Saturn's rings are disappearing, and we don't know how much longer they will be around. Astronomers have known since the 1980s that Saturn's icy innermost rings are steadily eroding onto its upper atmosphere. It's driven by the effect of the Moon's gravity on the rotating Earth. Tides raised in the oceans cause drag and thus slow the Earth's spin-rate. The resulting loss of angular momentum is compensated for by the Moon speeding up, and thus moving further away.