# The Logic of Time-Travel Stories



## Elckerlyc (Aug 12, 2021)

I have always had mixed feelings, a kind of love-hate relationship, with time-travel stories. On the one hand it is interesting to see how the writers used the inherent paradox to tell a compelling story (or failed to do so), on the other hand there is this annoying wrinkle in logic that ruins the fun. Well, for me anyway.
What wrinkle am I talking about? Well, let’s have a freestyle look at how the grandfather’s paradox is generally been depicted:

_It is 2135. After decades of solely scientific use the time-machine has fallen prey to commercialism and been made accessible for the general public. (Go everywhen for just $0.99 per hour distance! - [be sure to read the small print first.]) You only need to sign a document, declaring that you shall refrain from any actions that could perceivably interfere with history. [That’s just theoretically, folks, for legal purposes only. History is quite foolproof and looks after its own.]
Of course, that last statement only invites disturbed people to go and try anyway. Our protagonist, suffering from severe self-hatred, decides to go back in time and kill both of his grandfathers (just for good measure) and see what would happen. He sells his house, joins a group of 12 other time-tourists and soon finds himself in the year 2067, bang in the middle of the Chaotic Sixties..
All goes as planned and a month after his arrival the already violent year 2067 lists 2 extra murders that hadn’t been registered before. A time-traveler is suspected but escapes custody by dissolving into smoke that soon is blown away by the wind. At the same moment (sic!) in 2135 his parents, just visiting their neighbours, suddenly feel dizzy, become transparent and disappear completely. The neighbours almost immediately forget they had visitors and wonder why there is a 3rd cup on the table and another, broken one on the floor, as if having been dropped. At the TTT Office (Time-Travel for Tourists) a signed document mysteriously gets unsigned.
In time, twelve exuberant tourists return home, no one is reported missing. Nor is there anyone aware history has been corrupted. (So much for signing legal documents.)
The End._

You can detect the inconsistencies from a mile distance. But the thing I wish to point out is the absence of logic in the chronological order of events.
All the consequences of the extra ‘new’ murders in 2067 manifested itself in 2136 only _after_ the time-traveler departed to 2067 to commit his heinous version of suicide. The story is told, and the causal consequences are effectuated, observed from the timeline of the perpetrator, not that of History itself
This makes no sense. If the action took place in the past then the effects must always have been clear, long before the time-traveler left his home in 2135.
The time-traveler has either traveled to the past or he has not. There is no uncertainty in this and thus cannot be used as excuse for the delay in the rewriting of history. Nor is there any kind of a ‘re-play’ of the past for the convenience of the time-traveler to make his desired changes to the time-line. Every moment is a singular, unchangeable event. So, if there was a time-traveler (thinking he is) tampering with events, it was part of that history from the start. He wasn’t changing history, but creating, shaping it, together with all other people involved.
I was happy to notice I wasn’t the only one thinking along this line when I encountered this on Wikipedia:
_The Novikov self-consistency principle, named after Igor Dmitrievich Novikov, states that any actions taken by a time traveller or by an object that travels back in time were part of history all along, and therefore it is impossible for the time traveller to "change" history in any way. _

I love time-travel stories as long as they explore the bootstrap paradox, like _By His Bootstraps_ (Robert Heinlein) and _The Anubis Gate _(Tim Powers) or consider history unchangeable, like _Doomsday Book_ (Connie Willis), but Willis' later ‘Oxford’ novels _To Say Nothing of the Dog_ and _Blackout / All Clear _contradict that principle. Unfortunately almost all movies or TV-series about time-travel concern altering history.
I am quite capable of suspending disbelief or apply some hand-waving. But any world-building should result in an internally consistent universe, in which logic follows universal pathways.
Should we treat time-travel stories differently?


----------



## AllanR (Aug 12, 2021)

Some time travel stories put great effort to internal consistency, others not so. Some have so many holes, yet can still be fun.

In recent(ish) movies and shorts:
*Primer* is a good example of one that tries for consistency.
A short called *Stealing Time *is on of the few I've seen that considers the movement of Earth, it's called _space-time_ for a reason (they sort of do this, don't do the math, at least it's acknowledged) and they work very hard to keep the frame consistent
or *One Minute Time Machine *for its dealing with the present when the traveller goes to the past.
Oh, and *41 *was pretty consistent (my memory of it at least)


----------



## atsouthorn (Aug 12, 2021)

I recently read "The order of time" by Carlo Rovelli (non-fiction). Whenever I read about time and spacetime, there's no logical way for my brain to think of how reversing time would work, unless it's just a case of witnessing time, but not being a part of it/changing it.

So that said, in any story that throws up time travel, I just completely shut my brain off and try and enjoy the story for what it is because it's already in the realm of the ridiculous.


----------



## Ursa major (Aug 12, 2021)

Elckerlyc said:


> The time-traveler has either traveled to the past or he has not.



Yes and no.... Sheldon Cooper can explain it better than I can (mainly because I haven't really thought about this at all**):





​** - Because, for me, time travel is pure fantasy (and only pretending to be SF).


----------



## Lumens (Aug 12, 2021)

This is a brilliant site that covers many movies and discusses temporal problems with them:





__





						Temporal Anomalies in Popular Time Travel Movies
					





					www.mjyoung.net


----------



## Wayne Mack (Aug 12, 2021)

As long as the writer tells an interesting story, I am perfectly willing to overlook a lot of anomalies. If I am paying attention to the anomalies, then the writer has failed to engage me with the plot and characters.


----------



## Ursa major (Aug 12, 2021)

Wayne Mack said:


> If I am paying attention to the anomalies, then the writer has failed to engage me with the plot and characters.


I agree.


----------



## Elckerlyc (Aug 12, 2021)

It is not so much the anomalies but the illogic that bothers me. ruins the fun for me.
I would agree though that time-travel is more Fantasy than SF. But even Fantasy should abide to some laws of logic.


----------



## Elckerlyc (Aug 12, 2021)

Lumens said:


> This is a brilliant site that covers many movies and discusses temporal problems with them:
> 
> 
> 
> ...


The site seems a strong proponent of the possibility of altering history and quite dismissive, in a condescending way, of people who oppose that notion.
I am not sure I would categorize it as brilliant, but can't deny they put a lot of effort in analyzing the topic as depicted in various movies.


----------



## Dave (Aug 12, 2021)

www.britannica.com said:
			
		

> Science fiction is a form of fiction that deals principally with the impact of actual or imagined science upon society or individuals.


A story must be interesting, and characters must be well-drawn, but given that we are discussing science fiction, then I would suggest that the "actual or imagined science" must necessarily be believable, logical and in keeping with current scientific theory. Otherwise, it's simply fantasy. I'll accept that there is a sliding scale between hard science fiction and science fantasy. I'll also accept that Time Travel backwards is impossible with current scientific theory, and that forward time travel is improbable, and therefore Time Travel can never be hard science fiction, and may always be fantasy. However, I would like the author to at least try to give it some authenticity, and any "temporal problems" or "anomalies" as you describe them, are a sign that they don't really care very much. I would suggest that if they pay so little attention to the "logic" then they are likely to have also paid little attention to the characters and plot.


----------



## Ursa major (Aug 12, 2021)

Elckerlyc said:


> The site seems a strong proponent of the possibility of altering history and quite dismissive, in a condescending way, of people who oppose that notion.


I don't want to appear selfish, but I only exist because of the First World War...

....so would be more than a little inconvenienced if anyone went back in time and prevented it from happening....


----------



## BAYLOR (Aug 12, 2021)

Ursa major said:


> I don't want to appear selfish, but I only exist because of the First World War...
> 
> ....so would be more than a little inconvenienced if anyone went back in time and prevented it from happening....



If the US has opted to Launch Operation Downfall and Invade the Japanese home Islands , I think it very unlikely that I would be here now.


----------



## JunkMonkey (Aug 13, 2021)

One of the better uses of time travel in a movie is the low budget  _The History of Time Travel_ from 2014 which, according to my film diary, and who am I to argue with its author, is a 





> smart (but not unflawed) mocumentary about the fictional history of the US wartime time travel program which suddenly has a jarring WTF? moment in the middle of it. Just as you are starting to think you've missed something (like a reel of the movie) it becomes obvious that the 'reality' of the events being discussed by the various talking heads are, in fact, being altered by the uses to which the time travel device was put. The version of history they were talking about a few screen minutes ago no longer exists as far as they're concerned.



I'm not sure the movie stands too much analysis - what time travel film does? - but well worth 90 minutes of your time.


----------



## tinkerdan (Aug 13, 2021)

I just read an interesting novel that addresses some of this.




__





						Schrödinger's Dog: A Science Fiction novel of time paradox and romance (i-Vector Series): Brewer, Allan: 9798511135724: Amazon.com: Books
					

Schrödinger's Dog: A Science Fiction novel of time paradox and romance (i-Vector Series) [Brewer, Allan] on Amazon.com. *FREE* shipping on qualifying offers. Schrödinger's Dog: A Science Fiction novel of time paradox and romance (i-Vector Series)



					www.amazon.com
				



What they initially do is change time in such a way that they can undo it and then they set a timer for the undo to be several minutes away.
In the story this crates a strange(what I will call temporal rotoscope)effect for the time between the change and the undo. It's an interesting explanation for what might happen with the twisted explanation that they know that they experience something strange but they are not sure that the test worked. They figure out a creative way to leave a marker to show their momentary success in such a way that it doesn't vanish with their memory of the event.  Still a bit of handwav-ium--but cleaver handwav-ium at that.
Check it out.


----------



## Elckerlyc (Aug 13, 2021)

Ursa major said:


> I don't want to appear selfish, but I only exist because of the First World War...
> 
> ....so would be more than a little inconvenienced if anyone went back in time and prevented it from happening....


We'll wait with traveling back to assassinate the grandfather of Gavrilo Princip until after you died. You won't notice a thing.


----------



## Dave (Aug 13, 2021)

Ursa major said:


> I don't want to appear selfish, but I only exist because of the First World War...
> 
> ....so would be more than a little inconvenienced if anyone went back in time and prevented it from happening....





Elckerlyc said:


> We'll wait with traveling back to assassinate the grandfather of Gavrilo Princip until after you died. You won't notice a thing.



This situation would be by no means unusual. I'm a family and local historian. Everyone must have similar pinch points at which circumstances prevailed that allowed their ancestors to meet. I'll give you an example from my own family history:

In Gateshead, in October 1854, there was a terrible industrial disaster ( Great fire of Newcastle and Gateshead - Wikipedia ) that killed 53 and injured hundreds including distant cousins and a direct ancestor. If I could go back in time and stop it from happening then surely that would be a good thing?

Wrong!

If I prevented the fire starting and the explosions from happening, then another direct ancestor, my 3x great grandfather, and his family would never have relocated from London to Gateshead to take up a vacant position there, which had resulted from the death of another man from falling masonry during the explosion. My 2x great grandfather and mother would then never have met and had a family. I would not exist. 

So, I would be unable to go back in time and stop it. So, I would exist once again......???

Captain Janeway said Temporal Mechanics always gave her a headache.


----------



## Venusian Broon (Aug 13, 2021)

Elckerlyc said:


> It is not so much the anomalies but the illogic that bothers me. ruins the fun for me.
> I would agree though that time-travel is more Fantasy than SF. But even Fantasy should abide to some laws of logic.



I agree with you, in SF the 'idea' is just as important as plot and characters. That doesn't mean that we need to have masses of exposition and telling, but the idea needs to be strong, consistent and at the heart of the story. Without the idea, we are going into SF-fantasy or pastiche - which can also be excellent reads, don't get me wrong - but a lot of the time it feels that authors throw in SF tropes and cliches not having thought them through because they want to put the veneer of SF on their work. (Or don't know any better)


----------



## Elckerlyc (Aug 13, 2021)

Dave said:


> This situation would be by no means unusual....



Absolutely true. In each person's history you will find some incident, great or small, which determined fate. (I suspect time-travelers  )

My parents met during WW II, but would never have if not for the bombing of the dykes of Walcheren by the RAF Bomber Command in October 1944, as a prelude to the Battle of the Scheldt. The bombing and the resulted flooding killed 180 civilians and made many more homeless.
One of those families, a parson with his wife and 4 children, ended up in the small village where my father grew up. The parson's wife was heavily pregnant at the time. This led my grandfather to send my mother to this village to aid her elder sister, which was quite a journey in wartime.
What my mother didn't know, but the parson, her brother in law, by that time did, was that the church next to their home harboured a hiding place below the organ, which was frequently being used by my father, to dodge forced labour in Germany.
The make a long tale short, at some time they bumped into each other.
That small village soon found itself on the front-line in Southern Netherlands, which held from Fall 1944 till Spring 1945. But that's another story.


----------



## Vladd67 (Aug 13, 2021)

Ursa major said:


> I don't want to appear selfish, but I only exist because of the First World War...
> 
> ....so would be more than a little inconvenienced if anyone went back in time and prevented it from happening....


Being as I met my wife when we were both members of The Sealed Knot Civil War re-enactment society, this means our children would not have been born if King Charles hadn't raised his standard at Edgehill.


----------



## M. Robert Gibson (Aug 13, 2021)

Elckerlyc said:


> I was happy to notice I wasn’t the only one thinking along this line when I encountered this on Wikipedia:
> _The Novikov self-consistency principle, named after Igor Dmitrievich Novikov, states that any actions taken by a time traveller or by an object that travels back in time were part of history all along, and therefore it is impossible for the time traveller to "change" history in any way._



You can put me in the camp of being able to go back in time and doing whatever you want without consequences in the future, _because it's already happened_.


----------



## Dave (Aug 13, 2021)

Having read/watched a great many time travel stories, there is an alternative to the immutable timeline which has already happened and is set in stone, and that is that certain events can be changed by the time traveller, but these have absolutely no real consequences because "Fate" would dictate that the future will adjust and never significantly differ from a set path. I don't know if this idea has a name. I've called it "Fate".

Personally, I don't believe in "Fate." I'm with Han Solo: "Kid, I've flown from one side of this galaxy to the other. I've seen a lot of strange stuff, but I've never seen anything to make me believe there's one all-powerful force controlling everything. There's no mystical energy field that controls my destiny."


----------

