Sunday, July 10, 2011

Thoughts on a Possible Time Travel Paradox

I love science - pretty much all science but especially astronomy, physics, and biology. Unfortunately, I have no (academic) background in science. However, I'm constantly reading and learning about science from blogs, articles, books, videos, TV and podcasts.

Time travel is a topic that is profoundly interesting to me. There are many things in my life that I wish I could change - I'm sure I'm not alone. I've often played with the idea of starting my life over and how I would do things differently. The problem, however, is that life is about learning - you need to live to learn. Therefore, effectively, I would lose all the lessons I've learned and get nowhere if I were to get my wish and start over. Alas.

Time travel is, also, filled with paradoxes, seemingly contradictory realities, which perhaps pique my interest even more, like enigmas requiring to be solved. I've written a story with extensive explanatory notes (that's right) on some time travel paradoxes, so I'm not going to go into detail here. However, I propose to add another paradox to the already long list. (Forgive me if someone else has already come up with the idea, which is coming up.) I remember long ago Stephen Hawking making the brilliantly simple point that if time travel were possible, then where are all the time travelers from the future? Surely, this proves that there is no such thing. Well, not exactly. Michio Kaku, for instance, in discussing this very paradox, points out that since we are on the verge, now, of developing invisibility, it is not infeasible to suppose that they are just invisible. You can't argue with that. Except, that point begs the question: Why they hell don't they say, "Hello." I mean, you'd think we'd be interested to know. Yeah, ok, the government would most likely have them kidnapped, raped, and tortured to find out the secrets of their technology, but, presumably, they'd be able to escape with their super advanced future tech. Arguing this point is not the crux of my proposed paradox, so let's just say, for argument's sake, that the time travelers don't want to reveal themselves for some reason - perhaps something to do with causality or changing the timeline, or maybe something to do with Ronald Mallett's design, which would only allow people from the future to travel back in time to the point at which the time machine was first turned on.

Let me, also, discuss, briefly, the Fermi paradox, from which I draw inspiration. In a nutshell, Fermi states this: Estimates for the existence of intelligent alien civilizations are quite high in the scientific community. From Sagan to Kaku to Greene, they all talk about how there are hundreds of billions of stars in the Milky Way (a rather average size galaxy) and over a billion galaxies in the universe, making the possibility of life elsewhere highly probable - from a purely mathematical point of view. Also, they say, given the life of the universe, some 13.7 billion years, and that the Earth formed 4.5 bya, life first evolving 3.7 bya (less than a billion years after the Earth formed), (intelligent) life could have had billions of years to evolve in star systems much younger than our solar system. Well, says Fermi, where's the pudding? If aliens exists, where are they? Again, I go back to a Kaku explanation - the Kaku anthill analogy. Essentially, Kaku says that, if the aliens are millions of years more advanced than we are, perhaps we are to them as ants are to us - that is, uninteresting. (Unless, you're an entomologist - then you are the uninteresting one.)  Why do we think we're so special? Again, it's hard to argue with the man. There's, also, the possibility that we just can't detect them. If they are really much more advanced than us, then they could even be living among us and we wouldn't know it. Maybe I'm one. (I'm kidding - please don't report me to the FBI.)

OK, on to my little paradox, which you might have guessed by now. In brief, physics highly supports the idea of time travel. I'm not a physicist, and I know that entropy is used to explain the arrow (or unidirectionality) of time. However, Einstein's equations allow for time travel since one's "clock" slows down with greater acceleration achieved or under immense gravity (see time dilation). Further, in quantum mechanics, as I (barely) understand it, we see that positrons can be interpreted as electrons traveling back in time. Therefore, time travel is a real possibility - not simply science fiction.

What I have to say, which I hope is, at least, somewhat original, is: If one looks at the past, specifically at the worst events in history (the wars; the murders; assassinations; genocide; rape; the great fires and natural disasters, killings scores of innocent people, including many women and children), one would have to conclude that, if time travel were possible, such events would have been first on the universal list to change the past. I mean, who wants innocent people to die (besides Rupert Murdoch)?

Now, there are several ways to solve this paradox that I'm aware of. Perhaps time travelers are unable to alter the timeline, so traveling into the past would have no effect on the future because if it did, the laws of physics, seeking consistency, would prevent it. However, if the multiverse theory proves correct, then a parallel universe is created instantaneously once one travels back in time, thus preserving the original timeline while creating a new one, and the previous argument would not hold. Nevertheless, it could be argued that perhaps we live in such a parallel world where the timeline was altered and perhaps really horrible events were prevented, but not everything was, for time traveling again, having seen that the work (of improving history) is incomplete, would engender the creation of yet another universe with yet another timeline, leaving our universe simply imperfect. Perhaps there's no way for a time traveler to return back to his original timeline since all subsequent travel would only engender more parallel universes - which could, also, explain why time travelers from the future haven't shown up: they're lost. (That's one one-way ticket, though, I'd actually consider.)

Another, darker argument is that an evil genius created the first time machine, and it was used not to stop all the horrible events of the past from occurring but for what all evil geniuses truly desire: world domination. (Arnold Schwarzenegger?)

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