Leo Szilard

The native form of this personal name is Szilárd Leó. This article uses Western name order when mentioning individuals.

Leó Szilárd
Szilárd, c. 1960
Born	(1898-02-11)February 11, 1898 Budapest, Austria-Hungary
Died	May 30, 1964(1964-05-30) (aged 66) La Jolla, California, U.S.
Citizenship	Hungary Germany United States
Alma mater	Technische Universität Berlin Humboldt Universität zu Berlin
Known for	Nuclear chain reaction Szilárd petition Einstein–Szilárd letter Cobalt bomb Absorption refrigerator Szilárd Engine Einstein-Szilard refrigerator
Awards	Atoms for Peace Award (1959) Albert Einstein Award (1960)
Scientific career
Fields	Physics
Institutions	Budapest Technical University Technical University of Berlin Humboldt University of Berlin Columbia University University of Chicago Brandeis University Salk Institute
Thesis	Über die thermodynamischen Schwankungserscheinungen  (1923)
Doctoral advisor	Max von Laue
Other academic advisors	Albert Einstein
Notable students	Bernard T. Feld Maurice Sanford Fox

Leó Szilárd (Hungarian: Szilárd Leó; German: Leo Spitz until age 2; February 11, 1898 – May 30, 1964) was a Hungarian-American physicist and inventor. He 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 was born in Budapest in the Kingdom of Hungary, and died in La Jolla, California.

Early life

Leó Spitz was born in Budapest, Hungary, on February 11, 1898. His middle-class parents, both Jewish, Louis Spitz, a civil engineer, and Thekla Vidor, raised Leó on the Városligeti Fasor in Pest, Hungary. He had two younger sibling, a brother, Bela, born in 1900, and a sister, Rozsi, born in 1901. On October 4, 1900, the family changed its surname from the German "Spitz" to the Hungarian "Szilárd", a name that means "solid" in Magyar. Despite having a religious background, Szilárd became an agnostic. From 1908 to 1916 he attended Reáliskola high school in his home town. Showing an early interest in physics and a proficiency in mathematics, in 1916 won the Eötvös Prize, a national prize for mathematics.

Leo Szilárd at age 18

With the First World War raging in Europe, Szilárd received notice on January 22, 1916, that he had been drafted into the 5th Fortress Regiment, but he was able to continue his studies. He enrolled as an engineering student at the Palatine Joseph Technical University, which he entered in September 1916. The following year he joined the Austro-Hungarian Army's 4th Mountain Artillery Regiment, but immediately bas sent to Budapest as an officer candidate. He joined his regiment in May 1918, but in September, before his regiment was sent to the front lines, he 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. He was discharged honorably in November 1918, after the end of the war.

In January 1919 Szilárd resumed his engineering his studies, but Hungary was in a chaotic political situation with the rise of the Hungarian Soviet Republic under Béla Kun. Szilárd and his brother Bela founded their own political group, the Hungarian Association of Socialist Students. When Kun's government tottered, the brothers officially changed their religion from "Israelite" to "Calvinist". But when they attempted to re-enroll in what was now the Budapest University of Technology, they were prevented from doing so by nationalist students because they were Jews.

Convinced that there was no future for him in Hungary, Szilárd left for Berlin via Austria on December 25, 1919,and enrolled at Technische Hochschule (Institute of Technology) in Berlin-Charlottenburg. He was soon joined by his brother Bela. Szilárd became bored with engineering, and his attention turned to physics. This was not taught at the Technische Hochschule, so he transferred to Friedrich Wilhelm University, where he attended lectures given by Albert Einstein, Max Planck, Walter Nernst James Franck and Max von Laue. He also met fellow Hungarian students Eugene Wigner, John von Neumann and Dennis Gabor. His doctoral dissertation on thermodynamics Über die thermodynamischen Schwankungserscheinungen (On The Manifestation of Thermodynamic Fluctuations), praised by Einstein, won top honors in 1922. It involved a long-standing puzzle in the philosophy of thermal and statistical physics known as Maxwell's demon, a thought experiment originated by the physicist James Clerk Maxwell. The problem was thought to be insoluble, but in tackling it Szilárd recognized the connection between thermodynamics and Information theory.

Szilárd was appointed as assistant to von Laue at the Institute for Theoretical Physics in 1924. In 1927 he finished his habilitation and became a Privatdozent (private lecturer) in physics. For his habilitation lecture, he produced a second paper on Maxwell's Demon, Über die Entropieverminderung in einem thermodynamischen System bei Eingriffen intelligenter Wesen (On the reduction of entropy in a thermodynamic system by the intervention of intelligent beings), that had actually been written soon after the first. This introduced the thought experiment now called Szilárd's engine and became important in the history of attempts to understand Maxwell's demon. This paper also is the first equation of negative entropy and information. As such, it established Szilard as one of the founders of information theory; but he did not publish it until 1929, and did not pursue it further. Claude E. Shannon, who took it up in the 1950s, acknowledged Szilárd's paper as his starting point.

Throughout his time in Berlin, Szilárd worked on numerous technical inventions. For example, in 1928 he submitted a patent application for the linear accelerator,and in 1929 applied for one for the cyclotron, not knowing of Gustav Ising's prior 1924 journal article and Rolf Widerøe's operational device, and also the cyclotron. Between 1926 and 1930, he worked with Einstein to develop the Einstein refrigerator, notable because it had no moving parts. He conceived the linear accelerator (1928 He also conceived the electron microscope. Szilárd himself did not build all of these devices, or publish these ideas in scientific journals, and so credit for them often went to others. As a result, Szilárd never received the Nobel Prize, but Ernest Lawrence was awarded it for the cyclotron in 1939 and Ernst Ruska for the electron microscope in 1986.

Developing the idea of the nuclear chain reaction

An image from the Fermi–Szilárd "neutronic reactor" patent

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 feasibility 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:

We might in these processes obtain very much more energy than the proton supplied, but on the average we could not expect to obtain energy in this way. It was a very poor and inefficient way of producing energy, and anyone who looked for a source of power in the transformation of the atoms was talking moonshine. But the subject was scientifically interesting because it gave insight into the atoms.

Although the atom had been split and energy released, nuclear fission had not yet been discovered. Szilárd was reportedly so annoyed at Rutherford's dismissal that when his speech was published, 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-producing 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:

In London, where Southampton Row passes Russell Square, across from the British Museum in Bloomsbury, Leo Szilárd waited irritably one gray Depression morning for the stoplight to change. A trace of rain had fallen during the night; Tuesday, September 12, 1933, dawned cool, humid and dull. Drizzling rain would begin again in early afternoon. When Szilárd told the story later he never mentioned his destination that morning. He may have had none; he often walked to think. In any case another destination intervened. The stoplight changed to green. Szilárd stepped off the curb. As he crossed the street time cracked open before him and he saw a way to the future, death into the world and all our woes, the shape of things to come.

Szilárd first attempted to create a nuclear chain reaction using beryllium and indium, but these elements did not produce a chain reaction. In 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).

In 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 in 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".

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.

The Manhattan Project

The Metallurgical Laboratory scientists, with Szilárd third from right.

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. In August, 1939 he approached his old friend and collaborator Albert Einstein and convinced him to sign the letter, lending his fame to the proposal. 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!" 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 in 1942.

As the war continued, Szilárd became increasingly dismayed that scientists were losing control of 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.

Szilárd became a naturalized citizen of the United States in 1943.

Views on the use of nuclear weapons

In 1932, Szilárd read the science fiction novel The World Set Free by H. G. Wells, a book which he said made a great impression on him.

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 also worried about the long term implications of the usage of nuclear weapons, predicting that their usage by the United States would start a nuclear arms race with Russia. 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.

After the war

Szilárd and Norman Hilberry at the site of CP-1, at the University of Chicago, some years after the war (before 1957)

In 1947, Szilárd shifted his field of study from nuclear physics to biophysics and molecular biology, working extensively with Aaron Novick. The change is widely credited as Szilárd's zero interest to support the development of stronger nuclear weapons.

Szilárd married Gertrud Weiss in 1951.

Szilárd as both nuclear and bio physicist understood very exactly how radiation harms the life. In February 1950 he publicly alerted against the developed salted bombs, explaining in radio talk, that a cobalt bomb, a new kind of nuclear weapon using cobalt as a tamper, might destroy all life on the planet. In his new field, biophysics, he gave essential advice to Theodore Puck and Philip I. Marcus for their first cloning of a human cell in 1955.

U.S. News & World Report featured an interview with Szilárd in its August 15, 1960 issue, "President Truman Didn't Understand." Szilard argued against bombing of Hiroshima and Nagasaki that "violence would not have been necessary if we had been willing to negotiate."

In 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. When the European Molecular Biology Laboratory was established, the library was named The Szilárd Library and the library stamp features dolphins.

In 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 knew the properties of this isotope also from his estimates about the salted bombs with cobalt. A second round of treatment with an increased dose followed in 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.

In 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. On May 30, 1964, Szilárd died in his sleep of a heart attack at the age of sixty-six.

In February 2014, the UCSD Library announced that they received grant funding from the National Historical Publications and Records Commission (NHPRC) to digitize its collection of Szilard's papers, extending from 1938 - 1998.

Honors

• American Academy of Arts and Sciences 1954
• American Physical Society
• Atoms for Peace Award 1959
• National Inventors Hall of Fame
• Humanist of the Year 1960
• The crater Szilárd (34.0°N, 105.7°E, 122 km dia.) on the far side of the Moon is named after him.

Patents

• U.S. patent 2,708,656—Neutronic reactor—E. Fermi, L. Szilárd, filed December 19, 1944, issued May 17, 1955
• U.S. patent 1,781,541—Einstein Refrigerator—co-developed with Albert Einstein filed in 1926, issued November 11, 1930

References

• Bess, Michael (1993). Realism, Utopia, and the Mushroom Cloud: Four Activist Intellectuals and their Strategies for Peace, 1945-1989. Chicago: University of Chicago Press. ISBN 0-226-04421-1. OCLC 27894840. {{cite book}}: Invalid |ref=harv (help)
• Blumesberger, Susanne; Doppelhofer, Michael; Mauthe, Gabriele (2002). Handbuch österreichischer Autorinnen und Autoren jüdischer Herkunft. Vol. 1. Munich: K. G. Saur. ISBN 9783598115455. OCLC 49635343. {{cite book}}: Invalid |ref=harv (help)
• Calaprice, Alice; Lipscombe, Trevor (2005). Albert Einstein: A Biography. Greenwood Press. ISBN 978-0-313-33080-3. OCLC 57208188. {{cite book}}: Invalid |ref=harv (help); Text "Westport, Connecticut" ignored (help)
• Esterer, Arnulf K.; Esterer, Luise A. (1972). Prophet of the Atomic Age: Leo Szilárd. New York: Julian Messner. ISBN 0-671-32523-X. OCLC 1488166. {{cite book}}: Invalid |ref=harv (help)
• Frank, Tibor (2008). Double exile: migrations of Jewish-Hungarian professionals through Germany to the United States, 1919-1945. Exile Studies. Vol. 7. Oxford: Peter Lang. ISBN 3-03911-331-3. OCLC 299281775. {{cite book}}: Invalid |ref=harv (help)
• Hargittai, István (2006). The Martians of Science: Five Physicists Who Changed the Twentieth Century. Oxford: Oxford University Press. ISBN 978-0-19-517845-6. OCLC 62084304. {{cite book}}: Invalid |ref=harv (help)
• Lanouette, William; Silard, Bela (1992). Genius in the Shadows: A Biography of Leo Szilárd: The Man Behind The Bomb. New York: Skyhorse Publishing. ISBN 1-626-36023-5. OCLC 25508555. {{cite book}}: Invalid |ref=harv (help)
• Rhodes, Richard (1986). The Making of the Atomic Bomb. New York: Simon and Schuster. ISBN 0671441337. OCLC 25508555. {{cite book}}: Invalid |ref=harv (help)
• Szilárd, Leo; Weiss-Szilárd, Gertrud; Weart, Spencer R. (1978). Leo Szilárd: His Version of the Facts : Selected Recollections and Correspondence. Cambridge, Massachusetts: The MIT Press. ISBN 0-262-69070-5. OCLC 4037084. {{cite book}}: Invalid |ref=harv (help)
• Szilárd, Leo (1992). The Voice of the Dolphins: And Other Stories (Expanded edition from 1961 original ed.). Stanford, CA.: Stanford University Press. ISBN 0-8047-1754-0. OCLC 758259818. {{cite book}}: Invalid |ref=harv (help)

External links

• Leo Szilárd Online—an "Internet Historic Site" (first created March 30, 1995) maintained by Gene Dannen
• Leo Szilárd's page at atomicarchive.com
• Register of the Leo Szilard Papers, 1898-1998, Mandeville Special Collections, UC San Diego Library
• Einstein's Letter to President Roosevelt—1939
• Annotated bibliography for Leo Szilárd from the Alsos Digital Library
• Szilárd biography at Hungary.hu
• The Szilárd Library at the European Molecular Biology Laboratory
• Szilárd lecture on war
• Szilárd's math genealogy