Time Pseudo-Travel Models

Postby mwchase » Wed Oct 05, 2011 7:23 am

So, last night, when I should have been doing my homework, I was instead reading about a time travel model that was too confusing for the guy who came up with it to use. And then bringing it up with Coda. Anyway, I figured I'd bring it up here, since confusion is a beautiful thing that should be shared! Or something. While I'm at it, I figured I'd bring up my own pet model (again, I think?) and see if anyone else wanted to share time travel models that attempt to avoid paradox by eliminating actual retrocausality.

Since I said I'd bring up mine... the basic idea is that it's a physical process that only propagates changes forward in time, but alters the universe around it to make it seem as if the travel (more like copy and paste) had occurred. What this means is, in the apparent history, there is no record of successfully sending anything back in time, only of things successfully arriving, and, conversely, in the true history, plenty of sendings, but no arrivals. The real and apparent timelines are connected by "virtual" timelines that start at the target of a time-paste, and continue indefinitely; the real timeline asymptotically approaches the virtual timeline's state. The only wrinkle in this is what happens if someone in a virtual timeline pastes to "before" it began. I'm pretty sure the secondary virtual timeline would still contain the paste that produced the initial virtual timeline, but I'm not sure. Anyone have any thoughts?
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Re: Time Pseudo-Travel Models

Postby Brilliand » Sat Oct 22, 2011 6:33 pm

It looks like that "hypertime" concept solves the problem of time travel by postulating another dimension of time that can't be traveled in, and smooths out the wrinkles caused by traveling in the first dimension. That's sort of like answering the question of who created God by proposing that he was created by a greater, un-created God, in that leaves us no better off than not asking the question in the first case (because sooner or later someone will think of traveling in the second time dimension, which should be just as reasonable as traveling in the first time dimension). Of course you could then propose infinite time dimensions - "turtles all the way down" - but that isn't a terribly satisfying answer, despite technically solving the problem.

Attempting to "avoid paradox by eliminating actual retrocausality" basically means attempting to avoid paradox by rejecting time travel - though you could of course allow something that looks like time travel, such as creating new universes (or splays) on a whim (which is arguably more powerful, though less useful) without allowing actual time travel.

I prefer to fully allow time travel, and let the quantum particles worry about what happens. "The distinction between cause and effect in physics is not made at the most fundamental level" (taken directly from Wikipedia's article on retrocausality), so although our ideas of cause and effect might be thoroughly messed with, the quantum particles should handle it just fine, and the universe should go on. We shouldn't be surprised at the laws of physics doing bizarre things when we're doing something crazy like time travel. I imagine on a macro level, this would manifest as everything just coincidentally turning out OK... hmm, that isn't all that bizarre after all. I suppose then that on a macro level, "paradoxes just never happen" is my position.
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Re: Time Pseudo-Travel Models

Postby mwchase » Sat Oct 22, 2011 7:56 pm

I find the idea somewhat appealing because, while the idea of messing around with different times is interesting, it seems difficult to write logically consistent stuff in a sensible fashion. Even if Novikov self-consistency is how things "would actually work", it's a real pain to write correctly, and, if we look at most time travel in fiction that's not showcasing Novikov (I can't think of any such fiction offhand besides Umlaut House and UJ/PDH/TSH), it's clear that that's not the rules they're using. Eliminating true retrocausality makes it easier to bring in established story-telling techniques that implicitly assume linear causality, and is more honest than using those techniques with what's supposed to be time travel.

While there are infinitely many viable models of ways that different "eras" could seem to interact, I feel like Novikov doesn't really translate into satisfying storytelling. Have to go watch ponies soon, so I'll see if I have anything more to say in twenty minutes.
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Re: Time Pseudo-Travel Models

Postby Brilliand » Sun Oct 23, 2011 12:36 am

mwchase wrote:While there are infinitely many viable models of ways that different "eras" could seem to interact, I feel like Novikov doesn't really translate into satisfying storytelling. Have to go watch ponies soon, so I'll see if I have anything more to say in twenty minutes.


Aye, realism is often not the best thing for a story. In the situation that you describe in the first post (i.e. someone from 2100 travels to 2000, sticks around for a year, then goes back to 1999 and stays permanently), then I would intuitively expect him to meet himself showing up in a time machine in 2000, since from the audience's perspective, that event has definitely happened and hasn't been prevented in any obvious way. To answer your question directly - yes, the secondary virtual timeline would still contain the paste that produced the initial virtual timeline. The new paste would always be a copy of the same timeline that the time traveler left.

Of course, the story itself has much to say about what simplification of time travel is appropriate - or alternatively, what time travel model you use will to a large extent determine what sort of story appears.
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Re: Time Pseudo-Travel Models

Postby mwchase » Sun Oct 23, 2011 8:02 am

Mmm... I'd actually been thinking about it from a pure storytelling potential point of view: if new virtual timelines don't contain old pastes, then it should be possible to jam time travel by spamming electrons back in time at short enough intervals that they all blur together due to lack of simultaneity, and that would render the whole exercise pointless. (Why electrons? Because it makes intuitive sense to me that the energy requirements would be at least the equivalent energy of whatever you're pasting, so it pays to go small.)

Of course, this situation does give anyone using this model a chance to do something slightly tamer than this. In that, if someone pastes back (they have access to a matter conversion device or something, I dunno), and then pastes back again to mess with stuff, then the original paste may have to deal with a timeline drastically different than what they were expecting. Seems like a fun basis for a mystery story. Guy travels back in time for... some reason. Finds post-apocalyptic wasteland/utopia/dinosaur-people/cephalopods in seawater-filled environment domes (okay, that's... a little silly), has to figure out what his original paste did to cause this.
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Re: Time Pseudo-Travel Models

Postby Brilliand » Sun Oct 23, 2011 6:38 pm

mwchase wrote:Mmm... I'd actually been thinking about it from a pure storytelling potential point of view: if new virtual timelines don't contain old pastes, then it should be possible to jam time travel by spamming electrons back in time at short enough intervals that they all blur together due to lack of simultaneity, and that would render the whole exercise pointless. (Why electrons? Because it makes intuitive sense to me that the energy requirements would be at least the equivalent energy of whatever you're pasting, so it pays to go small.)


I don't think that the spamming electrons would work - it would create a whole bunch of extra splays that no one cares about, but the time traveler would still get his own splay to mess with, same as if the electrons weren't being sent. Also, I would think that the size of the thing being sent back wouldn't make any difference to the difficulty in this case, since you're cloning the whole universe regardless (though if that makes for an interesting plot point, then go for it).

By the way, this model of time travel quickly results in an inifinite number of splays - basically any time travel that doesn't prevent itself from occurring creates an infinite number of pastes.
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Re: Time Pseudo-Travel Models

Postby mwchase » Sun Oct 23, 2011 7:56 pm

Oh, wait, got it, you're missing one of the subtleties. The virtual timelines created by pasting act as a way to influence the parent timeline after the paste is sent. The parent timeline asymptotically approaches the virtual timeline. It's sort of like splitting the difference between a couple different non-Novikov models. In other words, the pasting process doesn't create new matter/splays, it creates a template that the parent timeline will gradually come to follow.

I might be missing something else I need to explain, but to me, this model has the following properties: free will is as valid a concept when taking pastes into account, as when not; actions not only have consequences, but don't simultaneously not have consequences (a weakness of typical splay models) (TSH at least got around this by acknowledging the other splays, giving them closure, and then showing us how things go nuts in the viewpoint splays); causal loops are unlikely to form, and therefore, don't have to be treated in writing (I think Homestuck has the best means of dealing with causal loops; I'm not sure how well anachronic order works for other writers, though); explaining that: in a truly stable setup, the apparent history created by pasting will include no outgoing pastes (because outgoing pastes overwrite the timeline until it stops having outgoing pastes), but a truly staggering number of incoming pastes; while it does feature many coincidences, they're removed from the typical focus of the action, and don't appear at all in the final apparent history; in general, I feel like it's intuitive, has just a few interactions with itself, all well-defined, and basically just represents an excellent set of tradeoffs for the majority of time travel plots.

I guess it does have the unfortunate effect, for going very far back, that any civilization that develops time travel will not be visible in the apparent history, which kind of means that any time travelers from such a civilization are probably, in a chaos theoretical sense, responsible for the pre-downfall of their civilization/species. Or, well, it depends. At least one of them is.

So, either you clone yourself, or you prevent your own birth. I... think I just found an in-story justification for avoiding excessive time travel.
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Re: Time Pseudo-Travel Models

Postby Brilliand » Mon Oct 24, 2011 3:17 am

mwchase wrote:The parent timeline asymptotically approaches the virtual timeline.


But how would this work? The state of the universe is an incredibly complex thing. There's really no halfway point between two different versions of history. In particular, since human beings keep track of history, the parent universe state doesn't truly match the virtual universe state unless all record of the time travel is wiped out. You seem to be indicating that the parent timeline's version of the time travel itself - that the time traveler left, but did not arrive - would "win", but that in nearly every other respect, the virtual timeline would "win". Determining how things turn out (in a mixed case like that) seems like it would be nearly impossible to do in an objective way.
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Re: Time Pseudo-Travel Models

Postby mwchase » Thu Oct 27, 2011 4:32 pm

It depends on whether you think of the virtual timelines as actually existing. If you come at this from a "okay, let's see what this alternate universe stuff is like" perspective, then it's really weird, and kind of redundant. If you come at it from a "How would I avoid shenanigans with branching universes, paradoxes, and shit like that?" perspective, I think it kind of makes sense at most levels, with the caveat that this is obviously impossible. However, it's an impossible thing that can be reasoned about more easily than most impossible things, and more easily than what we believe to be true.

That said, if proliferating timelines with no effect on the parent timelines is alright with you, then the reasoning about this doesn't have to be substantially changed to accomodate that.

Hmm... thinking about this some... Since my model uses "pastes" (because actual travel doesn't make a terrible amount of sense, all told), it's not as much of an issue, but...

I'm sure this has been done, and I'm just not familiar with it. What's out there, about the psychology of someone who'd time travel in a branching timeline model? The whole point of such a model is that nobody influences their own past, and there isn't really an obvious way to get back to one's own timeline under such a model. What kind of person would leave everything behind, permanently, for a life where either nobody, anywhere, knows them, or they're stepping on their own toes, just by existing? I mean, it's justified in Homestuck, because the doomed timelines a) are terrible, b) unravel afterwards, and c) can be escaped in odd ways, more or less, but...

Oh, hey, Eternal Sunshine of the Spotless Mind. That seems relevant to this tangent. I ought to watch it again, sometime.

I mean, in models where travel is travel, it's basically one of the most expensive and elaborate ways possible to commit suicide, from the perspective of everyone left behind.
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