Maybe they are all mostly dead and ever-more-feral survivors ridden by the crippling radiation- and pollution-borne genetic sicknesses are birthing still-born and slowly dying out while picking through the debris left from the civilizational collapse caused by global warming, ai, and the resulting world wars.
And the last stronghold of civilization are genetically superior, warlike, numerous, but illiterate Tate descendants hidden in the mountains of Romania, unable to build anything more advanced than a cudgel used in the rituals to determine the alpha leader.
Looking at the actual link itself, is this one of those papers that takes a thought experiment and tries to evaluate it using abstract mathematics/statistics? That's what it looks like it's doing. How is it actually useful to apply Markov chains to such unknowable suppositions? Is this analytical philosophy
Maybe you can only create rifts, and you need to create one before travelling back and forth. So only time travelling after the first time travel rift has been opened. Otherwise it'd break continuity.
EDIT: If you created such rift and nobody would come out, then you'd have to start worrying.
> Therefore, I conclude that, assuming my model, time travel is self-suppressing: the timeline is continually rewritten until it inevitably reaches a timeline with no time machines ever being constructed. At this point, no further changes to the timeline are possible.
This is just the one model of time travel, isn't it? It's a bit weird how it uses the notion of rewriting to continue until there can be no rewriting. If there could never be any rewriting then you still permit the single universe model of time travel. Things can only ever happen the way they happen, if that was because of a time traveller, it always was. It permits the grandfather paradox, but I can't help but think that this papers argument could be reshod to say the the grandfather paradox is self-suppressing.
I'm partial to the idea that time travelers need a "gate" to arrive at, and until we have that, no traveling to the past. However the universe really likes avoiding being forced to compute a paradox, so it may well be many timelines.
The conclusion is basically (Larry) Niven's Law of Time Travel. From "The Theory and Practice of Time Travel" (1971):
> If the universe of discourse permits the possibility of time travel and of changing the past, then no time machine will be invented in that universe.
The entire essay is worth a read, of course. Meanwhile the paper in the OP goes for a more mathematical approach.
Could it be that time travel suffers from the dark forest problem?
A hostile and aggressive alien species with time travel capabilities would naturally use it to go back in time and eliminate any evolved species that similarly discovers time travel.
The energy required would definitely be enough to annihilate planets.
Time travel, like flight and invisibility, are a product humanity's imaginative nature: "What if I were not bound by the laws of the universe, what could I achieve?"
It's great for fiction, because of so many creative ways that you can structure your rules-violating-universe.
There was an amusing story in the July 1979 issue of Isaac Asimov's Science Fiction Magazine called "The Merchant of Stratford" about what it would be like for people who were visited by time travelers from the future. The Internet Archive has that issue [1].
Here's a summary from memory (which probably has some errors since I read the story in 1979).
It's about the first time traveler. They decided the first trip will be to visit Shakespeare.
Shakespeare has no problems accepting that he's being visited by a time traveler, and asks what gifts the traveler brings.
The traveler is a bit confused, so Shakespeare explains that the early ones all bring gifts. The traveler has brought some gifts, including a nicely bound volume of Shakespeare's plays. Shakespeare looks at it, comments on the nice binding, says something about maybe he can sell it, then decides probably not, and tosses it on a pile of other such volumes brought by other time travelers.
The first time traveler is now getting pretty confused, and says something like "but I'm the first time traveler!", to which Shakespeare answer "but not the first to arrive". This is something often overlooked in time travel stories--just because you are the first to leave for a given destination doesn't mean you are the first to arrive.
Shakespeare mentions that he's frequently bothered by time travelers, but at least doesn't have it as bad as Jesus--that guy can barely do anything without a time traveler showing up. Shakespeare explains he knows because a time traveler thought it would be interesting to take Shakespeare to meet Jesus once. All the great figures of history are frequently visited.
Somewhere in there Shakespeare provides some drink and tries to calm down the inexperienced time traveler, who is freaking out over all this. Shakespeare is an old hand at dealing with newbie time traveler freak outs.
Then a bunch of other time travelers arrive, but not to see Shakespeare. They are reporters from the first time traveler's future, there to interview him about his historic visit to Shakespeare.
wouldn't backwards time travel merely create an alternative timeline? for all we know, we simply live in the timeline that had to exist prior to the invention of time travel technology itself
I like the approach taken by several authors from Asimov in "The End of Eternity" to Star Trek or Loki on TV: Time travel is not allowed except for entities that live outside of time in a way that is not meaningfully perceived by anyone else; When unsanctioned travel happens, it is easy to detect and retroactively suppress by these entities. Of course this can all be refuted or at least declared a transient state at most by the mess Time Cop is; Or how things end up in any of the other stories.
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[ 3.3 ms ] story [ 46.3 ms ] threadhttps://archive.org/details/dli.ernet.526852/mode/2up
where it makes sense because people established an orthogonal dimension of time and this movie
https://en.wikipedia.org/wiki/Predestination_(film)
based on another Heinlein classic
https://en.wikipedia.org/wiki/%27%E2%80%94All_You_Zombies%E2...
where you can't because it's all just a knot.
And the last stronghold of civilization are genetically superior, warlike, numerous, but illiterate Tate descendants hidden in the mountains of Romania, unable to build anything more advanced than a cudgel used in the rituals to determine the alpha leader.
EDIT: If you created such rift and nobody would come out, then you'd have to start worrying.
> Therefore, I conclude that, assuming my model, time travel is self-suppressing: the timeline is continually rewritten until it inevitably reaches a timeline with no time machines ever being constructed. At this point, no further changes to the timeline are possible.
Fails right there. No strong argument was constructed to why this is inevitable.
(Incidentally, the Bible describes a singular Being Whom exists outside time.)
> If the universe of discourse permits the possibility of time travel and of changing the past, then no time machine will be invented in that universe.
The entire essay is worth a read, of course. Meanwhile the paper in the OP goes for a more mathematical approach.
A hostile and aggressive alien species with time travel capabilities would naturally use it to go back in time and eliminate any evolved species that similarly discovers time travel.
The energy required would definitely be enough to annihilate planets.
It's great for fiction, because of so many creative ways that you can structure your rules-violating-universe.
Here's a summary from memory (which probably has some errors since I read the story in 1979).
It's about the first time traveler. They decided the first trip will be to visit Shakespeare.
Shakespeare has no problems accepting that he's being visited by a time traveler, and asks what gifts the traveler brings.
The traveler is a bit confused, so Shakespeare explains that the early ones all bring gifts. The traveler has brought some gifts, including a nicely bound volume of Shakespeare's plays. Shakespeare looks at it, comments on the nice binding, says something about maybe he can sell it, then decides probably not, and tosses it on a pile of other such volumes brought by other time travelers.
The first time traveler is now getting pretty confused, and says something like "but I'm the first time traveler!", to which Shakespeare answer "but not the first to arrive". This is something often overlooked in time travel stories--just because you are the first to leave for a given destination doesn't mean you are the first to arrive.
Shakespeare mentions that he's frequently bothered by time travelers, but at least doesn't have it as bad as Jesus--that guy can barely do anything without a time traveler showing up. Shakespeare explains he knows because a time traveler thought it would be interesting to take Shakespeare to meet Jesus once. All the great figures of history are frequently visited.
Somewhere in there Shakespeare provides some drink and tries to calm down the inexperienced time traveler, who is freaking out over all this. Shakespeare is an old hand at dealing with newbie time traveler freak outs.
Then a bunch of other time travelers arrive, but not to see Shakespeare. They are reporters from the first time traveler's future, there to interview him about his historic visit to Shakespeare.
[1] https://archive.org/details/Asimovs_v03n07_1979-07/page/n123...