| Time Travel | 2005-06-28 17:32 23 comments |
 by Flemming FunchArticle last week: New model 'permits time travel'. Researchers are trying to find models for time travel that avoid the good old paradox, of what would happen if you went back in time and stopped your grandfather from meeting your grandmother, or you killed your dad before you were conceived. Which would make it sort of impossible that you're still there, then. So, it has been used to sort of prove that time travel is impossible. Now, these new thoughts don't sound terribly much better. Even scientists have a hard time wrapping their mind around time. So, let me help them out a little bit. Here's how I think it works. Time is a dimension, just like the 3 dimensions of space. There probably are more dimensions. String theory seems to predict something like 12 dimensions. So there's most likely more directions to move in than the 4 of spacetime. But there certainly are those. Despite time being just another dimension, we seem to be wired to perceive it as a one-directional stream. Something happens, and then it gets frozen in the past, as the history that leads to this point. And the future hasn't happened yet. So, both the past and the future seem equally inaccessible to us. But that's really just the fault of our perceptual wiring. Doesn't actually have much to do with Reality with a big R, the stuff that's really there. It is just the reality that we construct from our perceptions, and our abstract conclusions about those perceptions, which keeps time in that format. However, we can learn something about time as a dimension by studying the dimensions of space, which we perceive ourselves moving more freely in. Let's say I'm standing on the town hall square, and then I walk down to the train station. I can remember that I was at the town hall square. Now, if I walk back to the town hall square, will I catch myself standing there? No, of course not. Not even if I do it really quickly. That's logical for us in space. But really it isn't all that different with time. Our lives are objects in 4 dimensions, at least. Even if you take just your body. It has length, width, breath, and it has an extension in time. It extends backwards in time from where you are now, and forward in time to its death. All of that sort of sticks together. It might change in various ways, but it does have a certain coherence. Let's take a mobile item with some spatial size, like a bus. It might be 15 meters long, but it sticks together. If the front end moves, the back end moves with it. Whatever influences the front has an influence on the back, and vice versa. It won't be entirely the same, but it will be connected. If the front end stands in the sun, the back end will get warmer too, even if it doesn't. If somebody puts a sign on the front, saying that now this is a school bus, then the meaning of the back will suddenly change too, even if nothing else changed about it. Your life is kind of like that too. Good actors will prepare for much more than the role they're asked to play. They will sit and write down what they think the past history is of this character. They will construct events in his or her life that might have made him what he is. They will construct emotions from past experiences. They will decide where he's going, what he wants to do, and why. And that creates a much more full character in the present. The past is where you're coming from - the path and experiences that add up to who you are now. The future is where you're headed - the path and the experiences you'll go through if you continue as you are now, and with the history you've had. In principle both that past and that future are changeable. If you suddenly change, you'll need a different past history to explain it, and you'll suddenly be pointing towards a different future. But it is difficult to suddenly change, because there's a lot of inertia in all this stuff. There's a considerable weight in your past history. It adds up quite convincingly to explain who you are now. The most likely way of changing it is to re-interpret it, and get a different meaning out of it. But it would also just have to change, if you really change. All of it is quantum probabilities, so it is really a lot more moldable than what a 10ton bus seems like to us. It seems so solid. But really it is all the holodeck. It can be whatever you want it to be. We just have so much invested in all the stuff we've observed and what we've concluded it is, so it is very hard to just change it arbitrarily, and observe something else. But there's nothing that makes it impossible. Anyway, back to time travel. My life is like this bus that is moving. It sticks together, but it sometimes changes. The lives of everybody connected to me are also all intertwined. So, let's say I go back in time with the intention to meet my dad, and stop him from meeting my mom. But the problem is that they're part of the back end of my bus. If I move, they move with me. They're not standing back at the bus depot any more, because the bus moved on. Just like I'm not standing back at the town hall square when I go and check. Because I moved. Duh. In part because of our language, we often make the mistake of assuming that a place is the same, even as time changes, or other things change. You know, this is my office, and I can talk about my office yesterday, or last year, and in my mind I tend to think it is the same office. I believe it is the Hopi that have a language that doesn't do that. My office yesterday is not "here", it is "over there". Over there in yesterday. And they probably have a point. It isn't the same office. It looks a good deal like it, but it is different, the time is different, and a lot of the sub-atomic particles are probably different. We short-circuit our logic when we fall for the misconception that places and times are "the same" when they really aren't. So, if I go back to where my father met my mother. Well, we could say that they no longer are there, because they moved on, got married, got me, etc. So, if there's only one of each of them, they're no longer there. The bus left. If you wanted to change things, you've have to catch up with the bus where it is. Or, are they still there? See, that gets us into the more fantastic subject of parallel realities and multiple versions of ourselves. The funny thing is that most people intuitively would expect that if time travel were possible, they would go back and find exactly what "was there". I.e. your dad and mum exactly as they were, ready to have their first kiss at the drive-in, playing "Rebel without a Cause". But that requires that we keep existing at all times and places we've been. That there are a zillion you's stretching far back, and probably forward. That's entirely possible, that it works like that. That the past isn't just a memory in your brain, but it is real, it is there, it is alive. So, let's say they still are there. They're, however, also still connected with you, as part of a probable past that let to you being born. And, incidentally, to you getting around to go back in time at some stage in your life. It is all connected. Not two separate events, you and them. Rather, part of one bigger spacetime event. One possibility is that you might find that the past event has already changed from what you thought it was. The later events in their and your lives might have redefined what really happened. Maybe the original event was a happy kiss in the drive-in. But later on they got divorced and got therapy and decided it all was different. Like, he was really a brute who raped her. So maybe that's what you'd see if you went back. Because the whole gestalt is connected backwards and forwards. But then we have to touch on the possibility of what happens if the past changes. We're talking about objects in 4 or more dimensions. A bit like the screenplay of a movie. It is all connected, the characters, the timeline, the events, the climax. If we change one part, we'd have to change others. If we rewrite the script a little bit, and make the main characters meet in Paris rather than in Rome, then a bunch of things will change. Their kids will speak French rather than Italian, etc. If you had already shot the movie in the first version, then the next version will be a different movie, even if the story is similar on many points, and some of the characters are roughly the same, and even if it has the same name. Quantum physics seem to say that things exist if somebody has perceived them in a particular way. If they haven't been perceived, it is uncertain what is there. Could me many things, but the reality hasn't been frozen. So, if nobody was there to hear it, we don't know if the tree fell in the forest and made a sound. We don't know if Schroedinger's cat is alive or dead, unless we look. So, my past is a certain way because I perceive it to be so. Not really that I *have* perceived it that way. More that I'm doing it now. If I stop perceiving it, it might go back to uncertainty. Or if I succeed in perceiving it differently, it becomes something different. You'll notice that science skips rather quickly over the mystery of who it is who perceives things, as consciousness isn't a popular subject for people in the material sciences. So they usually just talk about "measuring", rather than awareness or consciousness. But it is unavoidable. Things are real when there's somebody there who perceives them. It would all become a little more logical if we accepted that there were such a thing as consciousness, and that it probably is extremely basic to how the universe works. Now, what if you get to a fork in the road in your life? You might go left, you might go right. Your life develops differently, depending on which one you pick. Before you make the choice, the two possible futures are maybe equally probable. Once you make the choice, your future falls into a certain groove, and that choice becomes part of your past that explains how you got to where you are. But how about if you also took the other road from the fork? No, not the you who's here today, who went left. But there's maybe a parallel aspect of you who took the path on the right, and went on from there. There might or might not be. Depends on whether anybody's there to experience it. If there were a consciousness which found the right side path interesting, it might have turned from the realm of uncertainty into a reality. In your life there has been many forks in many roads. Possibly many or all of those turned into realities. One of which is the one you're sitting in now. They're related, at least by their common branching points, but they're otherwise different. The Flemming who decided to move to Rio and be a street performer would clearly be a different character than me, even though we might have a lot in common, and part of our history would be exactly the same. So, back to those time paradoxes. If you try to go back and meet your mom and dad, before they conceived of you, then several things might happen. If you focus on the path that is part of your past, you'll probably find difficulty in trying to interfere. That's not as mysterious as it might sound. It is a bit like trying to spin around to see oneself from the back. No matter how fast I do it, I'll miss, because my back moves at the same time as the front. So, the same with the characters in your past. You might be surprised to find that they just walked out before you walked in. Because they're connected with you. The difficulty of doing so depends a bit on how long the tail is. You can't see yourself from the back by spinning around. But if you were a snake, you could grab your own tail, because there's enough dimension there. The front of the bus can't see the back, but a litte train with many wagons maybe could. So, in time travel, you might have trouble getting to meet a recent version of yourself. But if you go far enough back, it isn't so hard. So, maybe it is not any great problem to go back and meet your parents. But remember that there's a considerable inertia towards them doing roughly what they did, because there's already a well-perceived future reality in front of them, which they're connected with. There's a certain pull in that. But maybe if you exert enough energy, you might make something else happen. You manage to throw a Molotov cocktail into their car, and they burn to death. Then what happens? Really just that you created a fork. Your parents would still have met in that drive-in, and you don't suddenly disappear. But there's now another timestream which develops differently. It will include a few hundred people for whom the mysterious tragedy in the drive-in in '62 happened, with the stranger who blew up a young couple, who claimed he was from the future, and was carrying strange electronic devices in his pocket. And that reality develops differently from the one you knew, in small or big ways. Might be huge, with time travel technology being then discovered in 1962, from somebody studying what you had in your pockets, or it might just be a minor ripple, and it becomes a world very similar to ours, just without your parents, but with you as an older criminal. And back here in our reality, we'll wonder why you never came back, but everything will otherwise continue as normal. So, there is no paradox. There are just potential paths, and actual paths taken. Sometimes multiple parallel paths might be taken. Sometimes you might go back and take a different path. None of which changes that all of the paths, that somebody perceived themselves taking, were real. Back to one little detail. That article mentioned that of course we aren't seeing any people who suddenly disappear because their past changed, so obviously that isn't happening. I wouldn't be so fast on that. OK, forks might happen in the past that lead to different realities. But this reality might also change. It is just that everything in it is connected and relatively consistent with each other. Remember, it is a 4 or more dimensional "object". So, if somebody succeeds in changing something about it, everything connected to it changes. Like, the whole history of why things are the way they are, and everybody's memories of what happened, which explains things. And that is probably hard, because there's a lot of inertia, and a whole lot of things to change. But probably possible, if enough energy is exerted. So if your neighbor across the street got written out of the story, it wouldn't be that his house suddenly, poof, evaporates, and everybody stands there wondering what happened to him. No, you'd be quite sure that there had never been a house on that lot, and you'd have no recollection of anybody with that name, and it would all be very logical, and everybody could confirm each other's stories. I'd say that stuff like that probably happens once in a while, but you most likely wouldn't have noticed, except for maybe an odd feeling that something was off, which you couldn't put your finger on. If you rely only on your perceptions and your memories, nothing would reveal that anything changed, because they would have changed at the same time. I have little doubt that we'll figure it all out eventually, and that there's somebody somewhere who already can travel freely in time and space. See, it doesn't matter if it takes a million years to develop the technology, because that's just "right over there" in spacetime. And it is probably unavoidable that the spacetime multiverse becomes one big subway system, if it isn't already. |