The Moon is drifting away from Earth at about 3.8 centimetres a year, roughly the rate your fingernails grow.

Earth's tidal bulge sits slightly ahead of the Moon because the planet spins faster than the Moon orbits. That misplaced mass tugs the Moon forward, nudging it into a wider orbit, and the energy comes out of Earth's rotation. We know the number to the millimetre because Apollo left mirrors up there and observatories still bounce lasers off them.