Leo Szilard: Biography & the Atomic Bomb

Instructor: Matthew Bergstresser

Matthew has a Master of Arts degree in Physics Education. He has taught high school chemistry and physics for 14 years.

Leo Szilard was a physicist from Austria-Hungary who was a major part of the development of the atomic bomb. This lesson will introduce you to him with a focus on nuclear weapon development.


At the end of the Great War in 1918, world had seen more death and destruction than it had ever wanted to see. The war was fought differently than previous wars, with the introduction of the tank, aircraft, and submarines as new ways to destroy people, and property. In the 1930s the world once again found itself on the brink of war, however they had no idea of the new weapon on the horizon. It was something so powerful and terrifying that since its use in 1945, it hasn't been used again. It is something physicist Leo Szilard envisioned, but later lobbied against its use. Let's take a look at Szilard's life and role in the development of the atomic bomb.

Tracks through Europe

Szilard was born in 1898 in Budapest, Austria-Hungry, and was somewhat of an awkward child. He would invent games to play, but wouldn't play the games with the other kids. He wasn't athletic either, but he was an apt student in science and engineering.

In 1917, Szilard was plucked from his engineering studies to serve in the Austro-Hungarian army. While serving as an ordnance cadet, he caught the Spanish flu, which possibly saved his life because he was excused from serving at the Italian-front where his unit was decimated.

Szilard became disinterested in engineering, and began to pursue his interest in physics at the University of Berlin, which, at that time, was ground zero for cutting-edge physics research. Among the scientists there were Max Planck and Albert Einstein.

Szilard attended physics lectures where Planck, and Einstein were in attendance. He was intrigued with Max von Laue who was a 1914 Nobel laureate. Szilard asked von Laue to be his advisor, and became good friends with Albert Einstein when he took Einstein's course in statistical mechanics. Szilard produced a paper on thermodynamics, and with Einstein's encouragement, showed it to von Laue who accepted it as his doctoral thesis. It was 1922, and for the next couple of years Szilard would become somewhat of an academic drifter.

In 1925, Szilard and Einstein would work together on a pump-less refrigerator. Szilard continued inventing, but didn't seem interested in it. In 1929, he met a woman, Gertrud Weiss. She took the physics course he was teaching, and they became friends. She was undecided between pursing physics or medicine, and Szilard pushed her towards medicine because he felt she wasn't smart enough to be a physicist. She took his advice, and returned to live with her parents in Vienna where she eventually became a physician. Thus a friendship developed.

In 1933, a day before the Nazi regime began the crackdown on Jews, Szilard left Berlin for Vienna, Austria-Hungry. Eventually, he would help organize the resettlement of faculty and students that were kicked out of Berlin's universities to relative safety in London. Szilard made it to London too, which led to an enlightenment.

Berlin circa 1930s

Talking Moonshine

While in London, Szilard attended lectures given by Ernest Rutherford. ''Talking moonshine'' was the phrase famed scientist Ernest Rutherford used to describe the effort to harness the power stored in atomic nuclei. Szilard wanted to prove Rutherford wrong, and while he was walking through London one night he imagined a nuclear chain reaction releasing tremendous energy.

In 1939, German physicists created a fission reaction whereby they split uranium atoms into two roughly equal-sized pieces. Six years later, American forces dropped a uranium-based atomic bomb over Hiroshima, Japan named Little Boy.

Szilard made it to the United States in 1938, and worked with Enrico Fermi where they pursued creating a mini nuclear reactor. The powers that be in the United States knew the Germans were on the trail of developing a nuclear super-weapon. Szilard knew the Germans could do it, so he reasoned that it would be better if the United States developed one first. He wrote a letter to President Franklin D. Roosevelt in 1939, and Albert Einstein signed it. The letter informed, and encouraged the president to pursue the development of the atomic bomb.

Dr. Leo Szilard

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