You should cite all sources from which you get outside information. For example, if I'm writing an essay about cats, and I know that cats are fluffy, I can write that down with no need for citation. However, if I don't know that cats are felines until I read a Wikipedia page about them, then I need to site that page.
But it appears to rise and set because of the Earth's rotation on its axis. It makes one complete turn every 24 hours. It turns toward the east. As the Earth rotates toward the east, it looks like the sun is moving west.
