Colliding/orbiting planets chatter (split from "The real PTM

[Tunnelcat]

A point mass is attracted to an object's center of mass, but the earth is a bunch of points. Since the points on the earth closest to the moon experience greater gravitational pull by the moon than the points furthest from the moon, it's harder to rotate the points closest to the moon away from it than it is to move the points furthest from the moon facing it.

Very true, I'm just not seeing how it affects the moon yet

Most of the earth's mass is in the iron core. Everything around it is made of lighter materials, so most of the earth's gravity pull would be concentrated towards the central core.