Four Models of Time Travel

Now that I’ve written a time travel story, I have a deeper appreciation of the genre’s challenges. It’s hard to make time travel work logistically and still have compelling drama. So here are my thoughts on the good and bad ways time travel has been handled on screen. I’ll focus on four models: (a) the single timeline, (b) multiple timelines, (c) the repeated loop, and (d) the universe fights back.

A. Single Timeline (Everything Predestined)

The most elegant model is the single timeline, or time stream, or universe, which amounts to a closed loop. In its simplest terms: the future time traveler was always in the past. Any “changes” made to the past are not changes at all, because they already occurred. It’s impossible to change the past, since the past has already happened. Which came first, chicken or egg?

A famous example of this model is used in Harry Potter and the Prisoner of Azkaban (2004). In the story Harry and his friends are saved from dying by their futures selves, and so Harry later realizes that he has to go back in time to save his past self. Everything plays out exactly as before, and there’s no change on the timeline.

A more obscure example is the romance Somewhere in Time (1980), which uses the trope of self-hypnosis as the means of time travel. A playwright named Richard Collier travels from 1980 back to 1912, after being haunted by an encounter with an old woman who approached him out of the blue and told him to “Come back to me”, then disappeared. He later learned that she was a stage actress named Elise McKenna. Through self-hypnosis he sends himself back to 1912, where he meets Elise and they fall in love; their romance is later interrupted when he unintentionally transports himself back to 1980. Like the Harry Potter story, this forms a closed loop: Richard sends himself back in time because Elise tells him to; but Elise can only tell him to because she has already lived through their love affair when he sent himself back in time.

The following three films are my favorite examples of the single timeline model, in which everything is predestined. When I say “predestined”, I don’t mean that in a philosophical or religious sense. Single timelines have nothing to do with the issue of free will. I mean simply that everything has already happened: the future self was always in the past to begin with. The future self is not changing anything or creating new events by traveling to the past; it’s impossible to change the past.

1. Predestination (2014). The gold standard of the single timeline model is based on a short story written by Robert Heinlein, and portrays what sounds impossible: four characters of different genders and living in different times are the exact same person: Jane from 1945-1963; John from 1963-1970, and then 1985-1992; the Barkeep from 1992+; and a terrorist known as the Fizzle Bomber sometime in 21st century. Again, they are literally the same person. (In the above photo, Barkeep John is on the left, speaking to younger John on the right, in 1970.)

This single person interacts with him/herself as follows: The Barkeep is from the late ’90s, but he has a time machine, and he bases himself in the year 1970, to await a meeting with his younger self. After listening to his younger self vent rage against a world that has treated him unfairly, the Barkeep takes him back to 1963, and drops him off for a night, where he impregnates Jane who is himself. She has the baby who is her own self, but there are complications with the birth that require a sex change surgery. After the operation, she takes the name of John. The Barkeep travels from the future to steal the baby after she is born, and he then takes her back in time to the year 1945, and leaves her at an orphanage, so that she can start growing up from the year 1945. The Barkeep takes John to the year 1985, where he becomes a counter-terror agent. In 1992 John encounters the Fizzle Bomber, and his face is maimed in an explosion. John now looks totally different — he has the face of the Barkeep. He acquires a time machine from his employer, and retires, traveling back to the year 1970 where he bases himself, to await the younger John, and fulfill the above cycle of events. Barkeep John returns to his time in the future, and at some point in the 21st century encounters the Fizzle Bomber again, but this time he sees that it is himself, much older, with grey hair and a beard. He vows that he will never become a terrorist and shoots the Fizzle Bomber on the spot. The movie ends with the clear implication that he will eventually become the Fizzle Bomber, as he is being slowly driven crazy by all the jumps he has taken through time.

Here’s how it maps out:


I don’t think any writer has ever outdone Heinlein on this concept — that four people of different genders can be the same person in four different time periods, and all from the same (closed) time stream. The filmmakers adapted it superbly.

2. Timecrimes (2007). A rustic Spanish countryside isn’t a typical setting for a time travel story, and the novelty is refreshing. A man named Hector travels back one hour in time, and then does so again, so that there are three versions of himself for the duration of that hour. During that hour, the second and third versions of himself uphold the initial sequence of events, sometimes intentionally, sometimes by accident. The only exception is when the third version of Hector tries to kill the second version (thinking that he’s protecting his wife from himself), but fails in the attempt. Everything plays out as before, and nothing is changed. It’s a fatalist drama of the single time stream, but it delivers plenty of surprises nonetheless.

The key is to understand that throughout the film there are always three Hectors in the hour duration. Hector 3 was always in the background, plotting his shenanigans against Hector 2. He fails to kill Hector 2, but he does injure him (as he himself had been injured in the same way), which causes Hector 2 to bandage his face and enter the forest with a woman whom he assaults. This prompts Hector 1 to investigate, which is what we see towards the start of the film: The first version of Hector sits on his house lawn looking into the forest with a pair of binoculars; he sees a woman being attacked by a “stranger” in a head bandage, and so goes to investigate, gets stabbed by the “stranger” (who is himself), and then flees up the forest path. He comes to an isolated shed where a scientist has created a time travel bath. The bath can only send people back in time for as long as it has been turned on, and Hector 1 hides inside it, not knowing what it is, and gets sent back in time one hour, where he becomes Hector 2. And so forth. The following diagram maps out the hour’s events:


What’s interesting is that Hectors 2 and 3 go out of their way to uphold the original events they’ve experienced (with the single exception of Hector 3’s failed attempt to kill Hector 2). On some level, the Hectors understand that changing time, if it were even possible, would wreak havoc by killing his own self. There is brilliant tragedy in the way Hector 2 finally returns home still bandaged and accidentally causes his wife (or who appears to be his wife from a distance) to fall off the roof of their house and die. This is why he goes back in time again, to become Hector 3: to kill Hector 2, even though this would result in his own death. Hector 3 fails, but he manages to save his wife by sacrificing another innocent woman in her place — who of course was really the one killed all along. Timecrimes is an underappreciated effort, and my second favorite of the closed loop model.

3. The Terminator (1984). Forget the lousy sequels — and yes, I’m including Terminator 2 in that indictment — the first is the only good one. Not surprisingly, it’s also the only one that forms a singular timeline in which nothing changes. In the far future, machines have taken over the world and are warring on humankind. A man named John Connor leads the resistance against them, and he stands a good chance of turning the tide. The machines become desperate, and decide to send back a terminator in time, to kill John Connor’s mother in the year 1984, so that she will never give birth to John — a preemptive abortion, in effect, before she even gets pregnant. However, the humans in the future learn what the machines are trying, and so they too send back a man, Kyle Reese, to protect Sarah Connor from being assassinated by the terminator. It turns out that Reese is John Connor’s father, but Reese doesn’t know this. In the past, while protecting Sarah against the terminator, he falls in love with her and gets her pregnant. The terminator eventually kills him, and Sarah succeeds in killing the terminator. Sarah knows she will have to teach her son someday that he is destined to lead the war against the machines, and that he will have to send Kyle Reese back to protect her, so that he (John) can be born. The spare robot parts left behind by the dead terminator ensured that machine technology will evolve in such a way that will allow the machines to take over some day. All of this forms a closed loop: neither past nor future is changed.

Unfortunately, the franchise ruined a good thing (as franchises often do), serving up sequel after sequel in which history changes in cheesy and non-compelling ways. In Terminator 2 we learn that the arm and chip of the first terminator technology was improved dramatically. Most significantly, the protagonists are able stop the apocalypse of Judgment Day — which means that not only will John Connor never lead a war against the machines (in the present timeline), he will never have been born (in any future timelines), since he has no reason to send Kyle Reese back in time. Films 3-5 try salvaging new drama from this, and the result is a mess. Here’s the plotting of all five films:

It’s not that there is anything wrong with the multiple timeline approach — as I explain below, I actually think it’s the superior model — only that the Terminator franchise didn’t use it well; the stories of T2-5 are lame. Let’s look now at the better ways the model has been used.

B. Multiple Timelines (Changing History)

Changing history is fun and offers high-stakes drama, but it’s hard to do right by. Most filmmakers blunder at some point. The idea is simple enough: the act of time travel automatically changes the past and forces the universe on to a different trajectory. It creates a new timeline, or an alternate history, a new causal chain, or a parallel universe — whatever you want to call it (see right diagram). Because it is a new timeline, it operates independently of the original one. That last part is what often gets muddled.

The most celebrated example of this model is Back to the Future (1985). Marty McFly goes back in time, and when he returns to the present, he finds that his parents are much more enjoyable people. For the most part the logistics are handled well, but there are some silly elements, as when for example Marty’s body starts to fade as he intervenes in the past, and starts to prevent his parents from falling in love. This misses the whole point of new time streams. Marty can’t possibly erase himself, because he comes from a time stream in which those threats to his existence never happened. If his parents don’t hook up, all that means is that there won’t be a version of himself born in the new timeline; it has no bearing on any versions of himself in or from other timelines.

Another fan favorite is Looper (2012), a thriller about time-traveling hit men. As a film it’s pretty good, but it gets hopelessly lost up its ass in mixing the two models. On the one hand, sending someone to the past creates a new timeline. On the other hand, that new timeline is treated as singular and closed, as when we see older versions of time travelers effected by what’s happening to their younger counterparts. So for example, when Young Joe carves “Beatrix” into his arm, it instantly appears on Old Joe as a scar. The problem is that Looper is supposed to be about a closed time loop when it’s really about a malleable future. On top of that, Joe’s sacrifice at the end is for nothing, because it won’t necessarily do anything to stop the Rainmaker’s creation. Looper does okay as a dramatic thriller, but it fails as a time travel story.

Here are two films which use the multiple timelines model flawlessly. And they’re excellent drama besides.

1. Deja Vu (2006). Arguably Tony Scott’s best film, Deja Vu is a film I could talk about all day. One critic has called it a digital version of Vertigo, for the way it explores obsession, fractured identity, and time travel. Considering the terrorist theme, Déjà Vu is surprisingly apolitical, and unlike Scott’s other films (like Man on Fire), it finds its solution not in revenge, but in the obsessive desire to go back in time and prevent the whole thing from happening — to save hundreds of lives, especially the one person you can’t stop thinking about, even if you don’t stand much chance of surviving the trip. Who else to play such a hero than Denzel Washington?

Denzel is Doug Carlin, a law official who has been recruited by a team of government agents who use a time machine to look into the past and solve difficult crimes. But Doug’s ambitions exceed theirs, and he persuades them to use the machine for time traveling purposes, so as to change events and prevent a ferry bombing from ever happening. First he sends a note back to himself, and when that fails (doing far more harm than good), he sends himself back, saving Claire and the hundreds of people from being killed.

People have criticized Deja Vu as if it aspires to the single timeline model. They say it’s impossible for Doug to have gone back in time, because he ends up saving the day. Since he prevents the ferry explosion, there is no crime to investigate, and so he will never be recruited by the surveillance team who use the time machine, and will never be sent back in time; the new future isn’t the old one. That’s missing the colossal point. The new future isn’t supposed to be the old one. Doug changed the past in order to save lives. This isn’t the predestination model; it’s the multiverse model, and the film clearly telegraphs that when the team of scientists debate the nature of time, and Shanti starts talking about divergent time streams.

Here’s a map of the time streams in Deja Vu:

It’s an excellent map, though hard to read; you have to click on it twice, then scroll around. I’ll summarize the timelines, and highlight in blue the events we see play out in the film.

There need to be at least four streams to account for all the nuances in Deja Vu, though there could obviously be more; we simply don’t know how many times Doug had to send himself back in time until he finally saved the day. But at a bare minimum:

  • In Timeline 1, the terrorist calls Claire about the availability of her Bronco van on Sunday evening, but because she can’t meet his deadline, he buys a Blazer van from someone else instead. He uses the Blazer to blow up the ferry Tuesday morning at 10:50 AM, and Claire remains safe and alive in this timeline. When Doug comes on the scene, he is recruited by the team with the time machine, and they use the machine to send a note back in time, to warn himself about the ferry bomber who is casing the ferry early Monday morning. Sending back this note in time creates Timeline 2.
  • In Timeline 2, the terrorist calls Claire about the availability of her Bronco on Sunday evening, but because she can’t meet his deadline, he buys a Blazer from someone else instead, just as in Timeline 1. However, the note sent by Doug to himself from the future (in Timeline 1) arrives on his desk early Monday morning around 4:00 AM, and his partner Larry sees it. Larry takes action and goes to the ferry, where the terrorist shoots him, but not before Larry puts enough bullet holes in the Blazer that causes the terrorist to seek out Claire after all. On Tuesday morning he steals Claire’s Bronco, kidnaps her, takes her to his house, and then kills her, burning her alive and dumping her in the river. He then uses the Bronco to blow up the ferry at 10:50 AM. When Doug comes on the scene, he goes to the coroner’s and sees Claire’s body (not in a red dress), and when he investigates her home, there is no message for him on the fridge. As in Timeline 1, he and his team use the time machine to send a note back in time, to warn himself about the ferry bomber casing the ferry early Monday morning. But later, he also demands that he be sent back in time (to Monday evening), so that he can try to save Claire. Sending back the note and himself creates Timeline 3.
  • In Timeline 3, the events start out exactly as in Timeline 2, but now Future Doug (from Timeline 2) arrives in a hospital on Monday night at 7:00 PM, where he is barely resuscitated. He wakes up on Tuesday morning at 8:05 AM, steals an ambulance, and goes to the terrorist’s home; he rescues Claire but gets shot by the terrorist, who gets away in Claire’s Bronco. Future Doug then takes Claire back to her house, where she changes into a red dress, and helps bandage him. In case he fails, he writes a message to himself on the fridge: “u can save her”. He leaves Claire at the house and goes to the ferry alone at 9:45 AM. The terrorist returns to Claire’s house, kills her, and dumps her body in the river. He then proceeds to the ferry, where Future Doug fails to stop him and is killed. The terrorist uses the Bronco to blow up the ferry at 10:50 AM. When Doug — Present Doug, who belongs to this timeline, and the Doug we first see in the film — comes on the scene, he goes to the coroner’s and sees Claire’s body, in a red dress, and when he investigates her home, there is a message left by his future self (from Timeline 2), saying “u can save her”. As before, he and his team use the time machine to send a note back in time, to warn himself about the ferry bomber casing the ferry early Monday morning. Later, he demands that he be sent back in time (to Monday evening), so that he can try to save Claire. Sending back the note and himself creates Timeline 4.
  • In Timeline 4, the events proceed exactly as in Timeline 3, up to the point that Future Doug (from Timeline 3) rescues Claire and takes her back to her house, where she changes into a red dress, helps bandage him, and he leaves the note to himself on the fridge. But this time he does not leave Claire at the house; he takes her with him at 9:45 AM to the ferry, even though he doesn’t want to. He does this because he remembers seeing the blood swabs in Claire’s trash bins in Timeline 3, which look exactly like his own right now from being bandaged; he realizes that if he doesn’t do something different, or against what he wants to do, events will simply repeat as before. The terrorist goes back to Claire’s house to kill her, but she isn’t there. He then proceeds to the ferry, where Future Doug and Claire both stop him and save the day, though Doug is killed in the process. The film ends at this point: The new Present Doug comes on the scene, and he will have no crime to investigate and so will not be recruited by the surveillance team. He won’t see the clues left for him by his future self on Claire’s fridge; and he won’t need them. In saving the day, his future self finally closed the loop. All he will have to account for is a dead body — his own — when it is found. He sees Claire on the ferry and gets an odd feeling of deja vu, as if they’ve met before.

That’s how you write a good time travel story. And it raises interesting questions about the phenomenon of deja vu. When we experience it, is it because we’re “remembering” things that happened or are happening to ourselves in different time streams in different ways?

2. Primer (2004). It’s the most realistic time travel film ever made, and not surprisingly, since it was scripted by a scientist. The plot centers around two young geniuses, Aaron and Abe, who accidentally create a time machine in their garage. They can use the machine to go into the past, but only as far back as when the machine was first turned on. This is actually how a time machine would probably work if we ever succeeded in creating one. A physics professor at the University of Connecticut, Ronald Mallett, has been trying to create a device like this for years now — by using a series of circulating laser beams that swirl into a time tunnel. Walking into this tunnel would allow someone to go back in time, as long as it was to a point after the machine was switched on. So if you turned on the machine on September 1 and left it continually running to December 31, you could go back four months, but no more. That’s how the time machine works in Primer, and also how the time bath works in Timecrimes, which I covered above.

The first time Aaraon and Abe use the machine, they go back six hours (which takes six hours to do, sitting in the box of the machine), and make good money for themselves in stock trades since they know how the market will perform. That’s the easy trip to understand, shown in the first chart below. By the end of the film, things have become so complex that it’s virtually impossible to keep up with all the multiple versions of the characters intersecting multiple timelines. To understand the full picture — which may take four or five viewings — click on the larger chart below the first one.



The logistics in Primer are handled with an incredible level of precision, and even if you can never keep all the details straight, it’s an amazing viewing experience, one that I keep finding myself drawn back to.

Anything goes?

It’s worth noting that while the multiverse theory is the one increasingly embraced by scientists, for others it seems like an inelegant solution. Steven Lloyd Wilson is one such curmudgeon, expressing his dislike as follows:

“While the multiple timelines model has the appeal of being logically consistent, it has a glaring problem. It’s a brute force hammer of solving the problem, like multiplying by zero to demonstrate both sides of the equation are equal. It’s just plain inelegant. It also has the story flaw of essentially rendering time travel moot. If anything that can happen, has happened in an alternate timeline, then the actions of the characters do not matter one bit. Going back in time and killing Hitler as a baby doesn’t change anything, because there is still an original timeline in which he doesn’t die.”

I fail to see how time travel is rendered moot by the fact that there are other timelines — millions of them, probably — in which events proceed either slightly differently or very differently. This is what scientists talk about all the time, even aside from the question of time travel. And to say that the actions of the characters don’t matter is nonsense. If I can go back and save the life of a friend by creating a new reality, that obviously matters to me. I don’t care how many alternate realities there are in which my friend dies, because I’m able to experience the new reality in which he lives. The actions of the characters matter to themselves, even if they don’t matter to critics like Wilson who want the “elegance” of all time streams producing the same result (which is ridiculous). Or as Doug Carlin says in Deja Vu, “You can be wrong a million times, but you only have to be right once.”

I believe the multiple timelines model is the superior model. It’s the harder one to nail down and make dramatically effective, but when done right, the result is sublime.

C. The Repeated Loop (The Do-Over)

In the do-over, scenarios are repeated until the protagonist triggers a reset, usually by dying, going to sleep, or getting knocked unconscious. The protagonist then wakes up and repeats the scenario again, making different choices, until he or she can finally escape the loop.

For whatever reason, do-overs are often saturated with comedy. Perhaps it’s because repeating yourself over and over again is something you have to roll with and play for laughs in order to keep your wits. In Groundhog Day (1993), the Bill Murray character relives the same day over again, until he finally obtains love and happiness. In The Edge of Tomorrow (2014), Tom Cruise gets dropped on the field of battle after brutal training sessions, continually killed and reset until he destroys a monster alien. In Happy Death Day (2017), the Jessica Rothe character keeps waking up on her birthday and getting murdered later in the day, until she figures out who the killer is (her sorority roommate). In all of these examples, the tone asks us to not take the story too seriously.

My favorite examples of the do-over are one that almost no one has heard of, and another that everyone knows.

1. All the Time in the World (2017). This episode from Dark Matter (season 3, episode 4) runs the gamut with hilarious comedy, emotional poignancy, and dark tragedy. For my money, it’s the best do-over ever scripted. One of the Raza’s crew members starts living the same day over and over again, and half the battle is trying to convince his fellow crew members that they are caught in the same loop, even though he’s the only one who can remember reliving the events. They never believe him, even though he can predict every little thing each one of them is about to say and do. Finally he persuades the ship’s android to teach him French, so that when the crew hear him speak a language he’s never known or studied, they’ll start taking him seriously. There is also a serious side to this episode, as the crew are able to use his foreknowledge of the day’s events to foil an attack on the ship. And once the source of the time loop is discovered (a device confiscated from a scientist), the android tries an experiment, and in the process, she experiences a tragic future where all the crew are dead except the girl Five, who is now aged and offers dire prophecies. Five also tells the android how to break the time loop. I have made a video-clip of Three’s French tutorial and his hilarious breakthrough in persuading Two. And also the end clip — Five’s doomsday prophecy of the far future — for a complete switch in tone.

2. A Christmas Carol (1843). Dickens’ classic is a variation of the do-over. Scrooge gets to visit the future of his current timeline, and even though he can’t affect the timeline directly, he observes things which allow him to change his actions in the present. So instead of the timeline he’s on which results in Tiny Tim’s death, he’s able to make a different choice, and create a new timeline in which Tiny Tim lives. A Christmas Carol is probably the best do-over ever written, though few people think of it as a time-travel story.

D. The Universe Fights Back

This is technically a multiple timelines model, because it is possible to change the past. But doing so results in cosmic disaster. The universe resists any attempts to reorder it, and nasty shit happens when those attempts succeed. That implicitly appeals to the single timeline model: the timeline “must be protected from change” at all costs — or else.

A famous example is Stephen King’s 11/22/63, in which Jake Epping goes back to prevent JFK from being assassinated. He finds it extremely hard to do; the closer he draws to saving Kennedy, things work strangely against him. He manages to save Kennedy, but the world eventually goes to hell as it’s torn apart by world wars. It’s a fatalist view, and a lot like the single time stream model: the past is destined to stay the past; if it doesn’t, then calamity rains down. So Jake undoes his mistake and allows JFK to die after all; this gets the universe back on track.

It’s a silly idea — that the cosmos would “care” about altered events so as to “react” against them — but it produces potent drama if done right. As in this story:

Father’s Day (2005). The plot is simple, and the resolution predictable, but only in way the tragedy often is; the drama is brilliant, and the acting Oscar-worthy. Rose persuades the Doctor to take her back in time to when her father was killed by a motorist, and despite being forbidden to alter the past, she saves him anyway, ushering in Doomsday. Everywhere on earth people are suddenly assaulted by Reapers, winged parasites that act like antibodies, destroying everything in wounded time until the paradox is gone. Rose’s father, realizing he should be dead, sacrifices himself to get the world back on its proper course.

As I said, the premise is silly, and it doesn’t help that script writer Paul Cornell can’t seem to decide whether he wants his story to be a multiple timeline or single. In a scathing review of Father’s Day, Martin Izsak writes:

“People today don’t seem to appreciate how ridiculous it is to try to protect a past timeline as if it’s the only one in existence, and will let the boogeyman out of the closet if it’s messed with. You can experience as many other versions [of a person, or an event] as you can time-travel back to, and it would be nearly impossible to make all the ‘right’ choices to re-live any of them exactly as you remember them. So the Doctor, sadly, makes an ass of himself trying to defend Cornell’s model of time, and rightly gets tripped up when Rose confronts him for being hypocritical about the heroics he proudly displays in almost every other setting he lands in… I officially present Father’s Day with the Wooden Turkey Award for being the stinker of the 2005 Doctor Who season.”

I actually believe that Father’s Day holds up as one of the best Doctor Who episodes of all time, despite the accuracy of Izsak’s criticisms.


One thought on “Four Models of Time Travel

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s