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 Albert Einstein. 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 uranium might be turned Hungary in 1919. He traveled to the University of into a new and important source of energy by a chain Berlin, 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 Thermodynamics 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 James Clerk Maxwell. E=mc2. That and other ideas that transformed science'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. nuclear weapon, 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 work, included pub­ I t led to the top-secret Manhattan Proj ect, and the lication of a theory in statistical mechanics 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 neutron-based chain reaction was hardly as famous patents for an electron microscope, as well as for a linear as Einstein. He was an Einstein protege named Leo Szi­ accelerator and a cyclotron, 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 physics, he also understo~d invention. His uncle, Jacob box. And that's how the relatively obscure Leo Szilard 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 Budapest 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 mechanical engineering professor at diploma from the Federal Institute of Technology in Union College in Schenectady. N.Y. Zurich 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-Einstein refrigerator 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 photoelectric effect" Physics of the 1920s provided Einstein and Szilard the was specifically cited when he was presented the Nobel excitement of discovering mysteries of nature, 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 physicists Ernest Rutherford and tential benefit of preserving food, but the early models Niels Bohr proclaimed the neutron to be an important relied on ammonia, 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 heat-driven, absorption-cycle refrigerator. Circulation Chain Reaction was achieved by their invention of an electromagnetic Leo Szilard was crossing a London 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 United States of freon to could release tremendous amounts of nuclear binding replace ammonia and of the sealed electric compressor 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 Columbia University to join an­ other refugee, Enrico Fermi, who had taken refuge II1IIII1II Szilard's new fear from Fascist Italy. Fermi had received the 1938 Nobel Prize 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 neutrons 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 graphite 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 isotope. The other possibility arms race."" was to use surplus neutrons in a critical reactor to produce fissionable plutonium 239 from the more abundant U-238 isotope. Szilard was alarmed at the implications. A German physicist, 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.