American Prometheus

by Kai Bird

ON SUNDAY, JANUARY 29, 1939, Luis W. Alvarez—a promising young physicist who worked closely with Ernest Lawrence— was sitting in a barber’s chair, reading the San Francisco Chronicle. Suddenly, he read a wire service story reporting that two German chemists, Otto Hahn and Fritz Strassmann, had successfully demonstrated that the uranium nucleus could be split into two or more parts. They had achieved fission by bombarding uranium, one of the heaviest of the elements, with neutrons. Stunned by this development, Alvarez “stopped the barber in mid-snip, and ran all the way to the Radiation Laboratory to spread the word.” When he told Oppenheimer the news, his reply was, “That’s impossible.” Oppenheimer then went to the blackboard and proceeded to prove mathematically that fission couldn’t happen. Someone must have made a mistake. But the next day, Alvarez successfully repeated the experiment in his laboratory. “I invited Robert over to see the very small natural alpha-particle pulses on our oscilloscope and the tall, spiking fission pulses, twenty-five times larger. In less than fifteen minutes he not only agreed that the reaction was authentic but also speculated that in the process extra neutrons would boil off that could be used to split more uranium atoms and thereby generate power or make bombs. It was amazing to see how rapidly his mind worked. . . .”