What kind of engineering background do you have?

I studied math and computer science in college, and even started a graduate program in math, but I quit after a few days, because I realized it was going to be difficult to do my own research—I would be doing a lot of other people's research.

An entrepreneurial spirit took over, and I felt that whatever I did was going to be on my own terms, so I decided to make some money and apply that toward whatever venture I chose. I started writing software in C and C++ for a flight simulator at Hughes Aircraft and then got into Web work. I did back-end database design and then started consulting.

How did you end up becoming an independent moviemaker?

All this time I was writing, and as time went on, my writing veered more and more toward a screenplay format. I realized that writing a screenplay and turning it into a movie was the thing I was going to try and do. I continued working to save up cash, and when I thought I had enough, I quit.

Did you have an engineering-oriented movie in mind from the beginning?

I always knew thematically what the story was going to be: it was going to start with two guys that were close at the beginning and then, because of the introduction of power, they would not be close by the end. But the setting came about because I was reading a lot of nonfiction books about the history of the transistor, of Bell Labs, of calculus, of the number zero, and so on. There seem to be many commonalities between [these stories]. What really happens in innovation is that nobody knows exactly what they're doing; they're just kind of pulling pieces together. I wanted to see that play out in my movie.

Are the characters based on people you know?

Not specifically. It seems that everybody I know in Dallas has a day job but aspires to something else on the side, some kind of entrepreneurial venture. That's where these guys come from.

There's a lot of technical conversation in the movie. Were you worried general audiences would be turned off by the jargon?

I've had some former engineers who are now in the film world come up to me after a screening at a festival and say something along the lines of "I can't believe you have all that engineering in your film—I don't know who you think would get any of that!"

But those scenes that are jargon-heavy are written with a couple of purposes. I really did want the science to be something I believed, but at the same time, even if you can't understand a word of the jargon, the scenes make sense in that there's also information in there about the politics of the group.

If people are into the jargon, they'll appreciate it, and if not, they're still going to get something out of it. Whatever the subject matter is, if you handle it authentically, people recognize that, even if they're not part of that world.

The time machines in Primer are much more limited than most science-fiction time machines. The characters can't use a machine to go back to a point in time earlier than the moment a machine is first turned on, for example. Where did you get the idea for the machine's operation?

I knew that I wasn't interested in doing the kind of time travel where you can arbitrarily jump around—that however Primer's machines worked, it was going to be something that you paid a price for. If you wanted to go back in time six hours, you had to experience every minute of those six hours as the machine sent you back in time. And the science is a lot more realistic this way because if you could just jump back 24 hours, you'd find yourself in empty space. as the Earth would be a day back in its orbit.

The threads of the two main characters' lives begin to fray as overlapping time travel loops begin to shred their—and the audience's—ability to distinguish between past, present, and future. Is it possible to reconstruct a linear narrative from the chaotic events of the movie's second half?

It all makes sense; all the information is there—except for one thing. There's no explanation in the film of how Granger [a minor character] gets to a time machine. That's because the main characters don't have any way of knowing either: it's something that lies in their future.

I chose to make it obtuse because then the audience shares the position of the main characters, of wanting to know something very badly and finding themselves for the first time in someone else's past. The two main characters both react a little differently to this situation, and that spurs the disintegration of their relationship. But everything else is in there.

What's next after Primer?

If I get to make another film, I think it will be a romance with no science in it! However, I do have other stories with elements of science that I feel strongly about telling. But if I'm fortunate enough to make all these stories into films, I would love to be able to go back to math and do some research.

Nonlinear dynamics is huge for me; it's the kind of thing that I think is most applicable to where we are right now. Solving combinatorics and many-body problems—just understanding the recursive nature of all these types of problems—is something that I believe is going to be important to our species' next big step in understanding.