I’ve read a story like this, but unfortunately have no idea who wrote it, or when I read it ('70s?), or what the title was. Don’t even remember if it was a novel or something shorter. But the time spiral was wound so that jumps were IIRC 28 years, so while time travel was possible, travellers could only move 28 years, or 56 years, or 84 years, or any other multiple of 28 years.
Hmmm… Maybe @Andy_L can identify the story.
There’s an episode of the original Star Trek called “All Our Yesterdays”. Kirk, Spock, and McCoy visit a planet who’s sun is about to explode, and they discover that all the planet’s inhabitants have escaped death by travelling into the past. That wouldn’t work. If someone travels back in time and has kids, and those kids have kids, that makes the whole problem worse, and not better.
There is mention of a process which prepares people to live in the past. It would have to sterilize them.
In the Trancers movies time travel is not physical. People in the future use a drug to take control of an ancestor in the past. This allows them to affect the past future without some types of
anomalies.
I am totally on board with the idea that free will is an illusion, and have argued that. I struggle myself, every day, with how much of our choices in life are even any tiny part free will; or are simply dictated by genes, upbringing, and random circumstance.
But, how does that relate to time travel? I don’t know when I might get to reading your sources, so a ‘Cliff’s Notes’ version would be welcome. I guess, if you travel to the past, you are barred from changing it, because of your lack of free will? I don’t buy that though, because your very existence once you travel to the past has changed things irrevocably. Every step and movement you make, every molecule of oxygen you breathe in changes the past.
One of my favorite time travel movies is the Japanese Summer Time Machine Blues. Very funny, and great depictions of time travel. The whole thing is on the Internet Archive, I strongly recommend it.
Expanding from that, there is a very weird anime series called The Tatami Galaxy (available on Crunchyroll) where each episode involves alternate timelines where the main character has joined different college clubs in each episode (but it really defies easy explaination). Years after both Summer Time Machine Blues and The Tatami Galaxy came out, an anime remake of Summer Time Machine Blues came out called Tatami Time Machine Blues that takes the characters and style from The Tatami Galaxy but uses them to fairly closely tell the story of Summer Time Machine Blues, which is kind of weird, it is a little like when Family Guy remade Star Wars, but played absolutely straight. Tatami Time Machine Blues is available on Disney+.
If you go only partly down this rabbit hole, at least try the (live action) movie.
But it doesn’t change anything, because you always traveled to the past. There is no past-in-which-you-had-not-traveled, no change in the timeline, and indeed your “choice” to travel to the past was no choice at all because there was no free will involved. And when you are in the past, everything you do had already happened that way - it’s already part of a fixed timeline.
Consider The Terminator. The T-800 appears at Griffith Park observatory next to a garbage truck. There is no “initial timeline” where this didn’t happen - Skynet sends him back always, that sending cannot be stopped by anything that happens between the two events. Kyle Reese appears later that same night in an alleyway, as he always had done. Events happen as you see them in the movie, and forward to the point when John Connor sends Reese backward in time to close the loop. He knows that Reese is essential, and perhaps even knows Reese is his father, but he has no choice in the matter - not just figuratively, but literally.
Presumably with that interpretation, it means that the Grandfather Paradox just cannot happen, i.e. something, anything, will happen to stop you from killing your own grandfather? I think Futurama (Roswell That Ends Well, if my memory serves) sort of did this in a way, although Fry was trying desperately to not have his grandfather die. And then it turned out that Fry was the cause of (who he had thought was) his grandfather’s death anyway and he was in fact his own grandfather.
I recall a story where a time traveler made a point of ensuring that his own death would create a time paradox; and when someone tried to shoot him the bullet slowed and stopped in midair, turning red-hot as its kinetic energy spontaneously turned into heat “as the universe itself intervened to save him”.
In that setting a time paradox was physically impossible, so by making sure his death would cause one he made it so it was literally against the laws of physics to kill him.
Asimov wrote a story called “The Cosmic Corkscrew” with that premise, but I think it’s a “lost story” - but a fellow named Michael Burstein wrote a story with that title in the 1990s, which might have used that idea (taking inspiration from Asimov perhaps, who talked about the lost story several times)s.
It occurs to me that the title of this thread is kind of funny. Time travel in Fiction? Are there non-fictional time travel stories?
@SunUp, ok, sure, I’m well familiar with the ‘causal loop’ time travel plot, à la The Terminator. And I’ve enjoyed The Terminator and other entertainments with similar plots. But, it’s really its own paradox- a causal loop paradox, in which a situation or thing is created out of nothing- or, as you say, has always existed with no initial impetus to its creation- similar to the "Somewhere in Time’ pocketwatch. It’s kind of the inverse of the Grandfather Paradox-- something exists that shouldn’t, instead of the GP, where something no longer exists that should.
That’s why, again, I like the alternate timeline theory of time travel to the past. Take the old Grandfather Paradox-- it’s no longer a paradox at all, because the instant you travel into the past you’ve created a new branching timeline. If you kill your grandfather, you don’t cease to exist because you came from the original timeline. You simply are now in a timeline where a second you will never be born.
Sure. I linked to this article upthread. Kind of a fascinating story of a theoretical physicist who for years secretly researched the possibility of time travel, because his dad died when he was young and he wanted to see his dad again and try to save his life. He kept it secret for years because he didn’t want his peers to ridicule him. He didn’t actually travel back in time though (that we know of…).
Well, this is awkward. I’m sorry, but we decided not to tell you the truth because
They didn’t do that, so it doesn’t matter. But if they hadn’t, then the keys wouldn’t be there.
I suspect that physicists who entered the field because they wanted to invent a time machine, and who quietly did research on the topic, are not at all rare.
If the widget going back in time has negative mass, then you have 1 widget + 1 widget - 1 widget = 1 widget. Or maybe it is not that kind of movie?
Oh, and speaking of supposedly ‘non-fictional’ time travel stories, many of us on the SDMB are probably familiar with the story of ‘John Titor’. But if not, it’s an interesting footnote from the early days of the internet:
I successfully exercised my free will and did not subscribe at $199 per year, or even $3.90 per issue, to read the linked article.
If you choose not to subscribe, you still have made a choice!
I don’t know wherefore the spurious paywall (all those stories except maybe the most recent week’s issue used to be freely available last I checked), but here is another link to the same PDF:
http://www.concatenation.org/futures/whatsexpected.pdf
Right. You can just remain undecided, leave it up in the air, and make no decision if you really want them to feel it.
I would say go back in time and tell your librarian not to order anything from Springer-Verlag, but we already have been saying just that for at least 20–30 years.
Whoah…heavy maaan 
Good one! 
Thanks, fun story! It reminded me of a very real phenomenon, which has nothing to do with time travel but does point very strongly to the fact that we do not have free will-- brain scans show that we unconsciously make decisions several long seconds before we are aware of making the decision. So our unconsious is really running the show, it seems, and then retroactively we tell ourselves “I made the choice of my own free will!”.