So, I thought of a neat little time travel mechanic.
What I want to talk about today is yet another Fixed History Model. For mechanical reasons, instances of time travel are always paired sequentially. You could call this time splicing. Or better yet, a time share :^)
Maybe it’s a spell, or superpower, or tachyon-activated resonance bifurcation, but retrocausation requires two deeply similar if not identical objects. Perhaps traditionally, this will be a pair of prophetic slates, but a cute premise might have the protagonists be a pair of identical twins, who find themselves becoming enmeshed in a (rare, if not outright unheard of) case of living time travel.
Anyway, the twist to this system is as follows. First label the two targets A and B. At time T=0, target B is mutated by timey wimey magic until its molecular structure perfectly reflects target A’s future state at some time T=n.
Now, once this first step of the spell is complete, the objects may experience a physical attracted to each other (and for living things, the future copy may be feel a compulsion to approach). When they make contact (or just enter a certain too-close radius), a time-spark leaps between them. Would you look at the time, it’s T=n already.
Now, our premise here was that time travel is necessarily consistent — but for explanatory purposes, let’s suppose it isn’t. If the current state of target A at T=n does not actually match what we transformed B into at T=0, the timeline will be promptly destroyed.
In short, to exploit time travel, you want to keep past!A and B future!A apart for however long it takes to do useful precognitive work.
But here’s where things become splicey. At the moment where A’s state is (essentially) checked for consistency, the original A is mutated to reflect the state of past!B at T=0, when B was mutated to reflect the state of future!A.
This will last for n units of time; B lives in A’s body for exactly as long as A “spent in the past”. In effect, B gets transported into into the future, trading its allotted time in the present with a future A.
But: when original!A is replaced with past!B, future!A (originally B) will be replaced with a B from still further in the future.
It’s symmetrical: just as there were effectively two As running around for the 0–n leg of the time travel, in the n-2n future there will be two Bs running around, for just as long. Then when those two sync with another time-spark, future!A is put back in their original body, having time-skipped n-2n. The effect finally ends.
If I understand correctly:
You have two slates, A and B. A is red, B is green.
You timeswap them. A is red, B is now blue.
You paint A blue. A is blue, B is blue.
The timeswap moment occurs. A is green, B is pink.
You paint A pink. A is pink, B is pink.
The second timeswap moment occurs. A is blue, B is pink.
That sounds right — though I’ll admit, I had to think a bit to keep track of it. Here’s a scenario that’ll make what’s going on clearer.
Alice and Bethany do the timeswap dance. Alice’s voice comes out of what once was Bethany’s mouth, declaring: “Your lucky numbers are 4, 6, and 1, dear.” You roll a six sided die three times, and sure enough, you roll just as predicted. The newly-prophetic Alice looks at her original and shakes her hand, then the other Alice widens her eyes as if in sudden revelation.
Now Bethany narrows her eyes, and says “Expect a six of spades.” You wait for more, but she’s going to keep you in suspense. You draw a card; she’s right. “Then nine of hearts.” Draw. “Then six of tiles.” “Who calls them tiles?” “Whatever, just draw. And there you go. We done here?”
The other Bethany, watching attentively, gets a quick forehead tap, blinks, and then Alice checks her watch.
But I digress. This is cute in its symmetry and specifics, but it’s not actually all that different from the Fixed History travel you’ve seen before, so many times.
Personally, I’ve been thinking about precognition since I was a teenager first getting into online fiction. Even back then, I soon developed a model of time travel so functional that one of my first ever programming projects was implementing a cellular automata with time travel.
The thing about consistent time travel is that you’ll wind up prey to the bootstrap paradox — that is to say, self-causing events. In stories, this can be cute, but if we’re imagining truly reductionist phenomena that don’t have some godly/authorly/magical thumb on the scale ensuring that things stay narratively sensible and humanly legible, I think things must get weird fast.
You see, a different way to think about this model isn’t as a Single Fixed History, but as something where every time a time travel event takes place, the timeline splits off into astronomically many branches.
Each timeline proceeds in lockstep until one of them encounters a paradox, whereupon it is summarily terminated, and in the long run, only the consistent timelines survive.
But from the perspective of someone living in one of those timelines, what actually happens is the invocation of time magic plucks random bits of data from the space of all possibilities. The only constraint is that it must be eventually consistent
If the time traveller can have much impact on the world (and they ought to, if there’s a point to this), then every single time you mess with time, you’re going to get random butterflies mutating and contorting the timeline into a randomized yet consistent series of events.
And this poses a bit of problem on the meta level — how do you write a story that faithfully portrays that kind of sheer arbitrariness? Should you — would it even be any good?
Now, you could sanity check it a bit. You can require the data written on the prophecy slate to adhere to some hash or formality, and you can have the ARWASFAE subject time travelers to interviews that ensures they’re of sound mind and their memories of the future are intact and make sense.
But today I thought of potentially a more algorithmic approach.
And more importantly, I think it at least provides a bit of a heuristic for reasoning about what sort of timelines ought to be more likely.
What if, rather than branching into 2billion timelines immediately, time itself effectively does pathfinding. Maybe tries first of all to change nothing at all, having the “future self” be identical to the “past self” (which of course can’t yield a consistent timeline, unless the effect immediately ends). When a timeline doesn’t work, it goes into a loop trying out small changes, iterating different possible “futures” until it finds a consistent fixed point.
Incidentally, if this really is a pathfinding algorithm, it might always result in the strictly least disruptive time travel possible. (Thus, part of the engineering challenge of time travel is ensuring that the path of least resistance is at least resist-y enough to allow for interesting stuff to happen stuff.)
Another possible algorithm is approachcing the “search for fixed points” problem from a different angle. Whenever you encounter a paradoxical timeline, seed the next timeline with the inconsistent future state.
In effect, you get a time loop that repeats until a stable, consistent history is created.
But I’m not sure this is a good algorithm, at least when you get to the scale of humans, because obviously your no-loops past self will not and can never really wind up the same as your seasoned looper, not unless you combine this with pathfinding so that in effect each “loop” branches into innumerable copies with scrambled brains.
Wait, no.
This objection to time loops doesn’t quite make sense — “future” is ambiguous here, so I got confused by time travel grammar.
If you do this right, then it’s not actually a proper time loop, it’s a weird sort of… relay race time loop?
Because what we send into the past shouldn’t be the looper — of course that would never work — but the unlooped past self.
They’ll never accumulate a loops’ worth of memories, just the one. Instead of a direct memory of past loops, they get the secondhand effect of meeting a future self who behaves weirdly because they met a future self who behaves weirdly because—
And that seems a lot more likely to eventually homogenize into something fixed point-y at the asymptote, doesn’t it?
The so-called rule of three is more of an iron law, so I’ll give one last possibility: what if we incorporate my initial objection of “author fiat” into something more diegetic? Suppose there is an intelligence guiding the selection of consistent histories.
This provides different heuristic for what’s likely, but a valid one, if you suppose that the timeline you wind up with is one that satisfies an agenda while adhering to a rigid contract of necessary-consistency. (Imagine an evil demon who tries to find the worst possible timeline that’s still stable — which would slot ARWASFAE into the familiar role of devil’s bargainers.)
Something that’s implied by my earlier exposition, but is probably worth making an explicit point of: the fuel in the engine for this model of time travel is precommitments. It’s as if the universe reacts to your intent to do something, but only if your will is ironclad.
When the medium of precognition is no more than inscribing text on a slate, it would be so easy to copy verbatim, simply by reading the future slate (perhaps you must avert your eyes).
The truth is, you will be acting as a filter to decide the very existence of timelines. In other words, so you need to be willing to consign the universe around you to nonexistence if it means ensuring your other timeline counterparts can pull off a clever bit of prescience.
And this is at least part of why I’m not the biggest fan of the “time loop” algorithm — because it feels like a direct acknowledgement of the uncomfortable fact that other timelines exist.
Whenever I think about this model of time travel, I always want to find a way to keep the eaten cake and have time travel be based on the exclusion of inconsistent timelines without, you know, those timelines existing.
Should you find yourself in a doomed timeline, is it morally justifiable to destroy it? Is every time traveller committing repeated omnicide?
At least part of the conceit here is that the universe must be some sort of hyper-computer, and so somehow it’s capable of always-already knowing which timelines are ok before the branching even takes place. In very technical terms, it’s a magic oracle.
But still… don’t they exist? Aren’t they causally implied by the nature of the timelines that persist, ghostly in that negative space? If you can recover information about the doomed timelines, isn’t that isomorphic to those computations really happening, somewhere, in some ontological sense?
Does a simulation really need to be run?
I don’t know, but I guess that’s all I wanted to talk about tonight.
Well, not quite. That was a conversation starter, not an ender, and as you may have gathered from the random quote block near the beginning, the chatroom discussion where I originally wrote all this spawned further discussion.
Of course all of this leads into an important question- What are the best story-driving conflicts to derive from this system?
I’ve always been partial to the idea that repeated time travel caused madness from the random perturbations.
And if you allowed time travelers to interact with their past self, it just gives them even more latitude to inflect self-replicating madness on their past self.
So breaking the rules of ARWASFAE has a tendency to create evil puppets of fate itself.
But there’s other approaches you can take. Here’s a more sociological one. When I was first working this out on my walk earlier today, the original conception of all this didn’t include the sequel/bonus time mechanic, wherein the victim also gets to time travel.
Nor did the constraint that the two targets needed be near-identical exist in the beginning.
So as a result, you had a society where there’s an underclass that sells chunks of their life for time mages to go joyriding in.
But the idea I’m liking more the more I think about is a bit of a departure from what’s described here.
What could be really fun is taking some very insecure/selfish character, and the inciting incident is that she’s traveling back from the future to stop her past self from fucking everything up — she’s probably even read time loop stories before — but future knowledge isn’t enough. She’s a stubborn fool and every time she fails and has to go back to the start and push that boulder again.
Maybe a few times, her past self reacts badly, turns uncooperative and ultimately tries to betray herself, seeking to trigger the time travel mechanism to send her (the past self) back instead of the looping future self, but of course she’s no match for their badass future self who’s seen this all before.
And once we’ve watched many, many loops play out, and the newest loop is coming a climax, it becomes clear that the whole story we’ve been reading up to now was just the looping future self writing or narrating to the past self.
But she’s been lying to you. To herself.
The big twist is… remember how sometimes, the past self tries to betray the future self? No, that happens every time.
And every time the past self goes back, putting on airs pretending to be the future self, that nothing’s amiss. We the audience haven’t seen any loops, just a dramatic retelling of them. A telephone game across time.
Most likely, her past self is always an ass to the future self when they first meet, demanding cumbersome proof she’s really who she says she is and never really trusting it, which starts them off on the wrong foot every time.
The two — one? — always come into conflict because even if she realizes the vicious cycle of the loop, her future self’ll panic and realize she’s going to die and that ignorant bitch will survive instead. So of course she does everything she can to prevent that, never revealing the truth lest she give her past self ideas, and so on.
So the final loop could only happen when she stops pretending, starts letting her past self steer events. She can’t try to control everything — if her past self can’t figure it out with a few nudges, how will past ever imitate future?
In a way, this would be an anti–time loop or post–time loop story — because the only way it resolves is if the protagonist lets go of the idea that the loop mades her smarter or more competent, that if she can just hang on everything she gained from the loop she can fix everything.