We find out if we’re likely to lose our Moon one day

Asked by Tim Ball

The Moon’s orbit around Earth is getting larger, albeit by a minuscule amount. Every year its orbit increases by about 3.8 centimetres (1.5 inches), but compared to its orbit of 384,000 kilometres (240,000 miles) this is tiny.

The reason for the increase is due to the nature of the Moon’s orbit. It takes 27.3 days for our lunar companion to orbit Earth, while our planet rotates in 24 hours. Therefore, as Earth rotates, the tidal forces between the two mean that our planet tries to ‘speed up’ the orbit of the Moon. This has a tiny effect of making the Moon’s orbit larger, but also makes it travel slower.