American Prometheus (39 page)

The first colloquium was convened on April 15, 1943, in the now empty schoolboys’ library. Standing before a small blackboard, Oppenheimer offered some perfunctory words of welcome and then introduced Bob Serber, his former student. Serber, he explained, would brief the assembled scientists, numbering no more than forty, on the task at hand. Speaking from notes with his habitual stutter, the shy and awkward Serber took center stage. “Security was terrible,” Serber later wrote. “We could hear carpenters banging down the hall and at one point a leg appeared through the beaver-board ceiling, presumably belonging to an electrician working up above.” After only a few minutes, Oppenheimer sent John Manley up to whisper in Serber’s ear that he should stop using the word “bomb” in favor of something more neutral like “gadget.”

“The object of the project,” Serber said, “is to produce a practical military weapon in the form of a bomb in which the energy is released by a fast-neutron chain reaction in one or more of the materials known to show nuclear fission.” Summarizing what Oppenheimer’s team had learned from their Berkeley summer sessions, Serber reported that by their calculations an atomic bomb might conceivably produce an explosion equivalent to 20,000 tons of TNT. Any such “gadget,” however, would need highly enriched uranium. This core of enriched uranium, approximately the size of a cantaloupe, would weigh about thirty-three pounds. They could also construct a weapon from the even heavier element of plutonium—produced via a neutron-capture process using U-238. A plutonium bomb would need far less critical mass, and the plutonium core might therefore weigh only eleven pounds and appear no larger than an orange. Either core would need to be packed within a thick shell of ordinary uranium the size of a basketball. This would bring the weight of either device to about a ton—still something deliverable by airplane.
¹¹

Most of the scientists in Serber’s audience already understood the theoretical possibilities inherent in the new physics—but compartmentalization had kept many of them in the dark about the details. Few had realized how many of the basic questions had already been answered, at least in broad outline. The obstacles remaining to building a practical military weapon were large but not insurmountable. Some of the physics of building an atomic bomb was still uncertain, but the real imponderables lay in the field of engineering and ordnance design. Producing sufficient amounts of either U-235 or plutonium would require a massive industrial effort. And even if sufficient bomb-grade materials could be produced, no one was quite sure how to design an atomic bomb that would detonate efficiently. But even a onetime skeptic like Bethe understood, as he later put it, “That once plutonium was made, it was almost certain that a nuclear bomb could be made as well.” Thus, the real news to Serber’s audience was that they had a mission that could contribute enormously to the war effort. This fact alone lifted morale. Serber’s first talk conveyed what Oppenheimer wanted: a sense of mission and a realization that they had the means to change history. But could they solve the technical problems before the Germans? Could they indeed help win the war?

Over the next two weeks, Serber gave four more hour-long lectures, stimulating the kind of creative dialogue that Oppenheimer wanted. Among many other issues, Serber briefly summarized the actual mechanics of what he called “shooting”—the problem of how to bring together the critical masses of the uranium or plutonium so as to initiate a chain reaction. Serber dwelled on the most obvious method—the gun assembly—whereby criticality would be achieved by firing a slug of uranium into another mass of U-235, leading to an explosion. But he also suggested that “the pieces might be mounted on a ring as in the [accompanying] sketch. If explosive material were distributed around the ring and fired, the pieces would be blown inward to form a sphere.” The idea of imploding fissionable material had first been suggested by Oppenheimer’s old friend Richard Tolman during the summer of 1942, and he and Serber had thereupon written a memorandum on the subject for Oppenheimer. Tolman later wrote two other memos on implosion, and in March 1943 Vannevar Bush and James Conant urged Oppenheimer to explore the implosion design. Oppenheimer reportedly replied, “Serber is looking into it.” Although Tolman’s proposal had not included the notion of actually compressing solid material so as to increase its density, the idea was sufficiently well formulated to warrant inclusion in Serber’s lecture notes, if only as an aside. But this was enough to spark the interest of another physicist, Seth Neddermeyer, who asked Oppenheimer’s permission to investigate its potential. Soon, Neddermeyer and a small team of scientists could be found in a canyon near Los Alamos, testing implosion explosives.

Serber’s lectures would have a long life. Using Serber’s notes, Ed Condon typed up the lectures as a twenty-four-page summary. This became a mimeographed booklet, titled
The Los Alamos Primer,
which was passed out to newly arriving scientists. Among others, Enrico Fermi attended some of Serber’s lectures, and he then remarked to Oppenheimer, “I believe your people actually want to make a bomb.” Oppenheimer was struck by the note of surprise in Fermi’s voice as he said this. Fermi had just come from Chicago, where he found the atmosphere among the scientists oddly subdued in comparison to the exhilaration he often encountered among the men in Oppie’s mesa laboratory. Everyone, whether in Chicago or Los Alamos or elsewhere, held the sobering thought that if an atomic bomb was possible, the Germans might be ahead in the race to build one. But whereas at Chicago, many of the senior scientists were troubled and even depressed by this realization, at Los Alamos, under Oppenheimer’s charismatic leadership, this awareness seemed only to inspire the men to forge ahead with their work.

Fermi took Oppenheimer aside one day and suggested another way to kill large numbers of Germans. Perhaps, he said, radioactive fission products could be used to poison Germany’s food supply. Oppenheimer seems to have taken the proposal seriously. After urging Fermi not to mention the matter to anyone else, Oppenheimer reported the idea to General Groves and later discussed it with Edward Teller. Teller reportedly told him that separating out strontium-90 from a chain-reacting pile was feasible. But by May 1943, Oppenheimer had decided to recommend a delay in action on the proposal—for a gruesome reason: “In this connection,” he wrote Fermi, “I think that we should not attempt a plan unless we can poison food sufficient to kill a half a million men, since there is no doubt that the actual number affected will, because of non-uniform distribution, be much smaller than this.” The idea was dropped, but only because there seemed no efficient way to poison large numbers of the enemy population.

Wartime compelled some mild-mannered men to contemplate what was once unthinkable. In late October 1942, Oppenheimer received a letter marked “secret” from his old friend and colleague Victor Weisskopf, who wrote to report alarming news in a letter he had just received from the physicist Wolfgang Pauli, then residing in Princeton. Pauli had written that their former German colleague, the Nobel Prize–winning physicist Werner Heisenberg, had just been appointed director of the Kaiser-Wilhelm Institute, a nuclear research facility in Berlin. Moreover, Pauli had learned that Heisenberg was scheduled to give a lecture in Switzerland. Weisskopf reported further that he had discussed this news with Hans Bethe, and the two men had agreed that something should be done immediately: “I believe,” Weisskopf wrote Oppenheimer, “that by far the best thing to do in this situation would be to organize a kidnapping of Heisenberg in Switzerland. That’s what the Germans would do if, say you or Bethe would appear in Switzerland.” Weisskopf even volunteered himself for the job.

Oppenheimer immediately wrote back, thanking Weisskopf for his “interesting” letter. He said he had already learned of Heisenberg’s scheduled visit to Switzerland and had discussed the issue with the “proper authorities” in Washington. “I doubt that you will hear further of the matter, but [I] wanted to thank you and assure you that it is receiving the attention it deserves.” The “proper authorities” with whom Oppenheimer had indeed already talked of this matter were Vannevar Bush and Leslie Groves, and he now passed on Weisskopf’s letter to them. But he did not endorse the proposal—even a successful kidnapping of Heisenberg would alert the Nazis to the high priority the Allies assigned to nuclear research. On the other hand, Oppenheimer could not refrain from remarking to Bush “that Heisenberg’s proposed visit to Switzerland would seem to afford us an unusual opportunity.”

Much later, Groves seriously pursued the notion of kidnapping or assassinating Heisenberg; in 1944 he dispatched OSS agent Moe Berg to Switzerland, where the former baseball player stalked the German physicist in December 1944—but ultimately decided not to attempt an assassination.

CHAPTER SIXTEEN

“Too Much Secrecy”

. . . this policy puts you in the position of trying to do an
extremely difficult job with three hands tied behind your
back. . . .

DR. EDWARD CONDON to Oppenheimer

THE DIRECTOR’S FIRST REAL ADMINISTRATIVE CRISIS occurred early that first spring. With General Groves’ approval, Oppenheimer had appointed his former Göttingen classmate Edward U. Condon as associate director. Condon’s job was to relieve Oppenheimer of some of his administrative burdens and to serve as liaison with the Army’s military commander at Los Alamos. Two years older than Oppenheimer, Condon was both a brilliant physicist and a seasoned laboratory administrator. After earning his doctorate at Berkeley in 1926, Condon had won postdoctoral appointments in Göttingen and Munich. For the next decade he taught at several universities, including Princeton, and published the first English-language textbook on quantum mechanics. In 1937, he left Princeton to become associate director of research at Westinghouse Electric Company, a major industrial research center. Over the next few years, he supervised the company’s research in nuclear physics and microwave radar. By the autumn of 1940, he was working full-time on war-related projects, primarily radar, at MIT’s Radiation Laboratory. In short, Condon was, in terms of experience at least, significantly more qualified than Oppenheimer to lead the new laboratory in Los Alamos.

Condon had not been as politically active as Oppenheimer in the 1930s, and he certainly was not affiliated with the Communist Party. He thought of himself as a “liberal” New Dealer, a loyal Democrat who voted for Franklin Roosevelt. Raised as a Quaker, Condon once told a friend, “I join every organization that seems to have noble goals. I don’t ask whether it contains Communists.” An idealist with strong civil-libertarian instincts, Condon believed that good science could not come without a free exchange of ideas, and he lobbied vigorously for regular contacts between physicists at Los Alamos and the other labs around the country. Inevitably, he quickly attracted the ire of General Groves, who heard repeated reports of security infractions from his military representatives in Los Alamos. “Compartmentalization of knowledge, to me,” Groves insisted, “was the very heart of security.”

In late April 1943, Groves was angered to learn that Oppenheimer had traveled to the University of Chicago, where he had discussed the production schedule for plutonium with the director of the Manhattan Project’s Metallurgical Laboratory (Met Lab), the physicist Arthur Compton. The general blamed Condon for this ostensible infringement of security. Descending on Los Alamos, Groves stormed into Oppenheimer’s office and confronted the two men. Condon stood his ground against the general, but, to his astonishment, he realized that Oppenheimer was not backing him up. Within a week, Condon decided to tender his resignation. He had intended to stay for the project’s duration, but had lasted just six weeks.

“The thing which upsets me most is the extraordinarily close security policy,” he wrote Oppenheimer in his resignation letter. “I do not feel qualified to question the wisdom of this since I am totally unaware of the extent of enemy espionage and sabotage activities. I only want to say that in my case I found that the extreme concern with security was morbidly depressing—especially the discussion about censoring mail and telephone calls.” Condon explained that he was “so shocked that I could hardly believe my ears when General Groves undertook to reprove us. . . . I feel so strongly that this policy puts you in the position of trying to do an extremely difficult job with three hands tied behind your back. . . .” If he and Oppenheimer truly could not meet with a man like Compton without violating security, then “I would say the scientific position of the project is hopeless.”

Condon concluded that he could better contribute to the war effort by returning to Westinghouse and working on radar technology. He left saddened and perplexed by Oppie’s apparent unwillingness to defy Groves. Condon was unaware that Oppenheimer had yet to receive his own security clearance. The Army’s security bureaucracy was still trying to block Oppenheimer’s clearance and Oppie knew he could not press Groves about security—not if he wanted to keep his job.

Oppenheimer had much invested in his relationship with Groves. The previous autumn, each man had taken the measure of the other and arrogantly calculated that he could dominate their relationship. Groves believed the charismatic physicist was essential to the success of the project. And precisely because Oppenheimer came with left-wing political baggage, Groves thought he could use Oppie’s past to control him. Robert’s calculation was equally straightforward. He understood that he could keep his job only if Groves continued to consider him far and away the best director available. He realized that his communist associations gave Groves a certain hold over him, but by demonstrating his unique competence, he believed, he would convince the general to allow him to run the laboratory as he saw fit. Oppenheimer didn’t disagree with Condon; he too was convinced that onerous security regulations could smother the scientists. But he was confident that over time he would prevail. After all, in the end, Groves needed Oppenheimer’s skills as much as Oppenheimer needed Groves’ approval.