Question

If there were a hollow planet, something like Mario galaxy's planets- if you know what I mean;

the planet's interior is empty space but the outer shell is strong enough to maintain its shape despite its gravitational force that is similar to Earth's gravity.

Now If you could make a hole on its surface and jump to it, ... Would you fall orbiting in spiral round the planet's empty center of mass? What happens when you reach the center?

Answer 1

You can use Gauss's Law to show there would be no gravitational field interior to the shell of mass... but outside all would seem normal

Answer 2

isn't that about electricity?

Answer 3

Gauss's Law does in fact deal with electric fields, so I have no idea what that is pertaining too.
Gravity interacts between any particles, so you and the "shell" would interact gravitationally. Both the shell where you jumped in and the shell opposite would attract you, but because it is an inverse square relation, the shell opposite you would not pull you nearly as much. As a result, you would simply remain there on the side you jumped in.

Answer 4

In relation to Guass's law, at the very center of the sphere the force of gravity would cancel itself out on all sides and you would just float. But if you move towards any one side, the pull of gravity would become greater, thereby accelerating you towards that side.

Answer 5

so you would be like bouncing from inside to outside to inside to outside of the hole

Answer 6

I believe so, unless you entered the hole with a very high velocity necessary to get you to the center.

Answer 7

just take the example of earth if u made a pipe hole from one end of the earth to the other and throw a ball the ball will be attracted toward the center but because of its high velocity it over shots the center point and reaches the other end but here ball will just reach to the surface and again attracted toward center , this is the case with earth .
now here is the twist there is no mass at the center as u made the pipe hole just see the attachment

Answer 8

now if u take the case of hollow shell planet the same will happen the forces on the body, falling ,from all sides will pull that to the center and again body will overshot the center position because of its velocity and the body will oscillate as happened in case of earth.
its my view point but i am not sure ...

Answer 9

Stan was on the right track from the start. Although, instead of saying "Gauss' Law", which is specific to E&M, it should have been referred to as Gauss' Theorem or the Divergence Theorem. But that's just semantics, the idea is correct. All gravitational fields cancel within the shell. There's a discontinuity right at the surface. Then outside the shell everything looks like Earth.

Answer 10

As an addendum (and some formulae) to kfujioka's answer:
http://en.wikipedia.org/wiki/Shell_theorem
http://en.wikipedia.org/wiki/Gauss%27s_law_for_gravity

Gauss' Law can just as easily be applied to gravitational fields instead of electric fields with mass density being the "new" charge density as both types of fields follow an inverse square law.

Answer 11

My apologies I do stand corrected. Need to go brush up on my E&M!

Answer 12

thank you all