Unless "time" isn't as linear as we, or I, understand it, shouldn't time travel be impossible? Energy (mass is energy) cannot be created or destroyed. If you were to remove energy from one time period, and create energy in another, wouldn't that completely unbalance... uh... fucking everything?
I know what a wormhole is, aswell as the theory of relativity, but I assume you mean standing inside a machine and being transferred to the exact same spot at a different time?