AN EARTH-SIZED PLANET, bearing the exact blue-and-white swirls of our own globe, appears in the sky in writer/director Mike Cahill's Another Earth. It hovers there like an oversized moon, a mirror of our planet hanging in space. No explanation is offered for its presence, nor is any screen time devoted to scientific inevitabilities like gravitational impact—sure, the sudden materialization of an Earth-sized planet coming so close to our own would have cataclysmic effects, but that's not Cahill's point.
Later in Another Earth, there's a scene in which a scientist establishes radio contact with the other planet, which people begin calling Earth Two. Through a fuzzy, squawking transmission, the scientist realizes, chillingly, that she is, in fact, talking to herself—a complete, alternate version of herself living on the planet that seems to be identical to Earth in every way. This is a terrific premise for a science-fiction film, but Another Earth isn't that film. The scene is riveting, but the scientist is a minor character, and the film's sci-fi elements are a mere clothesline upon which the filmmakers hang their sad, small drama about Rhoda (Brit Marling, who co-wrote the screenplay with Cahill).
On the night of Earth Two's first appearance, Rhoda has had a few drinks. She's just graduated from high school and has been accepted to MIT. Racing along in her car, she peers out the window at the strange new thing in the sky, and then promptly plows headlong into the car of John Burroughs (William Mapother) and his family. John's wife and baby are killed in the crash; Rhoda goes to jail, and Another Earth picks up after her sentence and release.
Rhoda tracks down John—keeping her true identity secret, even though John doesn't seem to care, really, since he's turned into a total mess after the accident—and the two begin to slowly and tenderly heal one another. It's your standard indie drama, rendered in cool blues and arty-grainy video stock; Cahill's as interested in suspended flecks of dust catching the light as he is in his two solid lead actors. Meanwhile, Earth Two hangs tantalizingly outside the window—hinting, all the while, at a much more interesting story.