text: why does the earth rotate?   well, i don't know why it rotates. it just does, it's part of nature.  but if it didn't rotate on it axis then the night's darkness would last for 6 months. then it would be daylight outside for 6 months.  if the earth didn't revolve around the sun and it didn't rotate then it would always be dark for one side of the planet and bright for the other side.