At the University of Alabama in Huntsville, physicists last month placed a chip of a green, brittle compound inside a thermos-like container, doused it with frigid liquid nitrogen and sent an electric current through it. As the temperature dropped, they took careful measurements of the compound's electrical resistance -- its opposition to the passage of current.*
Suddenly, at 93 Kelvin (-292 degrees F), the resistance dropped precipitously. The substance had become a superconductor, able to transmit current with virtually no loss of energy. "We were so excited and so nervous that our hands were shaking," says Physicist Maw-kuen Wu. "At first...
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