A: The forces of gravity put into place when space matter coalesced to form the Earth over 4 billion years ago kept the forming solid steadily rotating, and it hasn't stopped because nothing has slowed it down. Plus, we are caught in the Sun's gravitational pull, so we go 'round the Sun every 365 days.
Q: How do you get in touch with someone if all you have is her email address and she hasn't written you back yet?