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If Fuchs did not give the Soviets the secret of the Teller-Ulam bomb, who did? Hirsch and Mathews suggest that Teller himself may have inadvertently - assisted the Soviets by pushing for an early test blast. The 1952 explosion peppered the atmosphere with a telltale assortment of radioactive debris, including new atomic elements that could have been created only by a compressed fusion reaction. When Hirsch and Mathews asked Bethe if that fallout could have tipped off the Soviets, Bethe instantly said yes. Says Hirsch: "It was as though he had been waiting 35 years for someone to ask him that question."
The Hirsch and Mathews account has received mixed reviews from the surviving members of the Los Alamos team. Carson Mark, who took over for Bethe in 1947, concedes that the U.S. monitored the Soviets' weapons research by examining the fallout from their blasts, but he doubts that the U.S.S.R. could have worked in the other direction, deducing the secret of Mike's construction by studying its debris. Teller and others believe that the late Andrei Sakharov, who built the Soviet H-bomb, was clever enough to have invented the device from scratch, without the help of Fuchs or anyone else.
One participant who welcomes Ulam's heightened status is his widow, Francoise Ulam, who will never forget the day she returned home for lunch to find her husband staring fixedly out the window. "I think I've found the way to make it work," he told her. "Make what work?" "The Super." Teller has partially confirmed his debt to Ulam. After suffering a heart attack in 1979, he dictated an account of the day Ulam walked into his office and said he had a way to make the bomb. Teller, though, heatedly disputes the notion that the key idea was Ulam's. "That is not correct," he says. "I do not want to say what is correct. It is a long and complicated story. Someday I will write it down."
But history may have already been rewritten. The revised account of Ulam's pivotal role appears in several new books, including a biography of Teller by Stanley Blumberg and Louis Panos to be published in February by Scribner's. And it is repeated in detail in the latest revision of the New Encyclopaedia Britannica, due out next month.