he did not cause to earth to reverse its spin. Here's how i understand:
Imagine anything you did 5 minutes ago, is real but when you really think about it, it's not. I mean, if you ate a candy 15 minutes ago, you know that you ate it, you might have started the digestion process but the act of eating the candy is gone, though it is real. It's just a virtual reality now. I know this is crazy.
Scientists say that the reality that happened a while ago, if was real, has to be real no matter when. That's how they came up with the worm hole thing. The reality in our past is somewhere in another dimension, but does exist. And you will be able to see it or even experience it only if you can travel in or above the speed of light.
Now comes superman. We know that he can travel fast, but I don't know if he can in the speed of light. If he does, that's what he's doing. He's traveling so fast that he can actually access those real things that happened in the past. To us, it seems like turning back the time because of dramatic conventions.