[Pazuzu]

There are lots of geometries where you can find zero-gravity regions and high-gravity regions. A cylinder of material has gravity on the outside surface, but not the inside surface. If that cylinder was spinning along it's axis, then there would be false gravity inside, on the inner edge, and the false gravity would get smaller as you got closer to the center of rotation. The same rotating cylinder could now have zero "effective" gravity on the OUTSIDE, if you spun it just right.


So many weird things. Why would you be concerned about gravity in an empty shell in the middle of the Earth?