The Dark Side of the Moon

The moon has slowed down to the same rotation rate and stuff. It's called tidal locking because it's connected to the concept of tidal forces. Gravity gets weaker as distances get longer, so if you're further away from the sun, its gravity is less powerful. But now imagine you're a pretty big object - part of you is closer to the sun, and then another part,. then part of you are going to feel stronger gravity than the other part. The earth basically turns the moon a little bit into a football.