Time-travel fiction with rules that make sense

(For lenient values of the word “sense,” of course.)

This thread is inspired by a discussionelsewhereon the infamous scene in Superman: The Movie, in which Man of Steel demonstrates that even causality is your bitch when you come from Krypton. As several posters there have already pointed out, that scene is incoherent, which makes it like 99.8755895215722364% of all time travel stories.

But not all. Occasionally the authors of such stories give more than half a second’s thought to what they’re describing and make up some coherent rules. Take, for example, Casey & Andy–a web comic which, despite its many flaws, at least involved a little planning when doing time travel arcs.

But that’s just one. Anybody care to list other examples? Or, contrariwise, to list especially stupid time travel stories?

In Robert A. Heinlein’s Time Enough for Love, it is assumed that the past is past and nothing, not even a visitor from the future, can change it. This makes it possible for Lazarus Long to visit his childhood epoch and family without fear of altering anything about the universe he knows 2,000 years later. The common-sensical reasoning might or might not persuade a physicist, but it does make for a very sensible story, as these things go.

Robert L. Forward, noted hard-core SF writer, churned out TimeMaster because he wanted to see a time-travel story done right. He didn’t believe in the Grandfather Paradox. There’s only one past, and whatever happens there is what happened. If you go back into the past and interact with yourself, then you already know what’s going to happen, and you can’t change it. It is what it is. He challenged people to come up with a mathematical proof of the grandfather paradox. And in his book, he has an older version going back in time and interacting with younger versions of himself.
Heinlein, of course, treated time travel several times, but most notably in two stories – “All you Zombies” (which seems to be better liked) and “By his Bootstraps” (which I prefer – it’s most intricately and consistently plotted. And it’s consistent with Forward’s ideas, too.)

I think All You Zombies is better liked by Heinlein’s fans partly because it’s more complex, partly because it comes to a more interesting end, because there really aren’t more than one or two characters in the story, and partly because it’s less well known. It’s like an “indie” band- fans will only admit to liking the music if it’s still underground. Once it’s mainstream, it’s crap. It’s become a shibboleth for Heinlein fans to think that All You Zombies is better- it proves you’re a real fan, not a dilettante.

“Bill and Ted’s Excellent Adventure” has time travel rules that make sense.

“Dang, we need your Dad’s keys!” “I know, let’s steal them and leave them for ourselves…underneath that rock!” “Cool, here they are!”

Also, “The Man Who Folded Himself” by David Gerrold. If you go back in time to advise your past self, pretty soon you’re going to be constantly dealing with older and younger versions of yourself.

I think the Back to the Future movies establish some consistent rules and play fairly with them, especially considering the series is more comedy than science fiction at its core.

Primer is so well thought out that the whole movie starts to break down because they’ve just done too much time travel and nothing makes much sense anymore.

The Connie Willis time travel books are also quite well done - the continuum protects itself from causality errors in a pretty believable way.

The book from 1980 “Timescape”, by Gregory Benford is an interesting attempt to make a scientifically correct time travelling story. Of course, the journey in time is not made by people, but by subatomic particles from the future, sent by late nineties scientists trying to warn scientist from the sixties about the impending ecological disasters. It makes complete sense even in the final twist:

It turns out that their efforts were doomed, as when there’s too much divergence between past and future, it only creates a different continuum

And this is an example of “time-travel fiction with rules that makes sense”? :slight_smile:

I second Bill & Ted’s Excellent Adventure, which is surprisingly sophisticated in its handling of time travel, and also mention, in the same vein, the fantastic 12 Monkeys and (for the most part) the handling of time travel in The Hitchhiker’s Guide to the Galaxy.

We’ve discussed this before, but it’s worth it again. i love the Back to the Future movies, but think there’s a logical flaw, and it’s the same one that’s in all stories/movies where you can create an alternate version by changing the past – how do you switch betwen alternate futures?

In Back to the Future II there’s a critical moment where Old Biff overhears Marty’s plans, so he steals the DeLorean, takes the sports book, and takes it back to the past to himself. this changes history. From Biff’s point of view, it’s a change for the better. Now he’s in the past with the de Lorean, and Doc and Marty are in the future without a deLorean. In order for the film to advance, they need the deLorean.

It makes no sense, since Biff can now go anywhere in time, but he goes back to precisely the time and place that he stole the car and leaves it there. to believe that he’d want to do that, with all the possibilities he has open to him, seems hard to believe.
But it’s even harder to believe that he can do it. He’s changed the future. He ought not to be able to get back to where and when Doc and Marty are. But he does, because otherwise the story can’t continue.
There are ways out – Doc could have built a new deLorean in the Future and then gone back to the past, but that probably would’ve made the movie too long and complex.

(by which I mean the whole “trilogy”, of course)

The original Terminator is actually comepletely sound and an example of meddling with the past just creates the future that already exists.

Well, yes. Things get out of hand because of the essential way time travel works in the movie - extra “you’s” start piling up, “you’ve” done things that you don’t remember and don’t understand, some of these people are copies of copies of copies, etc. Just because it’s confusing doesn’t mean it isn’t following the rules; the fact is, real time travel like that, abused in that way, would get really confusing in a big hurry.

Bill and Ted’s was a mixed bag though. The police station scene was good, but in the rest of the movie, they have a deadline to get the report done. And Rufus telling them that the clock in San Dimas was always running? Huh?

Poul Anderson’s **Time Patrol **books are pretty consistent in their treastment of the consequences of time travel - if you accept the premise that the future can be changed by a meddling time traveller.


There’s a difference between “an airtight theory of time travel” and “time travel rules that make sense.” As I said, given that the films are essentially comedies steeped in SF, they don’t require a rigorous approach to the rules of time travel in order to make enough sense to work. And that latter seems to be all the OP is asking for.

The use of time travel in Harry Potter and the Prisoner of Azkaban was completely logical, although Rowling was quite subtle about it(the movie threw all subtlety out window). A nice touch was when Harry et al. are sneaking out to see Hagrid underneath the invisibility cloak. They wait until they can’t hear anybody in the Great Hall before going through it. The last people they hear leaving dash off and slam a door closed behind them. Later, when Harry and Hermione travel back to try and rescue Sirius, they appear in the Great Hall, and they quickly run and hide in a broom closet before they can be spotted, slamming the door behind them.

I believe it’s explained that changes in the past take a while to affect the present. As for old Biff returning where he was, I think the plan was for him to visit 1985 and be disgusted with what his younger self did to Hill Valley so he returned to 2015 but the filmmakers couldn’t figure out how to get it to work.

I saw that movie in a room party at a Mensa convention and one of the guys groaned, “I hate closed logic loops!”

Tim Power’s The Anubis Gates is a very consistent time-travel fantasy (and a wonderful story to boot)