Actually, for a hollow sphere, the entire region inside the shell has gravity zero.
Because as you approach any point on the wall, even though the material you are receding from exerts less and less gravitational force on you, there is more and more of it in that general direction?
Well, it ain't hollow, so actually, you are all just wasting keystrokes.
The core of the Earth is the remains of a star.
The star goes supernova, eventually collapses into a neutron star with the attendant black hole.
Sooner or later, the star cools and expands, due to accretion of materials it has pulled in with it's gravity (which is a function of electromagnetic type forces still not understood, created by the energy source of the burning engine of the star).
The star loses it's black hole at an early stage in it's expansion.
If it has accrued enough matter, and doesn't expand too fast, it's rate of growth slows, and material continues to pile up, building a shell, or containment field, for the inner stellar furnace.
The EM type field emitted by the inner core is what causes the astral body to spin.
The solidified, cooled outer shell becomes the surface of a livable planet, with the inner furnace which generates beneficial EM and other type fields (Van Allen radiation belts), causes spin, solar inclination, gravity, generates ozone, and makes life possible.
All cold, all hot, no life. Center hot, outside cool, life. Star core= Shields up. The 'fields' provide protection from the harmful(to us) emissions in the EM spectrum.
This star cored shell, a life bearing planet, is similar to the creature you are made up of.
A Eukaryote, a cell with an internal engine/furnace.
Or, to qoute a famous source, "As Above(the heavens), So Below."