One of the many complexities of the character of J. Robert Oppenheimer is apparent in his response to the discovery of nuclear fission in January 1939. “The U business is unbelievable,” he wrote to a colleague once he had satisfied himself that uranium atoms really did split when bombarded with neutrons. “It is I think exciting, not in the rare way of positrons and mesotrons, but in a good honest practical way.” He meant that fission didn’t turn physics upside down and inside out like so many other discoveries of the first decades of the twentieth century. Fission was as practical as a hammer. The clincher for Oppenheimer was watching the dramatic green spikes on the oscilloscope of the Berkeley physicist Luis Alvarez when an atom split. “In less than fifteen minutes,” Alvarez wrote later,
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….
The speed of Oppenheimer’s mind would not have surprised those who knew him. At thirty-four Oppenheimer was famously brilliant. The surprise was his enthusiasm for the “good honest practical way” fission might be put to work. His whole life had been moving in an entirely different direction since his discovery of physics, and especially theoretical physics, at Harvard in the early 1920s, then at the Cavendish lab in Cambridge, England, and finally in the German university town of Göttingen, where he studied with Max Born, argued with his fellow students, and developed “some taste in physics.”
For a decade theory dominated his life and later his teaching in California until the mid-1930s when Oppenheimer suddenly discovered politics—specifically, the “popular front” politics of the American Communist Party as it tried to rally resistance to fascism. Oppenheimer’s politics were, however—like his physics—mainly theoretical. He always insisted he never joined the Party himself, and the FBI, despite a dozen years of relentless surveillance and phone-tapping, never managed to prove he did.
Oppenheimer early in the war readily agreed with a US Army security officer, charged with weighing his loyalty, and said it seemed he had “belonged to nearly every fellow-traveling organization on the West Coast.” He went to rallies, helped raise funds for refugees of the Spanish civil war, made substantial donations of his own to a representative of the Party, fell in love with one Communist, and was close to many others, including his brother Frank, who joined the Party in 1936 and remained until about 1942. For Oppenheimer in his Red period communism was a noble ideal, a way of conceiving a just world, and very likely—much in the way of his physics, his ambitious reading, his tailoring, his interest in art, food, wine, and martinis made exactly so—another…
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