Leo Szilard, Physicist and Contributor to the Manhattan Project

Leo Szilard, the Hungarian Jewish physicist, molecular biologist and inventor, worked on the Manhattan Project but expressed himself as a “scientist of conscience,” using his knowledge of nuclear chain reactions to consult with the American government and protest about the risks of nuclear warfare.

Leo Szilard’s Early Days

Leo Szilard was born Leo Spitz in Budapest in what was then Austro-Hungary in 1898. His father, Louis, was an engineer, and his mother, Tekla, was from a prominent family. Leo’s maternal grandmother built a house in Budapest for herself and her three daughters and their families to live in. Szilard had a happy and comfortable childhood with his “closely-knit” family, though they experienced financial difficulties later on.

Szilard followed in his father’s footsteps, enrolling in Budapest Technical University as an engineering student in 1916. In 1917, he enlisted in the Austro-Hungarian army, but was discharged due to illness before he ever saw active duty. He then returned to school, but soon left for Berlin as Hungary’s Horthy regime became increasingly repressive and anti-Semitic.

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Szilard’s Scientific Accomplishments

In Berlin, Szilard became a physics student of Nobel Laureate Max von Laue. In 1922, he earned his doctorate in physics. According to the Leo Szilard Papers at the University of California, San Diego, his “dissertation presented ideas relating to what would become the foundation of modern information theory.”

In 1926, Szilard began a seven-year period of working with Albert Einstein to create home refrigerators without moving parts. The Einstein-Szilard pump was the greatest fruit of this collaboration. Although the refrigerators were never manufactured, the system the men invented helped American scientists develop an atomic reactor in 1942.

In London, Szilard worked on inventions and registered patents, and had early thoughts of the possibility of a nuclear chain reaction, the process that would release atomic energy.

In 1938, Szilard was a visiting lecturer in the United States. With Europe on the brink of war, Szilard felt that England’s stance on Germany wasn’t strong enough; as a result, he decided to move to New York. At Columbia University, he worked with Walter Zinn to learn that “the element uranium might sustain a chain reaction.” More research with Enrico Fermi and others “demonstrated that a system composed of water and uranium oxide approached the requirements for a self-sustaining chain reaction,” UCSD notes.

With an endorsement from Einstein, Szilard wrote to President Roosevelt to ask for government funding for an experiment to prove that it was possible to create a sustained nuclear chain reaction was possible. Funding was granted, and Szilard began work at a lab at the University of Chicago that would come to be known as the Manhattan Project. Szilard and his team were able to demonstrate a nuclear chain reaction under the University’s Stagg Field in 1942.

The Rest of the Story

Szilard, who has been called the “scientist of conscience,” petitioned President Truman not to use the atomic bomb, which he had played such an important role in developing, against Japan in 1945. The petition was called the Franck Report.

In a 1960 interview with U.S. News & World Report, Szilard said that “many other scientists” agreed with him about the atomic bomb. Szilard intended to send a memorandum to President Roosevelt about his concerns. Unfortunately, Roosevelt died before the memo was delivered. Szilard then drafted the petition to Truman, but said he doubted whether it ever reached Truman.

Szilard formed the Emergency Committee of Atomic Scientists with Einstein, as well as the Council for a Livable World (then known as Council for Abolishing War), and went on to write many important works on the use of nuclear weapons and on “global cooperation.” Though diagnosed with bladder cancer, he was able to cure himself with a radiation treatment of his own design performed in New York City.

But he led a “peripatetic” life and had mostly loose connections with the institutions he worked for. In 1963, he was named a fellow at the Salk Institute for Biological Studies in La Jolla, California But in 1964, Szilard died of a heart attack, leaving a legacy of patents, inventions and forward-thinking philosophies behind him.