The novel The Hitchhiker's Guide to the Galaxy has a scene where Arthur Dent goes to a hyperspatial factory where planets are constructed. It made me wonder: What if I were in a spaceship inside that enormous sphere -- and I fell out of the ship?
In other words, what would gravity be like inside an enormous, hollow, planet-sized sphere?
Would you:
a) get pulled to the precise centre of the sphere, and stay there?
b) get pulled toward the nearest section of wall, and go splat?
c) just float around wherever you are?
I was very pleased to find that last week's Straight Dope column answered that very question.
Make your prediction, and I'll see you in comments.
Isn't that counter-intuitive? It's not what I thought.
ReplyDeleteSo it seems that, yes, you're close to some of the wall (and it's pulling you), but there's a lot more wall that's far away from you. It's pulling you, too, but it's farther away, so all in all, it balances out, and you're weightless.
This is elementary and I read about it in Asimov decades ago. The interior of a hollow sphere experiences no gravitational acceleration from the surrounding mass so everything is weightless.
ReplyDeleteOf course tidal forces from large masses orbiting outside the sphere will still be felt, as will the tidal forces of a star it orbits. Matter does not act like towards gravity like a "Faraday cage" does with electrical forces.
I and wife watched 'Journey to the Centre of the Earth' (newer version) last week, and I diatribed tediously about how there'd be no gravity in the centre of the earth (for the same reasons as for interior of sphere). Of course, in movie land, it was all earth-surface gravity pulling down, even tho there could be no down. a^{13}rgh!
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