Assuming time travel is possible (and according to Dr Ronald Mallet it is) — one of the following facts must be true... 1. There is only one reality, and time cannot be altered. So, if you go back in time and try to change something about the past that you remember, you will fail every time. If you go back and try to stop your dad from being hit by a car, something will happen to stop you every time. Also, no matter how many times you go back to the same place, you will never see more versions of yourself than you originally remember. 'Destiny' will make sure that time travel never actually changes anything. Hard to believe in that one, huh? So the following must be true: 2. There are an infinite number of realities, and everything that could happen does happen There is a universe where a future you appears right now and changes something. There is a universe where two future yous appear right now and change something. There are universes where other people appear right now. There are universes where aliens from other worlds appear right now. Every combination of stuff that could happen in the universe, does happen somewhere. Okay, that one is too hard to believe. Too mind-boggling! So it must be the first one. Destiny prevents people from changing time. No, wait, that one's too mind boggling! Aaaaargh!!!!