I don’t know why I haven’t figured this out before. It’s been staring me in the face, especially considering the fan I am of Bill and Ted’s Excellent Adventure. But the theoretical problems with time travel that I’ve had for years aren’t actually problems at all.
I’ve opposed the idea of time travel for a long time, not because I think it’s scientifically impossible (I’m not smart enough to know), but because it doesn’t make sense with the way history works. If one was to go back in time, then you would change so much that the world you came back to would be completely different. It’s Back to the Future times a hundred – Marty almost ceases to exist because he keeps his parents from meeting, but there’s so much more than that. Think of all the other people whose “destinies” he changed – which will change their impact on the world that he returned to. He couldn’t possibly return to the same world that he left: more than just the name of the mall would be different.
The trouble is that I forgot that time travel to the past, if possible, has already happened. It’s already changed the world. Whatever things Marty did in 1955 that changed the world of 1985 already happened, back in 1955. Here’s the heart of my revelation: traveling back in time does not change history. Any time travel to the past that we might participate in already happened, because it’s in the past. Any changes we might cause have already been caused in a sense.
I don’t know how much sense that makes, but it’s all clear in my head. Ask if you have questions or clarifications – that’s what comments on a blog are for, after all.