Oh, another thing about time travel ... if you did travel through time, would it not return you to exactly the same place in the past? Like, if the universe was on a 3D grid or something, you'd be in the same co-ordinate, but since the universe is moving you wouldn't end up in the same place on Earth. You'd probably end up floating in space.
I can't be bothered with watching the video, but would it have to be more of a rule than a ... Law of Physics? If you go back too far, how would you get back ... It would all depend on what type of Time-Machine we're talking about. Is it a portal that you walk through, a machine that you ride in, or a magic watch that magically zaps you through time.
im assuming the world will implode soon after time travel is discovred as it would cause many contradicting senarios, causing the universe to implode, causing a new big bang, and off we go again, a new universe, and intelligent beings will always be doomed to destroy their own world when they get scientificly adavance enough to time travel