Is there such a thing as "at rest"? I've been watching some lectures on relativity from a professor at Berkley and he brings up the central idea of the "reference frame" relative to being in motion or "at rest". He says that if I were to ask you if you were currently in motion or at rest, some of you could say "Yes, I'm at rest" whereas others could say "I'm moving at the same velocity of the Earth" and both of these would be true. If you put me in a car, and spray paint the windows black so its pitch dark in the vehicle, then drive around, I can certainly feel that I'm not at rest, but I can't exactly prove it. Regardless of your reference frame isn't the passing of the day to night (given what we now know about the universe around us) absolute proof that there is no "at rest" no matter my reference frame?