Newton's Hollow Earth

Contrary to what some believe, hollow planets are not in violation with Newton's law of gravity. Newton's contemporary Edmond Halley presented a paper in 1692 suggesting that our planet is hollow, and Newton did not object to this when he reviewed it.

The reason Newton did not protest was that the notion of a hollow Earth is in full agreement with Newton's Shell Theorem, which forms the basis of most calculations regarding gravity. According to this theorem, there is no net gravitational pull inside a hollow shell. There is nothing to pull matter towards the center inside a hollow planet, so a hollow, once formed, will remain in place.

The main divergence between Newton's gravitational model and the capacitor model of gravity is in what happens if a hollow planet was to expand. According to Newton, surface gravity would decrease with expansion unless matter was added in the process. However, the capacitor model predicts an increase in surface gravity with expansion, even without any added matter. This is because a growing shell increases its electrical capacitance with expansion.

Cross section of a planet as a hollow spherical capacitor

The capacitor model further predicts a hollow to be expected, while Newton's model merely allows for it. The capacitor model also predicts an element of repulsion between large bodies in close proximity to each other, making collisions less likely than what Newton's model predicts.

The essential difference between the capacitor model and Newton's model is that the capacitor model suggests that it is charge that attracts mass, while Newton's hypothesis is that it is mass that attracts mass. The difference in practical terms are in fact small. By and large, the two models predict identical behavior. The difference in what these models predict are limited to the case of expanding planets and large bodies in extreme close proximity to each other.