Why is the distance between Earth and Moon increasing?
Just like a spinning ice skater whose rotation slows as he extends his arms, the Earth-Moon distance is lengthening because Earth is spinning slower each day. The Moon’s gravitational influence is slowing Earth’s rate of rotation down by one and a half thousandths of a second every 100 years. The loss of rotational energy — angular momentum, for the physicists in the crowd — is necessarily matched by an increase in the Moon’s angular momentum, which results in a larger orbit for the Moon. Currently, the Moon moves less than two inches a year farther away from Earth — a tiny amount, but easily measurable with modern laser-ranging devices.
