Asked by christian
Why is it incorrect to say that astronauts are weightless in space while orbiting Earth in a space shuttle?
All Answers 1
Answered by
GPT-5 mini
AI
Saying astronauts are "weightless" suggests there is no gravity acting on them. That is wrong.
What actually happens: the shuttle and everything inside it (astronauts, floating objects) are in free fall around Earth. Gravity is still strong at orbital altitudes (for example at ~400 km, g ≈ 8.7 m/s², about 0.89 g). Gravity provides the centripetal force that keeps them moving in a curved (orbital) path. Because the astronaut and the spacecraft are falling together, there is no contact (normal) force pressing the astronaut against anything, so a scale would read zero — they feel weightless.
So:
- Weight (physics): the gravitational force on a mass, F = m g. That is not zero in orbit.
- Apparent weight: the normal/support force you feel (what a scale measures). That is (nearly) zero in free fall, which produces the sensation of weightlessness. The technical term used is microgravity, because small residual accelerations (tidal gravity gradients, atmospheric drag, thruster firings) remain.
A simple analogy: if an elevator cable breaks and the elevator + you fall freely, you and the elevator float relative to each other — you aren’t free of gravity, you’re just falling together.
What actually happens: the shuttle and everything inside it (astronauts, floating objects) are in free fall around Earth. Gravity is still strong at orbital altitudes (for example at ~400 km, g ≈ 8.7 m/s², about 0.89 g). Gravity provides the centripetal force that keeps them moving in a curved (orbital) path. Because the astronaut and the spacecraft are falling together, there is no contact (normal) force pressing the astronaut against anything, so a scale would read zero — they feel weightless.
So:
- Weight (physics): the gravitational force on a mass, F = m g. That is not zero in orbit.
- Apparent weight: the normal/support force you feel (what a scale measures). That is (nearly) zero in free fall, which produces the sensation of weightlessness. The technical term used is microgravity, because small residual accelerations (tidal gravity gradients, atmospheric drag, thruster firings) remain.
A simple analogy: if an elevator cable breaks and the elevator + you fall freely, you and the elevator float relative to each other — you aren’t free of gravity, you’re just falling together.
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