How does conservation of energy relate to Gravity? The moon seems to rotate around the earth for eternity (so it seems). But intuitively I would think that the energy of Gravity would eventually deplete and the moon would drift off into space. This apparently isn't the case. I know that Fg=Gm1m2/r2, but I can't get my pea brained head around the idea that this goes on for eternity; and the energy of gravity doesn't run out as long as their is two bodies of mass.