"But there’s a law of nature — something that’s conserved — that tells us if Earth’s rotation is slowing down, something else needs to happen to compensate for it. That law is the conservation of angular momentum, and the thing that compensates is that as the Earth’s spin slows down, the Moon spirals farther and farther out from Earth! And the farther away the Moon gets, the smaller its angular size, and thus the smaller it appears in the sky. As time goes on, more and more of the solar eclipses will be annular rather than total, as the Moon’s size will appear insufficient to block out the Sun."