First, I'm not a physicist. But I do think of the subject often. A simple observation, as you move away from Earth the gravitational pull decreases. OK let's say we can drill a hole through the center of the earth what is the gravitational pull as we reach the middle? Is your answer fact, theory, or accepted theory. I add this part, because I grow tired of answers being set forth as fact and not accepted theory. Therefore if it is fact, has it been proven? That is, given that we have drilled a few holes in the Earth more than a mile or so. And I admit I being somewhat silly here, has anyone drop something in it that proves what you are saying.