Capire il film Primer

Source: https://www.reddit.com/r/explainlikeimfive/comments/1a2zi9/eli5_the_movie_primer/

source: https://qntm.org/primer

"If you have it, you've gotta use it."

Primer (2004) is a complex and challenging film. This article is intended to help you get the most enjoyment out of watching it. Update: I've recorded a commentary track for the film. It covers most of what's explained below, but has some new stuff too! What should I know before watching Primer?

(If you want to go in totally blind, that's fine - skip the rest of this section.)

Primer has nothing that could be termed exposition. Nothing will be explained to you directly; you are essentially eavesdropping on other people's conversations as you follow them around. It's up to you to keep up. Consider turning on the subtitles. Some of the dialogue is muffled or occurs in the background where it's harder to catch. Even if you're firing on all cylinders, there's a point about 3/4 of the way through the film where everybody - everybody - loses it on the first watch. This is not your fault; this part of the film is very confusing and not explained very clearly. I will explain it later.

Now go watch the film and then come back. Here is a summary of what literally takes place in the film.

Aaron, Abe, Philip and Robert are four men who work at a semiconductor firm by day and sell home-made electronic products in their spare time. But while they've had some interesting patents, they haven't made major money from the side projects. They came close once, but a man named Joseph Platts stole their idea, leaving them with no recourse.

It's been agreed that they each take turns to put an idea forward. Robert's idea is to build a strange piece of hardware which can theoretically reduce the mass of an object inside it. It does this by "blocking information", cutting the object in the box off from the effects of gravity. This is just after Christmas time (hence Aaron's new refrigerator).

The box requires superconductivity. They can't generate the low temperatures they need, so in the brainstorm session they throw out an idea or two for doing it at room temperature. They cannibalise some home appliances for equipment and a catalytic converter for palladium, and build the thing in Aaron's garage. The box also has to be hermetically sealed and flooded with argon to work correctly. Aaron also makes some unconventional modifications to the box - "It looks like a dog digested it."

While experimenting, Aaron and Abe discover that the machine works. They put a blue weeble inside the box and register that it has decreased in mass. (While fiddling with the device, Aaron pokes his hand right the way into the field and Abe puts his hands over it to drop punched holes into the field. This becomes significant later.) Aaron and Abe instantly recognise the limitless applications and value of the device they have built. They immediately cut Robert and Philip out of the loop, saying that Aaron's garage has to be fumigated.

But at the same time, Aaron and Abe also realise that if they go public with their new invention too quickly, someone like Platts will take advantage of them again. They need to fully understand it first - which they don't.

Several months pass. The four men get funding from a Thomas Granger, while Abe establishes a relationship with his daughter, Rachel. (Aaron is of course happily married to his wife Kara, with a daughter, Lauren.) Abe tries to figure out how, exactly, the device does what it does - and he fails.

This is now March. Monday (video time code: 18:36)

The first bench scene: Abe approaches Aaron one morning. Aaron is listening to March Madness on an earphone (and continues to do so for the rest of the day). Abe persuades Aaron to take the day off work, then he leads Aaron through a series of discoveries that he has made.

After repeated experiments on the weeble, Abe realised that a weird fungus was growing on it. He took it for analysis and was told that the fungus was perfectly ordinary, but that the amount of growth he had seen was consistent with years of time passing, not days. Suspicious, he put his wristwatch in the box. He discovered that what they had built was a time machine, which works like this.

The two of them immediately reason that if an intelligent agent was put inside the box, it could deliberately exit the box before it entered, travelling backwards in time. Abe then reveals to Aaron that he has already done this:

Abe built a coffin-sized time machine, which we shall call Box A, and placed it in a unit at a self-storage facility. At 08:30 Monday, Abe primed Box A to activate itself in fifteen minutes. He drove away from the self-storage facility and isolated himself at a hotel in Russelfield. The box activated at 08:45 and was completely powered up at 08:49. At 15:15, Abe returned to Box A and switched it off. It took another four minutes to power down completely. As it powered down, he climbed inside. Abe waited six and a half hours (in the film the figure is repeatedly stated as "six hours"). At the correct time, he climbed out of the box just after it was activated - at 08:45 Monday. Abe then approached Aaron for the first bench scene.

Now it's 15:15 Monday again, and Aaron and Abe-2 are able to watch Abe-1 return to Box A, climb in, switch it off and disappear into the past. Tuesday (31:22)

Abe shows Aaron that he cunningly made a single excellent stock trade during Monday too.

On Tuesday, Abe goes through the same routine but this time Aaron insists on following along. By now, Aaron already has his own box built: Box B.

They switch on the boxes at 08:30 Tuesday, hide at the hotel all day and then return to the boxes at 15:15. Abe departs Box A at 08:45 Tuesday as expected, but Aaron gets jumpy towards the end of the ride, and exits Box B a minute or two early (or, from Abe's perspective, a minute or two late), suffering a severe physical reaction. The time is 08:50 Tuesday morning.

The dialogue during these scenes reveals a few more noteworthy facts.

Abe and Aaron are trying to modify history as little as possible. They isolate themselves at the hotel in order to minimise the effect. In particular, if they were to accidentally prevent their doubles from departing the timeline as scheduled, this would present a major problem, since there would now be multiple Aarons/Abes.

The other important line is "the boxes are one-time use only". What Aaron means by this is that after you have climbed out of a box, you CANNOT go back to it later, switch it off and climb in a second time - because that's what your past self did. You cannot use the same box to continuously loop through the same day.

This is not actually true. For the purposes of this plot summary, however, all we need to know is that Aaron and Abe both believe this is true and operate under this assumption.

They make some more money on the stock market. That evening, they have a slightly drunken conversation with Aaron's wife Kara about the prospect of having unlimited wealth. Aaron raises the hypothetical of punching Joseph Platts in the face, then going back in time and telling himself not to, making it so that it never happens. Abe says they "can't do that", not because it's morally wrong to punch Joseph Platts in the face, or because Aaron can't tell Kara about the time machine, but because this would result in there being two Aarons. Which is bad.

"But the idea had been spoken. And the words wouldn't go back once they had been uttered aloud."

Kara also mentions a mysterious noise in their attic. Birds? Rats? Wednesday (42:00)

The same routine again.

Aaron and Abe argue at the supermarket and the gas station that morning about paradoxes, free will, paranoia and predestination. One particular point that Aaron raises is the problem of living in a universe which has been engineered by somebody else. At the hotel, and then later on Wednesday afternoon at the library, Abe and Aaron discuss the problem that Aaron is keeping the time machines secret from Kara. They also discuss the problem of Robert and Philip. They agree to give them a certain amount of patent rights and/or equipment and/or cash in order to salve their consciences instead.

They loop back in time as normal. At 08:15 Wednesday, shortly after getting out the machine, Aaron is bleeding from his ear.

That day, make their successful trades. In the afternoon, they finally admit that the garage has been "sprayed", and work at the garage with Robert and Philip resumes. Robert and Philip have now received their gifts from Aaron and Abe.

Robert reports an interesting story. It seems that Monday night was Robert's birthday party. Abe wasn't there, but his girlfriend Rachel was there. So was Rachel's ex-boyfriend, who walked into the party brandishing a shotgun. So was Aaron, who by all accounts risked his life to defuse the situation safely.

On Wednesday evening, while Aaron and Abe are outside looking for Aaron's missing cat, Abe is angry that Aaron, a family man, risked his life in such a way. Abe is genuinely confused that Aaron acted so uncharacteristically irresponsibly. Aaron makes excuses and claims that since the discovery of the time machines he is seeing the world differently, referencing their conversations of earlier in the day. However, this does not fully explain his actions. Thursday (48:45)

The same routine again.

During the day spent at the hotel, Aaron's cell phone rings. It is Kara, asking about dinner. This is a mistake, since Aaron is supposed to be sequestered. Abe tells Aaron not to bring the cell phone back in time with him - this is a perfectly sensible way to avert the possibility of a paradox.

They loop back in time as usual. On the second time through Thursday, Aaron watches a sports match (whose outcome they already know) while Abe eats a muffin. Then, on the way to a restaurant, Aaron's cell phone (which he has foolishly brought back in time with him) rings again.

This is a problem, and a critical turning point in the film. There are two Aarons at this point (one at the hotel), and, due to Aaron's clumsiness, two of his cell phones (one at the hotel). If the phone in Aaron's hand is ringing then, so Aaron and Abe reason, the phone in the hotel cannot be ringing. Symmetry is broken and history has changed. History can be changed. Friday (52:10)

At about 02:00 on Friday morning some kids set off car alarms outside Abe's home. Abe goes to Aaron's house and gets him out of bed. Abe reveals that he has been routinely turning the boxes on at 17:00 and turning them off the following morning.

Abe then puts forward a confusing and potentially dangerous plan to visit Joseph Platts at his home, punch him in the face, then, around 03:00 Friday, to use these boxes to go back in time to 17:00 Thursday and make sure that neither the car alarms nor the punching happen. In theory, as a result, both Aaron and Abe's doubles would stay in bed all night, get into their boxes at 15:15 Friday as normal, and leave this timeline permanently, leaving just one of each of Aaron and Abe behind.

As they climb into the car, however, they realise they are being followed by Thomas Granger, Abe's girlfriend's dad and the project's main source of funding. Granger has several days' growth of beard on his face - but Aaron last saw him at 18:00 Thursday, when he was clean-shaven. Abe phones Thomas Granger's number and the guy who answers is indeed Thomas Granger… but he's not the guy who is following them. Something really weird is going on. This man is a different Thomas Granger who has come back in time using one of the boxes, probably exiting the box at 17:00 Thursday when Abe switched them on.

Aaron runs after Granger and when they get close to one another, Aaron trips and falls while Granger falls completely unconscious. They put Granger to bed at Abe's house; Aaron cannot approach him without somehow knocking him unconscious. They check that the boxes are indeed turned on. Aaron proposes shutting them off to see if Granger is inside, an act whose consequences would be exceedingly difficult to guess at. They do not do this.

Why has Granger come back in time? Obviously at some point in the future, Aaron or Abe told Granger about the boxes. Then, something happened to prompt Granger to head backwards in time to this point (the earliest he can go) and start observing them. They conclude that the situation would have to have been a real emergency but they have no clue what it could possibly be. "The permutations were endless." History has definitely changed now that Granger has come back, but they have no way of guessing whether the emergency in question has been fully averted by his brief interactions with them and the rest of the universe - he has only been out of the box for about eight and a half hours.

And so Abe loses his nerve.

It is now revealed that there is a failsafe box, built by Abe, in a second storage unit. This box has been running for 3 days 22 hours - in other words, since early on Monday morning. Abe started the box at about 05:00 Monday, then went back to bed until 08:30 when he returned to start Box A. At roughly 03:00 Friday, Abe returns to the failsafe box, with four days' oxygen and water and a small tank of medical-grade nitrous oxide, enters it and travels all the way back to 05:00 Monday. Monday again (59:06)

Abe (now Abe Two) exits the failsafe box at 05:00. He travels to his home and gasses his double in bed with the nitrous oxide. He stashes his double in his bathroom.

Now we come to the second bench scene. As in the first bench scene, Aaron is listening to what is supposedly basketball on his earpiece. Abe Two is ill, after four days of very little food, and in shock, after violently gassing his double. Aaron, however, repeats most of the same lines as last time.

In fact, when Abe faints, it is revealed that Aaron is not listening to basketball. He is listening to a recording of that very conversation. How can this be? The recording must have been made in some previous timeline. This is not the original Aaron. This is not the original timeline. It never was. This Aaron has come back in time from the future.

"At this point there would have been some… discussion."

Aaron and Abe confront one another and explain everything that has happened. This is the most difficult sequence in the film to follow, partly because of the complexity of the plot but mainly because, due to the lack of CGI, it was impossible to put more than one Aaron on the screen at the same time. The two major discussion points are:

How?

Aaron's line, "They are not one-time-use only. They are recyclable," means that although you cannot re-enter a box you climbed out of, you can bring another box with you, activate it once you climb out, and later use it instead, travelling back to the same moment in time again - or a few minutes later, at any rate.

In some previous timeline, Aaron discovered Abe's failsafe box, anchored 05:00 Monday. He then got inside the failsafe and used it to go back in time, taking with him a second, folded-up time machine. This is the Aaron with the hood.

On arriving home at 05:00 Monday, Hooded Aaron set up his second time machine as Failsafe Box B, let's say at 05:15 Monday. Hooded Aaron then went to his home and drugged his double's breakfast cereal milk, then stashed his comatose double in the attic. This is the noise that Kara mentioned on Wednesday night. This means that there are now two Aarons in this timeline, permanently. Hooded Aaron assumed his double's identity and recorded all of the week's conversations.

Then, he used Failsafe Box B (remember: he cannot re-use Failsafe Box A since he already climbed out of it once) to go back in time to 05:15 Monday yet again. He took yet another time machine with him, which he set up as Failsafe Box C (05:30 Monday). He becomes Aaron Three, with the white jumper, no hood. Aaron Three arrives at his house just as Hooded Aaron has finished drugging and stashing Aaron Prime. Aaron Three tries to subdue Hooded Aaron in turn, but this time he is too exhausted, and Hooded Aaron wins. After a conversation, however, Aaron Three persuades Hooded Aaron to leave. There are now three permanent versions of Aaron: Aaron Prime, who is drugged in the attic; Hooded Aaron, who has left town; and the Aaron we have been looking at since the beginning of the first bench scene, with the headphone in his ear feeding him lines, is Aaron Three and always has been.

Aaron Three has had a LOT of exposure to the boxes. This is why he began bleeding from his ear on Wednesday, and it also why his contact with Thomas Granger nearly killed them both.

It is Hooded Aaron who is the narrator of the story. The "primer" of the title is Hooded Aaron's phone call to Aaron Prime.

So which box did Abe use to come back in time? Logically, Abe must have used Failsafe Box C, since Failsafe Box A contained Hooded Aaron and Failsafe Box B contained Aaron Three. How did that happen? Aaron must have SWAPPED Failsafe Box A and Failsafe Box C. The box that Abe believed was Failsafe Box A (anchored 05:00 Monday) was actually Failsafe Box C (anchored 05:30 Monday). This is not seen or even alluded to in the film, but it is necessary to resolve this plot hole. Why?

Problems of logistics aside, the last remaining question is why Aaron chose to come back in time so far, sacrificing so much, permanently duplicating himself twice. What is he trying to set right, exactly?

The key to all of this is the party. It is obvious, though left largely unsaid, that when Rachel's ex-boyfriend walked into the room with a shotgun, things could have gone considerably worse. Aaron Three, we remember, risked his life to successfully defuse the situation. We now understand why he would take this risk. There are two other Aarons in this timeline, one of them being Aaron Prime. Aaron Three does not matter - he is a non-person, a walking dead man, and he has no right to Aaron Prime's family. He has no life to risk.

If I may jump ahead in the film slightly, the basketball scene (which takes place sometime in the middle of Monday) is also important. This scene further establishes that it was Aaron who originally invited Will, Rachel's ex-boyfriend's cousin, to the party - and that it was Aaron who suggested that Will should bring Rachel's ex-boyfriend with him. In other words, whatever originally happened at the party was indirectly Aaron's fault.

Aaron Three thought the problem permanently settled. But the fact that Thomas Granger came back in time to 17:00 Thursday indicates that it was not, and something bad was still looming in Aaron and Abe's future. However, it is Monday morning again, and both Aaron Three and Abe Two are prescient now. They decide to engineer the situation to end better this time, with Rachel's ex-boyfriend actually arrested and jailed.

By Monday afternoon, Aaron and Abe are both suffering from the effects of a great deal of time travel - they are unable to write correctly. Remember when they put their hands into the machine?

At this point, the narrator, Hooded Aaron, reminds us that HE, of course, does NOT come from a timeline where everything worked out perfectly. In fact, he was never originally at the party. He has no idea how long it will take for Aaron Three to "reverse-engineer a perfect moment". From what we see in the film, though, for Abe Two and Aaron Three, it appears to work first time. The jealous ex is arrested and jailed. The End.

On Monday night Aaron Three crashes at Abe's house. Abe Two cannot sleep. And with that problem resolved, everybody lives happily ever after.

With the following exceptions. Tuesday again (1:09:28)

Aaron Prime wakes up in his own attic after being drugged for 24 hours by his double.

Abe Prime wakes up in his bathroom after being gassed for 24 hours by his double.

There are three running failsafe boxes which evidently nobody has thought to shut down, in addition to Abe Prime's original Box A, which hasn't been activated yet but is nevertheless operational. "They'll be building their own boxes in another day. And [Abe Prime] already knows what they built."

Aaron Three and Abe Two wind up at the airport. Aaron is going to steal his double's passport and leave the country, because he can never go home. He has lost Kara and Lauren to Aaron Prime. Abe, meanwhile, is going to stay behind so he can sabotage their doubles' attempts to build the time machines. And, more sinisterly, stay close to Kara and Lauren. And protect them from Aaron Three. What?

And finally, on the other side of the world, Hooded Aaron makes his phone call to Aaron Prime. Maybe Aaron Prime records it and believes it, maybe he doesn't. Hooded Aaron explains the entire story, including why he drugged Aaron Prime, and thus "[repays] any debt I may have owed you".

"You will not be contacted by me again. And if you look, you will not find me." Hooded Aaron hangs up, and begins construction on a time machine the size of a warehouse. The End.

Source: https://www.reddit.com/r/movies/comments/3aephh/can_anyone_explain_to_me_what_all_happened_in/ The two heroes accidentally create a small "box" that causes time-travel, although they don't know it.

One of the heroes - Abe - goes off on his own and makes a time-travel box big enough for a person.

He travels backward to the start of his day.

He drives off, grabs buddy Aaron, and he shows Aaron himself (from 3) going into the box.

They have two boxes now, and they travel back to the beginning of their day.

They do this a few times with some success, gaming stocks to make money.

Aaron's wife complains about the sound of rats in the attic.

Aaron takes a call from his wife during the day, uses the box at night, goes back to the beginning of the day, then takes the call again, beating "himself" to the punch, proving that time-travel is not a closed loop. Things can be changed.

They see a man they know named Granger who looks disheveled; they call his house and he's there. So at some point, Granger will use the box, go to the past, and pop out in the state he's in now.

Abe, unhappy with these complications, heads to a secret time-travel box he's made called the "failsafe," which takes him back to the day he told Aaron about time-travel (see 4).

He has to drug his original self so he can "replay" the days without that original intervening.

He goes back, sees Aaron with an earpiece, and collapses.

When he comes to, it's revealed that Aaron learned about Abe's failsafe a while ago, stole it away and replaced it with a different failsafe (one that starts a little bit later).

Aaron's since gone back in time, drugged his original self, stuck his original self in his own attic (see 7), and "replayed" the events of the film.

Aaron tries to go back in time and drug himself again, but he's too weak, and his original self fights him off. At this point, there are three Aarons in the film - the original, the one who drugged the original, and the one who failed to drug the last one.

The original drugged Aaron breaks out, the second one flees the country to build a bigger time machine, and the third one stays in town to continue as Aaron proper.

The drugged Abe busts out about the same time his newer self vows to find a way to prevent them from ever discovering time-travel. Of course, he can't, because he'll never be able to go as far back as Aaron can, because of that failsafe switcheroo.

I've left out the party stuff because my brain fullness is already at critical.

Source: http://friendsinyourhead.com/primer/

I asked a member of our forum to explain Primer to me, because he seems smart and I do not. This was the email I got in reply. -Teague

This is a fucking novel. If you read the whole thing I will be legitimately astounded.

Okay, so the awesome thing about "Primer" is that there are at least two whole movies going on that we never get to see, and maybe three. The events depicted on screen comprise no more than a third, and maybe less, of the events that transpire during the course of the story.

First, a word about the time machine and how it works. I'm gonna talk about this because the movie actually treats the time machine in two completely different and incompatible ways.

Before we dive into it, go to Google and search for "Rotating Cylinders and the Possibility of Global Causality Violation." That'll get you to a 1973 paper by a physicist named Frank Tipler. The short-bus version for those wimps out there who can't follow covariant tensor calculus: the Einstein field equations describe the curvature of spacetime in the presence of matter and energy. According to some solutions of those equations, it's possible for there to exist closed timelike curves through spacetime. Traversing a closed timelike curve is a lot like going for a walk around the block. When you walk around the block, you start out at a point in time and space, then you move, then you return to the same point in space at a later point in time. But if you move along a closed timelike curve, you return to the same point in space AND time.

Nobody knows whether closed timelike curves are a real phenomenon, or just an artifact of the Einstein field equations. But at least according to the current understanding of modern physics, they're not explicitly impossible. (They do appear only to form around massive rotating bodies, however, so it's not like "Primer" is TOTALLY science-fact. But whatever. It's just a movie.)

I bring this up because time travel in "Primer" is based around the idea of a closed timelike curve.

Let's imagine a time traveler, Alice. Alice has a time machine in her garage. It's pretty simple, just a box with a button. When Alice presses the button, the machine turns on; this takes a few seconds, because the machine has to "warm up," so to speak. If she presses the button again, the machine turns off, again taking a few seconds to "cool down."

The sole complication is that Alice has rigged her machine up to a timer. The need for this will become apparent shortly.

We'll start by describing Alice's day from her point of view. She wakes up in the morning on March 1, 2010. She goes out to the garage and starts the timer on her machine at exactly 7:45. Then she goes inside and has a coffee, then goes on about her day. For sake of argument, let's say she locks herself in her spare bedroom and stays there. At 8:00 a.m. exactly, the timer she started goes off and the machine starts to power itself on. Again, it takes a few seconds for it to warm up, but soon it's humming along nicely.

Alice spends her whole day locked in her spare bedroom. Maybe she reads a book or something, whatever.

At 6:00 p.m. — still on March 1, the same day — she leaves her spare bedroom and goes to the garage, where she pushes the button that turns off the time machine. The machine has been running for exactly ten hours at this point. After a few seconds it powers down, and just when it does, she climbs inside. When she does, she hears the machine power itself up again (let's assume the machine hums or something). Then she waits there for ten hours.

By Alice's wristwatch, it was 6:00 p.m. when she climbed into the box. After ten hours, by her wristwatch it's 4:00 a.m. on March 2, 2010. Let's call the time according to Alice's wristwatch AST — Alice Standard Time. At 4:00 a.m. March 2 AST, she hears the box start to power itself off again. A few seconds later, when the machine is fully off, she gets out of the box.

The clock on the wall of Alice's garage reads 8:00 a.m. on March 1. She has gone back in time. (We're going to call the time according to the wall clock UST, for Universe Standard Time.)

Now Alice can do whatever she wants. She can go to work, or watch TV, or do anything at all she cares to do. Just for sake of giving her something to do, let's say she goes to the movies, runs some errands and hangs out at the beach. Whatever she does with her time, let's stipulate that she doesn't get back home for twelve hours — 4:00 p.m. March 2 AST, 8 p.m. March 1 UST. She has a light supper and goes to bed, exhausted from the fact that it's been more than 32 hours, subjectively, since she got up that morning but otherwise totally normal.

Now let's describe Alice's day from an imaginary "objective" point of view, say that of an observer in Alice's house. Alice gets up on the morning of March 1, starts the machine at 7:45 and locks herself in her spare bedroom. At 8:00, Alice gets out of the machine.

We pause here to make an important point. It's tempting to say that there are two Alices, the one in her spare bedroom and the one in the garage. This is incorrect, and will just lead to confusion. Instead, remember that there's only ONE Alice, but she happens to be in two places at the same time. Remember, when we went through her day from her point of view, there were no branches or divergences. She never cloned herself at any point. Instead, she experienced everything in totally ordinary, boring, linear fashion. What we're seeing as "objective" observers — that is, observers moving along an inertial trajectory through spacetime — is Alice at two different points in her own personal history.

I could go off on a tangent here about the concept of simultaneity and how it works in a universe where the speed of light is a constant in all inertial reference frames, but hell, we all took high school physics. Maybe we don't all remember the math, but in this context it's enough to say that events which APPEAR to be simultaneous in one reference frame will not necessarily APPEAR to be simultaneous in all reference frames. In the reference frame of the comoving observer, it APPEARS that Alice is both in her spare bedroom and climbing out of the box simultaneously, but this is just an illusion. From Alice's point of view, one of those events followed the other by several hours.

Remember: there are no privileged reference frames. There's no objectively "true" sequence of events in a relativistic universe.

Anyway. Back to Alice's day. It's 8:00 a.m. on March 1, and we see Alice in her spare bedroom, and also in the garage getting out of the box. Alice-in-the-garage leaves the house; we do not see her again for twelve hours. Alice-in-the-spare-bedroom waits until 6:00 p.m., then goes to the garage and turns off the box and climbs inside, and apparently never gets out of it. If we were to follow her into the garage, wait until she gets into the box and then peek inside, we'd find it both off (because she turned it off) and empty (because she got out of it at 8:00 that morning, ten hours earlier).

We dick around Alice's house for another couple hours, just to see what happens, and at 8:00 p.m. we see Alice return home from her day out. Maybe she's looking a little ragged, like she recently pulled an all-nighter, but other than that, she's just totally normal Alice.

That's the FIRST way time travel is handled in "Primer." Maybe it's a little confusing if you don't have a good grasp of relativistic physics, but really it's very straightforward. Time is linear and entirely conventional both for Alice and for a notional objective observer. It's just that events which appear to be sequential to Alice appear to be simultaneous to the rest of the universe.

This is the paradigm Abe and Aaron follow when they pull the stock-market trick. To them, time is purely sequential; they start the machines, wait, get into the machines, wait, get out of the machines, go on with their day. To the comoving observer, two Aaron-and-Abe sets exist simultaneously, but again, that's just an artifact of relativity.

A digression now to talk about exactly how the stock-market trick worked. Abe and Aaron are changing events, right? They're watching the market, gathering information about it, then going back in time and using that information to change it, aren't they? Well … not necessarily. See, Carruth's choice of the stock market was either wise or lucky, because it leaves enough ambiguity for the story to work either way. Yes, maybe Abe and Aaron are changing history with their actions, but it's equally possible — in fact, a more likely and consistent explanation — that they're really not. See, Abe and Aaron look, at the end of the day, for stocks on which significant profits were taken. They have no information about WHO took those profits; that information is not available to them. Then they go back to the beginning of the day and take profits on those stocks. What they were actually observing at the end of the day (earlier in their reference frame, later in the universe's reference frame) is the effect of their own trading. The trick wouldn't work — or at least wouldn't fit the story — if they looked to see who won the lottery, got their lotto numbers and then went back and played those numbers. They'd obviously be changing the outcome in that case. But in the case of the stock market, there's only one set of events, but Abe and Aaron experience that set of events in a different order than the rest of the universe. No rules are being broken with the stock-market trick.

Now. If the movie stopped there, it would still be way interesting. But it doesn't. It goes to a different place. And to explain that, we need to ask ourselves two questions: Why the timers, and why the hotel rooms?

Remember Alice? Alice went to the garage and started a timer, then locked herself in her spare bedroom. Why? Why didn't she just mash the button that would turn the machine on? The answer is causality, and more specifically Abe and Aaron's lack of understanding of causality.

When Alice gets into the box at 6:00 p.m. on March 1, it's turning itself off. Once inside, she perceives it powering itself back up again. What's really happening, though, is that Alice is experiencing the box powering itself DOWN, only "played back in reverse," because she's now moving backwards in time relative to the universe. After five hours inside the box, Alice's wristwatch reads 11:00 p.m. on March 1, but the clock on the wall of her garage reads 1:00 p.m. on March 1. A minute later, her watch says 11:01 p.m., but the wall clock says 12:59 p.m. She's moving forwards in time in her own reference frame — as everyone always does, obviously — but backwards in time in the universe's reference frame. (Put the other way around, when Alice is inside the box, the universe is moving backwards in time relative to her reference frame. Same difference; there are no privileged points of view.)

After ten hours in the box, Alice perceives the machine powering down. This is the machine powering UP, "played back in reverse," because Alice's trajectory through spacetime is backwards relative to the universe. When, from Alice's point of view, the machine is fully powered down, she gets out. It's now 8:00 a.m., and the timer just went off and the machine is just starting to power up.

Now the need for the timer becomes obvious: If Alice just went into the garage and mashed the button at 8:00, she'd immediately be greeted by HERSELF emerging from the box. Abe and Aaron want to avoid this, because they simply don't know what would happen. Their heads are filled with sci-fi fantasies of paradoxes and antimatter explosions and god knows what else, and they just want no part of it. So they avoid the question entirely by rigging up the boxes on a delay timer, giving them an opportunity to vacate the premises before anything happens.

Of course, the more interesting question is … what if they pushed the button on the box and nothing came out of it? What would that mean? Again, that falls into the category of shit-they-want-no-part-of, so Abe and Aaron never try to find out.

The other thing to ponder is the matter of Alice's spare bedroom. After she starts the timer, she locks herself in her spare bedroom for the day. (And Abe and Aaron lock themselves in a hotel room.) Why is that? What's the point of having a time machine, after all, if you have to bolt yourself in a room and avoid interacting with the world for your first trip through your day? The answer is that Abe and Aaron don't want to fuck with their own personal histories. The reason they're able to emerge from the box in the morning is because they entered the box in the afternoon; entering the box is part of their own personal histories. But from the viewpoint of a comoving observer, Abe and Aaron have NOT entered the box yet at the time they emerge from it. From THEIR point of view, entering the box is in the past; it's done. But from the comoving point of view, that event hasn't happened yet … AND MAY NOT.

Once again, Abe and Aaron are scaredy-cats. They don't even want to know what might happen if they fail to get into the boxes "after" (in the comoving reference frame) having emerged from them. A moment's thought on this subject reveals that it's really not even worth worrying about. Again, there aren't really TWO Abes or two Aarons; they haven't been CLONED. They only appear to be in two places at the same time because of an artifact of relativity. In fact, by the time Abe and Aaron emerge from the boxes, they've already gotten into the boxes; this happened in their own personal histories. It's fact, irrevocable and true, and cannot be changed. THERE ARE NO PRIVILEGED REFERENCE FRAMES. The fact that Abe and Aaron appear to exist simultaneously to an outside observer doesn't trump the fact that they exist in a purely linear, continuous fashion just like everybody else.

Except … no.

Now at this point, you can either criticize the movie for breaking its own rules, or admire it for having the balls to say that what the characters (and the audience) THOUGHT the rules were weren't actually the rules at all. "Primer," for all its mind-bending nonlinearity, sticks relentlessly to the point of view of its two main characters. The film sets up rules for time travel that make perfect sense (if you have an advanced degree in physics) because those are the rules Abe and Aaron figure out. Except Abe and Aaron are wrong. Time travel in "Primer" doesn't work at all like what I described above. In fact, while time travel in "Primer" resembles a logical method that's consistent with relativity, the way it actually works flies in the face of not just relativity but even the idea of conservation of energy.

It starts with the phone call.

On one of their "trips," Abe and Aaron are in the hotel room when Aaron's cell phone rings. He was supposed to leave it at home, but he forgot. The guys, after a moment of panic, decide that everything's okay, as long as Aaron does not take the phone back to that morning with him. He lets the call go to voicemail, and they go on with their day.

Except he DOES take the phone back with him, and later that day (in Aaron's reference frame) it rings again. The guys debate whether BOTH phones are ringing, or just the one in Aaron's pocket right then (in their reference frame). They don't know the answer — and according to the commentary track on the DVD, the companies that make cell phones aren't even clear on what would happen in that situation — but Aaron answers the call anyway. It's totally mundane, but it still raises the possibility: What if they changed their own personal histories? In their histories, Aaron's phone rang when they were in the hotel room. But if the phone exists in two places at once, and if it DOESN'T ring in both places, then the fact that Aaron's phone rang later (in his reference frame) means it didn't ring before, except it clearly did in his own history. So … what? Are they dealing with an Einsteinian universe where causality is fixed but simultaneity is an illusion? Or is it something more mysterious? They don't know … but they're no longer sure they understand what's going on.

This is where the movie starts to get complicated. No, seriously. Stop laughing.

It's at this point that the Platt-punching idea comes back up. Earlier in their personal histories, Abe and Aaron (and Aaron's wife) were talking about what they would do if they could act without consequences. Aaron says that he'd punch someone named Platt right in the face. It's never made clear just who this Platt was, but it's obvious from context that he's somebody who wronged Aaron on some level. What Aaron imagines is this: He turns on a machine, later enters it, goes back, finds Platt and punches him, then subsequently stops his earlier (from his reference frame) self from getting in the machine in the first place, ensuring that the trip back never occurs and Platt never gets punched.

Abe tells Aaron they can't do that. It's not clear whether he means they LITERALLY can't, or that they mustn't. It's possible that Abe believes, at this point, that what Aaron proposes is literally impossible, that their time machines don't work that way. (In other words, he's speaking under the assumption that they live in an Einsteinian universe where simultaneity is an illusion but causality is real and fixed; things can appear to happen out of order depending on your reference frame, but effect always follows cause and the past [ANY past, regardless of reference frame] cannot be undone.)

But later, after the phone call incident, it's not at all clear that that's the case. If ONLY later-Aaron's phone rang the second time (in Abe and Aaron's reference frame), then the first call (still in Abe and Aaron's reference frame) never happened; they inadvertently changed their own histories. But the thing is, they don't KNOW that's what happened. Aaron never answered the phone the first time (in his reference frame) it rang, so he doesn't know whether the call was also, simultaneously (in the universal reference frame) ringing his phone later (in his reference frame).

That's when Abe gets the idea to do an experiment. After one of their stock-trading adventures, he goes back to the U-Haul and turns on both boxes. He does this specifically so they can do an experiment with causality. He comes to Aaron's house in the middle of the night and tells Aaron that the boxes are running, and they decide what the hell, to give it a shot. They leave to go to the U-Haul place and screw around with time.

Except they never get there, because they see Granger. Granger, a wealthy businessman and Abe's sort-of girlfriend's father, found one of the boxes that Abe started and uses it to go back in time. Remember how I said the stuff we see on screen is just a fraction of the events that happen in the story? We NEVER see this, or even any hint of it, in the film. We have absolutely no idea how Granger found the box, or when. It could have happened at virtually any point in the indefinite future, as long as the box Granger used was running continuously from the time Abe turned it on. (It's not even entirely clear just WHICH box Granger found, which I'll get to in a minute.) We also are never told WHY Granger used the box … but hints are provided that lead to a pretty comfortable assumption which I'll explain later.

Anyway, Abe and Aaron, on their way to the U-Haul, see a Granger that's obviously traveled in time. They chase him, but he falls into a coma for no apparent reason. It seems clear that Granger didn't stay in his box until it turned itself off; rather, he got out early (in his reference frame), while the box was still running. This has an unspecified but detrimental effect on anybody who does it; this is established earlier in the film when on Aaron's first trip he messes up the timing slightly and gets hurt by it. So now there are two Grangers simultaneously (in the universe's reference frame), and one of them is in a coma, perhaps permanently.

It's at this point that Abe says enough.

I'm gonna talk now about the failsafe box.

Again, what happens on screen is just a fraction of the events of the story. What we see is that Abe figures out how the machine works, builds a larger version and uses it, then spends his second pass through his day giving Aaron his big demo. What actually happens is that, unseen and unmentioned until later in the film, Abe constructs another box and sets it up in another unit in the storage facility and turns it on. This is his failsafe box. Once that box has been turned on, at any point in the future Abe can go back to it, turn it off and climb inside, emerging at the moment the box was originally turned on. He turns this failsafe box on before he does anything else related to time travel, theoretically giving him the chance to go back to before-the-beginning and change events if anything bad should happen.

Even at the beginning, Abe knows — or at least suspects — that all that stuff I said before about illusory simultaneity and fixed causality — everything Einstein ever assumed, in other words — is bullshit. At the very least, he wants to be prepared just in case.

The moment when Abe turns on his failsafe box represents a fixed point in time and space in the film. We have no idea when it happens — it's never depicted — but we know it happens before Abe tells Aaron about the machine's properties. This box is the first one that ever gets turned on — the first human-scale one, that is. It is, therefore, the earliest point in time to which anyone can ever go back.

So Abe, freaked out by the Granger incident and (perhaps more so) by how close he and Aaron came to deliberately fucking with causality, decides to use the failsafe box, go back in time to the morning of the day he first told Aaron about the machine's properties, and reset everything.

His plan is to go back, find his earlier self (relative to his reference frame), knock him out with gas to, then take his place and meet Aaron in the park and NOT tell him about the machine. It almost works, too. Except when Abe gets to the park, he's completely exhausted, having spend DAYS in the failsafe box "riding" back. By the time he meets Aaron, he can't carry on, and he collapses.

And that's when the REAL twist comes: We learn that Aaron has also somehow traveled back in time. He's been listening to recordings of previous conversations on his earpiece.

Let's switch gears and talk about Aaron's story, because — no, seriously — it's the most complicated of all.

Abe tells Aaron about the machine's properties, just as we see in the film. He shows Aaron the box he'd used to go back in time. He does NOT show Aaron the failsafe box. Sometime later — we have no idea when, relative to any reference frame — Aaron discovers that Abe had rented two storage units at the U-Haul. He goes into the second, secret one and discovers the failsafe box, running. He figures out that Abe put it in place in order to have a way to go back to before the beginning.

Now, this part we know: At some point prior to Abe's use of his failsafe, Aaron uses Abe's failsafe box. What we don't know is when or (entirely) why. But again, we're given enough clues to suss it out, although they're presented so tangentially as to be practically baffling at first. It's all related to the party, Rachel, Will, the shotgun, and maybe even somehow the Granger incident.

I'm gonna tell this from Aaron's reference frame. When I use words like "before" and "after," I'm speaking in terms of Aaron's subjective experience.

We know that three events took place, but we have no clues as to the order of those events (in any reference frame) or the causality of them. We know that Aaron discovered Abe's failsafe box; this is one of the few turning-point events in the story that's actually shown on screen, God bless America. We know that Aaron uses Abe's failsafe machine to go back and establish his own, separate failsafe machine. And we know that something bad happens at a party.

Aaron's use of the failsafe machine looks like this: He builds and collapses two boxes and enters Abe's failsafe box with both of them. He emerges from Abe's failsafe box when Abe turned it on, back before the beginning. Abe's failsafe box is now not usable again; once the box has been turned off (in the objective future), the timelike curve is closed, and it can't be turned on again without creating a new timelike curve. So Abe's failsafe box is, for all intents and purposes, destroyed.

Aaron sets up one of the two boxes he brought back with him and puts it in place of Abe's failsafe box. He sets up the other box somewhere else; that box becomes Aaron's private failsafe box. He turns on his own private failsafe box first (because he wants to be able to go back in time farther than anyone else), and then minutes or hours later turns on the new box that replaced Abe's failsafe box. This new box is the one Abe takes back later, believing it to be his own failsafe box that he set up.

Aaron now goes to his own house and spikes the milk he'll later use on his cereal with propofol. He waits around until his earlier self has breakfast, at which point he (his earlier self) passes out. Aaron then hides his earlier self in the attic and takes his place. He wears an earpiece under the pretense that he's listening to March Madness games, but he's actually recording the day's conversations. Aaron is thinking ahead: he knows that he might need to go back and relive these events at some point in his personal future.

The upshot? The Aaron that Abe meets in the park for the first time (in Abe's reference frame) has already traveled in time at least once. And possibly many, many times.

Now, about this party. The party is an oddity in the film; it's barely depicted at all, and only discussed directly a couple of times. But it remains the crux of the whole story.

Everything I've said so far I'm fairly, not totally but fairly, confident about. It's all more-or-less explicitly supported by the events we see on screen. But this part I'm basically making up. I think it fits the story, but I don't think much of it is EXPLICITLY supported by the film itself.

I think the party happens for the "first" time (relative to any of our time-traveling characters) before Aaron first uses Abe's failsafe box. It's not clear to me whether it happens before or after Aaron DISCOVERS Abe's failsafe box, but I think it happens before he actually USES the failsafe box. In fact, I think Aaron uses Abe's failsafe box because of the party.

The first time (relative to any of our characters) the party happens, the sequence of events goes like this: Aaron invites Will to the party. Will shows up with a shotgun. Something bad happens, maybe even something fatal. Aaron, horribly guilty because he invited Will to the party in the first place, decides to use Abe's failsafe box.

Aaron goes back, does all the stuff I described above, then goes to the party again, this time with foreknowledge. He tries to create a different outcome.

And here's the good part: We have absolutely no idea how many times Aaron does this. He can use the fold-up-a-box-and-take-it-back trick basically indefinitely, each time giving himself another chance to loop through events again. There's even a line in the film that alludes to this.

Eventually Aaron loops through the party events a sufficient number of times to become the hero. But the outcome isn't optimal. In any case, for reasons never explained, Aaron stops looping through the events of the party — maybe he just grows weary of it — and goes back to the stock-market stuff with Abe. Right up to the Granger incident.

After Abe panics and uses what he thinks is his original failsafe machine — in actuality, the original failsafe machine is long gone, used up by Aaron and replaced the first time he went back to correct the events of the party — he encounters an Aaron who's on at least his third pass through the events of that day. (The first time through, he experienced events for the first time; the second time, he recorded his conversations. Since he's listening to playback of that recording when Abe meets him post-failsafe, we know it's at least his third time through that day, and maybe more. He's been time-traveling an indeterminate number of times in order to change the Rachel incident.)

Because Abe failsafed back to before the events of the party, Aaron has no choice but to traverse those events again. This time he inducts Abe into his conspiracy, and they concoct a way to get the shells out of Will's shotgun before he takes it into the party. They succeed, Will goes to jail.

Now there are two Abes and two Aarons; there's the Abe and Aaron who went to the party, and there's the Abe that's locked in his apartment, and the Aaron who's locked in his attic. It's at this point that Abe and Aaron have the airport conversation we see toward the end of the movie. Aaron decides to leave; we're never told where he's bound. Abe stays to prevent the original versions of the guys from ever building the machine in the first place.

Movie ends.

Except … that's not it. I've left out one thing, and it's fucking huge.

Let's talk about Aaron again. Aaron finds Abe's failsafe box, is inspired (I think by the Rachel incident) to use it. He goes back, drugs his earlier self and hides his earlier self in the attic. But then another Aaron shows up! What the hell? Where did this Aaron come from? This Aaron used his OWN failsafe after Abe decides to use (what he thinks is) his original failsafe.

For sake of clarity, I'm going to call this Aaron "older Aaron," because he's literally older, subjectively; he has experienced more time. I'll call the Aaron who drugs the milk "younger Aaron," because he is. The Aaron who drinks the milk we don't care about, because he gets locked in the attic for the rest of the story.

So why did older Aaron use his failsafe? This might actually be explained in-film, but if so I've never caught it. Maybe he thinks Abe might somehow "erase" him by changing the past, even though we've seen no evidence that time works that way. Whatever his reason, older Aaron decides, after Abe panics, to use his failsafe to go back to the beginning.

Younger Aaron (who used Abe's original failsafe box) goes back and spikes the milk, with the intention of taking his earlier self's place. Older Aaron (who used his own failsafe box, which was set up and turned on by younger Aaron) catches younger Aaron just after the act. They struggle. Younger Aaron subdues older Aaron, but after they talk, older Aaron convinces younger Aaron to leave and let older Aaron impersonate his earlier self. Older Aaron has already experienced all the events of the story so far; older Aaron went back in Abe's original failsafe box, older Aaron looped through the Rachel incident, older Aaron recorded all his conversations, all that stuff. Younger Aaron hasn't done any of that yet. Younger Aaron has just gotten out of Abe's original failsafe box, and has no firsthand knowledge of any of the events that older Aaron experienced subsequent to his own first trip back in Abe's failsafe.

Older Aaron convinces younger Aaron to leave … and it's younger Aaron who becomes the film's narrator. He makes a phone call to Abe — which Abe, exactly? I'm not certain, but I've got a theory I'll get to shortly — and that phone call makes up the film's narration.

It's also younger Aaron, I think, who we see in the movie's last shot, somewhere in France, building a box the size of a room for purposes unknown. A bigger box could carry more people and things, obviously, but it could also make longer trips back more practical. It's left entirely open-ended just what younger Aaron plans to do. Remember, this Aaron hasn't experienced any of the bad aspects of time travel yet; he may in fact have made only a single trip back, the one time he used Abe's original failsafe. He's a complete loose cannon; there's no way to guess what he's planning.

It's also at this point that we can finally see clearly how time travel in this story works. We have two Aarons now, existing simultaneously from the point of view of the non-time-traveling universe. Except they have divergent personal histories. When Abe and Aaron first started using the boxes, they kept their personal histories strictly linear; whenever two Abes or two Aarons existed simultaneously (in the reference frame of the universe) one of those Abes or Aarons existed in the other Abe or Aaron's past; the Abe in the hotel room was in the immediate and linear past of the Abe trading stocks. But our two Aarons aren't like that at all. One of them used Abe's failsafe, went back, impersonated his younger self and had many time-travel-related adventures. The other used Abe's failsafe, got his ass kicked by the other one, and decided to leave and go to France. The two Aarons are entirely divergent now, in a way that makes ABSOLUTELY no sense in the context of time travel as I first described it, and as the characters first thought they understood it.

And for the physics nerds in the audience, this is where we can most clearly see the flagrant disregard for conservation of energy. In the first, simpler time-travel paradigm, energy was still conserved despite the illusion of simultaneity. Each time traveler had a straight and linear world line in his own reference frame; he only appeared to be in two places at the same time in the universe's comoving reference frame. But in the more complex time-travel paradigm, we end up with two Abes and three Aarons all existing simultaneously, all with divergent personal histories, none in the linear subjective past of any of the others. In other words, there's no reference frame — Abe's, Aaron's, Aaron's wife's, Granger's, nobody's — in which the personal histories of the characters are linear. There's no coordinate transform we can make, to use math lingo, that would result in only a single Abe or Aaron existing continuously in flat spacetime.

But you know what? Even this isn't TOTALLY crazy, in context of modern physics. The conservation of energy is a theory, one that's generally agreed to hold at the macro scale. But physics is riddled with what appear to be violations of this principle. Hawking radiation is a prime example. Everywhere in space, all the time, particle-antiparticle pairs are constantly popping into existence and annihilating each other. When this happens in the vicinity of a black hole's event horizon, sometimes either a particle or an antiparticle crosses the event horizon (thus disappearing from the universe at large) while its partner scatters off into space. This is how black holes can emit radiation, and it's also a local violation of conservation of energy. General relativity throws the whole notion of conservation of energy into disarray, and the implications are still being worked out to this day.

So from a physics-nerd point of view, we can imagine our two Abes and our three Aarons as being analogous to particles "emitted" by a black hole through Hawking radiation. (This is just a metaphor; it makes no sense literally.) Even though time travelers who appear to exist simultaneously in the frame of reference of the universe SHOULD "collapse" back into a single worldline, they don't have to, and when they don't, another complete individual comes into existence, with his own unique past worldline and his own independent future worldline.

So that's "Primer" in a nutshell. Two guys invent a method of time travel that appears to conform to known and proven interpretations of relativity, but in fact it doesn't. It has its own rules, inconsistent with the theory of closed timelike curves. The two guys discover this the hard way, and in the end three instances of one character exist and two instances of the other. At the end of the movie, the older instance of one character vows to stop the "original" two characters (the two subjectively youngest) from inventing the time machine in the first place, while the second-oldest instance of the other character goes off to build another, bigger time machine for reasons never elaborated upon.

Now, I've attached a purty pitcher. Lemme walk you through it. (Available for download here.)

Follow the blue arrows. That's Abe's worldline. His first trip through time is when he does his "demo day" for Aaron; he gets into box 1 at the end of the loop, travels back to the start of the loop, exits the box and then spends the day showing Aaron how the boxes work.

Then he and Aaron do three days of stock trading, each time with Abe in box 1 and Aaron in box 2.

After the Granger incident, Abe decides to take his failsafe box back to the beginning. Unbeknownst to him, Aaron has already replaced his failsafe box (box 0) with a new box (box 4). He takes box 4 back to the start of its loop, gases himself and impersonates his younger self. At this point, Abe's personal history changes; the older Abe was never gassed and stuffed into a closet. So now there are two Abes, each with independent personal histories. One goes on about his life none the wiser, except for having been knocked out and locked in a closet inexplicably. The other one (who is our original Abe, from the beginning of the story) apparently works to prevent the time machines from ever being used, or at least that's what he says during the airport scene.

Abe's worldline is by far the simpler one.

Now trace the red one; that's Aaron's. He doesn't travel in time for the first time until after Abe already has. He takes his first trip the first day he and Abe trade stocks. Sometime after this first day-trading adventure — shown here between the first and second trading days, but the exact sequence is indeterminate in the film — Aaron discovers Abe's failsafe box, box 0. He takes it back to the beginning, bringing boxes 3 and 4 along with him. He sets them up, then goes to drug himself. This is the first of two events in which Aaron's history diverges. Aaron hides his unconscious younger self in the attic and impersonates him.

At this point, things get really INCREDIBLY complicated.

We're now at the spacetime event on the diagram labeled "Aaron convinces his younger self to leave town." At this point in Aaron's personal history, he has just taken box 0 back to the beginning of everything and drugged his younger self. But now he meets another, older version of himself, one who's just taken box 3 back. This version of Aaron is in our Aaron's subjective future; he has not yet become this Aaron. But there he is. The two Aarons fight, then talk. The older Aaron (the one who emerged from box 3) convinces the younger Aaron (from box 0) to leave town. The younger Aaron does, going to France where we see him at the end of the film. But in affecting this sequence of events, the older Aaron (from box 3) manages to alter his own past. Because he WAS the younger Aaron from box 0; he remembers drugging his younger self and impersonating him. Those events transpired in his subjective past; they're part of his personal history. Only now those events are prevented, because he has just talked younger Aaron from box 0 into leaving the country.

Now remember, there is no indication in the movie that there's anything like "meta-time." It makes no sense to refer to spacetime events happening more than once. We can imagine that the "first time" Aaron passes through this event there is no older Aaron there, and he goes through with his plan for impersonating his younger self, then later goes back to that event a "second time" and changes it. But this is simply nonsense; time doesn't work that way either in the movie or (as far as we have any reason to believe) in real life.

Some folks on the Internet have gotten around this by subscribing to the many-worlds interpretation of quantum mechanics. Whenever anyone uses one of the boxes to travel through time, a parallel universe is created where the same events can have different outcomes. This is lazy, to my mind. No, the proper solution to this puzzle is to embrace ambiguity. The spacetime event labeled "Aaron convinces his younger self to leave town" must — by the rules of the film — be a superposition of different outcomes. One outcome is that the Aaron from box 0 never appears, and the Aaron who's never traveled in time goes on to meet Abe and learn about the boxes. Another outcome is that the time-virgin Aaron is drugged by the Aaron from box 0, and the Aaron from box 0 goes on to meet with Abe for what is for him the second time. A third outcome is that the Aaron from box 0 is interrupted by the Aaron from box 3, who convinces the Aaron from box 0 to leave town.

All three of these things must result from the spacetime event labeled "Aaron convinces his younger self to leave town" on the diagram. All three things must happen. Which one a subjective individual experiences when traversing that spacetime event is a matter of probability, and of which events lie in that individual's subjective past. If Aaron in that spacetime event has none of the other events in his subjective past, the overwhelming probability is that he will not be drugged, and will not encounter any other instances of himself. But if Aaron in that spacetime event has box 3 in his subjective past, the overwhelming probability is that he'll meet Aaron-from-box-0 and talk him into leaving. It's baffling, but it's consistent with both the story we see on screen, and also quantum mechanics.

What would an objective observer have seen at that point in space and time? Well, obviously the superposition of all three outcomes. You'd see Aaron-from-box-0 spike the milk, then you'd see time-virgin-Aaron collapse, then you'd see Aaron-from-box-3 appear and talk Aaron-from-box-0 into leaving. Not coincidentally, this is exactly what we see depicted in the film; in fact, this is the only version of events we see. Which makes sense, because this is the only thing that "really happened," from the reference frame of an outside observer. It is, in a sense, the "final version" of events; the other two outcomes are just first drafts.

So anyway. That's "Primer." At least I think so.

(I didn't do dick today. Obviously.)