Faster Than Light-Based Time Travel

My apologies for the long absence. Work, school, holidays, and PROCRASTINATION have kept me busy doing everything but working on this website, and when I finally got around to writing a post, it turned out to be a much hairier topic than I expected, and I took almost two months to write it. But it is finally here! Enjoy!

One thing that has bugged me a lot about science fiction is what seems to be the prevailing theory on the faster than light (FTL) method of time travel. The common concept is that, because time slows down for an object approaching the speed of light, then if that object could somehow surpass the speed of light, then it would start traveling backwards in time. In more technical terms, what this is saying is that spatial acceleration in the direction of spatial motion is either the same as, or inherently tied to, temporal acceleration in the opposite direction of temporal motion.

But what this appears to neglect is the very relativity it is based on. From the perspective of the traveler, as the ship speeds up, time for the contents of the ship proceeds as normal, while time for the outside world speeds up. However, from the perspective of a stationary observer, time for the observer will remain stationary, while time for the ship slows down. As the traveler approaches the speed of light, time for the outside world will approach an infinite speed as time proceeds normally for him, whereas from the perspective of the stationary observer, the ship will stop experiencing time altogether, though it will continue moving in space.

Wow, does my brain hurt just getting this far.

This brings up the problem of traveling at the speed of light. Depending on the perspective we look at this scenario from, we get contradictory results: from the observer’s perspective, time for the traveler stops, but from the traveler’s perspective, it does not. In mathematical terms, time becomes undefined, because we are dealing with numbers that just don’t work with our math (try calculating ∞-(∞-1), and play around with the order of operations, given that ∞-∞=0, and ∞-1=∞, and you’ll see what I mean–math just doesn’t work here)

So traveling at the speed of light appears to be a mathematical impossibility, but we can conjecture what it would look like, as long as we limit our perspective. With that foundational understanding, let’s move on to speeds greater than that of light.

The easiest way to think about FTL speeds is from the perspective of an outside observer, so that is where I will start. An observer will perceive the traveler as experiencing time more and more slowly as he approaches the speed of light, ultimately ceasing to experience time altogether at the speed of light. Thus, it is only logical that, once the speed of light is exceeded, time for the traveler will reverse, and he will travel back in time. This is the standard view of what would happen if someone exceeded the speed of light.

But this is where things really start to get interesting: from the perspective of the traveler, time for the outside world is accelerating until, when he reaches the speed of light, time for the outside world is traveling at an infinite speed, so when he accelerates past the speed of light, why would time for the outside world suddenly reverse speed? There is absolutely no reason to expect this. In fact, our entire concept of time, even altered by Einstein’s Theory of Relativity, simply breaks down.

This concept contains two instances of paradox. The first is that relativity begins to affect time in completely different ways, depending on the perspective you choose. The second is the fact that travel at speeds greater than that of light cannot follow the same rules of relativity as speed up to that point.

I  hypothesize two possible explanations for this: the first possibility is that light speed is actually is an absolute barrier, and for more reasons than we realize. I still have no idea why the universe would behave this way, or if the scientific community has any theories. It seems completely arbitrary, but if I have learned one thing, it is that God does not do arbitrary, so there must be a reason. The second possibility, both less likely and cooler to think about, is that once the speed of light is exceeded, you begin interacting with the fifth dimension. I might be able to cook up some ideas on how that would work, but right now I think this post is long enough, and has been long enough in coming, plus it’s getting pretty late, and my this topic hurts my brain at my best.

What do you guys think?


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