Tuesday, March 3, 2009

Three theories of time travel

This post is intended to open speculation about time travel. As far as I've seen, there are three main theories of how time travel works, depending on what you're watching/reading.

1. Time is a slate--anything can be can be changed! Be very careful, you might prevent your own birth. (ala Back to the Future). Paradoxes are a major problem--if you change antyhing you could prevent yourself from going back which would keep you from going back to prevent yourself from going back--and so on.

2. Time is a tree. You can change things, but all you'll do is create an alternate timeline. That is by making a change you just force yourself down a different branch. You can't prevent your birth, but you can send yourself down a branch where you were never born. (ala Back to the Future II, which doesn't seem to use the same concepts as Back to the Future)

3. Time is written in stone. Whatever happens in the past has already happened, observed events are 100% unchangeable. For me to believe in this one, I feel I also need to believe in a higher power (a fate or a god or what-have-you) to make sure everything is neat and tidy. (ala 12 Monkeys)

To me #1 is unlikely. If this were the way time travel worked, the space-time continuum would have ripped a long time ago, or a long time from now, which amount to the same thing when you're talking about the space-time continuum.

#3 can only work if there's a higher power, because something needs to decide what events are "allowed" to happen.

#2 is the most likely in my mind, though it opens the door to another discussion--alternate realities. Each branch of possibility creates new realities that may exist only in potentia. Changing events instantiates these realities.


Juliette Wade said...

I'm not sure I entirely agree with your assessment of option #3, where time is unchangeable. This may be one interpretation of the unchangeability - maybe the way things happen in The Time Machine, for example. But another way of working that model is to say that for events to have occurred as they have, all attempts to change them must have already had their effect, and the end result is the end result because those effects have already been taken into account.

Just my thoughts, for what they're worth.

David Steffen said...

Thanks for the comment. :) To me, I really have trouble believing that past events could ever remain immutable once people have the ability to change them. Once the secret to time-travel technology is unlocked, I'm assuming it will be available indefinitely (or at least for quite some time). The probability that some person in the future won't try to come back and change things is very low, perhaps even 0. Forearmed with knowledge of the past and technology from the future, the chance to create a change in a recorded historical event has to be very high. It's not a certain success, but if you sent a few people back, I feel that it would be certain to change something, even if it's not in the way you intended. The only way I could see this as not being true is if some controlling fate or deity were watching over events and making sure circumstance always opposed change.