Every year, the Moon quietly moves a little further away.
Every year, the Moon quietly moves a little further away. About 3.8 centimetres — roughly the rate your fingernails grow. It sounds trivial, but the mechanism behind it is reshaping Earth itself. Tidal forces between our planet and the Moon are gradually bleeding energy from Earth's rotation, and that's slowing our spin. Hundreds of millions of years ago, a day on Earth lasted only around 22 hours. We've gained two full hours since then, and we're still gaining. There's a consequence waiting further down the line as well. As the Moon retreats, it will appear smaller in our sky — eventually too small to block the Sun completely. Total solar eclipses will become impossible. We happen to live in the narrow window of time when they're still there to see. Follow Deep Field Vault for more of the universe.