In Primer, why aren’t there six Aarons?

Question

At the end of Primer, we know that

there are 3 permanent Aarons: the one in the attic (“Primer” Aaron), the one who left (“Hooded” Aaron), and the one who goes through the story (“Earpiece” Aaron).

“Primer” gets locked in the attic, thus “Hooded” (and later “Earpiece”) wouldn’t be able to exist if — like in most on-screen time-travel — he needs to enter the fail-safe again on the second Thursday, especially considering that Hooded leaves and can’t go back to create Earpiece.

Therefore you must conclude that if Aaron enters a box in timeline A, there are two Aarons in timeline B, whether or not Aaron A enters the box in timeline B.

If so considering, that Primer definitely entered the box between Tuesday and Thursday in timeline A, and Earpiece in timeline C, then in timeline D (the one where they both use the fail-safe) there should be six Aarons from 9-5 on Tuesday-Thursday (and three Abes): Primer (1), Primer B (2), Hooded (3), Earpiece (4), Earpiece B (5), and the final incarnation (6).

So, if they exist, where are these six Aarons?

Answer 1

It's made pretty clear that in the Primer "universe" that a loop can only exist if someone both enters and exits a box. Although there are (at one point) six Aarons existing simultaneously, only three of them will ultimately continue to exist by the end of the film. The other three are either earlier iterations of the "Prime" Aaron or dead-end loops (in one case literally) that will simply disappear when the final loop is collapsed.

Although there are a number of differing timeline diagrams you can refer to in order to "help" you to understand the various timelines created and destroyed, the reality is that they're all based on massive assumptions of what's happening off-screen before the start of the film and during the film when we're following other characters.

There's also a very detailed (and largely canon) explanation of the plotline here. Be prepared to go completely cross-eyed trying to work out what's happening in each sequence though...

Answer 2

In Primer, you can't change the past, the only thing you can do is prevent something from happening again in a different (later) timeline.

That being said, if Aaron doesn't travel back in timeline B, he won't be there in timeline C, but there will still be two of him in timeline B.

And to stretch this a bit more, if Aaron A doesn't travel back in timeline B, then even after the point where he traveled back in timeline A, there will still be two Aarons, to demonstrate:

Timeline A:

• Monday: nothing
• Thursday: travel back to Monday
• Friday: no Aaron

Timeline B:

• Monday: Aaron B arrives, Aaron A: nothing
• Thursday: Aaron B - nothing, Aaron A doesn't travel back
• Friday: 2 Aarons

Answer 3

So essentially a traveler does not “wink out” of existence if his double decides not to enter the box.

E.g. Aaron 1 enters a box in the afternoon and comes out in the morning as Aaron 2. Aaron 2 then waits until the afternoon and watches Aaron 1 arrive at the box and tells him not to enter. If causality is preserved then Aaron 2 should not ever had existed, but in the movie apparently he can. If Aaron 1 then resets the box waits a few hours and gets in, creating an Aaron 3, the process can repeat itself with Aaron 1 “spawning new Aarons over and over.