Thin Man (nuclear bomb) Thin Man (nuclear bomb) "Thin Man" was the code name for a proposed plutonium gun-type nuclear bomb using plutonium-239 which the United States was developing during the Manhattan Project. They aborted its development when they discovered that the spontaneous fission rate of their nuclear reactor-bred plutonium was too high for use in a gun-type design, due to the high concentration of the isotope plutonium-240. In 1942, prior to the Army taking over wartime atomic research, Robert Oppenheimer held conferences in Chicago in June and Berkeley, California, in July at which various engineers and physicists discussed nuclear bomb design issues. A
Bulletin of the Atomic Scientists legal and ethical considerations. Once the Soviet Union developed atomic weapons, the concern surrounding the world's destruction was a great fear of the scientists working on the "Bulletin." The proximity of nuclear devastation was a popular interest and, as a result, "Bulletin" co-editor Hyman Goldsmith asked landscape artist Martyl Langsdorf to create a cover for the June 1947 magazine. Langsdorf, who was married to Manhattan Project physicist Alexander Langsdorf, first considered using the symbol for uranium but then realized that a clock would better convey "a sense of urgency." The resultant Doomsday Clock, which only has bullets labeling the numbers