The four were also neighbors. By spring 1942, Bohm and Lomanitz had moved into a duplex in a working-class neighborhood just south of campus. Joe and Merle Weinberg rented a one-bedroom apartment on Blake Street, just around the corner. Joined by Friedman, the group gathered often for dinner at the Weinbergs’ home, where they listened to Joe’s coveted collection of classical records and discussed politics and philosophy late into the night.139
That May, Oppenheimer asked Lomanitz to look over a theoretical paper that two other graduate students, Stanley Frankel and Eldred Nelson, had written on how to improve the focusing of the Calutron beam.140 While uranium was never specifically mentioned, the purpose of the “experiment” was clear.141 Offered full-time employment at the lab by Oppie, Lomanitz understood all too well where such work was headed and balked. Subsequently invited to his mentor’s home on Eagle Hill, Rossi admitted to having ethical qualms about participating in the creation of such a terrible weapon. But Lomanitz, like his professor, had also begun to feel guilty about sitting out the war. He was thinking about quitting school and going to work in the East Bay shipyards or even enlisting, Rossi told Oppenheimer.142
Two days later, running into Oppie on campus, Lomanitz accepted his offer. As he had done with his brother, Frank, Oppenheimer made Lomanitz and all those working on the project pledge to give up political activity. Oppie had evidently decided against recruiting Weinberg because of Joe’s previous reputation as a campus radical.143
By that summer, three of the four—Lomanitz, Bohm, and Friedman—were engaged in some form of classified work related to the bomb. Oppenheimer assigned Lomanitz to refining calculations dealing with the Calutron’s magnetic field. Bohm and Friedman supported the efforts of Eldred Nelson and Frankel to better focus the beam. Despite Lawrence’s promise to Conant, the urgent need for results had pushed concerns with security into the background. All three were given interim clearances, pending a more complete background investigation. Until they could be put on the government payroll, Lawrence agreed to pay the salary for Oppie’s students out of the Loomis fund.
Rossi used his sudden windfall to purchase two blue suits, a phonograph, and a collection of jazz and classical records that he hoped would one day rival Weinberg’s. With gas rationing in effect, Lomanitz used the last of the money to buy a bicycle to commute to his new job at the lab.
4
AN ADVENTUROUS TIME
BY SUMMER 1942, Oppenheimer had become all but indispensable to building the atomic bomb, even as OSRD officials dithered about whether to grant him a security clearance. In May, Gregory Breit had suddenly quit the project—citing, ironically, lax security as the reason in his letter to Bush.1 Arthur Compton promptly assigned Oppie the task of calculating fast-neutron reactions, crucial to the design of the weapon.
By mid-June, Oppenheimer was at Chicago’s Met Lab to be briefed on the work inherited from Breit. Even Berkeley’s wunderkind found the job and its deadlines daunting. Oppenheimer decided on the spot to invite the country’s top theoretical physicists to Berkeley for an impromptu seminar on bomb physics. It was the start of what Oppie would later describe as “an adventurous time.”2
First to arrive on campus was Robert Serber, a slight, soft-spoken former student of Oppenheimer’s from the University of Illinois. In 1934, Serber had been on his way to a postdoctoral fellowship at Princeton with his wife, Charlotte, when the couple stopped off at Ann Arbor, Michigan, where Oppie was teaching quantum physics during the summer. Quickly falling under the master’s spell, Serber had followed Oppenheimer back to Berkeley instead.3
Every spring since, Serber and Charlotte had crowded their possessions into a battered Nash roadster and joined the gypsy caravan of young physicists who migrated south to Caltech with their mentor. In Pasadena, they shared a garden apartment with Frank and Jackie Oppenheimer for $25 a month.
Like Oppie and Frank, Serber, too, married into radical politics: Charlotte was the daughter of Morris Leof, a Russian émigré and prominent Philadelphia physician who supported a variety of progressive causes in the city. Leof headed the local chapter of a medical aid committee for the Spanish Loyalists. Together with Jean Tatlock and Mary Ellen Washburn, Oppie’s former landlady, Charlotte organized a similar chapter in Berkeley. (Robert Serber evidently inherited his wife’s views. Teller claimed to have been shocked by Serber’s summer 1940 description of the war in Europe as “a clash between capitalist interests.”)4
Having both physics and politics in common, the Serbers soon became close friends of Oppie and Kitty and were frequent summer guests at Perro Caliente.5 Even after Serber left Berkeley for Urbana, Illinois, in 1938, he and Oppenheimer stayed in touch with weekly letters.
Anticipating the need for additional theorists, Oppie recruited Serber to the bomb project during a walk in a cornfield near the Illinois campus just before Christmas 1941. Arriving in Berkeley the following spring, the Serbers moved into the apartment above the garage at the Oppenheimers’ house on Eagle Hill. Charlotte found a job as a statistician at the Kaiser shipyards in nearby Richmond.6
Oppenheimer assigned Serber to oversee the work being done by Nelson and Frankel, who had, in turn, enlisted the assistance of Oppie’s grad students. The latest task was to calculate, using data from the M.A.U.D. report, the critical mass and efficiency of an atomic explosion.7 Distrusting Breit’s estimates, Nelson and Frankel decided to do the laborious neutron diffusion calculations from first principles. Oppenheimer worried that their paper would not be ready in time for his seminar.
From campuses around the country came those whom Oppie called the “luminaries,” including Harvard’s John Van Vleck and University of Indiana physicist Emil Konopinski, then at Chicago’s Met Lab. Physicist Felix Bloch
