It’s basically “time goes backwards inside the box when it’s turned on”. So you can turn the box on in the morning, immediately see you-2 climb out of it, then both of you coexist for a day and you-2 shares some future information with you, then in the evening you set the box to wind-down and climb inside it, then you wait several hours inside the box, then climb out as you-2 at in the morning and relive the events of the day from that perspective, then you-1 climbs into the box and is never seen again, and you remain.
When put this way, it’s nice and consistent. But in the movie some copies actually stop their originals from getting in the box, resulting in permanent duplication. And that seems really hard to explain even with a branching timelines model. If there’s a timeline that ends up with two permanent Bobs, there must be some other timeline with no permanent Bobs at all, due to conservation of Bobs. The only way such a timeline could appear is if Bob turned the machine on, then nobody climbed out and he climbed in, but Bob could simply refuse to do that.
Another cool thing is that the time machine can also provide antigravity. Consider this: you assemble a box weighing 50kg and turn it on. Immediately, Bob-2 climbs out, weighing 70kg. So the box has to weigh −20kg until Bob-1 gets in it and it shuts off again. In the movie that’s not spelled out, but it does spell out that they first started working on antigravity and then got time travel by accident, so that’s really good writing.
I’m not sure why you say it’s hard to explain with branching timelines. To me this is just branching timelines. The movie voiceover states at one point that the last version of events seems to be the one that holds true, meaning that you see the last branching timeline, usually the one with the most Bobs. I don’t think you have to belive this part of the voiceover, though; this is just the opinion of someone trying to make sense of events. You could instead say that the movie has a convention of showing us later splits rather than earlier.
Branching timelines have to come with probabilities and that’s where the wheels fall off. Imagine you’re Carol, living on the other side of town, not interacting with the machine at all. Then events similar to the movie happen. Before the events, there was one permanent Aaron. After the events, there’s either one or more permanent Aarons, depending on which timeline Carol ends up in. But this violates conservation of Aarons weighted by probability. A weighted sum of 1′s and 2′s (and 3′s and so on) is bigger than a weighted sum of just 1′s. Some Aarons appeared out of nowhere.
Things could be balanced out if there was some timeline with reasonably high measure, consistent with the behavior of folks in the movie, which ended up with 0 permanent Aarons. But what is it? Is it some timeline where a box never had an Aaron climb out of it, but had an Aaron climbing into it later? Why would he do that?
The characters in the movie take a lot of precautions to isolate themselves from their time-clones, meaning that they don’t really know whether they got out of the box at the start. Therefore, they just have faith in the plan and jump in the box at the end of the loop. So long as they don’t create any obvious paradoxes (“break symmetry” as they call it), everything works out from their perspective, and they can assume it’s consistent-timeline travel rather than branching, so they don’t think they’re creating a timeline in which they mysteriously vanish.
When they start creating paradoxes, of course, they should realize. The fact that they don’t think about it this way fits with the general self-centeredness of the characters, however.
I agree that it makes sense to think of this probabilistically, but we can also think of it as just all timelines existing. I’m happy to excuse the events of the movie as showing one particularly interesting timeline out of the many. It makes sense that the lens of the film isn’t super interested in the timelines which end up lacking one of the viewpoint characters.
If we do think of it probabilistically, though, are the events of the movie so improbable that we should reject them? By my thinking, the movie still fits well with that. Depending on how you think the probabilities should work out, it seems like that first timeline where the person just vanishes is low-probability, particularly if they create a relatively consistent time-loop. In a simple consistent loop, only the original branch has them vanish, while each other branch looks like an internally consistent timeline, and spawns another just like itself. The probability of a timeline like “one Abe, then two Abes, then back to one” seems high, if Abe is careful to avoid paradoxes. With paradoxes, the high-probability timelines get chaotic, which is what we see in the movie (and in the comic I linked).
Yeah, I guess “they don’t bother checking whether they get out of the box” is the right explanation for the movie. Though still, if timelines where a person just vanishes are low-probability, then timelines where the number of people permanently increases (like the one shown in the movie) should be just as low-probability. The start and end of a long chain. And the middle of the chain should be mostly like 1-1-1-1… Or something like 2-0-2-0… but that would require weird behavior which isn’t seen in the movie (e.g. “I’ll get in the box iff I don’t see myself come out of it”).
They do deliberately try to set up an “I’ll get in the box if I don’t see myself get out” sort of situation in the movie, though they don’t succeed, and they don’t seem to realize that it would result in 0-2-0-2-… across metatime.
Good point about how permanent increases have to be as improbable as permanent decreases! I should’ve gotten that from what you were saying earlier. I suppose that leaves me with the “movies follow interesting timelines” theory, where it’s just a convention of the film to look at the timelines where characters multiply.
It’s basically “time goes backwards inside the box when it’s turned on”. So you can turn the box on in the morning, immediately see you-2 climb out of it, then both of you coexist for a day and you-2 shares some future information with you, then in the evening you set the box to wind-down and climb inside it, then you wait several hours inside the box, then climb out as you-2 at in the morning and relive the events of the day from that perspective, then you-1 climbs into the box and is never seen again, and you remain.
When put this way, it’s nice and consistent. But in the movie some copies actually stop their originals from getting in the box, resulting in permanent duplication. And that seems really hard to explain even with a branching timelines model. If there’s a timeline that ends up with two permanent Bobs, there must be some other timeline with no permanent Bobs at all, due to conservation of Bobs. The only way such a timeline could appear is if Bob turned the machine on, then nobody climbed out and he climbed in, but Bob could simply refuse to do that.
Another cool thing is that the time machine can also provide antigravity. Consider this: you assemble a box weighing 50kg and turn it on. Immediately, Bob-2 climbs out, weighing 70kg. So the box has to weigh −20kg until Bob-1 gets in it and it shuts off again. In the movie that’s not spelled out, but it does spell out that they first started working on antigravity and then got time travel by accident, so that’s really good writing.
I’m not sure why you say it’s hard to explain with branching timelines. To me this is just branching timelines. The movie voiceover states at one point that the last version of events seems to be the one that holds true, meaning that you see the last branching timeline, usually the one with the most Bobs. I don’t think you have to belive this part of the voiceover, though; this is just the opinion of someone trying to make sense of events. You could instead say that the movie has a convention of showing us later splits rather than earlier.
Branching timelines have to come with probabilities and that’s where the wheels fall off. Imagine you’re Carol, living on the other side of town, not interacting with the machine at all. Then events similar to the movie happen. Before the events, there was one permanent Aaron. After the events, there’s either one or more permanent Aarons, depending on which timeline Carol ends up in. But this violates conservation of Aarons weighted by probability. A weighted sum of 1′s and 2′s (and 3′s and so on) is bigger than a weighted sum of just 1′s. Some Aarons appeared out of nowhere.
Things could be balanced out if there was some timeline with reasonably high measure, consistent with the behavior of folks in the movie, which ended up with 0 permanent Aarons. But what is it? Is it some timeline where a box never had an Aaron climb out of it, but had an Aaron climbing into it later? Why would he do that?
The characters in the movie take a lot of precautions to isolate themselves from their time-clones, meaning that they don’t really know whether they got out of the box at the start. Therefore, they just have faith in the plan and jump in the box at the end of the loop. So long as they don’t create any obvious paradoxes (“break symmetry” as they call it), everything works out from their perspective, and they can assume it’s consistent-timeline travel rather than branching, so they don’t think they’re creating a timeline in which they mysteriously vanish.
When they start creating paradoxes, of course, they should realize. The fact that they don’t think about it this way fits with the general self-centeredness of the characters, however.
I agree that it makes sense to think of this probabilistically, but we can also think of it as just all timelines existing. I’m happy to excuse the events of the movie as showing one particularly interesting timeline out of the many. It makes sense that the lens of the film isn’t super interested in the timelines which end up lacking one of the viewpoint characters.
If we do think of it probabilistically, though, are the events of the movie so improbable that we should reject them? By my thinking, the movie still fits well with that. Depending on how you think the probabilities should work out, it seems like that first timeline where the person just vanishes is low-probability, particularly if they create a relatively consistent time-loop. In a simple consistent loop, only the original branch has them vanish, while each other branch looks like an internally consistent timeline, and spawns another just like itself. The probability of a timeline like “one Abe, then two Abes, then back to one” seems high, if Abe is careful to avoid paradoxes. With paradoxes, the high-probability timelines get chaotic, which is what we see in the movie (and in the comic I linked).
Yeah, I guess “they don’t bother checking whether they get out of the box” is the right explanation for the movie. Though still, if timelines where a person just vanishes are low-probability, then timelines where the number of people permanently increases (like the one shown in the movie) should be just as low-probability. The start and end of a long chain. And the middle of the chain should be mostly like 1-1-1-1… Or something like 2-0-2-0… but that would require weird behavior which isn’t seen in the movie (e.g. “I’ll get in the box iff I don’t see myself come out of it”).
They do deliberately try to set up an “I’ll get in the box if I don’t see myself get out” sort of situation in the movie, though they don’t succeed, and they don’t seem to realize that it would result in 0-2-0-2-… across metatime.
Good point about how permanent increases have to be as improbable as permanent decreases! I should’ve gotten that from what you were saying earlier. I suppose that leaves me with the “movies follow interesting timelines” theory, where it’s just a convention of the film to look at the timelines where characters multiply.