| Leó Szilárd | |
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Leó Szilárd (1898–1964)
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| Born | February 11, 1898 Budapest, Austria-Hungary |
| Died | May 30, 1964 (aged 66) La Jolla, California, U.S. |
| Residence | Hungary Germany United States |
| Nationality | Austro-Hungarian Hungarian German American |
| Fields | Nuclear physics |
| Institutions | Technical University of Berlin Humboldt University of Berlin Columbia University University of Chicago Brandeis University Salk Institute |
| Alma mater | Technische Universität Berlin Humboldt Universität zu Berlin |
| Doctoral advisor | Max von Laue |
| Other academic advisors | Albert Einstein |
| Notable students | Bernard T. Feld |
| Known for | Nuclear chain reaction Szilárd petition Einstein–Szilárd letter Cobalt bomb Absorption refrigerator Szilárd Engine Einstein-Szilard refrigerator |
| Influenced | James L. Tuck |
| Notable awards | Atoms for Peace Award (1959) |
Leó Szilárd (Hungarian: Szilárd Leó, February 11, 1898 – May 30, 1964 German: Spitz, Leo until age 2) was an Austro-Hungarian physicist and inventor who conceived the nuclear chain reaction in 1933, patented the idea of a nuclear reactor with Enrico Fermi, and in late 1939 wrote the letter for Albert Einstein's signature that resulted in the Manhattan Project that built the atomic bomb. He also conceived three revolutionary devices: the electron microscope, the linear accelerator and the cyclotron. Szilárd himself did not build all of these devices, or publish these ideas in scientific journals, and so their credit often went to others. As a result, Szilárd never received the Nobel Prize, but two of his inventions did.[1]
He was born in Budapest in the Austro-Hungarian Empire, and died in La Jolla, California.
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Szilárd was born in 1898 to middle class parents in Budapest, Hungary as the son of a civil engineer. His parents, both Jewish, Louis Spitz and Thekla Vidor, raised Leó in the Városligeti fasor of Pest, Hungary. From 1908–1916 Leó attended Reáliskola high school in his home town. Showing an early interest in physics and a proficiency in mathematics, in 1916 took the Eötvös Prize, a national prize for mathematics.[2][3]
He enrolled as an engineering student at Budapest Technical University during 1916. The following year, he was drafted into the Austro-Hungarian Army as an officer-candidate. Prior to his regiment being sent to the front lines, Szilárd fell ill with Spanish Influenza and he was returned home for hospitalization. Later he was informed that his regiment had been nearly annihilated in battle, so the sickness probably saved his life.[4] He was discharged honorably at the end of the war.
During 1919 he resumed engineering studies at Budapest Technical University but soon decided to leave Hungary because of the chaotic political situation and the rising antisemitism under the Horthy regime. Szilárd continued engineering studies at Technische Hochschule (Institute of Technology) in Berlin-Charlottenburg. He soon changed to physics there and took physics classes from Einstein, Planck, and Max von Laue. His dissertation on thermodynamics Über die thermodynamischen Schwankungserscheinungen (On The Manifestation of Thermodynamic Fluctuations) during 1922 was praised by Einstein and awarded top honors. In 1923 he was awarded a doctorate in physics from Humboldt University of Berlin.
He was appointed as assistant to von Laue at the University of Berlin's Institute for Theoretical Physics during 1924. During 1927 he finished his habilitation and became a Privatdozent (private lecturer) in physics at University of Berlin. During his time in Berlin he was working on numerous technical inventions. For example, in 1928 he submitted a patent application for the linear accelerator and, in 1929, he applied for a patent for the cyclotron. During the 1926-1930 period, he worked with Einstein to develop a refrigerator, notable because it had no moving parts.[5] Szilárd's 1929 paper, Über die Entropieverminderung in einem thermodynamischen System bei Eingriffen intelligenter Wesen" (On the reduction of entropy in a thermodynamic system by the interference of an intelligent being) Z. Physik 53, 840-856, introduced the thought experiment now called Szilárd's engine and was important in the history of attempts to understand Maxwell's demon.
Szilárd went to London in 1933 where he read an article in The Times summarizing a speech given by Ernest Rutherford in which he rejected the possibility of using atomic energy for practical purposes. Rutherford's speech remarked specifically on the recent 1932 work of his students John Cockcroft and Ernest Walton in "splitting" lithium into alpha particles, by bombardment with protons from a particle accelerator they had constructed:
Although the atom had been split and energy released, nuclear fission had not yet been discovered. However Szilárd was reportedly so annoyed at Rutherford's dismissal that on the same day the article about the Rutherford speech was printed in the morning paper, Szilárd conceived of the idea of nuclear chain reaction (analogous to a chemical chain reaction), using recently-discovered neutrons. The idea did not use the mechanism of nuclear fission, which was not then known, but Szilárd realized that if neutrons could initiate any sort of energy-producting nuclear reaction, such as the one that had occurred in lithium, and could be produced themselves by the same reaction, energy might be obtained with little input, since the reaction would be self-sustaining. The following year he filed for a patent on the concept of the neutron-induced nuclear chain reaction. Richard Rhodes described Szilárd's moment of inspiration:
Szilárd first attempted to create a nuclear chain reaction using beryllium and indium, but these elements did not produce a chain reaction. During 1936, he assigned the chain-reaction patent to the British Admiralty to ensure its secrecy (GB 630726). Szilárd also was the co-holder, with Nobel Laureate Enrico Fermi, of the patent on the nuclear reactor (U.S. Patent 2,708,656).
During 1938 Szilárd accepted an offer to conduct research at Columbia University in Manhattan, and moved to New York, and was soon joined by Fermi. After learning about the successful nuclear fission experiment conducted during 1939 in Germany by Otto Hahn, Fritz Strassmann, Lise Meitner, and Otto Robert Frisch, Szilárd and Fermi concluded that uranium would be the element capable of sustaining a chain reaction. Szilárd and Fermi conducted a simple experiment at Columbia and discovered significant neutron multiplication in uranium, proving that the chain reaction was possible and enabling nuclear weapons. Szilárd later described the event: "We turned the switch and saw the flashes. We watched them for a little while and then we switched everything off and went home." He understood the implications and consequences of this discovery, though. "That night, there was very little doubt in my mind that the world was headed for grief."[7]
At around that time the Germans and others were in a race to produce a nuclear chain reaction. German attempts to control the chain reaction sought to do so using graphite, but these attempts proved unsuccessful. Szilárd realized graphite was indeed perfect for controlling chain reactions, just as the Germans had determined, but that the German method of producing graphite used boron carbide rods, and the minute amount of boron impurities in the manufactured graphite was enough to stop the chain reaction. Szilárd had graphite manufacturers produce boron-free graphite. As a result, the first human-controlled chain reaction occurred on December 2, 1942.[8]
Szilárd was directly responsible for the creation of the Manhattan Project. He drafted a confidential letter to Franklin D. Roosevelt explaining the possibility of nuclear weapons, warning of Nazi work on such weapons and encouraging the development of a program which could result in their creation. During August 1939 he approached his old friend and collaborator Albert Einstein and convinced him to sign the letter, lending his fame to the proposal.[9] The Einstein–Szilárd letter resulted in the establishment of research into nuclear fission by the U.S. government and ultimately to the creation of the Manhattan Project; FDR gave the letter to an aide, General Edwin M. "Pa" Watson with the instruction: "Pa, this requires action!"[10] Later, Szilárd relocated to the University of Chicago to continue work on the project. There, along with Fermi, he helped to construct the first "neutronic reactor", a uranium and graphite "atomic pile" in which the first self-sustaining nuclear chain reaction was achieved, during 1942.
As the war continued, Szilárd became increasingly dismayed that scientists were losing control over their research to the military, and argued many times with General Leslie Groves, military director of the project. His resentment towards the U.S. government was exacerbated by his failure to prevent the destructive use of the atomic bomb through having a test explosion that could be witnessed by Japanese observers who would then have the opportunity to surrender and spare lives.[11]
Szilárd became a naturalized citizen of the United States during 1943.
During 1932, Szilárd had read about the fictional "atomic bombs" described in H. G. Wells's science fiction novel The World Set Free. This inspired him to be the first scientist to examine seriously the science of the creation of nuclear weapons.
As a scientist, he was the first person to conceive of a device that, using a nuclear chain reaction as fuel, could be used as a bomb.
As a survivor of the political and economic devastation in Hungary following World War I, which had been eviscerated by the Treaty of Trianon, Szilárd developed an enduring passion for the preservation of human life and freedom, especially freedom to communicate ideas.
He hoped that the U.S. government would not use nuclear weapons because of their potential for use against civilian populations. Szilárd hoped that the mere threat of such weapons would force Germany and/or Japan to surrender. He drafted the Szilárd petition advocating demonstration of the atomic bomb. However with the European war concluded and the U.S. suffering many casualties in the Pacific Ocean region, the new U.S. President Harry Truman agreed with advisers and chose to use atomic bombs against Hiroshima and Nagasaki over the protestations of Szilárd and other scientists.
During 1947, Szilárd switched topics of study because of his horror of atomic weapons, changing from physics to molecular biology, working extensively with Aaron Novick. In February 1950 Szilárd proposed a cobalt bomb, a new kind of nuclear weapon using cobalt as a tamper, which he said might destroy all life on the planet. U.S. News & World Report featured an interview with Szilárd in its August 15, 1960 issue, "President Truman Didn't Understand." He argued that "violence would not have been necessary if we had been willing to negotiate." During 1961 Szilárd published a book of short stories, The Voice of the Dolphins, in which he dealt with the moral and ethical issues raised by the Cold War and his own role in the development of atomic weapons. The title story described an international biology research laboratory in Central Europe. This became reality after a meeting in 1962 with Victor F. Weisskopf, James Watson and John Kendrew.[12] When the European Molecular Biology Laboratory was established, the library was named The Szilárd Library and the library stamp features dolphins.[13] Szilárd married Gertrud Weiss in 1951.[14] During 1960, Szilárd was diagnosed with bladder cancer. He underwent cobalt therapy at New York's Memorial Sloan-Kettering Hospital using a cobalt 60 treatment regimen that he designed himself. He was familiar with the properties of this isotope from his work on the cobalt bomb. A second round of treatment with an increased dose followed during 1962. The doctors tried to tell him that the increased radiation dose would kill him, but he said it wouldn't, and that anyway he would die without it. The higher dose did its job and his cancer never returned. This treatment became standard for many cancers and is still used, though linear accelerators are preferred, when available. During 1962, Szilárd was part of a group of scientists who founded the Council for a Livable World. The Council's goal was to warn the public and Congress of the threat of nuclear war and encourage rational arms control and nuclear disarmament. He spent his last years as a fellow of the Salk Institute in San Diego alongside his old friend Jacob Bronowski. During May 1964, Szilárd died in his sleep of a heart attack at the age of sixty-six.
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