I know about the shell theorem and that the force of gravity due to the mass of the shell is zero inside a spherical shell. I have some questions that may easily be answered. 1. Does this same conclusion hold for an ellipsoid and/or a disk with the shell on the exterior rim ? 2. How is the gravity force inside a spherical solid affected if it has two layers and a central core all with different but homogeneous densities ? Especially inside the middle layer that has the least density and least mass ?