Genius in the Shadows

by William Lanouette

  In early 1939 the public read mixed messages about uranium fission. The new process was the greatest discovery since radium, the press reported, yet it also called into question Fermi’s assumption that there are elements heavier than uranium—the so-called transuranic elements he and others had tried to create for several years.25 Science Service, a respected news agency, played down the dangers of fission:

  First of all, the physicists are anxious that there be no public alarm over the possibility of the world being blown to bits by their experiments. Writers and dramatists (H. G. Wells’s scientific fantasies, the play “Wings Over Europe,” and J. B. Priestley’s current novel, “Doomsday Men”) have overemphasized this idea. While they are proceeding with their experiments with proper caution, they feel that there is no real danger except perhaps in their own laboratories.26

  Science Service also dismissed “forecasts of the near possibility of running giant ocean liners across the Atlantic on the energy contained within the atoms of a glass of water”; or of replacing steam and hydroelectric plants with “atom-motors”; “or the suggested possibility that the atomic energy may be used as some super-explosive, or as a military weapon. . . .” After all, uranium is very scarce and contaminated with nonfissionable elements. “This means that the release of atomic energy can only be achieved by direct intent, in the laboratory, and then only with considerable ingenuity of experiment.”27 Exactly what Szilard had in mind as he thought of Germany’s moves toward war.

  While awaiting his beryllium shipment from Oxford, Szilard tried to enlist scientists and financiers in a scheme to sponsor nuclear research and devised the Association for Scientific Collaboration, a legal entity for atomic research that he incorporated to raise money for experiments.28 He rode the train to Washington with Strauss and there enlisted Teller as the association’s representative. On his return, Szilard stopped in Princeton, where Wigner agreed to join the cause.

  Despite earlier rebuffs, Szilard appealed to Strauss for money. In a letter written on February 13, Szilard shared his excitement over the pace of activities around him. “Almost every day,” he wrote, “some new information about uranium became available, and whenever I decided to do something one day it appeared foolish in the light of the new information on the next day.”29 Teller added to Szilard’s urgency on February 17 when he sent from Washington a handwritten note, in Hungarian, reporting that scientists at the DTM were eager to experiment with uranium. Bohr had told them that only scarce uranium235 would fission, not uranium238, the most plentiful form found in nature. But the DTM scientists had to defer any experiments because they lacked large amounts of uranium and were, in Teller’s words, “cautious (perhaps a little too cautious),” Their chief concern was a reluctance to accept research money from the federal government. (Unlike conditions today, most scientific research before World War II was privately sponsored, by industrial investment or university endowment.) Teller closed by reporting “a chain-reaction mood” in Washington. “I only had to say ‘uranium’ and then could listen for two hours to their thoughts.”

  Finally, on February 18, Szilard walked into a US Customs Department office in downtown Manhattan, paid a fifteen-cent postal fee, and walked out with his beryllium cylinder.30 It was time to dispatch Zinn to collect the rented gram of radium. Zinn rode the subway to the Eldorado Radium Corporation’s office in Manhattan, expecting to carry away the tiny sample in his coat pocket. But when he presented Szilard’s receipt, Zinn discovered that the gram of radium came stored in a 100-pound lead casket. “By taxi I dragged this load to Columbia,” Zinn later recalled, and after “several days of concentrated effort” fitted the experimental neutron counter with Szilard’s radium-beryllium source.31

  Szilard, usually energetic and expressive, became even more outspoken, at times frenetic, as he thought about the news that uranium could fission. For weeks after, he rushed about to the Columbia labs, to the small post office on Amsterdam Avenue or the Western Union office on Broadway, to his cluttered hotel room, to colleagues’ offices, bearing witness in any way possible to the great and dreadful events he foresaw. As he dressed hastily each morning, Szilard failed to notice that he kept putting on the same pair of shoes and that their heels had scraped down to the uppers. Even when Bela pointed this out, Szilard was too busy to change or repair them. Suddenly, Szilard was infatuated, and frightened, by the reality of fission and the thought that it might lead to chain reactions. More than any other person at the time, he was convinced that chain reactions were essential to winning or losing an impending world war: a fear he had lived with for five years.

  As Bohr and Fermi appeared together at several scientific meetings during the spring of 1939, Bohr became more concerned, and outspoken, about the destructive potential for fission, while Fermi refused to predict any timely uses, commercial or military. After a discussion on February 24, New York Times science writer William L. Laurence buttonholed Fermi and asked him if he thought that fission could be used for weapons. At first, Fermi demurred. Then, slowly, he spoke. Such development was twenty-five to fifty years off, he said, if it proved practical at all.32

  Remaining unknown to reporters (and to most other scientists), Szilard was increasingly anxious to have the United States begin studying fission for possible military uses—before the Germans did. In a February 22 “bulletin” he sent to Strauss, Szilard focused attention on the rare uranium235 isotope. If separated and refined, he wrote, “a chain reaction could be set up in the concentrate.” Szilard reported that at the time Fermi was convinced natural uranium (99.3 percent uranium238 and 0.7 percent uranium235) was “no good” for producing chain reactions. Wigner wasn’t sure. And Szilard’s “own feeling is somewhere between Wigner’s and Fermi’s.” As it turned out, the first chain reaction was created in 1942 by a Fermi-Szilard design that used natural uranium, but it was known by then that only the rare isotope sustained the fission process.

  To certify when he thought up different ideas, Szilard liked to date them by mail, and on February 24 he posted himself an eight-page manuscript about uranium235 separation. He mailed another manuscript on March 3, describing his inventions in isotope separation, including the Szilard-Chalmers effect. Separating uranium isotopes, he suspected, would soon be important.33 Later that same day, Szilard and Zinn met at a two-room laboratory on the seventh floor of the Pupin building and worked into the evening, when, at last, their uranium-fission experiment was ready.

  For this effort Szilard and Zinn planned to bombard uranium with slow neutrons, tracing their movements on a cathode-ray oscillograph screen—a device resembling a small television set. The neutrons would appear on the screen as gray streaks, their speed revealing whether they were fast or slow.

  “If flashes of light appeared on the screen,” Szilard explained later, “that would mean that neutrons were emitted in the fission process of uranium, and this in turn would mean that the large-scale liberation of atomic energy was just around the corner.” As the picture tube heated up, Szilard and Zinn watched intently. No flashes appeared. They waited. Still nothing. Szilard felt relieved. Perhaps his chain-reaction theory was moonshine! Perhaps no one would make atomic bombs!

  Then Zinn noticed a problem. The screen was not plugged in. The two men chuckled nervously, and with the device connected, they looked again. “We saw the flashes,” Szilard recalled later. “We watched them for a little while and then we switched everything off and went home. That night there was very little doubt in my mind that the world was headed for grief.”34 Before retiring, Szilard placed a long-distance telephone call to Washington, interrupting a Mozart duet that Teller, on piano, and a friend, on violin, were practicing. In Hungarian, Szilard spoke a single sentence, “I have found the neutrons,” and hung up.35

  His fears confirmed, Szilard called on Fermi again to report the disturbing conclusions. Meanwhile, Fermi and his assistant, Herbert Anderson, had tried a similar uranium-fission experiment, but with inconclusive results.

&nbs
p; “In your experiment,” Szilard said, “you use a radon-beryllium source. That source, as you know, has rather energetic neutrons. How do you know that some of the neutrons are coming not from fission but from a direct (n, 2n) reaction?” In this way one neutron (n) hits a nucleus and knocks out two neutrons (2n) but does not actually split or fission the atom. Fermi conceded the point, while Szilard, restraining a powerful temptation to tease, showed irrepressible satisfaction.

  “It just so happens that I have a radium-beryllium photoneutron source that produces neutrons of much lower energy,” Szilard said. “With it, you won’t have the problem of the (n, 2n) reaction.” Fermi agreed to use it and in his next experiment unmistakably saw the fast neutrons.

  “In our paper” reporting their results, Anderson recalled, “we acknowledged a curious organization called the Association for Scientific Collaboration, a Szilardian creation.”36 This entity, formed to solicit money for nuclear research, technically owned Szilard’s radium-beryllium source. On the day after his decisive experiment with Zinn, Szilard tried to arrange a meeting to discuss fund-raising for his association. He wanted Fermi to attend and hoped that Strauss would invite his wealthy acquaintance, Lord Rothschild, then visiting New York. Another target of Szilard’s fundraising was W. T. Richards, brother-in-law of Harvard president James Conant.37

  Szilard cabled Strauss on March 6 that the chances for a chain reaction were “NOW ABOVE 50%,” telephoned to underscore his excitement,38 and met with him for breakfast on March 8. The next day, assured where his research was leading, Szilard appeared before a patent attorney, raised his right hand, and swore a notarized oath. “I verily believe myself to be the original, first, and sole inventor of the improvements in apparatus for nuclear transmutation as described and claimed . . . .” he said, renewing his 1935 US patent application for the chain reaction. Just in case.39 A day later, Szilard and Fermi met Rothschild over drinks at Strauss’s apartment, but the two physicists failed to persuade the financier to invest in chain-reaction research.40

  Germany had just annexed Czechoslovakia when Wigner visited Szilard in New York on March 16. They were upset by both the neutron experiments and the events in Europe and saw a link between the two: Czechoslovakia had Europe’s richest uranium reserves. During a long and emotional meeting with Pegram and Fermi, Wigner argued that they must approach the government for support; Germany was on the way to building atomic bombs, he warned, and the United States must build them first or lose the war.41 Szilard hesitated, afraid that government red tape might stifle his work.42 To Pegram and Fermi chain reactions were only a theoretical possibility; atomic bombs, even more remote. They also saw war in Europe as unlikely, while Szilard and Wigner feared it was imminent.

  After this Columbia meeting, Szilard and Wigner went to Princeton, where, in Wigner’s office in Fine Hall, they met with Niels Bohr and other physicists. Bohr doubted that an A-bomb could be constructed because so much uranium235 must first be separated. “It would take the entire efforts of a country to make a bomb,” Bohr said. With Germany in mind, Szilard argued for self-censorship by all nuclear physicists outside that country.43

  Fermi went by train to Washington after the Columbia meeting, and the next day, March 17, briefed a group of navy scientists. But Fermi’s characteristic caution, his heavy accent, and his ambivalence about the meaning of uranium fission left his audience bemused. After Fermi’s talk, Ross Gunn, a navy technical adviser working on submarine propulsion, telephoned Merle Tuve at the DTM, who had also sat in on the briefing. “Who is this man Fermi?” Gunn asked. “What kind of a man is he? Is he a Fascist or what?” Still, a power source that used no oxygen was a submariner’s dream come true, and Gunn was intrigued enough by Fermi’s ideas to offer Tuve $1,500 for uranium experiments. This might have been the first federal money to study fission, but for policy reasons— chiefly a reluctance to accept government funding for scientific research—the DTM declined the navy’s grant.

  Szilard and Teller met Fermi in Washington over the weekend and while there learned that Joliot and his colleagues in Paris had published in Nature their finding that uranium frees extra neutrons when it fissions.44 Szilard and Fermi disagreed about how to report their own recent experiments; Szilard and Teller insisted that all uranium work must be kept secret, Fermi condemned censorship as unscientific. But, living in a democracy now, he proposed a vote, lost to the Hungarians two to one, and when back at Columbia, advocated censorship.45

  “I invented secrecy,” Szilard said after World War II.46 At the time, he took credit for something he wanted abolished, the US military’s monopoly on atomic-energy information. But from the moment on Southampton Row in 1933, when he first conceived the nuclear chain reaction, until 1945, Szilard schemed to keep all related work a secret. With Joliot’s article, Szilard felt betrayed, although word about uranium was also leaking out in America: Newsweek reported the possibility that atomic energy might create “an explosion that would make the forces of T.N.T. or high-power bombs seem like firecrackers.”47

  In late March, Szilard, Wigner, and physicist Victor Weisskopf from Rochester sent cables and letters to their European colleagues, pleading for self-censorship and hoping that Joliot’s article might be the only one published.48 It appears “very likely,” Szilard warned Weisskopf, that an A-bomb “will be too heavy to be carried by aeroplane” but could “probably easily be carried by boats” and with “engineering tricks” may cause an explosion whose destructive power “goes beyond imagination.”49

  One cable from Weisskopf to Joliot’s group arrived in Paris on April 1, and they took it for an April Fools’ Day joke. “To propose withdrawal of publication and communication by private letters,” Joliot’s colleague Lew Kowarski recalled years later, “between four countries, Europe being at that [time] what it was, was such a damn fool proposal . . . as a way to preserve secrecy.” Besides, Kowarski thought the Nazis would take note if articles were not published.50 And Joliot complained that Science Service had reported DTM’s results in February, prompting Szilard to reply that these concerned “delayed neutrons” that are “harmless,” not fast or slow neutrons. On April 6, Szilard asked Joliot, “kindly cable as soon as possible whether inclined similarly to delay your papers or whether you think that we should now publish everything.” His answer arrived the next day: “question studied my opinion is to publish now regards joliot.”51

  On the same day Szilard received Joliot’s rebuff, Bela knocked on his hotel-room door with another cable. From an uncle in Budapest came the news that their mother had died of cancer. Szilard was grief stricken but strained to control his emotions with intense reason, hiding his sadness even from Bela. Leo had not seen his mother since his last visit home in 1936, yet the time and distance had not erased his fondness for her. When living in Berlin, he simply signed “Leo, too” at the bottom of Bela’s letters, and in New York he also relied on Bela to convey messages to and from home. But by early in 1939, Szilard learned that his mother had cancer, and as a “gift” for her birthday in March he had written her a rare personal letter. The sorrow Szilard repressed must have hurt all the more a few days later when a letter arrived from his mother. Written in pencil in a frail hand from her Budapest hospital bed on April 1, the letter touched anew the deep personal and ethical bond that tied them together.

  My dear, good son!

  1st April 1939

  I thank you for your birthday present. The fact that you offered that to me proves that we have the same ideas about life. It seems to me that you are apologizing and that you are looking for an explanation for the rareness of our correspondence. Be calm about that; I couldn’t ever be angry at you, because in my innermost soul I sense that we always have been mutually honest and truthful and that therefore there could never be a misunderstanding between us. “Truthfulness” was, and always remained, what I was striving for. Thus, I would not like to fool either you or myself with respect to my illness. After all, it is not the most important thing how lo
ng one has lived but how and in what manner.

  Looking backward, I have the feeling that I always did my duty, had some sorrow here and there, but was on the other hand blessed by plenty of joy that fate let me have; it would be ungrateful to ask for more. What I now still have to expect, I don’t know.

  What we experienced with Father remains ours. When my physical condition does not bother me, then we sit quietly holding hands and not speaking many words. For the time being, he accomplishes the wish to make my remaining life as easy for me as possible; and this effort supports him. What should become of him later is my greatest worry. You should try to diminish the great distance between him and you; the letters from all of you will be his only support for his life. Sure, these will be only a substitute, which, however, should not be underestimated, in contrast to a lack of communication, from the point of helping him over the difficult times that are to come.

  Farewell, my good boy; the writing of long letters tires me out; so I will mostly write short answers.

  I wish for peace for you; try to achieve that by keeping away from reproaching yourself.

  I embrace you.

  Mother52

  Trying to extinguish his personal grief, Szilard confronted the crusade for scientific secrecy with a new intensity. But once the French reports on fission had been published, Szilard’s Columbia colleagues insisted on releasing their own work. They resented this visitor’s complaints, and some grumbled that his guest privileges in the department be ended. Rabi, the Columbia teacher closest to Szilard, took him aside and warned that his position in the laboratory was in jeopardy.53 Reluctantly, Szilard went along. On April 15 the Physical Review published “Production of Neutrons in Uranium Bombarded by Neutrons,” a March 1939 paper by Anderson, Fermi, and H. B. Hanstein, and the Szilard-Zinn paper on “Instantaneous Emission of Fast Neutrons in the Interaction of Slow Neutrons with Uranium.”54 Wigner urged Szilard that someone should alert the US government to the “possible sudden threat” of a German A-bomb, a threat made more real by Joliot’s article in Nature estimating the “Number of Neutrons Liberated in the Nuclear Fission of Uranium.”55 The Paris group’s conclusion that 3.5 neutrons were released later proved to be about one too many.56