Time travel is empirically impossible for the simple reason that there is no empirical past. The past exists only as memory and history. The atoms (molecules and subatomic particles) that composed the past have simply rearranged themselves and comprise the present. Travel to the past would require the atomic arrangements of the present be returned to the past configuration of the past to recreate the past. Even this would not be traveling to the past because this duplication of the past would still constitute the present. Likewise, the future does not exist until the atoms of the present rearrange themselves to become the future, but this only happens in present. Empirically, one is always locked into the present. Fortunately, time travel is possible in the imagination and in science fiction movies where it is often very entertaining.