It seems more and more movies these days make use of time travel as a main plot line. I am specifically referring to traveling to the past - as travelling into the future is not just plausible, it is proven to be possible.
The thing with traveling into the future - there is no breaking of any known physical laws.
Traveling into the past is another story. Forget the grandfather paradox. Why is nobody discussing the blatant violation of The Law Of Conservation of Energy? If you traveled back in time there would be two of you. Where did the energy come from to support your second copy? Conservation of energy must be amended to sum energy over a different temporal period than the current definition for time travel into the past to work.