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[[caption-width-right:350:What if it actually works?]]

->''"Look, everything we're putting into that box becomes ungrounded, and I don't mean grounded like to the earth, I mean, not tethered. I mean, we're blocking whatever keeps it moving forward, and so they flip-flop."''
-->-- '''Abe'''

''Primer'' is a 2004 independent film, written and directed by Shane Carruth. ([[CopiouslyCreditedCreator Also produced by Shane Carruth, starring Shane Carruth, edited by Shane Carruth, Shane Carruth as director of photography and with a soundtrack composed by Shane Carruth.]]) It was made on [[NoBudget a minuscule budget]] of $7,000, most of which went towards buying film stock. The film is a character-driven drama about two engineers who unexpectedly create a TimeMachine, and an examination of how TimeTravel (and the power it confers) affects them and their friendship.

Quite possibly the single {{nerd}}iest film ever made, and one that brings [[TechnoBabble technical jargon]] to a new art form, it is also one of the most believable via its starkly straightforward presentation.

The film opens with two engineers and entrepreneurs, Abe and Aaron, building electronics in Aaron's garage. After achieving some success with their latest project -- a room temperature superconductor -- they discover it has an unexpected side-effect: creating time loops. Everything they place inside the Box runs back and forth through time for roughly 1300 iterations.

By scaling up the Box, they're able to use it as a means to travel into the past. The device has its limitations:
* As it does not laterally bypass temporal mechanics, but rather inverts its progression, they have to take TheSlowPath: to go back in time two hours, one has to remain in the box for the same duration.
* As it alters time only within its own dimensions and during operation, and offers only one 'exit node' back into standard temporal progression, they can only travel back to the time that it was turned on, not before or after.

Even with the limitations, however, they figure out how to use time travel to make a nice profit, through effectively living through the same period a second time with foreknowledge of the stock market.

Then something goes wrong. And that's when things get [[TheEndingChangesEverything really confusing]]. The ''plot itself'' is non-linear. Most of the plot -- including several crucial events -- is neither shown nor described, just ''{{implied}}''. And on top of that, the characters communicate almost exclusively in dense TechnoBabble.

!!! Some helpful, spoilerific, graphs:
* [[http://en.wikipedia.org/wiki/File:Time_Travel_Method-2.svg A graphical representation of how time travel in the Box works.]]
* [[http://static.tvtropes.org/pmwiki/pub/images/PrimerTimeline.gif Abe and Aaron's paths through time.]]
* [[http://unrealitymag.com/wp-content/uploads/2011/09/primer-chart.jpg The timeline(s) of the entire film.]]
* [[https://www.youtube.com/watch?v=tUzy-xPf0MI Step-by-step breakdown and explantion of the film's plot.]]

Yes, this is a movie that requires graphs to get a handle on.

Shane Carruth later went on to direct (and write, produce, star in etc.) ''Film/UpstreamColor''.

%% General explanations of the subtle intricacies of time travel don't belong on this page.
%% Things which directly appear in the movie itself go here.

!!This film provides examples of:

* AnachronicOrder: Maybe! It's difficult to tell when a linear plot would be going back and forth in time as well.
* ChekhovsGun: [[spoiler: Aaron's headphones.]];[[spoiler: Rats in the attic.]]
* CheckPoint: Non-video game example; the Box's limit that you can only travel back to the point where it was turned on is similar to the function of a checkpoint.
* ClockDiscrepancy: Abe suspects that the Box is a time machine, and he confirms this by placing a digital watch inside it for a minute. Upon removing the watch, it's about 21 hours fast.
* CloneDegeneration: WordOfGod for states that [[spoiler:doubles created via TimeTravel are imperfect copies. This is the reason for Aaron and Abe's earbleeds and the degradation of their handwriting when they begin altering their past. It may also account for their personality swaps.]]
* CorruptCorporateExecutive: Platz is hinted to be one. At first, it seems like he's just your typical BadBoss but a bit of dialog earlier in the movie refers to an event that happened "last year" and one of the characters saying he knew someone with a legal background that knew about "cases like ours." Suggesting Platz took an intellectual property invented by the company (probably claiming that it was developed on company time with company resources, which is often covered in employment contracts.)
* DeadlyNosebleed: A symptom of improperly performed time travel. Granger leaped out of the box late (early from his perspective) because he didn't understand the precise mechanism.
* GambitRoulette: When you've already seen events play out, you can make plans work that involve [[JustifiedTrope things that would normally be completely unpredictable]], but sometimes even having seen it happen once [[ForWantOfANail doesn't mean it will happen the same way again]].
* GambitPileup: Two {{Chessmaster}}s, a TimeMachine, and no need to worry about causing a TemporalParadox. Things get complicated.
* HeterosexualLifePartners: Abe and Aaron, [[spoiler:but the events of the plot seem to push them apart]].
* HomemadeInventions: The time machine.
* HourglassPlot: Aaron starts off as a family man and rather risk-averse (note the scenes where he worries about needing eye protection and warns his wife against using the first batch of ice from the new fridge). Abe starts off unmarried and rather more devil-may-care. Over the course of the film, access to a TimeTravel-powered ResetButton makes Aaron become more aggressive and willing to take risks, and he eventually leaves his family. Abe, on the other hand, becomes increasingly worried about the side-effects of time travel and oddly protective of Aaron's family.
* IronicEcho: ''They/he took from his/their surroundings what was needed, and made of it something more.'' Overlaps with MeaningfulEcho.
* LimitedWardrobe: Abe and Aaron's work clothes might as well be uniforms. At one point, Abe is shown sleeping in them.
* MeaningfulEcho: ''They/he took from his/their surroundings what was needed, and made of it something more.'' Overlaps with IronicEcho.
* MisappliedPhlebotinum: Abe and Aaron could have made money in a number of ways more efficiently than playing the stock market, though the movie shows that they go about it this way because they're trying to be as careful as possible about the impact they have on causality, as they don't know which rules apply to their type of time travel, and they're trying to hide their invention's existence until they fully understand it.
* MistakenForGay: The pair speculates that this is bound to happen, what with the extended time they spend by themselves in a hotel room waiting to come out.
* NarratorAllAlong: [[spoiler:Hooded Aaron's]] phone message.
* NoEnding: We don't know whether Abe's plan succeeds, what Hooded Aaron is doing, or what Aaron Three is doing.
* {{Prelap}}: An ice machine is triggered on a refrigerator, but the sound is a piece of construction equipment from the next shot.
* ReedRichardsIsUseless: They invent a workable TIME MACHINE and the best use they can think of is to make money in the stock market?
* ResetButton: Various characters have back-up boxes going from the beginning of the story in case something goes wrong. Then they start folding up more boxes and bringing them back in the fail-safe one.
* SdrawkcabName: Abe Terger comes to regret his work at Emiba which leads to a ''mise en abyme.''
* SecondHandStorytelling: Half the reason the film is so {{mind screw}}y is because several key events are described rather than shown -- and the characters doing the describing would rather be laconic than descriptive.
* SetRightWhatOnceWentWrong: The plot involves [[spoiler: Aaron going back in time twice to save Abe's girlfriend, Rachel, from her psychotic ex-boyfriend. Thomas Granger, Rachel's father, is believed to have come back for similar reasons, but we never find out exactly what his motives were.]]
* ShownTheirWork:
** They researched what would happen if you had [[spoiler:two copies of the same cellphone. Turns out, some networks just look for the first one, and others ring both.]]
** Research into the physics of time has suggested that if a time machine was built, it would have at least one similar restriction as in the movie: it would only allow you to travel back to the point at which it was turned on.
* SpannerInTheWorks: [[spoiler:Granger's surprise time trip (given the place and time he shows up, he's probably there to prevent a disaster resulting from the punch-Platts experiment). Abe tries to fix the Granger problem two different ways, once with one of the Thursday 5:00pm boxes (we see him running to get into place behind the house before the other Abe leaves the car), and then with his fail-safe box. The former trip left him with a quantum entanglement with Granger, since he had a 50/50 chance of using the same box Granger did -- thus Granger lost consciousness whenever he got too close to Abe).]]
* TheSlowPath: In ''both'' directions. To go back two hours, you have to sit in the box for two hours. This causes enormous problems when Abe and Aaron use the failsafe boxes. They travel backwards for ''days''.
* TechnoBabble: In the absence of any solid RealLife physics supporting time travel, their hypothesizing about the technicalities can't be anything else. However, the language of mathematics and engineering has been leveraged to maximize plausibility. Within the framework of the film a lot of work has been done to keep things consistent.
* TimeIsDangerous: Excessive time travel causes strange physical problems in the protagonists: mysterious bleeding from their ears and deterioration of their handwriting. WordOfGod is that this is also a case of CloneDegeneration.
* TimeMachine: Closest it comes is to a ''{{Franchise/Terminator}}''-type, but it's really in a category all its own.
* TimeTravel: The central premise.
* TimeTravelForFunAndProfit: Abe and Aaron never got around to publicizing their time machine, because [[spoiler:they were too busy using hourly time travel to make money day-trading stocks.]]
* TimeTravelTenseTrouble: "Man, are you hungry? I haven't eaten since later this afternoon."
* TheEndingChangesEverything: The second act of the film involves the use of very limited Time Travel. However, [[spoiler:in the third act Abe learns that his friend Aaron has already used the time machine to change the past. So during the entire aforementioned second act, Aaron had actually been Aaron-from-a-week-in-the-future, manipulating current events for his own ends.]]
* ViewersAreGeniuses: The film leaves the viewer to figure a lot of the very complex plot out on their own.
* WhamLine: [[spoiler:"I hope you're not implying that any day is unimportant at Cortex Semi." A WhamLine not for the words itself, but for the fact that Aaron says it even though Abe had failed to remember the line that prompted it, revealing that he was reciting the conversation from memory, too]]. The lines before that also count, such as the fact that [[spoiler: Abe has a secret backup time machine which has been running for most of the movie.]]
* WhiteMaleLead: Abe and Aaron. Phillip, the one major character of color, is quickly sidelined out of the action, and the female characters never emerge from the background.
* WrongGenreSavvy: Abe comes up with a very thorough plan to avoid causing {{Temporal Paradox}}es, which turns out to be completely unnecessary [[spoiler:(or not, depending on your interpretation of Granger's fate; the idea that he is suffering from temporal paradox -- that the consequence of paradox is that the universe destroys you, rather than vice versa -- was put forth by Carruth himself, [[DeathOfTheAuthor whatever his opinion's worth]])]]. Still, points for trying.