Theory...the earths center is made of an element we have never seen before. This is because every large ball of matter (planets, moons, suns) has this element hidden deep in its center, and it is no longer floating freely in space as a raw material. This element is magnetic to all matter in the universe. The element creates gravity. If we were to extract this material, it would begin to pull objects to it. Don't believe me, extract it from the earth or moon and prove me wrong.