Time Travel Can Change the Past (To Be Exactly As It Already Is)
I’ve never been on good terms with time travel. Growing up I found stories about time travel to be fun and entertaining but the actual concept of traveling through time was annoying. Whenever I’d hear people talking about time travel or read about theoretical wormholes that would allow someone to travel into the past my mood would immediately sour. Why? Two reasons: the first is paradoxes, and the second is that I really would like time travel to be real.
Just about every sci-fi fan knows what a paradox is, but for those of you who don’t know (and because nerds, like hobbits, love to hear things that they already know about) a paradox (in time travelers terms) is a sort of looping contradiction of causality that can make your brain short-circuit just thinking about it. A specific and famous example is the “Kill Your Own Grandfather” paradox (not to be confused with the “Become Your Own Grandfather” paradox, which is a whole other branch of mind twister on its own). Let’s say you build a time machine, and because you’re a big fan of World War II you immediately jet off to 1943. Then, because who wouldn’t, you hunt down your grandfather back when he was a young bachelor. You say hi, introduce yourself, and then (because you’re a smart aleck and a sociopath) you shoot your grandfather dead with a .45. This leads us to the question: what happens next? Because if you kill your grandfather before he can sire your father then your father will never exist, and if your father never exists then he will never sire you, and if you don’t exist then you can’t build a time machine, go back in time, and kill your grandfather. So if you never go back in time and kill your grandfather then he lives to sire your father, who sires you, so you can build a time machine and go back and kill your grandfather….you can see where this is going. You’ve just created a logical impossibility. If you kill your grandfather then you do not exist, which means you can’t kill your grandfather, and so on. Congratulations: you just broke the universe.
Paradoxes by their very definition are things that cannot exist. Just as something can’t be both boiling hot and freezing cold at the same time you cannot ever have a paradox. They cannot possibly exist. Now if it was possible to travel back in time it would follow that it would be possible to create paradoxes. After all, we have free will. Of course that’s assuming we have free will; many people pondering the same questions concluded that if someone went back in time they would be forced to just let history take it’s course. That if you know what’s about to happen you have to just let it happen. I disagree with that. Sure it solves the problem of paradoxes, but it opens up a whole new problem: why the heck do you have to just let things happen? There’s no physical law of nature to stop me from trying to kill my own grandfather. What does the universe take control of my body and paralyse me to keep anything from changing? How does that work? It’s just solving a big problem with another big problem. So since paradoxes are impossible, and paradoxes can (and probably will) happen if it is possible to go back in time, then it must be impossible to go back in time. That’s the conclusion I reached and I was sad to reach it.
I really wanted time travel to be at least theoretically possible. It makes such a great story! From A Connecticut Yankee in King Arthur’s Court to Back to the Future time travel stories are just fun. The only problem is that they only work if you turn off your brain and stop thinking about it. I love Back to the Future but it just doesn’t make sense if you think about it too hard. Why does Marty remember the old version of the present if he went back in time and changed it? I mean when he comes back to the present and finds that his parents are cool and rich, then what happened to the Marty that grew up in that universe? Is he dead now? Did Marty somehow replace him? But theoretically even in that version of the present Doc Brown made the DeLorean and sent that present’s Marty back in time to 1955, but what 1955 did that Marty go to? Does he have to end up screwing up his parents meeting again? Only in his mind he wouldn’t be screwing up the meeting because the story he’s learned his whole life is that they got together after his mom dated a guy named Calvin Klein. But Calvin Klein was really Marty, so does this Marty have to pretend to be Calvin Klein? If he doesn’t, do they go back to being poor dorks? Does he return to the present to find one that sucks? I don’t know! It doesn’t make any sense! STOP THINKING ABOUT IT AND ENJOY THE MOVIE!
That would be your average sane person’s reaction, but I am a consummate nerd. I kept asking myself questions like these, and thinking about paradoxes and trying to kill Hitler to stop WWII. Finally I came to realize something, something that hit me like a bolt of lighting hitting a clock tower. The reason time travel seems impossible is because, as Doc Brown often said, we’re not thinking forth dimensionally! In movies and books we see time in a very linear fashion; Doc Brown invents a time machine, then Marty uses it to go back in time, then he accidentally keeps his parents from getting together, then the future is changed so that he won’t exist, then he has to get them back together to save the day, and finally he goes back to the present and everything is different. It’s a neat linear progression and it gives us all kinds of problems with paradoxes. It’s also not at all accurate to how actual time travel would work. You see when Marty hits 88 miles per hour he doesn’t suddenly appear in 1955 where he had never appeared before. You see 1955 has already happened. It occurred 30 years before Marty ever pumped that gas pedal. Everything that happened in the year 1955 already had occurred and was old news by the time Marty jumped back in time. Which means that, logically, when he appeared in 1955 things went exactly as they actually had. Now this is where we break off from the movie. In Back to the Future Marty acts as a time bull in a chronochina shop. Everywhere he goes he changes things by his presence there, from his parents relationship to the twin pine mall to the current mayor. He obviously was not supposed to be there and his actions are causing things to happen that never would have occurred. But if actual time travel could be achieved then when you traveled back in time you would change absolutely nothing, not because you physically can’t but because whatever year you jump back to already happened and everything turned out just like this.
Here’s an example: lets say you have a friend who wants to go back in time and stop WWII from happening. He’s built a time machine and he has it all planned out. He’s going to jump back to 1914 and prevent the assassination of Archduke Ferdinand, which will prevent WWI from beginning which will subsequently prevent WWII from ever happening. He’s looked at all the variables and done all the math and he knows if he can prevent that assassination then the horrific death toll of the 20th century will be drastically reduced. He’s shown you his work and it’s impeccable; but there’s just one problem, one that you point out to him as he’s about to make his time jump. He failed.
He might look at you quizzically. How can you say he failed? He hasn’t even started yet. You shake your head. No, you already have started because 1914 already happened and Ferdinand was killed. As soon as you go back in time you will find yourself there, in a year that has already happened. We know the result of it: it’s right there in the history books. If you had succeeded then it never would have happened. Since it did you logically must have failed. You have already failed. You failed almost 100 years ago.
He might smile and shake his head. You’re just trying to keep me from doing it, he might say, and if I don’t do it then of course it will happen this way. But as soon as I make this jump it’s all going to change. To which you should respond with the simple fact that if he makes that jump then he will already have been in 1914 and will certainly have failed. Unless of course your jumping to some other universe’s 1914; then maybe you might succeed. But the point was prevent this world from going through WWII, not some other alternate dimension, right? But we already know how 1914 turned out in this world. Ferdinand died. You failed in your mission. That’s not to say that you didn’t try; I have no doubt that you will. But you will fail. Not because of fate, but because of facts.
Does that make any sense to you? It can be a tricky concept to grasp. I’m not saying that if you go back in time you lose your free will. I’m sure you’ll make all kinds of choices; it’s just that the choices you make will inevitably end up not changing the future. The way I see it you have only three possible outcomes if you try to go back in time. The best outcome is that you accidentally cause something good that happened to happen; maybe that fellow WWII soldier who saved your grandfather’s life at the Battle of the Bulge was actually you. Maybe you tip off the guy who discovered penicillin that he should try looking at bread mold. Maybe you convince Eisenhower that it would be a good idea to help rebuild Europe and Japan instead of putting reparations on them. Good for you! You didn’t change the future but you did save lives! The second possible outcome is that you have no real effect on the future. You spend your whole time in the past encased in a sealed and invisible bubble, silently observing. You are not responsible for any part of the past, whether good or bad. The final outcome, of course, is that you cause some of the terrible things in the past to happen. You try to stop WWII and you end up helping it to happen. You try to “invent” some future technology to help people and you accidentally cause the Great Chicago Fire. When you go back in time you have to remember that the past already happened, and if you traveled back to it then it already happened with everything you actually did.
What does all this mean? It means that I can be a little happier because time travel is not impossible. That doesn’t mean we’ll ever actually be able to travel backwards in time, but it does show that the concept itself is not a logical impossibility.
What’s really interesting is seeing what books and movies get time travel right. Funnily enough the best example I can think of is the Time Turner from Harry Potter. The Time Turner works just like an actual time machine would; it only causes things to happen that actually already happened. The story isn’t that Harry Potter was killed by Dementors so then Hermoine goes back in time and prevents that from happening; the story is that Harry Potter would have been killed by Dementors if a mysterious wizard (who he first believes is his father) didn’t show up to save the day. They then later use the Time Turner and Harry Potter just happens to find himself right in position to save his past self; which of course he already had done, and always had done. They don’t actually change anything: they just end up making the present come true, so to speak.
This has been a long rant, but time travel is something I nerd out about. I’ll try to talk about something interesting to even non-nerds on Wednesday. No promises though.