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Home , Einstein refrigerator, Leo Szilard

Overshadowed by a legendary mentor.

Leo Szilard switched on the Atomic Age. By Frank Wicks Downloaded from http://asmedigitalcollection.asme.org/memagazineselect/article-pdf/128/11/40/6356252/me-2006-nov4.pdf by guest on 25 September 2021

istorians trace the birth of the atomic age to a War I into the Austro-Hungarian Army. The 1918 flu 1939 letter to President Roosevelt signed by pandemic that killed 20 million people probably saved . It was a month after Ger­ his life. He was bedridden while his artillery unit was many invaded Poland to begin World War II, slaughtered. the largest conflict in human history. The letter informed After the war, he escaped an anti-Semitic regime in Roosevelt that the element might be turned Hungary in 1919. He traveled to the University of into a new and important source of energy by a chain , where Albert Einstein, who had achieved fame reaction. It could also lead to an extremely power­ with his theories of relativity, was a research professor. ful bomb. The letter warned that Germany might have Szilard was assigned a dissertation topic by Nobellaure­ taken over the uranium mines in Czechoslovakia, and ate Max Van Laue. He concluded that the problem was added that the most important uranium source was the unsolvable, and redirected his attention to a contradic­ Belgian Congo. tion in the Second Law of known as The energy released by splitting a uranium atom had "Maxwell's Demon." It was a paradox defined 50 years been defined by Einstein's famous 1905 equation earlier by . E=mc2. That and other ideas that transformed 's Szilard proceeded to solve it, but it put him in the awk­ understanding of the physical world had made Einstein ward position of having solved the wrong problem. So famous. So the president took note. Szilard approached Einstein to explain his analysis and Adolph Hitler's Germany, for reasons that remain un­ dilemma. Einstein responded with a favorable review, certain, failed to follow up with the development of a and Szilard was awarded a Ph.D. , but Roosevelt responded to the letter Szilard and his mentor Einstein were both theorists with a modest program to investigate the possibility. who shared a practical side. Szilard's , included pub­ I t led to the top-secret Manhattan Proj ect, and the lication of a theory in that would be 1945 destruction of the Japanese cities of Hiroshima recognized a generation later as a seminal paper in infor­ and Nagasaki. mation theory. But the man who actually conceived ofthe possibility Szilard studied X-ray diffraction. He designed and filed of a -based was hardly as famous patents for an , as well as for a linear as Einstein. He was an Einstein protege named Leo Szi­ accelerator and a , which became instruments lard, who probably wrote the letter that went to Roo­ for probing the structure of an atom. sevelt over Einstein's name. While Albert Einstein is famous for theoretical Einstein later said he had only served as Szilard's mail­ , he also understo~d invention. His uncle, Jacob box. And that's how the relatively obscure Einstein, was an inventor who patented an electric gen­ made things happen. Szilard-called "Genius in the erator and meter. As a four-year-old in 1883, Albert Shadows" by his biographer, William Lanouette-once Einstein watched his father, Hermann, and his uncle in­ said he might live without any fixed home or position, stall the first electric lighting system for the Octoberfest but could call on Einstein and other associates placed to in Munich. advance his ideas and concerns for the fate of the world. Albert Einstein experimented with steam engines and Leo Szilard was born in Hungary in 1898. He studied other mechanical machines, and hoped to study engi­ engineering in until he was drafted for World neering, but he failed the entrance exams. Repulsed by the militarism he witnessed in Germany, he moved to Frank Wicks. a frequent contributor to this magazine. is a Switzerland, where he studied physics and received a nuclear engineer and a professor at diploma from the Federal Institute of Technology in Union College in Schenectady. N.Y. in 1900.

40 November 2006 mechanical engineering Downloaded from http://asmedigitalcollection.asme.org/memagazineselect/article-pdf/128/11/40/6356252/me-2006-nov4.pdf by guest on 25 September 2021

In "Atomic Power," a 1946 March of Time documentary, Einstein and Szilard reenacted their collaboration on the atomic bomb letter to President Roosevelt.

When he failed to get an academic position, his experi­ made the Szilard- obsolete. ence with machines and understanding of invention When Adolph Hitler came to power in 1933, it was served him. He was hired in 1902 as a clerk in the Swiss time to leave Germany again. Einstein accepted a posi­ Patent Office. He was good at the job. It gave him time tion at the Institute of Advanced Study in Princeton, for the abstract thinking that led to his revolutionary where he continued his interest in invention. He collab­ 1905 publications about relativity, quantum theory, orated with Gustav Bucky, a physician and inventor of atomic motion, and the equivalence of mass and energy. medical equipment, and in 1936 they received a patent for an automatic-exposure camera. It used the photo­ electric effect, which Einstein had explained in 1905. Seeking a Better Refrigerator "His discovery of the law of the " Physics of the 1920s provided Einstein and Szilard the was specifically cited when he was presented the Nobel excitement of discovering mysteries of , but Prize in Physics in 1921. seemed to be of little practical value. Meanwhile, the Szilard, meanwhile, escaped to England, where the world desperately needed a better refrigerator. neutron had been discovered by John Chadwick in 1932. Refrigerators were being introduced with the huge po­ Pioneering atomic and tential benefit of preserving food, but the early models proclaimed the neutron to be an important relied on , which was known to leak into scientific discovery, but did not predict any practical sig­ homes and had sometimes killed entire families. Szilard nificance, although the science fiction writer H .G. Wells approached Einstein to collaborate on the invention of a had described an atom bomb in a novel, The World Set safer refrigerator. It was an opportunity to do well finan­ Free, published in 1914. cially while doing good for humanity. They worked together for seven years to produce a -driven, absorption-cycle refrigerator. Circulation Chain Reaction was achieved by their invention of an electromagnetic Leo Szilard was crossing a street in September pump with no moving parts and minimal risk ofleakage. 1933 when he conceived of the possibility that a neutron Their refrigerator was licensed to General Electric in released by one atom could penetrate the nucleus of an­ Germany. Szilard was hired as a consultant. However, the other atom. It could be the basis of a chain reaction. It subsequent inventions in the of to could release tremendous amounts of nuclear binding replace ammonia and of the sealed electric energy for peaceful purposes, but could also be the basis

mechanical engineering November 200641 the start of World War 11 in Europe. Szilard traveled to to join an­ other refugee, , who had taken refuge II1IIII1II Szilard's new fear from Fascist Italy. Fermi had received the 1938 for performing neutron activation experiments was that the bomb that were similar to those that Szilard had been doing in secret in England. Fermi had discovered that proba­ would be used against Japan bility of capture was increased if fast were slowed down by collisions w ith a non-absorber or with unacceptable civilian moderator. A neutron source was set up next to a pile death and destruction, of uranium with for a moderator. Neutron multiplication was demonstrated. A purer form of graphite and the right fuel might result in a self-sus­

to be followed Downloaded from http://asmedigitalcollection.asme.org/memagazineselect/article-pdf/128/11/40/6356252/me-2006-nov4.pdf by guest on 25 September 2021 taining chain reaction. by a nuclear One option would be to enrich the uranium in the easier-to-split U-235 . The other possibility arms race."" was to use surplus neutrons in a critical reactor to produce fissionable 239 from the more abundant U-238 isotope. Szilard was alarmed at the implications. A German , Paul Harteck, had already in­ for a weapon of mass destruction. formed Hitler that an atomic bomb was possible and had Szilard applied for a secret patent in England. A chain commenced experiments. reaction would require finding an element or isotope with a high probability of absorbing neutrons followed by the release of more free neutrons. The element subse­ Informing the President quently would split to form smaller atoms. Szilard felt a Szilard's dilemma was how to inform President sense of excitement and despair. He was in the bizarre Franklin Roosevelt of the looming danger. Einstein, position of hoping to prove his invention was impossible. who at the time was enjoying a sailing vacation on Long Rutherford rejected Szilard's request to use his lab at Island, might be able to relay the warning. Paul Wigner, Cambridge, but Szilard received permission from a Lon­ who agreed to drive, and Szilard found Einstein, who don hospital. He proceeded to neutron-activate various was unfamiliar with the recent discoveries. Einstein lis­ elements and was relieved at his negative results. tened and responded that he had never thought of a Szilard came to the United States in 1938, and his fear chain reaction, but agreed with the possibility. of an atomic bomb returned a year later. He traveled to Szilard proceeded to draft a letter to Roosevelt. Once Princeton to see his old friend Paul Wigner, who would again he needed a ride, this time to get Einstein's signa- later win a Nobel Prize in Physics. They were both . ture. He recruited his fi'iend , who was also Hungarian natives and had worked together in Germany a refugee from Hungary. Years later, Teller would be before escaping the Nazis. Wigner informed him that known as the father of the bomb. He would the German radio-chemist had used neu­ joke about meeting Einstein as Szilard's chauffeur. trons to split the uranium atom. Einstein compromised his pacifism to sign the letter. Word had come out because Hahn had asked his long­ Germany invaded Poland in September 1939. The letter time collaborator, , who had worked with was delivered to the president in October by Alexander Szilard before she, too, had left Germany, to explain the Sachs, a businessman, biologist, and economist. creation of barium. Roosevelt called for action. With funding of $6,000, While taking a walk in a park, Meitner and her physi­ Szilard arranged for the production of graphite that was cist nephew, Otto Frisch; concluded that the uranium not contaminated by neutron-capturing . atom had been split, since barium is approximately half Szilard and Fermi moved to the , the mass of uranium. She used Einstein's E=mc2 to cal­ and designed a reactor using natural uranium and the pu­ culate the energy released. Frisch, who had been work­ rified graphite. A chain reaction was demonstrated in ing with Niels Bohr, calculated the same energy using a December 1942, a year after the United States had en­ surface tension model of the nucleus. They predicted tered the war. that a single atom could release enough energy to lift a It took four years from the discovery that uranium visible size grain of sand a visible height. could be split to the demonstration of a self-sustaining This news reached the United States via Niels Bohr, chain reaction. Thirteen years later, after the technology who attended a conference in Washington in January was declassified, Szilard and Fermi were awarded U.S. 1939. It is an accident of history that this apparently ob­ Patent No 2,708,656 on the basis of this first critical re­ scure discovery, which would ultimately change military actor. It was also the basis for their induction into the power structures throughout the world, corresponded to National Inventors Hall of Fame.

42 November 2006 mechanical engineering The clear energy while trying to stop the arms race and pre­ vent further use of nuclear weapons. In 1945, he called Development was dramatically escalated after the 1942 for civilian control of nuclear energy. He organized in­ demonstration of a chain reaction. The combined scien­ ternational conferences and the Council for a Livable tific and industrial program of unprecedented size and World. He undertook missions of personal diplomacy. secrecy was code-named the Manhattan Project. The di­ Szilard also resorted to humor, satire, and science fic­ rector was Gen. Leslie Grove, who had overseen the tion. He wrote the "Voice of Dolphins" and other para­ construction of the Pentagon. The research director was bles that addressed the arms race, the morality of war, Robert Oppenheimer, a Harvard-educated New York and the mismatch between the modern human's techni­ native who had studied theoretical physics in England cal capability and moral capacities. and Germany. Szilard shifted his research from physics to the life sci­ Huge secret facilities were built in Tennessee, Washing­ ences and became a cell biologist. He studied aging and

ton State, and New Mexico for uranium enrichment, mutations while inventing laboratory equipment. He be­ Downloaded from http://asmedigitalcollection.asme.org/memagazineselect/article-pdf/128/11/40/6356252/me-2006-nov4.pdf by guest on 25 September 2021 'plutonium production, assembly, and testing. The two friended Jonas Salk, whose vaccine had eliminated the options of enriched uranium 235 and plutonium 239 scourge of polio, and Szilard was named one of the five bred from uranium 238 were pursued. By the spring of founding fellows of the Salk Institute for Biological 1945, both methods were shown to be workable. Studies. Another fellow was Francis Crick, who in 1953 Einstein was briefly recruited to analyze uranium sepa­ had been a co-discoverer of DNA. ration, but was then excluded as a security risk. He was made an explosives consultant for the Navy at a fee of $5 per day. Szilard continued in Chicago, where he solved physics and engineering problems related to sustaining the chain reaction, fission prod­ ucts, structure, and cooling for the plutonium pro­ duction reactors. Meanwhile, he introduced the idea of a for civilian power. It would produce fissionable plutonium faster than it deplet­ ed fissionable uranium. By the spring of 1945, Germany was on the verge of surrender. It was learned that Germany had not made the atom bomb, while the United States would soon have both an enriched uranium and a plutoni­ um bomb. Szilard's new fear was that the bomb would be used against Japan with unacceptable civil­ ian death and destruction, to be followed by a nuclear arms race that would threaten civilization. Once again, Szilard shared his concerns with Ein­ stein, who signed one more letter to Roosevelt, dated March 25, 1945. The letter told the president of Szilard's great concern about lack of contact be­ tween the scientists developing a new weapon, and This photo of Franklin D. Roosevelt, in his quarters aboard the U.S.S. Houston, was the president and members of the cabinet responsi­ taken about seven months before he received the letter signed by Einstein. ble for formulating policy. There was no response. Roosevelt died 16 days later. In 1951, at the age of 53, Leo Szilard had married his Cabinet members informed Harry Truman about the friend Gertrude Weiss, a physician. When he developed bomb after he became president. , he and Gertrude worked together to de­ Szilard organized a petition that was signed by 155 sci­ velop radiation treatment that was successful. Szilard left entists who were working on the project. It was to in­ his hospital bed to discuss the arms race with Soviet form the new president of their moral doubts about the leader Nikita Khrushchev, who was visiting New York use of the new weapon. General Grove had been unsuc­ and the United Nations. Szilard proposed a direct tele­ cessfully trying to show that Szilard was a spy. He learned phone hotline between Moscow and Washington, but of the petition and stopped further circulation. no action was taken. The fears of Szilard and Einstein were soon realized. The and the United States came to the President Truman ordered the atomic bombing of the brink of nuclear war during the 1962 Cuban missile cri­ Japanese cities of Hiroshima and Nagasaki in August sis. The risk of accidental war was compounded by lack 1945. Einstein spent much of his remaining 10 years in of communications between Khrushchev and President Princeton trying without success to halt the nuclear arms John Kennedy. The hotline that Szilard had been propos­ race and failing to develop a unified theory of forces. ing was finally installed. Leo Szilard died in his sleep of a Szilard launched initiatives for the peaceful use of nu- heart attack two years later. •

mechanical engineering November 200643