Leo Szilard (pictured) penned a letter, signed by Albert Einstein and addressed to U.S. president Franklin D. Roosevelt, warning that Germany may develop atomic bombs, leading to the establishment of the Manhattan Project.

Leo Szilard

Hungarian-American physicist and inventor (1898–1964)

Leo Szilard was a Hungarian-born physicist, biologist and inventor who made numerous important discoveries in nuclear physics and the biological sciences. He conceived the nuclear chain reaction in 1933, and patented the idea in 1936. In late 1939 he wrote the letter for Albert…

Einstein–Szilard letter

1939 letter to U.S. president Franklin D. Roosevelt

The Einstein–Szilard letter was a letter written by Leo Szilard and signed by Albert Einstein on August 2, 1939, that was sent to President of the United States Franklin D. Roosevelt. Written by Szilard in consultation with fellow Hungarian physicists Edward Teller and Eugene…

Albert Einstein

German-born theoretical physicist (1879–1955)

Albert Einstein was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence formula E = mc2, which arises from special relativity, has been called…

Franklin D. Roosevelt

President of the United States from 1933 to 1945

Franklin Delano Roosevelt, also known as FDR, was the 32nd president of the United States from 1933 until his death in 1945. He is the longest-serving U.S. president, and the only one to have served more than two terms. His first two terms were centered on combating the Great…

Nuclear weapon

A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either nuclear fission or a combination of fission and nuclear fusion reactions, producing a nuclear explosion. Both bomb types release large quantities of energy from relatively…

Manhattan Project

World War II Allied nuclear weapons program

The Manhattan Project was a research and development program undertaken during World War II to produce the first nuclear weapons. It was led by the United States in collaboration with the United Kingdom and Canada.