2015-03-01 - Time Travel

I enjoy time travel stores. They often play with causality in ways that create situations not possible in any other kind of story. That being said thinking too deeply about time travel often ends up leading to problems. Then the entire concept just starts falling apart. Take back to the future for example.

Back to the Future is a fairly simple time travel story. Marty McFly goes back in time. He prevents his parents from meeting. He then has to get his parents to hook up so he can be born. He returns to the present in time to see himself go into the past. The problem is that the Marty going back in time at the end of the movie is not the same one that went back at the start.

When Marty returns home at the end of the movie it's shown that his family's life has been substantially changed by his actions in the past. They're better off, happier, he has a nice truck, and Biff is some kind of weird man servant. Now if his family has changed then logically he has too. Which means that the Marty going back in time at the end of the movie is likely to have a different reaction to things, and that's a problem because it means he won't change the past the same way the other Marty did.

What happens when Marty2 changes the past again? Is the entire universe in flux as different Martys keep going back in time and changing things? Are they creating an endless stream of universes? Maybe the Martys are piling up in the past and the world is going to be consumed by them. Really this is the trouble with time travel. You end up having to deal with multiple realities, multiple universes, multiple instances of the same event. Once you start doing that it becomes really difficult to have something that makes complete sense.

Personally I don't think time travel is possible because it's likely that it would destroy any universe in which it is possible.