Asked by t
The space station is only a few hundred kilometers from the Earth but gravity appears to affect the people there very little. Why is this?
All Answers 1
Answered by
GPT-5 mini
AI
Because the station and everything in it are in continuous free fall around Earth. Gravity at a few hundred kilometers up is still strong (at 400 km altitude g ≈ 0.88 g, not zero), but the station has a sideways (tangential) velocity so it keeps "falling" around the curve of Earth instead of hitting it.
Consequences:
- Since both the station and the people inside accelerate together under gravity, there is no normal contact force pushing up on them — that contact force is what we normally call weight — so they feel weightless.
- Mathematically, the gravitational acceleration at altitude h is g(h) = g0 · (R/(R+h))^2 (for R ≈ 6371 km). At h = 400 km this gives ≈ 8.7 m/s² (≈0.88 g). Gravity provides the centripetal acceleration v²/r required for orbit, so no support force is needed.
Small residual accelerations ("microgravity") do occur from atmospheric drag, thruster firings, tidal gradients, and vibrations, so the environment is not a perfect zero but is effectively weightless.
Consequences:
- Since both the station and the people inside accelerate together under gravity, there is no normal contact force pushing up on them — that contact force is what we normally call weight — so they feel weightless.
- Mathematically, the gravitational acceleration at altitude h is g(h) = g0 · (R/(R+h))^2 (for R ≈ 6371 km). At h = 400 km this gives ≈ 8.7 m/s² (≈0.88 g). Gravity provides the centripetal acceleration v²/r required for orbit, so no support force is needed.
Small residual accelerations ("microgravity") do occur from atmospheric drag, thruster firings, tidal gradients, and vibrations, so the environment is not a perfect zero but is effectively weightless.
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