On Time Travelling: Rigorous Categorization of Science Fiction Movies

Do you remember the scary moment when Ashton Cutcher alias Evan recognizes suddenly that his arms are crippled – and that they have been crippled since many years?

This is a scene from The Butterfly Effect: Evan discovers that he is capable of time-travelling to his troubled childhood. He tries to fix the present by changing the course of tragic events in this past – and most of the times the outcome in the present is somewhat unexpected.

I am finally living up to my promise on Dr. Dan’s(*) blog to come up with my musings on the logic of time travelling in movies. [Insert your favorite disclaimer about spoilers here.]
(*)As the future of this post is going to unfold below the reason for this formal address will become clear. Mind the Douglas Adams quote.

Based on thorough and extensive research I came to the conclusion that there are three distinct kinds of time travelling (in movies):

The Butterfly Effect is an example of what I denote as [1] The Immediately Changing Past as Remembered or Not by Conscious Beings, and so is Back to the Future:

Our heroes travel to the past, fuss about the timeline, and travel back to the present: And the present it different from what it had been before starting the round trip. Even more, the present indicates that all the events prior to this moment must have been changed as well. In The Butterfly Effect the reactions of his friends indicate that handicapped Evan has got along well, probably until he ‘suddenly’ re-discovers that he is crippled.

Marty McFly – stuck in 1955 – needs to make sure that his mother and father become a couple ‘again’ despite the mess he had introduced to the old timeline; otherwise Marty would cease to exist. When he is finally back to the future his family has ‘suddenly’ changed from cliché lower class losers to smart cheery middle class high-flyers.

How and if the main characters’ memories have been (will be) aligned with the new timeline is typically not explained in a satisfactory way. Do they remember the other timeline forever (in the future of the future)? Did the old timeline cease to exist or is it preserved merely as a representation in the main character’s mind? Does the representation in mind count as a version of a multiverse?

We need to distinguish this theory about time travel from [2] Twisted and Warped but Yet Fully Causal Timelines which denotes the infamous branching of times while indicating that the previous timeline is still preserved in history.

It can be illustrated by the first Star Trek movie released 2009, featuring the new old crew which is simply called Star Trek:

At the end of the movie we can start the history of the old enterprise crew all over which is a clever move of the movie producers from a commercial perspective. The new timeline can and will never be in line with the ‘original’ plots of the episodes and movies. The Romulan villain as well as Spock had travelled to the past  and created an alternate timeline. Young James T. Kirk asks Spock, the elder, if his (Kirk’s) father was alive in the original timeline (which he was).

As with [1] there are two (or more) distinct timelines but the important distinction is: At any point of time any human being (or alien for that matter) experiences a smooth unfolding of his / her / its personal story. Neither the elder nor the young Spock’s mind is subject to a sudden disruption.

I believe the underlying reason is that the physical and mental identities of all persons involved in [2] remain intact. Time travellers travel as physical beings, but you do not jump right back or forth into your younger self’s body which requires your minds to merge. Evan jumps mentally only – both forward and backwards. Marty jumps to the past physically, but on fast-forwading to the future he sort of merges with the self he left back (in the future) when travelling to the past.

I tag Minority Report as class [2] Fully Causal: John Anderton shows up as a future criminal in the precogs’ crystal ball – yet finally he decides not to commit a crime. But there was no mind-disrupting time travelling. Note that my categorizations does not care about the direction of time-travelling, and I do not distinguish between viewing the alternate timeline (only) in contrast to actively being part of it – as viewing it may be sufficient to introduce a change in the other timeline you are part of.

As you have noted, it is incredibly difficult to speak about time ordering in time travelling scenarios. (By the way Time Ordering is a scientifically rigorously term used in quantum field theory, applied to the quantum mechanical operators that dictate the time evolution of systems.)

Of course it was Douglas Adams who noted wisely in The Hitchhiker’s Guide to the Galaxy Vol.2 – The Restaurant at the End of the Universe:

One of the major problems encountered in time travel is not that of accidentally becoming your father or mother … There is also no problem about changing the course of history … All the important changes have happened before the things they were supposed to change and it all sorts itself out at the end.
The major problem is quite simply one of grammar, and the main work to consult in this is Dr. Dan Streetmentioner’s Time Traveller’s Handbook of 1001 Tense Formations. It will tell you for instance how to describe something that was about to happen to you in the past before you avoided it by time-jumping forward two days in order to avoid it.

I would conclude from this that Douglas Adams adheres to the [3] Predetermined and Eternal Timeline Theory: Even if or exactly because the characters know something about their futures and try to avoid the outcomes at any cost everything turns out exactly as it has been foreseen. This has been demonstrated in the TV series FlashForward. 

As you noted, this post is about movies, not about physics. In physics, special relativity demands that theories are causal which basically means that events in the future can only be influenced by events in the past (More precisely only events in the past lightcone can signal to events in the future lightcone in 4-dimensional space-time). However, a [3] Predetermined Timeline might imply that nothing causes anything else really – events just are and have always been ingrained into the fabric of space-time. It would not matter if we could signal from the future to the past as this is futile anyway.

But only an excessively warped space-time – not a very friendly environment for living beings are we know them, probably close to blackholes – might give a chance of influencing the timeline.

A direct link to the past via such a warped channel is proposed in Deja Vu starring Denzel Washington. We are able to watch the past unfolding real-time in parallel to the present time elapsing. A piece of paper with a note is sent backwards in time and past and present are constantly influencing each other. But I would still argue these are [2] Twisted But Yet Fully Causal Timelines.

Things get messy when Doug travels to the past himself, changes the timeline, rescues the future victim Claire, and dies heroically. But there is still another instance of Doug’s in the ‘present’ in the final scene that now is not aware his is alternative time traveller’s self’s history.

Believe it or not, but there is already an infographic on Wikimedia to explain this by proposing four different timelines – you need to enlarge the full-sized image at the Wikimedia page:

Deja Vu Timeline

This is very similar to the Star Trek movie analyzed above – complication arises due to multiple interactions between the timelines:

Describing the unfolding of event in causal terms, Timeline 1 was the first, and the interaction with the past at the ‘end’ (in the ‘present’) of Timeline 1 triggered Timeline 2 – and onward to Timeline 3 and 4 in the same way. So the whole universe is walking through these four timelines – or the observer is made aware of four parallel universes, each of them equipped with an eternal timeline that cannot be modified. If the latter is true, you should really not meet yourself in an alternate timeline or space-time will collapse. So the causal consistency of [2] in contrast to [1] comes with its risks.

In a similar way to the twisted plot of Deja Vu, the old enterprise crew has boldly gone where no man has gone before as we witnessed in the 1970s on black and white TV sets. Then the Romulan Nero and the elder Spock travelled from to past (from the perspective of bold old episodes and the 2009 movie this was / is the future) to meet the elder Kirk and the younger Kirk – both time travellers have interacted with the past at different times – very similar to the Deja Vu approach.

Every timeline-crossing event kicks off  a new timeline. In the most ‘causally recent’ Timeline 3 both entities of Spock do coexist of did two versions of Doug in Deja Vu – thus I tag Deja Vu as a class [2] movie, but the categorization should maybe be enriched with tags for complexity.

I owe to the members of the IMDB discussion board who started to discuss this movie – released in 2006 – a few days ago. What a coincidence. Even scarier than the spacefolding surveillance technology is the fact that members discuss the applicability of this tool to current investigations in Boston and that they watch the movie again right now because of the terrorist attack.

Most likely we need to do more research and setup a global project in order to come up with better categories and standards for time travel movies: This collection of the Top 10 Time Travel Movies is a starting point.

And I did not even mention the movie that has the closest resemblance to our daily lives. Groundhog Day does probably not qualify as an SF / time travel movie because looped structure of space-time is too realistic and too familiar.

Edit: I have just stumbled upon this on Google Plus – the definitive chart including many popular time travel movies:
All Time Travel Movies Explained in One Awesome Infographic and here is an update by the creator of that said chart.

36 thoughts on “On Time Travelling: Rigorous Categorization of Science Fiction Movies

    • Thanks, Phil! I agree – it is mind-boggling. You really need to draw diagrams similar to the one linked at the bottom. I have found several of them when researching for this post 😉

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  2. Great post. I agree that you have to watch ‘Looper’. The best quote is “The future is just a possibility that becomes fuzzier or clearer as I approach the current moment.”

      • Of course I was off on the quote and I had summarized it in my memory. 🙂 This is the older Joe talking to the Younger Joe.

        “My memory’s cloudy. It’s a cloud. Because my memories aren’t really memories. They’re just one possible eventuality now. And they grow clearer or cloudier as they become more are less likely. But then they get to the present moment, and they’re instantly clear again. I can remember what you do after you do it. And it hurts.”

  3. Pingback: Paradox & Tautology: Time Travel | I really just pretend to know stuff

  4. Awesome post! The issue of memory is an interesting one. Does time travel presuppose a distinction between ‘internal’ and ‘external’ time? For example, if I get in a time machine my internal clock will differ from the external clocks, right? So I’ll remember my personal timeline, but not necessarily external timelines that my activity may have altered.

    I consider Star Trek (2009) to be an example of multiverse theory time travel. In fact, I’ve had long conversations with friends about why it *must* be dependent on the multiverse in order to be coherent. I’ll spare you all the details of those conversations though.

    It’s been a long time since I saw Minority Report, but as I recall the issue there is whether the precogs see a timeline that can or can’t be altered. Are they seeing the future or some kind of counter-factual future? That’s an interesting question which speaks to whether or not the future can be changed (unlike category 3).

    Finally, you could add a category: time travel stories in which characters interact with past/future selves and those in which they do not. This would have implications for which theory of personal identity over time is at play. Interestingly, in Mr. Dalliard’s flowchart, he lists Terminator as time travel without interaction with self. This is true of the first movie, but debatable with respect to the Terminator ‘universe.’ In The Sarah Connor Chronicles, Derek Reese (Kyle’s brother, John’s uncle) sees himself as a kid in pre-Judgment Day LA. This suggests a different theory of personal identity over time than in the movies. But some might not consider The Sarah Connor Chronicles canonical.

    Anyways, I didn’t really have a point, just some random comments inspired by you post. We need to get some grant money for a interdisciplinary research project on time travel in movies!

    • I knew you would provide some authoritative comments based on your extensive research. If I would be a really subversive element I would craft a proposal on a research project and submit it to a respected agency (Offtopic: I liked the proposal of Death Star to be built by the US government).
      We really need some abstract hyperspace of categories that allows to attach different tags to movies. Probably many issues (you can discuss endlessly with friends after having watched the movie) arise from an inconsistent application of different concepts to a single movie? Your examples seem to support this – e.g. the underlying ‘philosophy’ utilized in Terminator has changed over time (time = real time in producing different movies). So in the research project we would need to work out which / if categories are really inconsistent, or if a combination of tags or their transmogrification(*) on the unfolding of the story.
      (*)Stolen from postmoderndonkey’s most recent poem, I am fascinated by this word.
      OK, this was a very random reply as well 🙂

      • It’s especially tricky now that every sci-fi movie is part of a ‘franchise’ with multiple films, writers, directors, etc. Does the theory of time travel have to be consistent across franchises — not to mention ‘extended universes’ — or on a film-by-film basis?

  5. Interesting post. [Sorry I’ve been so long in getting back to you.] I come to this issue from the position of evolutionary theory. Folks in my field have asked, many times, whether our world is the highly predictable outcome of any number of physical properties … or a statistically unpredictable and improbable outcome which could never be repeated? I (and others) argue that there are certain predictable features of this world which are bounded and would likely occur again if history were to be re-run. There are other features which are unpredictable and highly contingent. So … if you were to rerun history … you’d get a world … this world, in a general sense … but you and I might certainly not be here! Anyway … thought provoking post. Thanks for taking the time to think it through. D

    • Thanks for adding another discipline’s perspective! I believe that your approach is not fundamentally different from a physicist’s view as we also ‘believe in’ chaos and statistically defined outcomes. But on the other hand physics does typically not try to explain ‘life’ (But on the other other hand Maurice Barry has shared this article on twitter which deals exactly with a ‘physics explanation of life’:
      http://www.insidescience.org/content/physicist-proposes-new-way-think-about-intelligence/987 )
      Do you think that the emergence of life was one of those predictable outcomes or rather an unlikely one?

      Re time travel I am now pondering on: Even if we would be able to travel back in time (despite all those paradoxa) – we might influence history heavily even if we would not interact with persons in the past… but by changing some minor detail.

      • Absolutely … try Ray Bradbury’s short piece … A Sound of Thunder (1952 I think). Regarding the rise of ‘life.’ Richard Dawkins is known to have said … that given enough time, the impossible becomes probable. So, yes … given enough time … and given earthly conditions … I think life was inevitable. What say you? D

        • Thanks, Dave. I tend to agree, but I really don’t know so much about this – my knowledge about the emergence of life is due to some pop-sci accounts of experiments on complicated molecules coming into being after treating them with UV light 🙂

  6. Great Scott. that is heavy stuff… If you wanted to combine pretty much every one of your time travel in Movies categories… what would you end up with? Only THE sci-fi series that has been on the air for the longest ever: Doctor Who! Well, not yet so much with the butterfly-effect like sudden disruption, but a lot of other nifty time-travel reality-bending effects

    • Thanks NicoLite! Reading your comment the first time I considered replying ‘Great Scott – Scott as in Scott Adams or in Scotty, Chief Engineer’, but Wikipedia is my friend: http://en.wikipedia.org/wiki/Great_Scott. Quote:
      “Great Scott! is an exclamation of surprise, amazement, or dismay. … has been widely used as a catchphrase in popular fiction, including … Back to the Future films (Doctor Emmett Brown)” Spot-on!

      Doctor Who …. you are reminding me of more educational gaps. Due to whatever reason I have watched neither The Big Bang Theory nor Doctor Who – as I have already admitted in previous replies to Mark Sackler’s comments 😉
      Probably I should come up with a post on The Definitive Geek Culture Works of Art you need to know if you want to call yourself a true geek before I attempt to classify time travel literature.

  7. Wonderful positions. I find time travel movies almost inevitably lacking a thoroughness of logical consequence implied most often outside the scope of the plot, thus unaddressed by the director. Nevertheless, time travel in general seems metaphor for an opportunity at resetting or changing directions in life (after all, good plots are not so much about events as about the main character working out inner conflict through events which often represent the inner conflict analogously). In this way, we time travel daily by falling asleep, surviving an alternate construct, awaking hours later in a world evolved since we were engaged in it, and stepping out to deal with this new reality (and its echoes from a past reality remembered– like our jobs). Further, each decision, a nano event uncountable within a single day, represents a reality-changing outcome we only barely control. Organic activity goes on itself in a timeline less linear than circular like the mythological snake eating its tail as growth erupts from decomposition and multitudes of events shift around our consciousness with us unaware like alternate universes almost but not quite disconnected and irrelevant to our time line. And how Adams lived with himself under the weight of such insight is beyond my comprehension.

    • Very well said! It is true – it is not so much about physics as about fundamental questions related to identity and life. For example, Groundhog Day – one of my favorite favorite favorite movies – seems to count as a ‘time travel movie’ as it is on the chart linked at the bottom, but the supernatural sci-fi aspect of the time loop is not important – it is rather a perfect metaphor as ‘modern life’ is experienced by many of us.
      The snake eating its own tail is a powerful metaphor – I have seen it recently put into a geeky context but I cannot remember the details.
      And even if we sit still we are strictly speaking travelling in time already 🙂

  8. I also watched Loopers recently, and couldn’t help wondering about the contradictions of memory in the time travel loop. I look forward to you watching it, and reporting back. Back to the Future has been appearing as reruns on TV lately, and the question of memory occurred to me again.
    You’re right. This deserves consideration.

    I like how you’ve discussed the topic, keeping it relevant to your blog. I’ll try to rise to the challenge and see if I can offer a view of the topic. It will a challenge to meet your standards. 🙂

      • I was thinking that it would be an interesting experiment to challenge bloggers to write on any topic, in this case time travel, within the perspectives of their fields/work/study and write about in the context of their blogs. What a range of discussion we’d have.

        • Funny that you say that – I had actually considered to attempt at connecting something down-to-earth with time travel. Probably this was triggered by Maurice’s comment on Brussels Sprouts below. I pondered about heat pumps and time travel – I guess there is not a single sci-fi story out there featuring a time-travelling heater. Maybe I am also motivated by a great search “heat pump outer space”.

        • I know less then 50%, too:
          I can remember the following movies well: Paycheck, FlashForward, Groundhog Day, Butterfly Effect, Terminator 1-3, Planet of the Apes (several movies), Deja Vu, Premonition, Back to the Future 1-3
          I have watched these but cannot remember the details: Twelve Monkeys, Harry Potter (never been a fan).

    • Absolutely! If I would need to rate the movies I quote, Back to the Future would be number 1. This is probably due to my being an addict of 1980s clichés.

  9. On a more serious note, how would you classify the “sort of” time travel that takes place in the Ursula le Guin classic “The Lathe of Heaven.” In this case, the protagonist only travels to the past in his dreams–but his dreams change current reality retroactively, causing extreme shifts, as in the Butterfly Effect. Maybe this is type 1.2. By the way, it has twice been a made for TV movie–the older PBS version is by far the better one. It has never been made into a theatrical movie. I wish it would be as it is my favorite SciFi story of all time.

    • I tend to conjecture 😉 that a dream that impacts reality should not be considered a mere dream anymore but should be classified in the same way as any other interaction between timelines – such as physical or mental time travelling or employing precogs. It seems to similar to The Butterfly Effect – mental travel only, sudden disruption.

      I should try to enhance my model with different dimensions of categorization that are orthogonal to each other (I am talking about the abstract hyperspace of tags assigned to movies not, now of 4D space-time). The exact type of interaction as well as the ‘direction’ of time travel are appropriate criteria in addition to the ‘time travel category’. We need a large, well-funded research project – this is a colossal task!

    • It’s worse than that: I was not aware of imaginary time travel. If I recall correctly Stephen Hawking coined “imaginary time” as a concept in physics but it has been rendered incorrect by someone else (I forgot the refererence – and all the details). I ruled out anything imaginary when writing this post.
      But this video needs to be linked here – absolutely! I am quoting from Dan Mullin’s article on the movie The Time Machine that actually triggered this post “Younger readers may recognize it from its appearance on The Big Bang Theory.”

  10. Time travel movies, done well (many stories are not), are among the more interesting bits of fiction. For example “Looper” stands among those I have most enjoyed over the past few months. Funny, every time I read or view a bit about time travel I am confronted with the prospect of what I might do if I had a chance to ‘do over’ bits of my life. I am happy to say that, other than ever deciding to try Brussels Sprouts (the one and only food I truly detest) there’s nothing I would want to change. The more unpleasant items from my past were, it seems, either unavoidable or situations that shaped the person I am now in ways I do not wish to change. Perhaps there’s a lesson there too.

    • Thanks, Maurice, for pointing me to ‘Looper’!! I have now read a great review on this movie, including spoilers and an analysis of the time travel paradoxa. When I will see the movie I can fully concentrate on time travel logic:
      http://screenrant.com/looper-ending-explanation-time-travel-spoilers/all/1/
      Translating to my classification the movie seems to toggle between classes 1 and 2 (a quantum-style uncertainty applied to time travel movies themselves) and the reviewers claim to have detected a bunch of paradoxa.
      Re Brussels Sprouts: I am not extremely fond of that, but it is not too bad. Now Brussels Sprouts will forever be linked with Time Travel in my brain – a very Douglas-Adams-style association and probably something not yet exploited in movie plots.

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