches halfway to the Moon, around 10,000 km up
- barely there
- Atoms fly hundreds of km before hitting another
- escape zone
- Light atoms here leak into space forever
- satellite turf
- Many satellites orbit inside this ghostly layer
- no whoosh
- Too thin to carry sound or feel like wind
international space station — orbits at 408 km altitude, passing through the exosphere where atmospheric drag is measurable
hubble space telescope — operates at 547 km altitude in the exosphere, requiring periodic reboosts to counteract atmospheric drag
gps satellites — orbit at 20,200 km altitude in the exosphere, transmitting signals through the outermost atmospheric layer