The fact that China just retrieved rocks from the dark side of the moon confuses me. Does the moon rotate in the same manner as Earth does so we never see the “dark” side of the moon?
In: Planetary Science
It does rotate, at the exact same speed it orbits the Earth. This is called being “tidally locked”
Think about how the tides work here on Earth. The ocean closer to the Moon gets pulled up by the Moon’s gravity, causing high tide, and the sides further away have water pulled away, so they experience low tide.
Basically the same thing happened to the early Moon, except instead of oceans, it happened to rock instead of ocean. The friction between these rocks being shifted and squeezed turned the Moon’s rotational energy into heat, which radiates away and the Moon orbits slower. This happened up until the Moon became tidally locked, and now the rock is no longer shifting around because the same side is always facing the Earth, so the same parts of rock are always receiving the same forces, so there’s no shifting.
The Moon does the same thing to the Earth, and it is slowing the Earth’s rotation, but the Earth has so much more inertia that it takes longer for the Earth to slow down.
An example of two mutually tidally locked bodies would be Pluto and Charon, the same sides always face each other.
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