LEO SZILARD

• Bethe, Hans
• Chadwick, James
• Einstein, Albert
• Fermi, Enrico
• Feynman, Richard
• Franck, James
• Fuchs, Klaus
• Rotblat, Joseph
• Seaborg, Glenn T.
• Serber, Robert
• Szilard, Leo
• Teller, Edward
• Wigner, Eugene
• York, Herbert

Leo Szilard was born on February 11, 1898, in Budapest, Hungary, the son of a Jewish engineer and entrepreneur. Drafted into the Austro-Hungarian Army during the First World War, Szilard after the war went to Berlin and resumed his studies, initially in electrical engineering but then in physics at the University of Berlin, where he first met Albert Einstein and earned his Ph.D. in 1922. He did research at the Kaiser Wilhelm Institute until 1925 when he accepted a position at the University of Berlin. During his time in Berlin, Szilard filed for twenty-nine patents, some of them in collaboration with Einstein. Most of the patents filed jointly were on home refrigeration. In spring 1933, following Adolf Hitler's rise to power, Szilard fled to England. Here he helped organize financial assistance for other refugees from Nazi Germany. Here also he had what his good friend and fellow Hungarian émigré Eugene Wigner later described as the "most important event" in his life. Prompted by the discovery of the neutron by James Chadwick, Szilard, while crossing a London street in September 1933, had the sudden insight that if an element could be found that released more than one neutron when absorbing one neutron, then a chain reaction might be possible and, also, an atomic bomb. He suspected that beryllium might be such an element, but Szilard was a relative unknown in the nuclear physics community and he found little support for launching a major research project involving neutrons and chain reactions. In 1935, Szilard took a position at the Clarendon Laboratory at Oxford University. He came to the United States in 1937, deciding to remain permanently following the Munich agreement in September 1938.

The discovery of fission in uranium by Otto Hahn and Fritz Strassman in December 1938 brought the possibility of a chain reaction to the forefront. Szilard, who had heard the news from Wigner, now at Princeton, thought the production of power by means of nuclear energy would be too costly, but, as he wrote immediately after hearing of the discovery, there were

"possibilities in another direction. These might lead to large-scale production of energy and radioactive elements, unfortunately also perhaps to atomic bombs. This new discovery revives all the hopes and fears in this respect which I had in 1934 and 1935."

Given the imminence of another world war, Szilard concluded, experiments were needed urgently to determine if neutrons were emitted in the fission process. Szilard, securing a three-month guest appointment at Columbia University and financing the research on borrowed money, collaborated with Walter Zinn in experiments similar to those being done by Enrico Fermi, working in the same building at Columbia, the Pupin Laboratory, but on a different floor. Both efforts in March 1939 confirmed, as did a French team headed by Frederic Joliot-Curie, that about two neutrons were released for each neutron absorbed. The results did not please Szilard. "That night," he later noted, "there was very little doubt in my mind that the world was headed for grief." Publication of the results was now the issue. Fermi thought they should be published, Szilard and Edward Teller, yet another Hungarian émigré thought not. Szilard urged Joliot-Curie to delay publication, but any effort at self-censorship largely collapsed when Joliot-Curie refused to cooperate. Szilard and Fermi next turned their attention to producing a chain reaction using natural uranium. Finding a suitable moderator to slow down neutrons was a problem. In early July, Szilard suggested the use of graphite, but procuring large amounts of graphite and uranium, perhaps 50 tons and 5 tons respectively, would be expensive, around $35,000. Columbia was reluctant to provide support, especially with Fermi away at the University of Michigan for the summer. Szilard approached the Army and Navy, but neither would provide funding. Commiserating with Wigner and Teller, Szilard came up with the idea of approaching Einstein and enlisting his help. On July 16, Wigner and Szilard drove out to Einstein's summer house on Long Island. Einstein proved amenable, and over the next two weeks the plan evolved for Einstein to write a letter to President Franklin Roosevelt warning him of the dangers of a German bomb and the need for support for uranium research at home. Szilard helped Einstein draft the letter, and on October 11 Alexander Sachs delivered the letter to the President and discussed it with him. Roosevelt, in response, created a committee on uranium research. The committee convened on October 21, with Szilard, Teller, and Wigner in attendance, and limited government support was soon forthcoming.

Szilard continued to work with Fermi, in a supporting role, on producing the chain reaction. In early 1942, he went with Fermi to the newly formed Met Lab at the University of Chicago where, Arthur Compton had centralized plutonium production research. He was with Fermi when CP-1 (Chicago Pile #1) on December 2, 1942, produced the world's first sustained chain reaction, lingering until most people had left and then, turning to Fermi and shaking his hand, saying that this would go down as a "black day in the history of mankind." Szilard would remain at the Met Lab for the rest of the war, frustrated and something of a pariah, out of the mainstream of Manhattan Project activities. General Leslie Groves, military head of the project, took an instant dislike to Szilard, viewing him at best as troublesome and at worst as an enemy agent. Szilard's outspoken opposition to army compartmentalization of information, which forbade discussions beyond one's limited responsibilities, and his sense that scientists and not bureaucrats and engineers should lead the project ran counter to Groves's security and organizational instincts. In October 1942, Groves drafted a letter to the U.S. Attorney General, not sent only due to a hasty telegram from Compton, describing Szilard as an "enemy alien" and suggesting that he "be interned for the duration of the war." Groves continued to view Szilard with suspicion, keeping him under surveillance throughout the war. In June 1943, security officials recommended that the surveillance be stopped, but Groves replied that the "investigation of Szilard should be continued despite the barrenness of the results. One letter or phone call once in three months would be sufficient for the passing of vital information and until we know for certain that he is 100% reliable we cannot entirely disregard this person."

With time on his hands, Szilard ruminated on the forthcoming bomb and the postwar world. As early as September 1942, he urged the Met Lab to give more attention to the political aspects of the bomb effort. In January 1944, he wrote Vannevar Bush, who had directed the uranium research effort prior to the military takeover, urging him to expedite work on the bomb. Unless atomic weapons were actually used in the present war, he reasoned, the public would not comprehend their destructive power and would not pay the price of peace. In March 1945, Szilard prepared a long memorandum explaining how vulnerability to atomic attack made it essential for the United States to seek international control. Once again, he persuaded Einstein to write a letter of introduction to Roosevelt, who died on April 12 before a connection could be made. Szilard now sought access to President Harry Truman. An aide arranged an appointment with James F. Byrnes, who would become Truman's secretary of state, but the meeting did not go well, and Szilard's evolving ideas on international control fell on deaf ears. Szilard, nonetheless, continued to press on the issue. He was one of the seven signatories of the June 11 "Franck Report" that contended that postwar international control of atomic power was the only way to stop the arms race that would be inevitable if the United States bombed Japan without first demonstrating the weapon in an uninhabited area. In early July, he circulated a petition to the President arguing that the U.S. would set a precedent by using the bomb and might have "to bear the responsibility of opening the door to an era of devastation on an unimaginable scale." The U.S. would weaken its moral position so that it would be difficult for Americans to lead in bringing the new forces of destruction under control.

After the war, Szilard sought to work on peaceful uses of atomic energy at the new Argonne National Laboratory but was denied a position, largely due to the ongoing influence of Groves. Szilard, even so, remained active in efforts to formulate atomic energy legislation immediately after the war and, for the remainder of his life, to promote nuclear arms control and disarmament. He was a founding member, along with fellow Manhattan Project alumni Joseph Rotblat, of the Pugwash Conference on nuclear arms control. Denied a position at Argonne, his academic interests turned to biology. In 1946, he became a professor of biophysics at the University of Chicago. In 1956, he moved to the Salk Institute of Biological Sciences in La Jolla, California. Leo Szilard died on May 30, 1964.

• Bethe, Hans
• Chadwick, James
• Einstein, Albert
• Fermi, Enrico
• Feynman, Richard
• Franck, James
• Fuchs, Klaus
• Rotblat, Joseph
• Seaborg, Glenn T.
• Serber, Robert
• Szilard, Leo
• Teller, Edward
• Wigner, Eugene
• York, Herbert

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