After tornadoes struck the U.S. in 2011, University of Georgia students and geography professor John Knox used Facebook to track the distance that debris was carried by the storms. One piece of debris traveled 220 miles; multiple other items were carried more than 100 miles each. The study could have important implications if a future tornado were to pick up nuclear waste or some other hazardous material. "[S]omeday we may be worried about material falling from the skies that could cause harm," Knox said. "And we want to know in advance, where in the past these sorts of objects have landed."