Why are a lot of people comparing sci-fi movies to the known boundaries of science? There is fiction and there is non-fiction.. but there is also science-fiction, which is also non fiction. There is always a counterintuitive element in these movies and when you are nitpicking it its like unweaving a rainbow for no apparent reason, comparing apples and oranges etc. Just because a movie lacks a waterproof logical basis does not mean it can't be a great (B) movie. The sheer fact that time traveling on macro human-level can't be done according to what we know today would also dismiss great movies like Back to the Future, Terminator series, etc. If you want reality: do not watch movies, for they are at best based upon it. That off my chest, I can safely say I enjoyed this movie quite a bit through empirical proof. To me it is not even about the time traveling situation, its merely the cinematography of the desert, the americana of it all.