The Moon is slowly drifting away from Earth. But why? The answer lies with the tides.
What are the tides?
The tides are two bulges of water created by the gravity of the moon. When we experience one of these bulges, it is called high tide.
What do the tides have to do with the Moon retreating?
Because the Earth rotates, the tides don’t line up perfectly with the Moon. The high tide closer to the Moon is shifted ahead of the Moon, while the further one lies slightly behind. Due to the closer tide being ahead of the Moon, the Moon is gravitationally pulled towards it, slightly increasing its speed. Since faster speeds have a bigger orbit, the Moon is therefore spiraling away from Earth.