You could power the world for a year by capturing the solar energy that falls on the world's deserts in just six hours -- or, more practically, achieve the same goal by erecting solar plants covering just 4% of the world's deserts. Doing so would be technically challenging but is possible using existing technology, experts say. "From the technical side, I think we can do it. In fact, I know we can do it," says solar researcher Seth Darling.

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