Time travel movies are nothing new. They’ve been around for almost the entirety of the history of cinema. There’s stories about time travel as far as back 700 BCE (the story of Raivata from the Mahabharata), H.G. Wells’ The Time Machine is justifiably considered a literary classic, and Back to the Future is practically a perfect film (its script is taught in screenplay classes as being a perfect screenplay; no loose ends, plot holes, or fat, everything is either a set-up, a call-back, or a payoff.) And the most important part of time travel films is establishing the rules. Because there’s so many complications that can arise in such situations, you have to make sure the audience understands what is at stake, why it’s at stake, and the mechanisms that get us there. And Shane Carruth’s Primer is one of the most thought-out and tightly plotted ones out there.
Like I said, the rules of time travel in any movie are important, and often contribute to the plot mechanics therein. Can time be changed? Is causality followed? Are paradoxes allowed? Is the Butterfly effect something to be accounted for? How far back or forth can you go? If you change something, do your memories get rewritten, or do you remember the original timeline? Again, Back to the Future is the template most people seem to use now, where time can be changed, and it ripples out slowly from the even. But there’s also things like Doctor Who, which says that time CAN be changed, except for certain events which are fixed points. Terminator is another form, where time is a closed loop. John Connor sends Kyle Reese back to keep the T-800 from killing his mother; the event always happened. The current standard theory in quantum physics studies of potential time machines is that one can’t time travel back to before the time machine was first turned on. This handily explains why we haven’t seen any time traveler “tourists” anywhere. So you can’t go back to dinosaur times, ancient Rome, Victorian London, etc etc. But you can go back within your own timeline. Primer has its own rules, based heavily in theoretical physics and current theories of potential time travel.
I will not be recounting the plot here, because you should really see this movie, multiple times in fact. You just have to know there’s time travel involved, and that it is not an easy “jump into a machine, hit some buttons, and you’re there.” There is real tedium to it, patience and boredom. But the real genius of the movie, and one which can only really be parsed out after multiple viewings, is that there is also a lot of incidents left unshown, and only hinted at. There’s multiple infograms online attempting to explain the myriad of timelines in the film, and how events play out. (Here is one such attempt.) Because of the nature of the “machine”, one can’t be sure how many “travelers” there are at any given moment, especially once duplicates of duplicates start to show up. The narrator is unreliable; the movie has been essentially lying to you at various points, but it’s also been lying to itself. The discovery of time travel was an accident, like the discovery of penicillin, the proof of the Big Bang Theory, and x-rays. But the results, both physical and emotional, are as predictable and devastating as anything in any more flashy film.
And that is the main point, the essential thesis of the film: it’s not about the machine, or who conned who, or what the mechanism is. It’s that it all doesn’t really matter. Humans, even ones with the best intentions and the most meticulous planning, find things by accident all the time, and in some form or capacity use it to one up each other and try to get ahead. Chuck Klosterman, referencing Primer in an essay on time travel films, put it best, “It’s too important to use only for money, but too dangerous to use for anything else.” So ultimately, the movie isn’t about time travel. It’s about the ethics of friendship and the deterioration of human interaction. And that is ENDLESSLY more fascinating than trying to find out who Jack the Ripper is.