Tidal acceleration

Summary

Tidal acceleration is the slow exchange of angular momentum between the spin of a planet and the orbit of a satellite. It is caused by the tides that the satellite raises on the planet. For the Earth and the Moon it lengthens the day and pushes the Moon outward. Lunar laser ranging shows that the Moon recedes by about $3.8$ cm per year. Tides raised on a moon by its planet act in the same way and make many moons always show the same face.