The only person ever to win two Nobel Prizes in physics, Bardeen deserves special regard not only from the scientific community but also from consumers who use products arising from his work, including "boom-box" radios and desktopmicrocomputers. Bardeen's invention of the electrical transistor opened thedoor to today's electronic age, and his research on the phenomenon of superconductivity is now being used to develop more powerful computers and artificial intelligence. Born in Madison, Wisconsin, Bardeen earned his bachelor's degree in electrical engineering at the University of Wisconsin. Although he didsome graduate research, he left school to work for the oil industry as a geophysicist in Pittsburgh. After a few years, however, the attraction of pure science lured him to Princeton University, where he was awarded a Ph.D. in physics and mathematics in 1936. There he was introduced to the rapidly developing field of solid-state physics--the study of electronic devices that controlelectrical current without using moving parts or vacuum tubes. By the 1930svacuum tubes were standard in electronic equipment, but the limitations of these tubes restricted technological advances. Vacuum tubes were bulky and fragile, required large amounts of power, and needed cooling systems to protect them from overheating. Scientists who wanted to develop bigger computers werefrustrated by the huge, complex arrays of tubes and cooling systems that wererequired. To overcome this limitation, Bell Telephone Laboratories formed aresearch team to develop a solid-state device that could replace vacuum tubes. The most promising replacement appeared to be semiconductors --materials such as silicon and germanium that can either conduct or resist an electrical current. After teaching at the University of Minnesota for two years and working for the U.S. Navy during World War II, (developing new technology for thedetection of enemy submarines), Bardeen joined the research team at Bell Laboratories in 1945. Another team member, William Shockley, had suggested that electrical current could be increased or amplified using semiconductors and metals. When Shockley's tests failed, it was Bardeen who explained theoretically how a semiconductor device works. With the assistance of another researcher, American physicist Walter Houser Brattain , the team conducted groundbreaking experiments on semiconductor technology. By 1947, the team had succeeded in amplifying electrical current with a "transfer resistor," or transistor, that used a germanium semiconductor placed between metallic contacts. The invention of the transistor revolutionized electronic technology, making it possible for scientists to develop much more powerful computers. As a result, Bardeen and his co-workers shared the 1956 Nobel Prize in physics. In 1951, Bardeen left Bell Labs to become professor of physics and electrical engineering atthe University of Illinois. There he performed the research on superconductivity that won him a second Nobel Prize in physics, awarded in 1972. The phenomenon of superconductivity occurs at extremely low temperatures, just a few degrees above absolute zero. At that critical point, some metals completely lose all resistance to electrical current and become " super" conductive. Thiseffect had been discovered in 1911 by Dutch physicist Heike Kamerlingh Onnes(1853-1926), but scientists had been unable to explain it. Bardeen, working with Leon Cooper (1930- ) and John R. Schrieffer (1931- ), developed an interpretation of superconductivity which was named the BCS theory (for the three scientists' initials). According to this theory, electrons can attract one another and form pairs under certain conditions. Zero resistivity, they showed,occurs when there is not enough thermal energy to break the pairs of electrons apart. Using the BCS theory, scientists have greatly increased the operating speed of computers and produced exceptionally small and powerful electromagnets. Bardeen remained on the faculty at the University of Illinois until hisdeath in 1991.