Stability. Stability over a very long period of time, billions of years. Without the Moon, the Earth would 'wobble' much more on its axis. read more
The main way the moon affects the Earth is the tides. The moon plays an important role in protecting the Earth from space rocks, such as meteorites. More subtle effects of the moon include minor effects on climate, the heat of the crust and the speed of the Earth's rotation. read more