We'll See About That
Welcome to the middle section of my highly acclaimed trilogy on time travel! How do I know it's highly acclaimed when I've only written two of the three? Think about it, silly. (I'm a time traveler.)
Last post I discussed how time travel might (or might not) be possible (for someone other than me, who doesn't already have an awesome, quite functional, time machine). This article is about the paradoxes involved in time traveling. Or, rather, some of them. There's quite a few depending on which avenue of time travel you wish to explore. And most have existential and historical ramifications that can change who you are at the most fundamental levels one can think of.
Here is a good primer on some of the paradoxes one might be confronted with. Of the ones mentioned there, perhaps the most famous paradox is the grandfather paradox. The grandfather paradox states that if you were to go back in time and murder your own grandfather, would you still exist? Logically, why you would want to do this is beyond me, but I'll buy into the initial premise.
As outlined in Michio Kakus book, Physics of the Impossible, there are a few possible solutions to this problem. If you don't believe in free will, but rather some sort of destiny, then whatever happens in the past is the way it was meant to happen. This would also hold true for what happens in the future. This is a closed time loop. Whatever happened, happened. If you go into the past to change it, that means you were already there trying to change it and everything is going according to plan. Whose plan? I don't know, someones somewhere. Possibly the man?
Oh God I Hope This is The Man
There is also the idea that there is some natural law that would prevent you from ever altering the timeline in that fashion. If you were to point a gun at your grandfather, state you were going to kill him, underline the reasons for why you felt it necessary to kill him - perhaps he told one too many stories of this time a guy claiming to be from the future tried to kill him - and then tried pulling the trigger, something would happen.
The gun would jam. You'd have a crisis of conscience. Your grandmother hits you in the head from behind with a shovel. Your grandfather is actually Ozymandias from Watchmen and he catches your bullet before beating the snot out of you. Point being, some natural occurrence prevents the death of your grandfather from happening, and nothing major changes. This still allows for the fact that you have free will, as it only states that the past cannot change. For example, you may in you heart of hearts wish to fly, and you should be able to because of your free will, but you can't because of gravity.
The solution to almost any paradox is likely to be alternate universes. If you were to pull the trigger and shoot your grandfather dead, it wouldn't matter in your universe because it never happened there. You simply traveled along a different timeline where your grandfather did get murdered by your evil doppleganger.
How Do You Fight Yourself?!
This would ostensibly happen every time you traveled to the past or future to change something. However, the biggest flaw I see in this theory is that it's not actually time travel. It's simply going to a parallel universe where things have changed only slightly. Unless, because of your dicking around in the past changing things, you created a new universe with just your actions. But how would that work? Considering what a universe physically is (lots and lots of energy and a tiny bit of matter), how could one persons actions create an alternate timeline where things were the same up until the moment they changed them, and dramatically different thereafter? Seems to raise more questions than it answers if you ask me. This is one of the major issues with time travel my esteemed colleague, Anthony, has. We've spent countless hours in our smoking room drinking whisky discussing how it could be possible that our matter is transfered to a time before our matter existed. Or, how the matter of anything in the past can still exist if it's in the present.
Imagine this situation: You want to go into the past to stop your best friend from contracting herpes from this girl he met at a club one night. Now, let's ignore the impossibility (in my experience) of a girl actually being at a club for something other than dancing. You head back in time and see your best friend - but how? How could he exist in the past if he is still existing in the future? I proposed a few solutions that I admittedly pulled out of my ass. Obviously I went to the alternate universe theories first, Anthony countered with the fact they're parallel and therefore running on the same timeline as our universe. I was skeptical of this stance, but whatever. I also proposed that time is constantly repeating itself, somewhere and somehow. Kinda weak, that one. I moved on to the fact that matter has always been around in some form or another, since the big bang. I brought up wormholes, and the curvature of spacetime. I said, relighting my corncob pipe, which had gone out in our breathless debating, that perhaps because of this curvature, there is only a displacement of matter. I asked him to picture how a tornado tube works; The water in the top half of the tube can only go to the bottom half if there is a displacement of air. That's why it works, and that's why time travel works! Anthony took a long, pensive sip of his whisky, sent our servant to the kitchen for a fake steak dinner (he's a vegetarian), and wondered how there can be a displacement of matter in that way. I countered that it probably has something to do with quantum entanglement and I conceded that I did not know. My, what a tangled web of intrigue these paradoxes weave!
The April, 1976 issue of American Philosophical Quarterly tackled some of these same issues, to a less humorous effect. The author, David Lewis immediately throws away the alternate universe theory. What he does distinguish between, instead of a multiverse, is a difference between what he calls "external time" and "personal time". External time, in the way he describes it, is time as we know it. It's whatever is happening in the present. Personal time is whatever is happening for the individual in their present. Even if their present happens to be someone else's (even their own) past. It can be equated with biological time, but it does seem to encompass more than that. This would make it possible for things to be happening along different planes of time, but it still glosses over the fact that our matter would still be existing and interacting in two places at once. However, Mr. Lewis does insinuate that perhaps it's not the same matter that is interacting. Do our atoms change into something else over time, as we grow older in our personal time? This seems a likely answer, as people do biologically and, dare I say, atomically change over time.
So what is the grand answer to the question of paradoxes? I don't know, what do I look like? Bill Nye the Science Guy? Jeez, leave me alone.
Be sure to tune in soon for the exciting conclusion to this three-part series on time travel!
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