Leo Szilard

Leo Szilard (1898-1964) was a Hungarian-American physicist who helped conduct the first sustained nuclear chain reaction and was instrumental in initiating the Manhattan Project for the development of the atomic bomb.[5][2][1] He developed the idea of the nuclear chain reaction in 1933[4][2] and later became a prominent advocate for nuclear arms control and the peaceful use of atomic energy.

Early Life and Education

Leo Szilard was born Leo Spitz on February 11, 1898, in Budapest, Hungary[4][2][1], the oldest of three children to Louis and Tekla Spitz, a Hungarian Jewish couple.[4][6] They changed their last name in 1900 to Szilard, meaning "solid," because of governmental pressure to change foreign-sounding names.[4] Since their father, Louis, was an engineer, the boys received solid training in mathematics and the sciences.[4][6]

He received most of his instruction at home until the age of ten, learning German and French with governesses.[6] From the age of ten to 18 he went to a public school. His attraction to physics began when he was 13.[6] As a child, his interest in physics came at an early age of just 13 years old and he won a mathematics prize in 1916.[3]

In 1916, one year before his draft into the army, he entered the Hungarian Institute of Technology to study electrical engineering.[6] He was drafted into the Austro-Hungarian Army in 1917, where he attended officer's training school.[2][9] However, influenza prevented him from an active duty assignment.[2] His regiment was nearly annihilated in battle, so his sickness probably saved his life.[9][4]

Education in Berlin and Key Influences

After World War I ended, he left Hungary for Berlin in 1919.[2][6] In Berlin, Szilard studied Engineering at the Institute of Technology (Technische Hochschule).[6][2] In 1921 he enrolled at the University of Berlin to study Physics under Max von Laue.[2][3]

Szilard earned his Ph.D. in August of 1922 and completed his postdoctoral work at the Kaiser Wilhelm Institute in Berlin.[2][3] His dissertation "Uber die thermodynamischen Schwankungserscheinungen" (About the thermodynamic fluctuation phenomena) discussed the Second Law of Thermodynamics and how it affected not just mean values but the fluctuating values.[3] The ideas from his dissertation are now the bases of modern theories.[3]

During his stay at the Institute he became close friends with Albert Einstein.[2][18] He met several brilliant physicists such as Albert Einstein and Max Planck.[1][9] After completing his doctorate, Szilard worked at the Kaiser Wilhelm Institute in Berlin along with Hermann Mark, a chemist who is well known for his contributions for the progress of polymer science. During this time, the studies conducted by Szilard focused on how X-rays scattered in crystals and the polarization of x-rays when reflected by crystals.[3]

Collaboration with Einstein

One of his most significant early collaborations was with the renowned physicist Albert Einstein. Together, they developed the Einstein-Szilard refrigerator in 1926, an innovative refrigeration system that required no moving parts and operated without electricity.[7] Throughout his career, Szilard collaborated with prominent scientists, including Albert Einstein, to invent practical devices such as a refrigerator without moving parts and the Einstein-Szilard electromagnetic pump.[4] Although the refrigerator never gained widespread commercial success, it demonstrated Szilard's ability to think creatively across different scientific domains.[7]

Flight from Nazi Germany

In the early 1930s, Szilard's life was profoundly affected by the political upheaval in Europe. With the rise of Adolf Hitler and the Nazi regime in Germany, Szilard, along with many other intellectuals and scientists, recognized the growing danger posed to Jewish academics.[7] When the Nazis came into power in 1933, he went to Vienna and, in 1934, to London.[5][8][7]

There, with the British physicist T.A. Chalmers, Szilard developed the first method of separating isotopes (different nuclear forms of the same element) of artificial radioactive elements.[5] The results from this work became known as the Szilard-Chalmers reactions, or hot atom chemistry.[4]

Nuclear Chain Reaction Discovery

While crossing the street in London, Szilard has an epiphany that leads him to develop the idea of the nuclear chain reaction.[2] Ernest Rutherford quoted in London Times on September 12 as saying "anyone who looked for a source of power in the transformation of the atoms was talking moonshine." While walking through the streets of central London after reading this article — as he waited for a traffic light at the corner of Southampton Row — Leo Szilard conceived the neutron chain reaction.[21] Fleeing to London in 1933, he conceived the nuclear chain reaction, which he patented in 1934 and assigned to the British Admiralty as a military secret.[6][19]

Move to the United States

In 1937 Szilard went to the United States and taught at Columbia University.[5] In 1940 Szilard became an American citizen and moved to New York.[2] He began working at Columbia University (Pupin Laboratories) where he collaborated with Enrico Fermi, Walter Zinn, and Herbert Anderson.[2]

Manhattan Project

The Einstein Letter

In 1939 Szilard and Eugene Wigner alerted Albert Einstein to the potential for the creation of a nuclear chain reaction and persuaded him to inform the U.S. government.[5] Szilard and two other Hungarian-born physicists, Edward Teller and Eugene Wigner, had initially contacted Einstein because they were concerned with preventing the Germans from gaining access to uranium ore being mined in the Belgian Congo for their experiments with nuclear fissure.[12]

Meeting together again on July 30, 1939, Einstein and Szilard began work on the letter for President Roosevelt about developments in the science of nuclear chain reactions and the possibilities opened up by that research.[12] Szilard subsequently drafted the famous letter to Pres. Franklin D. Roosevelt, signed by Einstein, that advocated the immediate development of an atomic bomb.[5]

In August of 1939, Albert Einstein sent a letter to U.S. President Franklin Delano Roosevelt, advising him that the process of nuclear fission could potentially be used to create a powerful atomic bomb. The letter, often called the Einstein-Szilárd letter, was written by physicist Leó Szilárd and Einstein in an attempt to warn the president that Nazi Germany may be working on a fission bomb—and that the U.S. should begin work immediately on its own nuclear weapons research.[11] The letter would prompt Roosevelt to organize research into what would later become known as the Manhattan Project.[11][15]

Nuclear Reactor Development

He continued his work with Fermi at the Metallurgical Laboratory to construct the first nuclear reactor.[1] There, along with Fermi, he helped construct the first "neutronic reactor," a uranium and graphite "pile" in which the first self-sustaining nuclear chain reaction was achieved in 1942. Based on the carbon-uranium system, the chain reaction was first demonstrated at the University of Chicago's Stagg Field, on 2 December 1942.[6][14]

Later, Szilard moved to the University of Chicago to continue to work on developing the bomb.[1] In 1942, Szilard began work on the Chicago Pile (CP-1) during his tenure as chief physicist at the Chicago Metallurgical Laboratory (Met Lab) under the direction of Arthur Compton.[18]

Opposition to Bomb Use

As the war continued, Szilard became increasingly annoyed at the fact that he was losing power over his scientific developments to the military, and he clashed many times with General Leslie Groves.[1] By 1945, it was clear that the U.S. was planning to use the bomb against Japan. Szilard began a campaign against its use. He circulated petitions among the scientists demanding greater scientific input on the future use of atomic weapons.[1]

By 1945, Szilard instead feared the use of an American bomb. During the months before the Trinity test in July, Szilard drafted a petition among the Manhattan Project scientists in an attempt to avert wartime use of the bomb against Japan.[15] Szilard viewed the development and eventual production of the atomic bomb as a necessary evil or counter-measure to the possibility of a German atomic bomb. After Germany surrendered and the war ended in Europe, he organized his colleagues to collectively voice the need to adopt limitations regarding the use of an atomic bomb.[2]

Personal Life

On October 13, 1951, he married Gertrud "Trude" Weiss; however, they did not live together until his health began to fail in 1959. Szilard had met the Viennese woman in 1929 and was her mentor and longtime friend.[4][8] He suggested that she attend medical school because he thought that she was, in his words, too dumb to be a physicist.[4][8] She worked as a medical doctor in New York, and after 1950, she taught at the University of Colorado Medical School.[4]

When Szilard was stricken with bladder cancer in 1959, he arranged for a new type of radiation treatment with Trude as his doctor. The radiation treatment was successful.[4]

Transition to Biology

In 1947, Szilard decided to leave physics for molecular biology, working extensively with Aaron Novick.[1][2] In 1946, Szilárd's scientific priorities shifted from physics to biology. Jacques Monod explained the move in this way: "…because of its very complexity and uncertainties, biology needed ideas, many ideas to be discussed, tested, rejected, or temporarily accepted, that is, precisely the kind of goods that he knew he could provide in abundance and enjoyed dealing with."[20]

Between 1946 and 1954, he served as a part-time professor at the Institute of Radiology and Biophysics (University of Chicago), a part-time advisor at the Office of Inquiry into the Social Aspects of Atomic Energy (University of Chicago), and a visiting professor of biophysics at Brandeis University. In June of 1956, he became a professor of biophysics at the recently formed Enrico Fermi Institute for Nuclear Studies at the University of Chicago.[2]

In addition to his contributions to physics, Szilard also made significant advances in the biological sciences. After World War II, Szilard shifted his focus toward biology, where he applied his knowledge of physics to tackle biological problems. One of his most important contributions was the discovery of feedback inhibition, a regulatory mechanism that helps control the activity of enzymes in biological systems. This discovery had a profound impact on the field of molecular biology and helped scientists better understand how cells regulate their biochemical processes.[7]

Arms Control and Peace Advocacy

After the atomic bomb was first used, Szilard became an ardent promoter of the peaceful uses of atomic energy and the international control of nuclear weapons, founding the Council for a Livable World.[5] He continued his political activism, calling for international arms control, peaceful uses of nuclear energy, and improved U. S.-Soviet relations. In 1947, The Bulletin of the Atomic Scientists published a "Letter to Stalin" written by Leo Szilard. In the letter, he appealed to all world leaders to begin an open dialogue with the intent to exchange ideas to halt the rapidly escalating Cold War.[2]

In 1962, he founded the Council for a Livable World, a Washington lobby on nuclear arms control and foreign policy issues.[6][24][2] By Szilard's calculus, all states had two Senators, so votes came cheapest by supporting campaigns in the least populous states. The Council's first successful candidate was Senator George McGovern from South Dakota.[24] It is America's first political action committee for arms control and disarmament.[24]

Szilard's political activities even inspired Albert Einstein and Bertrand Russell. As a result, the International Conference of Concerned Scientists was formed. The first conference took place in 1957 at Pugwash, Nova Scotia. The "Pugwash" conferences have continued to the present day.[2]

International Institutional Building

In the autumn of 1962, Leo Szilárd met with Victor Weisskopf and Gilberto Bernardini to discuss Szilárd's idea that a European laboratory for molecular biology should be established. They then got in touch with a number of molecular biologists, including Sir John Kendrew, Francis Crick, Sydney Brenner and James[22]