I think that if you were to time travel back in time, and kill your grandpa or something, I think it would create a NEW dimension. Same if you go into the future.
Because, if you really think about it, what WOULD happen scientifically?
If we speed up time INTO a time that doesn't exist? It just doesn't make sense. I'm not saying it's not POSSIBLE, but it's improbable, and probably highly dangerous.