Could Earth really get so bad that we have to leave? That's the premise of Interstellar, the sci-fi epic of Homeric ambition and eonian length now filling the multiplexes.
Environmental decay is a familiar idea in space opera, although one that Interstellar has refreshingly turned around. In countless predecessors, from War of the Worlds to Oblivion, an alien planet goes haywire, driving the inhabitants to invade ours. Now it's Homo sapiens' turn to seek new turf.