Dark side of the moon

I've had to explain this to a lot of people lately and so I'm going to explain it to you, too.

There is no dark side of the moon.

Look, the implication of that phrase is that there's one side of the moon that never gets daylight. That's simply not true. The moon is tidal locked with Earth. That means that the rotation and the orbit are the same length so that one side always faces the body it's orbiting. It's orbiting the Earth, not the sun. The fact that the moon has phases means that at some point it all gets lit. Full moon means the side facing Earth is lit. New moon means the side facing the sun gets lit. There is no dark side of the moon.

Mercury was once thought to have a dark side. But closer observation reveals that it rotates 1.5 times for each orbit. This means that a Mercurial day is two Mercurial years long.

Earth's rotation is slowly slowing. Given enough time Earth will slow it's spin, but not it's orbit, until one side always faces the cold red lump that will be all that's left of the sun by then.