Superman had x-ray vision, which was useful for looking through walls when rescuing heroines and collaring villains. But beyond Holly wood, the best that engineers have been able to come up with to see inside buildings are devices that use radar. Some are portable enough to be placed against an outside wall by, say, a police unit planning a raid-and sophisticated enough to show, with reasonable accuracy, the location of anyone inside. But the best models cost more than $100,000, so they are not widely deployed. Now a team led by Neal Patwari and Joey Wilson of the University of Utah has come up with a way to peer through the walls of a building using a network of little radios that cost only a few dollars each.
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