What a pleasure it was to watch and discuss the science fiction film Primer (2004) along with other members of the Tacoma Film Club this month! I have not been hooked this hard by a first viewing of a film since Memento (2000). During my initial viewing of each of these films I had an impression that, even though I could not follow all of the intricacies of the plot, it was likely that there was a coherent narrative to be discovered with multiple careful viewings. That initial conjecture proved to be correct in the case of Memento.[see footnote 1] However, since Primer was produced with a budget of only about $7,000 I had less confidence that the time and effort spent doing multiple viewings would necessarily lead to a satisfactory feeling in my inner geek. After all, who could fault a director/screenwriter for a few unresolved plot threads or inconsistencies in a film made with a micro-budget?! I have now watched the film three times and am delighted to report that it met, even surpassed, my original expectations. And even though a part of me wishes this director could have had a decent budget to to make this film more accessible to a larger audience, at the same time another part of me thinks this little gem of a film has a perfection that a larger budget would likely only have spoiled.[see footnote 2]

My initial inclination about how to approach making sense of this film was to try to construct a graphical representation of the plotline. After a few rudimentary attempts I decided it was probably not worth the time and effort it would take me to accomplish this so I punted and did a search on the internet where I assumed others had likely already done this legwork. Sure enough, I found several sites that attempt to construct narrative and graphical representations.[see footnote 3] Even though the information found on these sites is somewhat inconsistent, perusing them can provide a good point of entry to making sense of this film, and I will not attempt to reinvent the wheel here. However, I did not find any sites that I thought provided a totally satisfactory comprehensive analysis of the film. In this posting I want to address a few major issues and themes related to the film that I have not seen discussed elsewhere, or where I think some of the discussion found on the internet is incomplete, misguided, or simply wrong.

One of the strongest features of the film is that it creates a [make-believe] universe that a scientist can appreciate. This is a universe that has “order” because it is governed by “laws of nature”. And these laws can be discovered by anyone paying careful attention while watching the film. Time-travel is not allowed to just happen willy-nilly in this universe – a specific set of laws rule how time-travel must operate, and these laws are consistently followed. So what are these laws? Here are a few I was able to discern while watching the film.

First, time-travel is not allowed to occur between arbitrary times or locations. A single excursion in time-travel is only allowed between two specific times, and is allowed only by using a box that was constructed in a certain manner. The box has a switch allowing it to be turned on at a specific time and then turned off at a later time. Someone entering the box as it is being turned off is allowed to exit the box at the time it was turned on.[see footnote 4]  So to give a specific example, if the box were to be turned on at 9 am in the morning and then turned off at 2 pm in the afternoon, someone entering the box at 2 pm would be allowed to exit at 9 am, 5 hours earlier.

A second law is that “time” for the person inside the box continues to operate normally. For example, if the person in our example was wearing a watch when he entered the box at 2 pm, the watch would register 7 pm when he exited, even though clocks on the wall outside the box now register 9 am.[see footnote 5]  For this reason a person entering the box will need to carry enough food and water to survive the duration of his (backwards) time travel.[see footnote 6]

A third law is that a single box can be used more than once, allowing it to be used for repeated visits back in time. This is not apparent early on in the film because the two main characters who discover how to make these boxes, Abe and Aaron, are initially under the impression that their boxes are good for one use only. However, it is revealed later in the film that this initial impression was wrong. A fourth law, also revealed late in the film, is that these boxes can be folded up and one put inside another. These last two laws allow a huge number of possible permutations of time-travel to be achieved. The, at times mind-boggling, complexity of trying to follow all of the plotlines during the later stages of the film is a reflection of the fact that the characters have learned increasingly sophisticated ways to exploit the implications of these laws in attempts to achieve their own aims.

A fifth law is that a time-travel excursion to the past is allowed to alter what happened in the past, and the implications of what that means are explored in a highly sophisticated manner in this film – Much more sophisticated than in most time-travel science fiction films, including those with much larger budgets to work with. These implications are not fully appreciated by Abe and Aaron early in the film (nor I suspect by 99% of those who view the film the first time), and the main thematic thrust of the plot has to do with how these implications slowly become apparent as the characters navigate repeated visits to their pasts.

A final sixth law that is stated explicitly in the film is that no matter how many time-travel excursions one embarks on, perhaps traveling back through the same time periods repeatedly following various paths, there will only be one “iteration” that counts in terms of having an influence on the “future”. I will be elaborating about what that means in the remainder of this commentary since it appears to be one of the main points of the film that has been missed by many of those who discuss the film on internet sites.

I will begin with a discussion of timelines, a term that I do not think is ever used in the film itself but shows up repeatedly in online discussions of the film. Many of these sites discuss concepts along the lines of “branching independent timelines” as though this is a valid interpretation of what is depicted in the film. It is not! But in order to demonstrate that I need to first describe what is meant by the concept of branching independent timelines. Lets reuse our example of entering a box at 2 pm in order to exit 5 hours earlier at 9 am. We will use the character Abe in this example and we will refer to him as Abe(1) for reasons that will become apparent soon. As Abe(1) travels through life, he can determine what time it is whenever he chooses to do so by looking at his watch. And Abe(1) can record events that take place in his life on a Timeline as shown by the thick horizontal arrow at the top of the Figure:

This timeline shows that at 8:45 am Abe(1) set a 15 minute timer that will turn the box on at 9 am. Then he leaves the area and goes about his daily activities until his watch shows 2 pm at which time he again approaches the box, powers it down, and enters it. The Abe who entered the box at 2 pm left the box at 9 am. Lets use the designation Abe(2) to refer to the time-travelling Abe who leaves the box. A little thought reveals that it does not make any sense to add the event of Abe(2) leaving the box at 9 am to this same timeline. Abe(2) only come into existence after Abe(1) enters the box (which of course has not happened yet at 9 am). So adding Abe(2) to this timeline would create a paradox. The “branching independent timeline” solution to this paradox is to assert that a new timeline is created at 9 am (The one shown by the thick horizontal arrow at the bottom of the figure). Abe(1) travelled alone down Timeline 1. When Abe(2) left the box he created an independent Timeline 2, and this new timeline contains a copy all of the events that were present in Timeline 1, including Abe(1), but in addition contains a new element, Abe(2).

As a schematic to help one keep the events depicted in the film in some kind of logical order, a graphic constructed along these lines using a number of branching timelines can be helpful . The problem arises when this diagram is treated as though it represents the (filmatic) metaphysical reality within which the events taking place in the film are supposedly playing out. That interpretation quickly degenerates into a form of solipsism. Achieving time-travel within a framework of metaphysical solipsism is easy, and if that is all the screenplay for Primer had accomplished I would not have found it especially impressive, not even interesting enough to spend any time and effort trying to untangle.

Lets go back to our same example to illustrate why “branching independent timeline” interpretations of the film degenerate into solipsism. I am going to add a third character to the example, myself. I am across the street on the roof, looking down at the box with binoculars, and I am wearing a watch that tells me that it is 9 am. As a Gedanken experiment, please answer the following question for me: Do I see Abe leaving the box? The answer to that question is going to be similar to the answer to the following riddle: How do I know I am not just someone else’s dream, and as soon as that person wakes up I will disappear? So, I guess if Abe(1) is the only person who exists in the universe and I am part of his dream, I will NOT see Abe(2) exit (my dream takes place on Timeline 1). However, if the only person who exists in the universe is Abe(2) and I am part of his dream that is taking place on Timeline 2, then I will see him exit. However, if I want to maintain the quaint notion that I actually exist as a separate person, independent of both Abe(1) and Abe(2), the concept of branching timelines is of no help to me in resolving the original paradox. When my watch shows 9 am I look at the box, and I either see Abe exit or not.

Now let me turn to a different interpretation of the film, one that is much more sophisticated than solipsism, and the one it seems obvious (at least to me) that the screenwriter/director, Shane Carruth clearly intended based on the clues imbedded in the film, including the six laws of nature I outlined above. In a nutshell, Carruth, has taken some concepts from quantum physics that apply within the domain of subatomic particles (for example, concepts derived from Richard Feynman and Erwin Schrödinger) and created a universe in which similar principles can apply on a more macro scale. There is a rough analogy between the paradoxes created by the type of time-travel depicted in the film and the well-known Schrödinger’s Cat paradox in quantum physics. The cat cannot be said to be dead or alive until the box is opened; until then it exists in some paradoxical state of statistical probabilities in which it is both dead and alive. Similarly, the boxes built by Abe and Aaron in Primer allow a paradoxical state of probabilities to exist during the time period between when the box is turned on and off. Within that period of time the time-traveler, Abe in our example, is, paradoxically, both Abe(1) and Abe(2). In the case of Schrödinger’s Cat the paradox is resolved when the box is finally opened and one observes either a dead cat or one that is alive, but not both. In the film, the paradox is resolved when the box is turned off (2 pm in our example). At that point either Abe(1) enters the box or does not. If Abe(1) does enter the box, he can not exist beyond 2 pm because once he enters the (backwards traveling) time box he ends up caught in a sort-of time-warp, forever looping backwards whenever he reaches 2 pm; In this case Abe(2) is the one who is allowed to pass by 2 pm and inherit the future. If Abe(1) does not enter the box at 2 pm, he is allowed to pass into the future; In this case Abe(2) never comes into existence so cannot pass into the future.  It does not matter how many time-travel excursions Abe has made back to this time period (multiple Abes might exist within this time period, Abe(1), Abe(2), Abe(3), … Abe(n)), at most only one will survive beyond 2 pm.

So what factors determine which Abe will survive into the future? Chance plays some role. However, the single most important factor in this determination is memory. Law number 2 in this hypothetical universe allows Abe to remember what has happened during each of his excursions through this time period. Abe(1) is traveling through this period for the first time so does not know anything beyond the future of his current moment. However, Abe(2) can use memory (or recording devices) to remember everything that happened to Abe(1). This is a distinct advantage for Abe(2). The bottom line is that the time traveler who can travel back the furthest in time will always have a distinct advantage in terms of controlling the future because that traveler will have access to more information than anyone else within the time-traveled period. This fact sets the stage for all of the complex interactions of the characters in Primer – There is a life-and-death struggle between the various instantiations of Abe (Abe1, Abe2, … AbeN) and Aaron (Aaron1, Aaron2, … AaronN) over who will control events in the past, and thus survive to live in the future.

So, who wins this struggle, Abe or Aaron?

[Possible spoiler alert for what is discussed below]

I have only watched the film three times so this conclusion is tentative and open to revision if I watch the film additional times in the future. However, at the moment the evidence revealed in the film seems pretty convincing to me that the winner is Abe. Let me throw out a few observations about some details that are shown in the film.

1) As others have noted on internet sites, early in the film, before the time travel boxes have even been invented, the audio track of the film at one point contains a muffled sound of what sounds like a recording of events that happen later in the film. Discussion of this fact on internet sites usually attribute this to a technical glitch in the film due to its low budget. But anyone who has watched this film carefully will immediately see the potential implications of such a recording on the plotline.

2) Similarly, several internet discussion sites have noted that the director uses editing to shuffle and fracture time and space over short periods (on the order of a few seconds or less) at various points during the film. This is generally interpreted as a method to instill in the viewer a sense that we are in a period of space-time that is unstable (as would probably be the case during time-travel of the type being depicted in the film). I would like to note that the first time this form of editing appears in the film, Abe(?) and Aaron(?) have not yet discovered how to build time-machine boxes.

3) Similarly, note the first time a black out screen is used as a transition between scenes. Later in the film this usually (perhaps always but I will have to watch the film again to be sure) signifies a transition backwards in time when a time-traveler exits the box. However, note the first time this is used in the film (hint – it is before Abe and Aaron have built the box).

4) And finally. Later in the film, one of the techniques some of the characters use to detect a time-traveler is the presence of a beard. This is because someone coming out of a box after being in it for a few days or more will have grown a beard. Hmmm – has anyone noticed that Abe has a beard in the first several scenes, the ones before the method for building the time-traveling boxes has been discovered?

Let me end with a technical comment about how the boxes might work given the laws of nature I described above. At first glance it might seem implausible that Abe had already time-traveled during the opening scenes of the film because we appear to have something akin to a bootstrap problem. It seems the boxes can only transport one back to the time when the box was first turned on and the box can not be turned on before it was built. But a good scientist always looks for confounds, and there may be one here. Look carefully at the following sentence reproduced from the paragraph above where I described the First Law of Nature governing this hypothetical universe: “If the box were to be turned on at 9 am in the morning and then turned off at 2 pm in the afternoon, someone entering the box at 2 pm would be allowed to exit at 9 am, 5 hours earlier.” In our discussions up until now (and in all of the discussions I have seen about this film on the internet, although I have not done an exhaustive search) we have assumed that the boxes take one back to an absolute time, the actual time the box was turned on, i.e., 9 am. But there is a confound. The boxes also take one back to a time relative to when the box was turned off, 5 hours earlier. So what is the relevant operating principle, the absolute time when the box is turned on?, or the duration the box has been turned on prior to when it is turned off?

Lets suppose the boxes operate on a principle of “time-travel relative to the time when the box is turned off” and see what implications that might have. In that case, here is what Abe would do if he wanted to travel back to the time when the film’s opening scenes take place (probably December since there is a Christmas tree present in one of the opening scenes). It is March when most of the scenes in the film play out, so assume Abe needs to travel back 3 months in order to gain control of everything that happens during the film. Here is what he will need to do. First build a box (Box 1) large enough that it will hold sufficient amounts of food, water, oxygen, and other supplies to allow him to survive for 3 months. On March 15 turn Box 1 on, and let it run for 3 months. While it is running, build a second box (Box 2) that is identical except that it is a little bit smaller such that it can be placed inside Box 1. At the end of 3 months (June 15), turn off Box 1, and while it is powering down crawl inside, pulling Box 2 along with him, and turn on Box 2 from inside Box 1. Three months “later/earlier” Abe can crawl out of Box 1 pulling Box 2 out with him. The date is now March 15, but Box 2 has now been running for 3 months. So, turn off Box 2 and crawl inside. Presto, Abe will emerge 3 months earlier – December 15.

Looks like Abe has won this battle for the future. Only way to possibly beat him now would be to build an even bigger box that would hold enough food, water, and other supplies to allow one to travel back to a date before December 15. Hmmm, wonder what Aaron is doing in France during the last scene of the film…

Ron Boothe


1. My analysis of Memento can be found on this same blogsite:


2. Consider what a dog Christopher Nolan’s Inception (2010) turned out to be (IMHO).

3. Here are a few I would recommend starting with:








4. I will discuss the issue of whether these are absolute times or relative times later, but for now I will discuss them as though they are absolute times since that makes the examples easier.

5. As far as I can tell, this rule precludes being able to use this form of time-travel to achieve immortality. Even if I were to crawl in a box that was started on the day I was born (for example one bequeathed to me by my parents), I would emerge from the box on my birth day an old man, or more likely in the case of someone my age, dead!

6. The time-travelers also need to carry enough oxygen for the duration of the trip because there happen to be poisonous gasses in the box due to the way they are constructed, but I don’t think that fact has any implications for the larger issues of time-travel that are explored in the film.


3 thoughts on “Primer (2004), A Film Not Fully Appreciated Since Tomorrow at 2 pm

  1. As much as I like the idea of a running box inside a running box letting one travel farther back in time than a box start date it doesn’t seem to work. Wouldn’t you emerge from box two back at the time where you turned it on. The box itself wouldn’t suddenly start traveling back in time in place. It would “move” back into the other box. Other wise a box would just appear out of nowhere months in the past. The earth is constantly moving. When the boxes are used they don’t remain at the spatial point where they were you exited. They are always in the place they were when you entered. Otherwise the movement of the earth would cause you to exit the box in deep space everytime. My guess is getting out of box two in your scenario would put you back at the point where you started it before entering box one.

    1. So nice to see your response. Been a long time since I watched this film or thought about it. I don’t think your argument is correct, but I would have to think about it for a while. Here is my initial response off the top of my head. If I have more to say about this issue after thinking about it some more I will add another comment.

      The issue you raise involves how “space” is handled during time travel. It seems pretty obvious that even the “one box” situation requires travel in space-time, not simply in time. Otherwise, as you point out, one would emerge from the box somewhere out in space, the earth having moved in the meantime. So, it will be stipulated that when one emerges from the box at an earlier time with respect to when the box was turned off, we have also moved in space, to where this location had been at an earlier time.

      One of the reasons the protagonist used a timer to turn the box on and left the area before it did turn on was so that he would not “bump into himself” when he emerged at that location. With the two-box situation that problem might be even more problematic. You would have to make sure the location where you placed box 2 was someplace where nothing was located at the earlier time when you emerge.

      Lots to think about. When I get a chance I will try to watch this delightful little thought provoking film again.

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