"Dude, are you hungry? I haven't eaten since later this afternoon."
Take equal parts pi, startup.com, Memento, The Man Who Folded Himself, The End of Eternity, Donnie Darko, add a little LSD, mix well, and you've got Primer (full title: Primer: What Happens If It Actually Works?)
A movie filmed for only $7,000, Primer is one of those movies that requires repeat viewings. You will not "get it" your first time through, maybe not even the second. Or the third. I myself have seen the movie four times, which is very rare for me, and I can't stop thinking about it even so. The movie requires you to pay attention to details, listen to the dialogue, and speculate on what it is you're really seeing. There's a lot of geekspeak, but that's just babble, usually meant to divert your attention.
As the movie begins we're introduced to 4 geeks who are trying to bootstrap a new hi-tech company out of a garage. They're not doing so well--none of them have quit their day jobs--but they've got some new ideas. Our two main protagonists, Aaron and Abe (I believe the two names are deliberately chosen to confuse the viewer) have an idea that they're keeping separate from their two partners.
It seems that whatever product they're working on is difficult to manufacture. At first. They're trying to make a way for, I think, ceramic to become lighter, using a process which can be done at near room temperature.
As these entrepreneurs follow their ideas down what seems, at first, a logical path, they begin to notice some strange anomalies. The machine they've constructed seems to be generating more power than what it's drawing from two car batteries. Eventually, the machine runs by itself with no visible power source, for a couple of minutes.
Then Abe notices that there's some kind of protein buildup on the ceramic Weeble they're using as a test object inside this machine. On his own (or so we're led to believe) he investigates what this buildup is.
What he discovers is amazing. The protein, in and of itself, is a common fungus, one that is omnipresent in our lives. It's the amount that's built up that makes every lab technician look at Abe like he's crazy. This Weeble is staying in the machine, off and on for five days at a time. The amount of fungus built up, though, is as if the Weeble were in the machine for five years.
It's never explicitly stated, but Aaron and Abe have built something that has an effect on time itself. They realize they've gone far, far, beyond their own capabilities and knowledge.
"We can publish."
"Yeah, we can publish."
Aaron and Abe, inquisitive by nature, realize that, somehow, objects inside this machine get trapped between the ticks of the clock, and while an inanimate object always comes out in the present, an intelligent object could, theoretically, exit the cycle on the "wrong" tick. Coming out ... in the past.
Abe, or so we're led to believe, takes the initiative and builds a coffin-sized machine, travels one day back into the past, meets up with Aaron and tells him what he's done. Aaron, dubious at first (or so we're led to believe), asks Abe to walk him through his entire day. So that's what Abe does, up to and including having Aaron watch an analogue of Abe ... Abe from a different timeline doing things that the Abe the viewer is following has already done.
From here on out, things, timelines, your subjective opinion, and what's really happening become very confusing. Both Aaron and Abe begin toying with the machine without, or so we're led to believe, the other's knowledge. There comes a point during the film (probably during your second or third viewing) that you are no longer sure at any point in the movie which "copy" of Aaron or Abe you're following at any one time. Timelines intersect. Multiple copies of these two guys are running around, interfering with what prior copies have done. Something in one timeline causes something "bad" to happen, and Aaron and Abe (or analogues thereof) begin traveling further and further into the past in an effort to get the drop on the other, to effect change on the timeline before whatever changes the other has made will have taken place.
"I mean, we're not talking frame-dragging or wormholes here, this is basic mechanics and heat 101.
"This is not mechanics and heat."
That's where I'll leave you, dear reader, to watch the movie. I don't want--I can't, really--to spoil you too much further. Even after four trips, emphasis on trip, through this strange little film I can only tell you what I think is happening. The movie defies conventional, chronological, or even linear, storytelling devices, making viewing this film extremely subjective. Is Aaron deceiving Abe? Or vice versa? How does the original "coffin" get built so "quickly" by only "one" "person"? Is Aaron4 is trying to change Aaron3's mind? What's in the attic, making that sound? What happens if you collapse one of the coffins, put it into another one, and send it back? If you're one of those geeks that watched all three Back to the Future movies to figure out how many analogues of the DeLorean there were at any one point in time, this movie will provide you a much greater challenge, I assure you.
"There's been no reason to show you what I'm capable of...but I'm telling you this now. Go out there. Do whatever the hell you want. There's no way in the world I can stop you. But don't come back here...and don't come near them. Any of them."
Memory is not history.
Reality is not truth.
Only the last revision counts.
Apparently.