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.
This fact alone means that any time traveler is most likely to arrive in the middle of empty space.
This is a misconception that bugs me. The problem isn't that the Earth isn't fixed in space, it's that there's no such thing as a fixed point in space. Position is only defined relative to other objects. If you're going to use time travel in a story or something then it has to use something like an anchor object to determine destination. I.e. the relative location of the traveler and the anchor is replicated from the future to the past.
In reality I'd bet neither are realistic, but that's what makes the stories interesting.
I am saying this trajectory calculation relative to current coordinates is impossible. Even modern satellites with super precise instruments still need regular ongoing “adjustments.” Time travel requires many order of magnitude more precision than satellite orbital maintenance.
The logistical impacts from that would yield plenty of storytelling material: If you want to travel back in time, you need some ancient cellar that has been undisturbed since the target timeframe. If you want to skip forward, you need to establish that cellar, and round trips are limited by the space available.
Of course the idea that your point of origin must be fixed from time A to time Z if you’re willing to allow for time travel is itself flawed. If you could somehow move an object to an arbitrary time you could move them to an arbitrary point in space, and your ability to calculate may be significantly greater on the grounds that you’d have more advanced technology than us. It’s all scifi woo though until someone actually time travels.
You’re very likely to travel into an undefined void even if you map out and calibrate the whole system.
Pick One.
Streisand Effect, people. If you hate someone and want them to go away you have to completely stop mentioning them online.
EDIT: If you created such rift and nobody would come out, then you'd have to start worrying.
If you go back in time to observe (but not interfere with) your younger self, your younger self will get old and go back to that exact time too. So there will be an infinite number of your old selves observing your younger self.
Not to mention that travelling back also means adding matter to the universe.
...and how would you actually do that if we assume that your travel has added matter to the universe, rather than completed an iteration of a time loop that was happening there already?
Or it takes a lot of energy or resources and you can send one person every few hundred years, severely limiting the flow of people.
e.g. the machine is a big box. You can "start" the machine once and "end" it once. When you "start" the machine it instantaneously teleports everything inside it from when you "end" the machine.
If you "start" the machine and break it before "end"ing it, nothing gets sent through, or there's a giant explosion, or the universe collapses, etc.
Alternatively, you can "receive" and "send" any number of times on the machine. But every time you "receive" you get a unique ID, and you can only "send" to that ID once.
> 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.
Dark Matter (the TV show) also does this very well (plus multiverses)
(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...
PaulHoule•5mo ago
https://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.
warrenm•5mo ago
PaulHoule•5mo ago
https://www.scribd.com/document/503128860/Larry-Niven-THE-TH...
In some of them (like that Heinlein story) there is just one timeline and you at best get causal knots, in others (like Asimov’s End of Eternity) a time traveller experiences different timelines and whatever other experience is ‘undefined behavior’
I don’t think Nicen wrote stories about traveling into the past but plenty about traveling into the future with cold sleep, stasis boxes, and relativistic travel with Bussard Ramjets, I guess you could have done it even more stylishly if you could afford to buy the secret of the Outsider reactionless drive.