‘Another Earth’ presents worlds of possibilities

“Another Earth’’ was a surprise Sundance favorite this year, taking home the Alfred P. Sloan Prize for the best film on themes of science and technology. Fox Searchlight bought the film for over $1.5 million. It opens here Friday.

“We all have these idealized pathways,’’ says director Mike Cahill, explaining the concept behind “Another Earth’’ during a Q&A after a screening earlier this month at the Coolidge Corner Theatre, “and sometimes your life takes a radical shift. If those two versions of yourself, the one that went down the ideal path and the one that did not, sat down together, it’s not so obvious, necessarily, which one had the better life or the more profound existence.’’

The film’s other Earth introduces the possibility that Rhoda could meet an ideal her, with her radical shift erased. Cahill got the idea by listening to audiotapes of a book by Richard Berendzen, director of NASA’s Space Grant Consortium. (Cahill eventually recruited Berendzen, whose voice he describes as “Darth Vader meets God,’’ to be the film’s science consultant and narrator, as well as to play a scientist character.)

Says Cahill, “We derived a lot of inspiration from science. We were interested in string theory, the idea of parallel universes, and the multiverse. But we bent all those things for metaphor.’’

In a sense, Cahill, 32, and Marling, 28, themselves chose to take the path less idealized. Marling, pretty enough to land superficial roles playing dumb blondes, speaks with intelligence and intensity, her sentences seeming to gain momentum each time she adds an “and.’’

An economics and studio art major at Georgetown, she took a year off after an internship at Goldman Sachs forced her to question her direction. “It became obvious to me that at 45 I would technically have done everything right but also not have lived,’’ she says on a recent visit to Boston to promote the film.

So she escaped to Cuba to work on a documentary called “Boxers and Ballerinas,’’ the brainchild of Cahill, whom she had met her freshman year.