Bad Astronomy: Misconceptions and Misuses Revealed, from ...

high tide
THE GRAVITY OF THE SITUATION 73
Earth and Moon as seen from above the north pole
low tide
Earth's rotation
Earth's rotation
low tide
high tide
Moon's orbital direction
The Earth spins faster (once a day) than the Moon moves around
the planet (once a month). A bulge caused by the lunar tide is
swept ahead of the Moon by the Earth’s rotation. This in turn tugs
on the Moon, pulling it faster in its orbit, and moving it away
from the Earth by about 4 centimeters per year. It is also slowing
the Earth’s spin at the same time.
This timing may seem like a miraculous coincidence, but it isn’t.
Tides force this situation.
All the time the Moon’s gravity is exerting a tide on the Earth,
the Earth is doing the same thing to the Moon. But the tides on the
Moon are 80 times the force of the ones on the Earth, because the
Earth is 80 times more massive than the Moon. All of the tidal
effects on the Earth are also happening on the Moon, but even
faster and stronger.
The Earth raises a big tide on the Moon, stretching it out.
There are two high tide bulges on the Moon, right in its solid rock.
When the Moon formed, it was closer to the Earth and rotated
much faster. The tidal bulge raised by the Earth on the Moon
started to slow the Moon’s rotation, just as the Earth’s high-tide
bulge does here. As the Moon slipped farther from the Earth, its
rotation slowed, until the rotation period was the same as its revolution
period (in other words, its day equaled a month). When