Would it be the rotational speed increasing or the speed at which the Earth revolves around the Sun? I take it in both cases Earth's speed being relative to the Sun. Now how would time on Earth slow down? Would this happen if the earth rotated faster, revolved faster, or both? Or are they the same thing? Is the Sun what we would usually use as the stationary body in this case? Would time just appear to slow down for the FOR of the Sun but we wouldn't feel it?