Because i like to see the sun rise in the morning and the gods agree
so the morning arrives.
Because Huitzilopochtli winds it up every night before he puts out the cat. That's why we can say, "The sun comes up like clockwork."
as its a rule or we might assume habit of nature ..
Because it's really hot surrounded by hot air. Everyone knows that hot air rises. :)
Incorrect phrasing created at a time when primitive man didn't know any better.
It doesn't rise in as much as the earth rotates it into view.
So all those morning people know when to get up and get their chipper butts on their merry way. That way us, non-morning people can get up later in peace.