So one of my major issues with time travel movies is they don’t science well. The Time Machine with it’s steampunk chair and wheel of fortune for instance, or even back to the future with the DeLorean. The problem with time travel as depicted in movies is there’s no basis in Einstein’s relativity. If I went back in time and stayed relatively in the same spot I’d end up in the vacuum of space because our entire solar system is barreling through the universe like this.
I’ve discussed this before in other places.
Now in Einstein’s relativity, you can go back in time, but you have to be travelling faster than the speed of light and away from the point of origin you want to go back in time. Think of how light reaches our eyes, if you’re going exactly the speed of light, if you looked back at the earth time would appear to stand still. If you go faster, you would see the light from the past. You would still be in normal time relative to the earth.
But here’s the rub, as you start moving towards the earth, earth time relative to you accelerates. Doesn’t matter if you go faster than light, slower than light, because of relativity you wind up at earth at a time past when you started. All is not lost through. What we need to do is add another concept of science fiction to the equation; space folding.
Imagine space is a fabric, or a peice of string. Instead of walking the entire length of the string, you bend it together, then simply walk over the gap. You still get from Point A to Point B, but you’ve just saved yourself some time by taking a shortcut. You’re not actually travelling any faster than light, you’re just taking a shortcut.
So in effect, time travel into the past should be possible using faster than light travel away from your point of origin, then using space folding on the return trip.
Any movie that has time travel that doesn’t involve a spaceship is kind of unrealistic. Even something like Star Trek. You can’t just whiplash around the sun and end up in the past. You could use that slingshot maneuver to accelerate, but you still need to go faster than light away from the earth to reach the past.
Food for though..