gravitcal forces inside a hollow space body

[PermaBanned]

But the centre of mass isn't in the middle surely?

No, the centre of mass is definitely in the middle of a sphere. If you're standing say on the inside of the sphere on one point, then the majority of the mass of the body will be above you and you'll be attracted to that. The point where you'll be attracted by the whole body equally will be in the centre.

 

[Liampope]

Perhaps I'm misunderstanding what you guys are saying. There will be zero net force anywhere inside the spherical shell - that's the point. It's obvious there will be zero net force at the centre of the shell, what's less obvious is that there is no net force everywhere inside the shell.

For those with a mathematical background, this is a direct consequence of the following facts:

1) Gravitational potential is harmonic on interior of shell.
2) By symmetry must be constant on surface of shell.
3) Weak maximum principle.

Newton's proof is more involved, but uses very basic (by today's standards!) mathematics.

Oh yeah - Newton's shell theorum and all that. You're right - no gravity anywhere in the room.

Oh wait - you can still be wrong . I was of course naturally assuming Kwerk's room is nice and practical - i.e. has air in it (and a sofa, etc). In that case there is still a net force towards the centre. Only a true hollow shell (vacuum inside) would have zero net force everywhere inside.

Plus that's all for spherical rooms - I reckon Kwerk would have a normal rectangular/cuboid room. So even if it was vacuum filled you'd still get... er... can't work it out in my head... obviously still zero net force at the very centre... maybe a net force towards the nearest wall if you're off-centre, or something like that, but dont quote me on that. Definately not zero at all points though as you dont have a spherically symetrical shell.

 

[The Dread Pirate]

if such a thing as a hollow core were possibubble I'd say if you were to centre his mass right in the centre of said room then he'd float or possibly be ripped apart but if he were uncentered he's be crushed up against the nearest wall. however due to the nature of most space bodies and gravities effect on them I doubt it would be possibubble to hollow out the core of a planet the planet would just collapse in on the hollow.

 

[asim18]

Nvm. Delete me.