Although the moon is much smaller than the Earth, it still has an influence on its bigger companion. Just as the Earth’s gravity pulls on the Moon, the gravity of the Moon pulls on the Earth, stretching it into a slight oval.
This distortion barely affects the solid landmasses, but it makes the oceans bulge on either side of the planet, producing the tides on either side of the planet.
The Moon takes the same time to orbit the Earth as it does to spin on its axis. As a result, the same side of the moon, the nearside, always faces the Earth. The slowing of the Earth’s rate of spin means that the Moon is gradually moving away from the Earth and spinning more slowly itself. If this continues the length of the Earth’s day and month would eventually be equal.
Originally posted: November 16, 2012