Leo Szilard (/ˈsɪlɑːrd/;Hungarian:Szilárd Leó[ˈsilaːrdˈlɛoː]; bornLeó Spitz; February 11, 1898 – May 30, 1964) was a Hungarian-born physicist, biologist and inventor who made numerous important discoveries in nuclear physics and the biological sciences. He conceived thenuclear chain reaction in 1933, and patented the idea in 1936. In late 1939 he wrotethe letter forAlbert Einstein's signature that resulted in theManhattan Project that built theatomic bomb, and then in 1944 wrote theSzilard petition asking President Truman to demonstrate the bomb without dropping it on civilians. According toGyörgy Marx, he was one of the Hungarian scientists known asThe Martians.[1]
AfterAdolf Hitler became chancellor of Germany in 1933, Szilard urged his family and friends to flee Europe while they still could. He moved to England, where he helped found theAcademic Assistance Council, an organization dedicated to helping refugee scholars find new jobs. While in England, Szilard, alongside Thomas A. Chalmers, discovered a means of isotope separation known as theSzilard–Chalmers effect.
Foreseeing another war in Europe, Szilard moved to the United States in 1938, where he worked with Enrico Fermi andWalter Zinn on means of creating a nuclear chain reaction. He was present when this was achieved within theChicago Pile-1 on December 2, 1942. He worked for the Manhattan Project'sMetallurgical Laboratory at theUniversity of Chicago on aspects of nuclear reactor design, where he was the chief physicist. He drafted theSzilard petition advocating a non-lethal demonstration of the atomic bomb, but theInterim Committee chose to use themin a military strike instead.
Together withEnrico Fermi, he applied for a nuclear reactor patent in 1944. He publicly sounded the alarm against the possible development ofsalted thermonuclear bombs, a new kind of nuclear weapon that might annihilate mankind.
His inventions, discoveries, and contributions related to biological science are also equally important; they include the discovery offeedback inhibition and the invention of thechemostat. According toTheodore Puck andPhilip I. Marcus, Szilard gave essential advice which made the earliest cloning of the human cell a reality.
Diagnosed withbladder cancer in 1960, he underwent acobalt-60 treatment that he had designed. He helped found theSalk Institute for Biological Studies, where he became a resident fellow. Szilard foundedCouncil for a Livable World in 1962 to deliver "the sweet voice of reason" about nuclear weapons to Congress, the White House, and the American public. He died in his sleep of a heart attack in 1964.
He was born as Leó Spitz inBudapest,Kingdom of Hungary, on February 11, 1898. His middle-classJewish parents, Lajos (Louis) Spitz, acivil engineer, and Tekla Vidor, raised Leó on the Városligeti Fasor inPest.[2] He had two younger siblings, a brother, Béla, born in 1900, and a sister, Rózsi, 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" inHungarian.[3] Despite having a religious background, Szilard became anagnostic.[4][5] From 1908 to 1916 he attended Föreáliskola (high school) in Budapest's 6th District . Showing an early interest in physics and a proficiency in mathematics, in 1916 he won the Eötvös Prize, a national prize for mathematics.[6][7]
With World War I raging in Europe, Szilard 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 thePalatine Joseph Technical University, which he entered in September 1916. The following year he joined theAustro-Hungarian Army's 4th Mountain Artillery Regiment, but immediately was sent to Budapest as an officer candidate. He rejoined his regiment in May 1918 but in September, before being sent to the front, he fell ill withSpanish Influenza and was returned home for hospitalization.[9] Later he was informed that his regiment had been nearly annihilated in battle, so the illness probably saved his life.[10] He was discharged honorably in November 1918, after the Armistice.[11]
In January 1919, Szilard resumed his engineering studies, but Hungary was in a chaotic political situation with the rise of theHungarian Soviet Republic underBéla Kun. Szilard and his brother Béla founded their own political group, the Hungarian Association of Socialist Students, with a platform based on a scheme of Szilard's for taxation reform. He was convinced thatsocialism was the answer to Hungary's post-war problems, but not that of Kun's Hungarian Socialist Party, which had close ties to theSoviet Union.[12] 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.[13]
Szilard's doctoraldissertation onthermodynamicsÜber die thermodynamischen Schwankungserscheinungen (On The Manifestation of Thermodynamic Fluctuations), praised by Einstein, won top honors in 1922. It involved a long-standing puzzle in thephilosophy of thermal and statistical physics known asMaxwell's demon, athought experiment originated by thephysicistJames Clerk Maxwell. The problem was thought to be insoluble, but in tackling it Szilard recognized the connection between thermodynamics andinformation theory.[17][18]Szilard was appointed as assistant to von Laue at the Institute for Theoretical Physics in 1924. In 1927 he finished hishabilitation and became aPrivatdozent (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 theSzilard engine and became important in the history of attempts to understand Maxwell's demon. The paper also introduced the first equation linking negative entropy and information. This work established Szilard as a foundational figure in information theory; however, he did not publish it until 1929 and chose not to pursue the topic further.[19][20]Cybernetics, via the work ofNorbert Wiener andClaude E. Shannon, would later develop the concept into a general theory in the 1940s and 1950s—though, during the time of theCybernetics Meetings,John Von Neumann pointed out that Szilard first equated information with entropy in his review of Wiener'sCybernetics book.[21][22]
Throughout his time in Berlin, Szilard worked on numerous technical inventions. In 1928 he submitted apatent application for thelinear accelerator, not knowing ofGustav Ising's prior 1924 journal article andRolf Widerøe's operational device,[23][24] and in 1929 applied for one for thecyclotron.[25] He was also the first person to conceive the idea of theelectron microscope,[26] and submitted the earliest patent for one in 1928.[27] Between 1926 and 1930, he worked with Einstein to develop theEinstein refrigerator, notable because it had no moving parts.[28] He did not build all of these devices, or publish these ideas inscientific journals, and so credit for them often went to others. As a result, Szilard never received theNobel Prize, butErnest Lawrence was awarded it for the cyclotron in 1939, andErnst Ruska for the electron microscope in 1986.[27]
An image from the Fermi–Szilard "neutronic reactor" patent
Szilard received German citizenship in 1930, but was already uneasy about the political situation in Europe.[29] WhenAdolf Hitler becamechancellor of Germanyon January 30, 1933, Szilard urged his family and friends to flee Europe while they still could.[20] He moved to England, and transferred his savings of £1,595 (£143,000 today) from his bank inZürich to one inLondon. He lived in hotels where lodging and meals cost about £5.5 a week.[30] For those less fortunate, he helped found theAcademic Assistance Council, an organization dedicated to helping refugee scholars find new jobs, and persuaded theRoyal Society to provide accommodation for it atBurlington House. He enlisted the help of academics such asHarald Bohr,G. H. Hardy,Archibald Hill andFrederick G. Donnan. By the outbreak of World War II in 1939, it had helped to find places for over 2,500 refugee scholars.[31]
On the morning of September 12, 1933, Szilard read an article inThe Times summarizing a speech given byLord Rutherford in which Rutherford rejected the feasibility of using atomic energy for practical purposes. The speech remarked specifically on the recent 1932 work of his students,John Cockcroft andErnest Walton, in "splitting"lithium intoalpha particles, by bombardment withprotons from aparticle accelerator they had constructed.[32] Rutherford went on to say:
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.[33]
Szilard was so annoyed at Rutherford's dismissal that, on the same day, he conceived of the idea ofnuclear chain reaction (analogous to a chemicalchain reaction), using recently discoveredneutrons. The idea did not use the mechanism ofnuclear fission, which was not yet discovered, but Szilard 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.[34] He wanted to carry out a systematic survey of all 92 then-known elements in order to find one that can allow the chain reaction, at an estimated cost of $8000, but he did not for lack of funds.[35]
Szilard filed for a patent on the concept of the neutron-induced nuclear chain reaction in June 1934, which was granted in March 1936.[36] Under section 30 of thePatents and Designs Act (1907, UK),[37] Szilard was able to assign the patent to theBritish Admiralty to ensure its secrecy, which he did.[38] Consequently, his patent was not published until 1949[36] when the relevant parts of thePatents and Designs Act (1907, UK) were repealed by thePatents and Designs Act (July 1949, UK).[39]Richard Rhodes described Szilard's moment of inspiration:
In London, whereSouthampton Row passesRussell Square, across from theBritish Museum in Bloomsbury,[40] Leo Szilard waited irritably one grayDepression 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 Szilard 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. Szilard 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 woe,[41]the shape of things to come.[42]
Prior to conceiving the nuclear chain reaction, in 1932 Szilard had readH. G. Wells'The World Set Free, a book describing continuing explosives which Wells termed "atomic bombs"; Szilard wrote in his memoirs the book had made "a very great impression on me."[43] When Szilard assigned his patent to the Admiralty to keep the news from reaching the notice of the wider scientific community, he wrote, "Knowing what this [a chain reaction] would mean—and I knew it because I had read H. G. Wells—I did not want this patent to become public."[43]
In early 1934, Szilard began working atSt Bartholomew's Hospital in London. Working with a young physicist on the hospital staff, Thomas A. Chalmers, he began studying radioactiveisotopes for medical purposes. It was known that bombarding elements with neutrons could produce either heavier isotopes of an element, or a heavier element, a phenomenon known as the Fermi Effect after its discoverer, the Italian physicistEnrico Fermi. When they bombardedethyl iodide with neutrons produced by aradon–beryllium source, they found that the heavier radioactiveisotopes of iodine separated from the compound. Thus, they had discovered a means of isotope separation. This method became known as theSzilard–Chalmers effect, and was widely used in the preparation of medical isotopes.[44][45][46] He also attempted unsuccessfully to create a nuclear chain reaction using beryllium by bombarding it withX-rays.[47][48]
Szilard visited Béla and Rose and her husband Roland (Lorand) Detre, in Switzerland in September 1937. After a rainstorm, he and his siblings spent an afternoon in an unsuccessful attempt to build a prototype collapsible umbrella. One reason for the visit was that he had decided to emigrate to the United States, as he believed that another war in Europe was inevitable and imminent. He reached New York on the linerRMS Franconia on January 2, 1938.[49] Over the next few months, he moved from place to place, conducting research withMaurice Goldhaber at theUniversity of Illinois at Urbana–Champaign, and then theUniversity of Chicago,University of Michigan and theUniversity of Rochester, where he undertook experiments withindium but again failed to initiate a chain reaction.[50]
Army Intelligence report on Enrico Fermi and Leo Szilard
In early 1938, Szilard would settle down at "what would become a haven for much of the rest of his life" when he took a room at the King's Crown Hotel in New York City, being nearColumbia University where he now conducted research without a formal title or position.[51] He encounteredJohn R. Dunning, who invited him to speak about his research at an afternoon seminar in January 1939.[50] That same month,Niels Bohr brought news with him to New York that nuclear fission had accidentally been observed by chemistsOtto Hahn andFritz Strassmann at the Kaiser Wilhelm Institute for Chemistry in Berlin on December 19, 1938. Hahn and Strassman's misunderstanding of their observation would be corrected theoretically and thus explained byLise Meitner andOtto Frisch, as Meitner had known of Szilard's theory back in 1933 and after re-conducting the experiment themselves, confirmed Szilard's theory to have been correct all along.[51] When Szilard found out about it on a visit to Wigner atPrinceton University, he immediately realized thaturanium might be the element capable of sustaining a chain reaction.[52]
Unable to convince Fermi that this was the case, Szilard set out on his own. He obtained permission from the head of the physics department at Columbia,George B. Pegram, to use a laboratory for three months. To fund his experiment, he borrowed $2,000 from a fellow inventor, Benjamin Liebowitz. He wiredFrederick Lindemann at Oxford and asked him to send a beryllium cylinder. He persuadedWalter Zinn to become his collaborator and hired Semyon Krewer to investigate processes for manufacturing pure uranium andgraphite.[53]
Szilard and Zinn conducted a simple experiment on the seventh floor of Pupin Hall at Columbia, using a radium–beryllium source to bombard uranium with neutrons. Initially nothing registered on theoscilloscope, but then Zinn realized that it was not plugged in. On doing so, they discovered significant neutron multiplication in natural uranium, proving that a chain reaction might be possible.[54] Szilard 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."[55] 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".[56]
While they had demonstrated that the fission of uranium produced more neutrons than it consumed, this was still not a chain reaction. Szilard persuaded Fermi andHerbert L. Anderson to try a larger experiment using 500 pounds (230 kg) of uranium. To maximize the chance of fission, they needed aneutron moderator to slow the neutrons down.Hydrogen was a known moderator, so they used water. The results were disappointing. It became apparent that hydrogen slowed neutrons down, but also absorbed them, leaving fewer for the chain reaction. Szilard then suggested Fermi usecarbon, in the form of graphite. He felt he would need about 50 tonnes (49 long tons; 55 short tons) (50.8 metric ton) of graphite and 5 tonnes (4.9 long tons; 5.5 short tons) of uranium. As a back-up plan, Szilard also considered where he might find a few tons ofheavy water;deuterium would not absorb neutrons like ordinary hydrogen but would have the similar value as a moderator. Such quantities of material would require a lot of money.[57]
Szilard drafted a confidential letter to the President,Franklin D. Roosevelt, explaining the possibility of nuclear weapons, warning of theGerman nuclear weapon project, and encouraging the development of a program that could result in their creation. With the help of Wigner andEdward Teller, he approached his old friend and collaborator Einstein in August 1939, and persuaded him to sign the letter, lending his fame to the proposal.[58] TheEinstein–Szilárd letter resulted in the establishment of research into nuclear fission by the US government, and ultimately to the creation of theManhattan Project. Roosevelt gave the letter to his aide,Brigadier GeneralEdwin M. "Pa" Watson with the instruction: "Pa, this requires action!"[59]
An Advisory Committee on Uranium was formed underLyman J. Briggs, a scientist and the director of theNational Bureau of Standards. Its first meeting on October 21, 1939, was attended by Szilard, Teller, and Wigner, who persuaded the Army and Navy to provide $6,000 for Szilard to purchase supplies for experiments—in particular, more graphite.[60] A 1940 Army intelligence report on Fermi and Szilard, prepared when the United States had not yet entered World War II, expressed reservations about both. While it contained some errors of fact about Szilard, it correctly noted his dire prediction that Germany would win the war.[61]
Fermi and Szilard met withHerbert G. MacPherson and V. C. Hamister of theNational Carbon Company, who manufactured graphite, and Szilard made another important discovery. He asked about impurities in graphite and learned[62] from MacPherson that it usually containedboron, a neutron absorber. He then had special boron-free graphite produced.[63] Had he not done so, they might have concluded, as the German nuclear researchers did, that graphite was unsuitable for use as a neutron moderator.[64] Like the German researchers, Fermi and Szilard still believed that enormous quantities of uranium would be required for anatomic bomb, and therefore concentrated on producing a controlled chain reaction.[65] Fermi determined that a fissioning uranium atom produced 1.73 neutrons on average. It was enough, but a careful design was called for to minimize losses.[66] Szilard worked up various designs for anuclear reactor. "If the uranium project could have been run on ideas alone," Wigner later remarked, "no one but Leo Szilard would have been needed."[65]
At its December 6, 1941, meeting, theNational Defense Research Committee resolved to proceed with an all-out effort to produce atomic bombs. This decision was given urgency by the Japaneseattack on Pearl Harbor the following day that brought the United States into World War II. It was formally approved by Roosevelt in January 1942.Arthur H. Compton from the University of Chicago was appointed head of research and development. Against Szilard's wishes, Compton concentrated all the groups working on reactors andplutonium at theMetallurgical Laboratory of the University of Chicago. Compton laid out an ambitious plan to achieve a chain reaction by January 1943, start manufacturing plutonium in nuclear reactors by January 1944, and produce an atomic bomb by January 1945.[67]
In January 1942, Szilard joined the Metallurgical Laboratory in Chicago as a research associate, and later the chief physicist.[67]Alvin Weinberg noted that Szilard served as the project "gadfly", asking all the embarrassing questions.[68] Szilard provided important insights. Whileuranium-238 did not fission readily with slow, moderated neutrons, it might still fission with the fast neutrons produced by fission. This effect was small but crucial.[69] Szilard made suggestions that improved the uranium canning process,[70] and worked with David Gurinsky andEd Creutz on a method for recovering uranium from its salts.[71]
A vexing question at the time was how a production reactor should be cooled. Taking a conservative view that every possible neutron must be preserved, the majority opinion initially favored cooling with helium, which would absorb very few neutrons. Szilard argued that if this was a concern, then liquidbismuth would be a better choice. He supervised experiments with it, but the practical difficulties turned out to be too great. In the end, Wigner's plan to use ordinary water as a coolant won out.[68] When the coolant issue became too heated, Compton and the director of the Manhattan Project, Brigadier GeneralLeslie R. Groves, Jr., moved to dismiss Szilard, who was still a German citizen, but theSecretary of War,Henry L. Stimson, refused to do so.[72] Szilard was therefore present on December 2, 1942, when the first man-made self-sustaining nuclear chain reaction was achieved in thefirst nuclear reactor under viewing stands ofStagg Field and shook Fermi's hand.[73]
Szilard started to acquire high-quality graphite and uranium, which were the necessary materials for building a large-scale chain reaction experiment. The success of this demonstration and technological breakthrough at the University of Chicago were partially due to Szilard's new atomic theories, his uranium lattice design, and the identification and mitigation of a key graphite impurity (boron) through a joint collaboration with graphite suppliers.[74]
Szilard became anaturalized citizen of the United States in March 1943.[75] The Army offered Szilard $25,000 for his inventions before November 1940, when he officially joined the project. He refused.[76] He was the co-holder, with Fermi, of the patent on the nuclear reactor.[77] In the end he sold his patent to the government for reimbursement of his expenses, some $15,416, plus the standard $1 fee.[78] He continued to work with Fermi and Wigner on nuclear reactor design and is credited with coining the term "breeder reactor".[79]
With an enduring passion for the preservation of human life and political freedom, Szilard hoped that the US government would not use nuclear weapons, but that the mere threat of such weapons would force Germany and Japan to surrender. He also worried about the long-term implications of nuclear weapons, predicting that their use by the United States would start a nuclear arms race with the USSR. He drafted theSzilárd petition advocating that the atomic bomb be demonstrated to the enemy, and used only if the enemy did not then surrender. TheInterim Committee instead chose touse atomic bombs against cities over the protests of Szilard and other scientists.[80] Afterwards, he lobbied for amendments to theAtomic Energy Act of 1946 that placed nuclear energy under civilian control.[81]
In 1946, Szilard secured a research professorship at the University of Chicago that allowed him to research in biology and the social sciences. He teamed up withAaron Novick, a chemist who had worked at the Metallurgical Laboratory during the war. The two men saw biology as a field that had not been explored as much as physics and was ready for scientific breakthroughs. It was a field that Szilard had been working on in 1933 before he had become subsumed in the quest for a nuclear chain reaction.[81] The duo made considerable advances. They invented thechemostat, a device for regulating the growth rate of themicroorganisms in abioreactor,[82][83] and developed methods for measuring the growth rate of bacteria. They discoveredfeedback inhibition, an important factor in processes such as growth and metabolism.[84] Szilard gave essential advice toTheodore Puck andPhilip I. Marcus for their first cloning of a human cell in 1955.[85]
Before his relationship with his later wife Gertrud "Trude" Weiss, Leo Szilard's life partner in the period 1927–1934 was the kindergarten teacher and opera singerGerda Philipsborn, who also worked as a volunteer in a Berlin asylum organization for refugee children and in 1932 moved to India to continue this work.[86][87] Szilard married Trude Weiss,[88] a physician, in a civil ceremony in New York on October 13, 1951. They had known each other since 1929 and had frequently corresponded and visited each other ever since. Weiss took up a teaching position at theUniversity of Colorado in April 1950, and Szilard began staying with her inDenver for weeks at a time when they had never been together for more than a few days before. Single people living together was frowned upon in the conservative United States at the time and, after they were discovered by one of her students, Szilard began to worry that she might lose her job. Their relationship remained a long-distance one, and they kept news of their marriage quiet. Many of his friends were shocked, having considered Szilard a born bachelor.[89][90]
In 1949 Szilard wrote a short story titled "My Trial as a War Criminal" in which he imagined himself on trial for crimes against humanity after the United States lost a war with theSoviet Union.[91] He publicly sounded the alarm against the possible development ofsalted thermonuclear bombs, explaining in a University of Chicago Round Table radio program on February 26, 1950,[92] that a sufficiently big thermonuclear bomb rigged with specific but common materials, might annihilate mankind.[93] His comments, as well as those ofHans Bethe,Harrison Brown, andFrederick Seitz (the three other scientists who participated in the program), were attacked by theAtomic Energy Commission's former ChairmanDavid Lilienthal, and the criticisms plus a response from Szilard were published.[92]Time compared Szilard toChicken Little[94] while the AEC dismissed his ideas, but scientists debated whether it was feasible or not; theBulletin of the Atomic Scientists commissioned a study byJames R. Arnold, who concluded that it was.[95] Physicist W. H. Clark suggested that a 50 megatoncobalt bomb did have the potential to produce sufficient long-lasting radiation to be adoomsday weapon, in theory,[96] but was of the view that, even then, "enough people might find refuge to wait out the radioactivity and emerge to begin again."[94]
In 1960, Szilard was diagnosed withbladder cancer. He underwentcobalt therapy at New York'sMemorial Sloan-Kettering Hospital using a cobalt 60 treatment regimen that his doctors gave him a high degree of control over. A second round of treatment with an increased dose followed in 1962. The higher dose did its job and his cancer never returned.[105]
Szilard spent his last years as a fellow of theSalk Institute for Biological Studies in theLa Jolla community of San Diego, California, which he had helped create.[106] Szilard foundedCouncil for a Livable World in 1962 to deliver "the sweet voice of reason" about nuclear weapons to Congress, the White House, and the American public.[107] He was appointed a non-resident fellow there in July 1963, and became a resident fellow on April 1, 1964, after moving to San Diego in February.[108] With Trude, he lived in a bungalow on the property of theHotel del Charro. On May 30, 1964, he died there in his sleep of aheart attack; when Trude awoke, she was unable to revive him.[109][110][111] His remains were cremated.[112]
^abGB patent 630726, Leo Szilard, "Improvements in or relating to the transmutation of chemical elements", published September 28, 1949, issued March 30, 1936
^Brasch, A.; Lange, F.; Waly, A.; Banks, T. E.; Chalmers, T. A.; Szilard, Leo; Hopwood, F. L. (December 8, 1934). "Liberation of Neutrons from Beryllium by X-Rays: Radioactivity Induced by Means of Electron Tubes".Nature.134 (3397): 880.Bibcode:1934Natur.134..880B.doi:10.1038/134880a0.ISSN0028-0836.S2CID4106665.
^Lanouette, William. (2013).Genius in the Shadows : a Biography of Leo Szilard, the Man Behind the Bomb. New York: Skyhorse Publishing, Inc.ISBN978-1-62873-477-5.OCLC857364771.
Bess, Michael (1993).Realism, Utopia, and the Mushroom Cloud: Four Activist Intellectuals and their Strategies for Peace, 1945–1989. Chicago: University of Chicago Press.ISBN0-226-04421-1.OCLC27894840.
Blumesberger, Susanne; Doppelhofer, Michael; Mauthe, Gabriele (2002).Handbuch österreichischer Autorinnen und Autoren jüdischer Herkunft. Vol. 1. Munich: K. G. Saur.ISBN9783598115455.OCLC49635343.
Esterer, Arnulf K.; Esterer, Luise A. (1972).Prophet of the Atomic Age: Leo Szilard. New York: Julian Messner.ISBN0-671-32523-X.OCLC1488166.
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.ISBN978-3-03911-331-6.OCLC299281775.
Hargittai, István (2006).The Martians of Science: Five Physicists Who Changed the Twentieth Century. Oxford: Oxford University Press.ISBN978-0-19-517845-6.OCLC62084304.
Lanouette, William; Silard, Bela (1992).Genius in the Shadows: A Biography of Leo Szilard: The Man Behind The Bomb. New York: Skyhorse Publishing.ISBN1-626-36023-5.OCLC25508555.
The Many Worlds of Leo Szilard, an invited session sponsored by the APS Forum on the History of Physics at the APS April Meeting 2014, speakers discuss the life and physics Léo Szilárd. Presentations by William Lanouette (The Many Worlds of Léo Szilárd: Physicist, Peacemaker, Provocateur), Richard Garwin (Léo Szilárd in Physics and Information), and Matthew Meselson (Léo Szilárd: Biologist and Peacemaker)
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