Why Does the Same Side of the Moon Always Face the Earth?
Left to its own device long enough, any celestial body would eventually come to a point where its spin and orbit are synchronous. The reason for that is momentum transfer and tidal effect. The Earth has a tidal effect on the Moon that is much greater than the tidal effect the Moon has on the Earth (and no wonder why: Earth is much more massive than the Moon), and that was even stronger billions of years ago as the Moon was then closer to the Earth than it is now. The tidal bulge progressively dragged the Moon’s spin down until the bulge remained at the same place, and since the Earth pulls a little more on the side of the Moon facing us than on the far side, this causes the Moon to be gravitationally stabilized in that position.
That is because the moon spins on its axis at exactly the same rate that it revolves around the earth. The Moon’s tidal deformation caused it to enter into a synchronous orbit long ago; the Moon is tidally locked to the Earth. http://physics.fortlewis.edu/Astronomy/a… .
