Primer part 3: shot gun party

This is our third installment on Primer, which began with the fundamental mistake the travelers make in trying to avoid changing "history", and continued with the example of the phone call.

The filmmakers make the film challenging in part by sleight-of-hand, introducing a narrator who suggests he is telling the entire story in order, lulling us into believing this is what we are seeing; then he omits parts and restores some later.  The first piece out of sequence concerns a party the night after that first trip Abe makes.  Abe explained things so well that Aaron figured out much more.  Exactly when Aaron knew what is never clear; but on that night Aaron used the machine without Abe's knowledge.

Abe's girlfriend Rachel was at a party.  Her former boyfriend came and waved a shotgun around.  No one was hurt, but Rachel was badly shaken.  Aaron hears about it.  Knowing there is a time machine running that will take him back to before the party, he goes to the party and becomes a hero.  The next day people are talking about how Aaron saved the day.

Eventually Abe discovers how Aaron played the hero for Rachel, and wants to change history so that he can be the hero.  Thus they travel back to attend the party, and Abe saves the girl.

There are two points very troublesome about this.

First, it is fairly clear that Aaron travels to that party once from the same night that it happens and again from a day or so later.  He mentions in the telling (we now know he is the narrator) that he knows what happened the night he was not there, and on the night he was the hero, but that only the last time through, when Abe was the hero, "counts".  There must thus be two versions of Aaron at that party, and the arrival of the second Aaron, with Abe in tow, is going to change history for the original Aaron, who now is going to hear about how Abe intervened.  He has no way to know that this was Abe from the future, or that he came because Aaron had done this once.  History has become terribly unstable; there is no reason for Aaron to travel back to play the hero once Abe has done so, but Abe does so because he learned that Aaron already did.

This is not insoluble, though.  In the original history the ex threatens everyone at the party, and Aaron hears about it.  He travels back and plays the hero, revising history; he later hears what he did at the party, and knows that he must have traveled from the future to do that, so will do so again.  History stabilizes.  Abe hears how Aaron saved the party, and decides to take Aaron's place.  He arrives in the past, and plays the hero, displacing Aaron.  Later that night Aaron will hear about Abe being the hero at the party.  Now he has no reason to make that trip, and he won't.  Thus we have a version of history where neither was at the party, then one with Aaron being the hero, then one with Aaron being there intending to be the hero but Abe replacing him (and Aaron is also there again with Abe, so there are two of him there), then one in which that first Aaron does not come at all.  However, Abe will eventually hear how he was the hero, and he will realize that he has to make that trip to save the day.  History is stable.

But there is the other problem here:  Aaron casually suggests that they repeated the trip several times to get it right.  That means they first (after Aaron's solo trip) traveled back a couple days, then didn't like the way it went so they traveled back a few hours to do it again, and again, and again--and the number of duplicate versions of Abe and Aaron at that party increases each time they try to "get it right", because every previous version of themselves must also be there.  But they will be in each others' way unless they take steps to prevent previous versions of themselves from acting; and if they do that, they tamper with their own pasts and prevent themselves from learning from mistakes they are now prevented from making.

Such a scenario does not work right under any familiar theory of time travel.  We could wonder what Aaron and Abe were thinking, but the real question is, what were the writers thinking?

At some point Aaron decided to make recordings of everything that happened on the day Abe showed him the time travel secrets, probably on this solo trip.  That is our problem next time.