The Moon is moving away from the Earth:
The Moon's orbit (its circular path around the Earth) is indeed getting
larger, at a rate of about 3.8 centimeters per year. (The Moon's orbit
has a radius of 384,000 km.) The reason for the increase is that the
Moon raises tides on the Earth. Because the side of the Earth that faces
the Moon is closer, it feels a stronger pull of gravity than the center
of the Earth. Similarly, the part of
the Earth facing away from the Moon feels less gravity than the center
of the Earth. This effect stretches the Earth a bit, making it a little
bit oblong. It is expected that in 15 billion years, the orbit will
stabilize at 1.6 times its present size, and the Earth day will be 55
days long equal to the time it will take the Moon to orbit the Earth.
