One of the best things about Another Earth is that, without making a big deal of it—I don't think writer-director Mike Cahill could show off even if he wanted to—it's genuinely unpredictable.
It's a movie about the discovery of another planet, identical to ours, whose inhabitants and lives are exact reflections of us. Each person on Earth has a corresponding twin on Earth II, who's led the same life and made the same mistakes. This premise is loaded, and Cahill exploits it by circling the ramifications instead of confronting them. The primary focus of Another Earth isn't the human response to this discovery, but rather a series of housecleaning visits.
Rhoda (Brit Marling, who co-wrote the script) has just been accepted to MIT when she makes a serious mistake that lands her in prison. Simultaneously, DJ Flava announces on the radio that another planet has been discovered. Funneling such a grand announcement through a generically named radio personality is no accident: Part of the movie's unpredictability comes from how low-key it keeps the nature of most of the happenings. Revelations never come across as earth-shattering, even though there are now twice as many earths to shatter.
Beginning after Rhoda's four-year prison sentence, Another Earth chronicles her attempts to make up for her misdeed (that's where the housecleaning comes in). Earth II hovers in Rhoda's consciousness as an escape, or maybe an answer, but it doesn't alleviate her feelings of guilt. Her need for forgiveness, or at least confession, is ostensibly the emotional center of the movie, but it's limp and unsurprising. Still, the way Cahill charts the uneasy relationship between everyday life and the limitless possibility hinted at by a parallel world more than makes up for it.
By only occasionally treating the discovery of Earth II directly, Cahill captures a strong atmospheric sense of how such a discovery might make us feel. If the main characters were NASA experts or astronauts, our response to the discovery would be filtered through people for whom the major repercussions are professional, scientific and philosophical. Instead, we follow people who find personal meaning in the discovery, even if they're not sure what that meaning is.
Any movie that has a line of dialogue that begins with "In Plato's allegory 'The Cave' ..." is bound to look a little sophomoric and too serious for its own good at times. Indeed, there's an overall problem with ponderousness here, in Marling's frowny performance, the movie's drab palette and the snippets of philosophy superfluously provided in voice-over from a to-be-identified source. (The premise is enticing enough for viewers to mull over without being told to do so.) Amusing touches are sprinkled in, mostly in the shape of eccentric responses to the discovery of Earth II, but they feel more like afterthoughts than tonal or thematic decisions. Another Earth is modest and earnest enough for all this to remain a small problem, but it's a bit too dry for a movie in which the words "space strawberries," scrawled on a sheet of notebook paper, constitute a major plot point.
The pace is slow; Rhoda walks to work, waits for the train some nights, lies around in her room. Earth II hangs in the sky as a looming presence, but not necessarily the dictator of the action. In spite of this—no, because of it—we can't stop thinking about Earth II. For the most part, the movie gives you space to ask tantalizing questions as you watch. Is it possible that the film is in fact cutting back and forth between activities on Earth I and Earth II? How would we know the difference? Should we call them aliens if they are us? Isn't that the opposite of alien? At times, the small quotidian details of the film can be hard to follow because the (mostly) unspoken questions are so huge. "It's too much," one character says, trying to think of a way to talk about how he feels about it. Thankfully, he stops there.
The whole thing feels tangibly, spookily possible. In its feel and treatment of premise, which plays a tiny bit with the idea that one planet could be a psychological projection of the other, this small film recalls Andrei Tarkovsky's more ambitious Solaris, and it's to Cahill's great credit that his film doesn't buckle under the comparison. Like his characters, Cahill doesn't have any great insights about what the existence of Earth II might mean, but I'm not sure that he needs any.