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Time Travel

Mark Spritzler
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    6

OK, so with Heroes having lots of time travel and changing the course of history, I thought I would add my two cents, or should I say really just re-iterate what lots of other people hypothesized.

So here is the dilemna. You go back in time and change something like buying stocks of companies that you know do really well, so that when you return back to the present time you will be rich.

So the question leads to many ideas.

1) Because you buy stock, when you didn't before, it is possible that the company actually never becomes successful and you are still not rich, and to you the world around you in the present doesn't change, well except that company isn't around any more

2) You come back rich and everything has changed. Your life is 100% different. You changed the present. How do other people see the new world. Do they know, do they think it was always like that, or are they the same?

So here is my theory with this issue.

When you change history the "time line" changes, and when you go back to the present, you are on that new time line. But the old time line still exists and everyone in the present now, stay in the present now and you are also in existence in this current timeline. This is the old parallel universes theory.

Why do I believe that theory. Because I think, if time travel would ever be invented, then someone would have time travelled and changed something. Yes, I know at first the couple people that know it exists will not do evil to change history, but as it becomes more popular, someone will do it. So if so, then that would mean that they already did, and well, the timeline I am on hasn't changed, so I think those that changed time already, are in their alternate universe already and not affect our current universe.

What do you think? Am I a lunatic? Maybe I went back in time and changed your opinion of me so that you would answer the way you are going to answer?

Mark


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Ernest Friedman-Hill
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Joined: Jul 08, 2003
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  34

I concur that this "many worlds" hypothesis is the only cosmology that's consistent with the possible existence of time travel.

If you're not familiar with the web comic Dresden Codak, you should take an hour and read the "Hob" storyline from beginning to end -- you'd like it!


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Henry Wong
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  40

The problem with this "many worlds" theory is that it causes writers to be lazy. I really like the old time travelling stories where stuff actually makes sense. There were loops in the timeline, but the story didn't have paradoxes, which can only be resolved with the "many worlds" theory.

Henry


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Henry Wong
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  40

And there is a flaw with the "many worlds" theory. What if you go and change the timeline to the point where you change yourself? And what if this "yourself" never went down the time travelling route? Does that mean that there will be, in some worlds, more than one of you? And in other worlds, where you simply just disappear?

Henry
Jeanne Boyarsky
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150

Heroes has made "time travel" so complicated that it is a plot device to change things at whim. It's so much easier to follow when things are self contained like in Harry Potter.


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Henry Wong
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  40

In my opinion, the terminator series is a perfect example of how writing about time travel has degraded.

In the first Terminator, everything is wrapped nice and tight. There was a time loop, but there were no paradoxes. Everything fits.

In the second Terminator, there is a paradox -- a major one. The future as we know it is happy again. This means that it won't be possible to send a terminator back, etc. etc. etc.

In the third Terminator, they didn't bother explain what changed. A terminator appears from somewhere to change it all back on track. This, of course, make even less sense.

Henry
Mike Simmons
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    9
[Henry]: The problem with this "many worlds" theory is that it causes writers to be lazy.

Sounds overstated to me. Perhaps you meant that it allow writers to be lazy? Not that it wasn't possible for writers to be lazy without many-worlds.

In fact, I tend to take the opposite position. Even as a teen I almost always found those supposedly "self-consistent", single-timeline time travel stories to be too pat and simple. Yeah, you can avoid paradox if the author carefully contrives events such that paradox does not occur. But it always seemed to me that that sort of thing only works if the character have no free will and always obey the script. I mean, if I ever encountered an apparently-working time machine, I would probably use it to travel one day into the past, go to my own home (at a time when I knew I hadn't been there, or was asleep), go to my closet, find whatever shirt it is that I (future-me) am/was/will-have-been wearing (at the time I found the time machine), and burn it. Because I'm not so sick as to kill my own grandfather, but I would need to know more about how this "time travel" actually worked. Can I burn the old version of the shirt I'm currently wearing, or not? If not, what prevents me? Do events just magically conspire to distract me? :roll: Or is there some measurable physical force that prevents me from lighting the match? What happens? Personally, I would want to know. Maybe that means that the Novikov self-consistency principle will prevent me from ever encountering a functioning time machine - oh well. I'd rather gain some understanding of how such a principle might be made manifest, than meekly accept that "che sera, sera". It beats playing lackey to some unknown scriptwriter, I say.

[Henry]: And there is a flaw with the "many worlds" theory. What if you go and change the timeline to the point where you change yourself? And what if this "yourself" never went down the time travelling route? Does that mean that there will be, in some worlds, more than one of you?

Well, yes. Wasn't that already implicit in the concept of time travel? At least, in any time travel within one's own lifetime? If I time-traveled forty years or less into the past, then there would be two of me. That's pretty much a given, isn't it? One might imagine some set of rules that might appear to prevent this situation - but I strongly suspect that such rules would just obfuscate the basic problem, rather than prevent it. If I were to journey back to ancient Egypt or whatever, I would still be existing side-by side with earlier versions of many of the same atoms and molecules which were eventually incorporated into my body by 2008 (or whenever I found the time machine). At the atomic level, there would be plenty of atoms caught in paradoxical time-loops. Unless there's some magical force preventing each and every atom on Earth (in ancient Egypt) from finding its way into my body (in the present day). Bear in mind, I'm talking about oxygen atoms too, and other gases. Those things diffuse pretty rapidly, and it's pretty much guaranteed that every person reading this has at least a few atoms in his or her body that were once part of, say, Rameses II. Or of John Q Pyramid-builder, Class of 2570 BC in Giza, Egypt. Or of some hypothetical time traveler who went to see construction of the Great Pyramid.

Pretty much any ancient time you might want to visit, chances are that there are a bunch of atoms in the air (and elsewhere) that eventually make it into your body (in the modern era). So if you go back to that time, there will be two copies of each of those atoms. Is that a problem? Maybe so, but it seems like something fundamental to the the concept of time travel, even if many writers ignore it. It's not just something that came up because of the many-worlds interpretation.

[Henry]: And in other worlds, where you simply just disappear?

Yeah, that was always my default assumption for many-worlds time-travel scenarios. I can't recall many fictional examples where it was addressed directly, at least not from the point of view of the original universe (now abandoned by the time-traveler). Timescape comes to mind. A damn good novel, that. Benford wasn't even talking about time travel, just communication, and quite limited at that. But the fact is that any communication (or travel) from future to past invites the possibility of paradox. Possibilities which Benford discusses at length in the book. Highly recommended.

Back to your original question, it's possible to imagine rules that would allow a traveller to return to his/her original reality, sometime after the previous departure. So maybe the traveler has't vanished for good, but may reappear later. However, to me that feels more like wish-fulfillment than like something likely in the real world. (Even moreso than for time travel in general, and that's quite a stretch.)

[Henry]: In the third Terminator, they didn't bother explain what changed.

AsI recall, they implied pretty clearly in the second and third movies that previous time travel did in fact change outcomes - at least in small ways. There's no one single self-consistent timeline. There's just one timeline that you, J Random Observer, happen to be in. Which can and does interact with previous timelines, and probably interacts with future timelines as well. The struggle then is to change things in larger ways, since it appeared that some events the rise of Skynet) still had a scary tendency to repeat themselves. Like a main theme repeated in a different key.

See the Planet of the Apes movies for a similar progression - it's clear that the world of the 3rd and 4th movie (and the crappy TV series that followed) cannot become the world that was seen in the 1st and 2nd movies. Not exactly. But in many ways they are still quite similar.

(At this point I feel obliged to point out that Terminator's current TV series is, while flawed, still much, much better than the Planet or the Apes TV series. I'm only drawing a parallel between the storylines; I'm not saying they're comparable in quality.)

In general, at this point I tend to assume that almost any time-travel story will have logical flaws if I choose to dig far enough - unless, maybe, it embraces a many-worlds approach. Often even then they'll have flaws, but oh well. I choose not to look too closely, most of the time.

Having said that, there are a few relatively recent films that use time travel (or past communication) well. The two that come first to my mind are Primer and Donnie Darko. OK, the latter is ambiguous about whether there's really any time travel at all. Much like Life on Mars, also very highly recommended. Really, at this point I find psychological ambiguity to be much more interesting than a hard SF approach - at least where fictional time travel is concerned. Show me a real time machine, and I may well change my mind.
[ October 04, 2008: Message edited by: Mike Simmons ]
Henry Wong
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Joined: Sep 28, 2004
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  40

AsI recall, they implied pretty clearly in the second and third movies that previous time travel did in fact change outcomes - at least in small ways. There's no one single self-consistent timeline. There's just one timeline that you, J Random Observer, happen to be in. Which can and does interact with previous timelines, and probably interacts with future timelines as well. The struggle then is to change things in larger ways, since it appeared that some events the rise of Skynet) still had a scary tendency to repeat themselves. Like a main theme repeated in a different key.


There is actually a subtle difference between the second and third movies. They both have paradoxes, which can only be explained by the "many worlds" theory. But in the second movie, you can still say there is a relationship between the cause and the effect. Meaning....

You can still argue that you are "branching" the timeline. You pick a point in time, you go back, and since you are effecting it, you are now causing a branch in the timeline. The return of the terminators branched the timeline.

In the third movie, you can't make that arguement. The terminator came from a future that wasn't the current timeline. Which implies that branching didn't occur and the terminator hopped from a different timeline... which leads to two questions / issues.

First, without branching, how can you say when you go back to a point in time, in order to change it, that you will get to a timeline that is exactly what you expect, so that you can change it. Second, if you don't branch, but jump to a timeline, how do you even know that you need to fix it? It is a timeline that you don't see.

(At this point I feel obliged to point out that Terminator's current TV series is, while flawed, still much, much better than the Planet or the Apes TV series. I'm only drawing a parallel between the storylines; I'm not saying they're comparable in quality.)


The Sarah Conner Chronicles is just a really good TV show. I just loved the season opener, for the current season, where they opened using a song about "Sampson and Delilah".

Henry
Mark Spritzler
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Posts: 17250
    
    6

I think I agree with Mike here, and I think he has thought it out much more than me.

I actually had had this idea for a movie, in which a guy finds a wallet. At that point the movie splits into two time lines. One where he returns the wallet and one where he keeps it. The two story lines then has complete opposites of everything, except for one person, (a girl of course) and Love of her is what re-unites the two time lines back into one.

When I thought of the idea, I was in high school back in 84, and so the characters were in high school. So in one time line the kid is a bookworm with glasses etc, and in the other time line the kid is a bad ass.

Mark
Mike Simmons
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    9
Henry: I don't remember details of T3 very well at this point, but I agree that there is a difference there, with travel from one branch to another. However I don't see this as necessarily a problem, as long as it isn't possible to travel from a child timeline to a parent timeline at a point prior to the child's creation. Because that would lead to the very paradox that many-worlds avoids.

Mark: sounds like it could have been a fun movie.
marc weber
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I like the phrase Vonnegut used in Slaughterhouse-5, in which Billy Pilgrim simply became "unstuck in time." The implication was our being stuck in time -- experiencing events "chronologically" -- was an oddity.

As I recall (with over 25 years since last reading the book), "history" was fixed from beginning to end, with participants merely along for the ride. The notion of free will to alter events was a result of our limited perception in being "stuck."


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John Smith
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Here is how I see it. It's very easy to change the future. Think about this. If I stop typing for five seconds, I changed the future, compared to what it would have been if I didn't pause. You are getting my message 5 seconds late, which constitutes a different state of the universe, even if doesn't lead to any cataclysmic events. Now, changing the past is not easy. That's because you'd have to reproduce the state of the Universe as it was in that moment in time. That means that all the god damned atoms in the entire Universe would have exactly the same position and velocity as they were back then. Only that would qualify as going back in time. While there is really nothing to stop this, it's extremely unlikely, statistically speaking. Basically, to go to the future, you change one atom. To go back to the past, you'd have to change all of the atoms. That's what makes the time appear as being unidirectional.

How does this answer the original question? Well, if you manage to go back to your past (which is, again, possible but highly unlikely to accomplish due to the probabilistic model which I outlined above), you could not kill your grandfather at his tender age or to burn your own shirt to "see what happens". Why? Because you were not there! That past had only one copy of you, so you are not reproducing it when you insert another copy of yourself from the future.

So, what happens, you may ask, if you do manage to reconstruct everything perfectly and exactly? Well, things would then have progressed precisely as they once already have from that point on. But again, there would be no multiple copies of "me", it's just the same me traversing the same trajectory for the second time. End of all paradoxes.
Mark Spritzler
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    6

I don't know John? It is an interesting idea, but I don't like it.

Which probably might mean that it is most likely correct. Wait did I just pause there for 5 seconds.

I think the big thing to consider here, is not if we invent time travel. But if in the future, at some point someone does invent a way to time travel, would we know now? Because someone in that time period must have travelled back to our time. Or will it be the concept of time travel only to time periods after time travel was discovered?

Mark
 
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