Far be it from me to turn this entire blog into a single extended rant on time travel, although that seems to be exactly what I’m doing. Unable to sleep this morning, I was stumbling around the internet, and a surprisingly low-glitz webpage appeared:
Frequently Asked Questions about Back to the Future, as answered by Robert Zemeckis and Bob Gale. It was adorable, but their justification for how time travel works in the movies sound like the rantings of a crazy person. I mean, they seem to adopt the picture that time travel creates parallel universes. In fact, Doc Brown actually says as much in one of the movies.
But here’s the thing, folks. If you allow for parallel universes in time travel, then if you go back in time — even if you kill your own grandparents, or prevent your parents from falling in love — then you haven’t prevented your own existence. You’ve “erased” your doppleganger from the new alternate universe. You (the original time-tinkerer) are just fine. Also, even assuming you somehow allow your parents to fall in love and eventually have kids, and even assuming the astronomically unlikely outcome that one of them ends up resembling you, odds are still pretty good that you go back to the future and find that alternate “you” still hanging around. I mean, if his life is so good, why should he go back in time and change the past? Why should he hang around a creepy old-man scientist in the first place? So now there are two of you in the present, in the alternate universe (and none in your original universe).