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.

As Interstellar opens, the problem is food and dust. Not enough of the first, and too much of the second. And while it's unclear what's generated all that particulate matter -- perhaps a strike by the International Housecleaners Union -- there's ample implication that uncontrolled climate change has turned our planet into a global reprise of the dust bowl. Growing food has become the career of choice -- indeed of necessity. STEM education is out, Future Farmers of America is in, and the only crop that can still be raised is corn. It's hard to ignore the fact that this is the very foodstuff abundantly available in the theater lobby, if you can afford it.

So our kids have somehow let the environmental rot reach the stage where no one can take it -- so they'll have to leave it. That's probably unrealistic, as it would require less time to fix what ails us than for Earth to become a planet-wide Black Hole of Calcutta. But there's little doubt that in the real world, life will eventually get tougher. There are only so many natural resources within easy reach on this planetary ball -- and I'm not talking oil; I'm talking harder things to replace, like copper, zinc, or platinum. In less than a century, many of these essentials will become so costly, burglars will break into your house, leave the big-screen TV alone, and rip the copper pipes out of the wall.

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