FRED ANSWERS YOUR QUESTIONS

Q: The Moon is moving a few centimetres from Earth each year, so gravitational and centrifugal forces are not balanced. How long before Earth and Moon become far enough apart to be independent of each other?

Peter Schaper, Biggenden, QLD

A: Never. Because of subtle tidal forces, the Earth and Moon separation will slow, eventually stabilising at about 500,000km. Earth’s rotation will also slow, lengthening a day to about 47 of our current days, with the same hemisphere always facing the Moon. But this is so far away that transformation of the Sun into a giant star may already have melted our planet.