The best science fiction films are only part fiction. The characters and locales are made up, but the themes are rooted in real human emotions and problems.

That’s the kind of film that Duncan Jones has made with Moon. His feature-length debut follows an astronaut named Sam (Sam Rockwell) living alone on a moon base. His mission is to mine a precious gas that could hold the key to Earth’s energy shortage. He lives in isolation during his three year contract, which is almost up. The only company he has comes in the form of taped video messages from his wife and daughter on Earth and some unfulfilling chit chat with the base’s housekeeping robot, GERTY (Kevin Spacey).

As the the end of his contract nears, someone does finally show up. But the new guy isn’t all that new. In fact, he looks just like Sam (mostly because he’s also played by Rockwell). Is he a clone? Where did he come from? And does the new guy have the veteran’s best interest in mind? All these questions are answered as the story unspools, but they all serve to pick at a larger idea.

“The question that the movie is asking is: If you met yourself, would you like yourself,” says Rockwell the day after the film screened at last month’s South by Southwest Film Festival.

That question is really one for the audience to answer. Jones and Rockwell were more concerned with how they would honor previous sci-fi films without ripping them off, and how can one actor best play two roles?

Rockwell took the lead in exploring the second. He says before shooting he spent days with an actor friend running through the scenes that he would eventually have to play alone. When a scene was finished, they’d switch parts to allow Rockwell to come at it from the opposite angle.

“It was infinitely challenging – technically, viscerally – it was like a math problem every day,” he says.

The actor and director also prepared by watching a slew of sci-fi movies, particularly ones that deal with the isolation of space. Among the choices were Silent Running, 2001: A Space Odyssey and Solaris. Moon has touches of all of those films in it but manages to maintain a level of originality.

“What keeps it from being a greatest hits [movie] is we had this core story we wanted to tell that wasn’t present in other films,” says Jones, also known as David Bowie’s son.

Before the second Sam shows up, Moon keeps a pretty slow pace. And it doesn’t have much in the way of laser beams or alien sightings – this isn’t Star Wars. But without all of that clutter, there is room to contemplate the question at the film’s center. If you don’t like having to do all that thinking, don’t worry. A summer full of mindless blockbusters is just around the corner.

Moon screens Thursday at 8 p.m. at NorthPark. It is scheduled to open this summer.