Every year, the Moon moves about four centimeters (about 1.6 inches,) farther
out into space, away from Earth. Right now, the Moon's rotation rate, and the
time it takes to orbit Earth are the same.
Four and a half billion years ago the Earth was about sixty percent formed,
though it did have a differentiated core, crust and mantle. In these primal
skies, there was no Moon.
One planet, about the size of Mars, probably had an orbit which crosses Earth's,
and eventually a collision occurred.
The debris around Earth began to condense into clumps and quite rapidly, a blink in cosmic time, formed a large glowing ball: our primal Moon. The Moon would have looked about ten times larger than it does today, and the Earth was changed forever.
Earth's gravity has caused the Moon to become tidally locked us as well as
increasing the distance between the two worlds.
But gravity lessens with distance and this means that the pull from the Moon is
stronger on the side of Earth that is facing the Moon.
clipped from: starryskies.com 
