How many scientists were involved in the Manhattan Project? Details explored ahead of Christopher Nolan’s Oppenheimer

As the highly anticipated film Oppenheimer releases on Friday, July 21, 2023, it shines a light on one of the most ambitious scientific projects in human history - the Manhattan Project. The project, which was led by J. Robert Oppenheimer, attempted to develop the world's first atomic bomb during World War II and subsequently succeeded at it.

The Manhattan Project was successful due to the groundbreaking research and scientific contributions of numerous scientists at the Los Alamos Laboratory, New Mexico, such as Oppenheimer himself, Leo Szilard, Ernest O. Lawrence, Klaus Fuchs, Hans Bethe, and Glenn Seaborg.

Led by the United States, the United Kingdom, and Canada, the Manhattan Project rewrote the history of arms technology worldwide, paving the way for a new generation of military policies.

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What is the Manhattan Project, and who led it?

The Manhattan Project was a novel research and development initiative centered around the ultimate weapon of mass destruction, the nuclear bomb, to be used in World War II. The project was named after its initial base of operations, which was Manhattan, New York.

With a budget of $2.2 billion, several hundred scientists put in their efforts to harness the power of nuclear fission to create bombs that could potentially end the ongoing war once and for all. Moreover, the Manhattan Project focused on gathering intelligence from the German Nuclear Weapon Project, which was set up four years prior.

At the heart of the project stood J Robert Oppenheimer, the American theoretical scientist around whom Nolan's Oppenheimer revolves. Oppenheimer's leadership skills and scientific resourcefulness were instrumental in the success of the Manhattan Project. He was recruited in 1942 and was appointed as the director of the Los Alamos Laboratory the following year.

In addition, his expertise in fast neutrons and bomb manufacturing helped the project reach its goal before Germany and by 1945. It was also Oppenheimer who pointed out the two crucial issues with the development of the atomic bomb - the development of a practical method for implosion and the purification of radioactive material, i.e., uranium or plutonium.

A rough estimate of the number of collaborators stands at 130,000, wherein engineers, chemists, professors, physicists, and support staff were involved.

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The brilliant minds involved in the Manhattan Project

Niels Bohr worked with the British Tube Alloys after escaping Denmark in the wake of The Holocaust. In 1943, he flew down to the States and met Brigadier General Leslie R. Groves Jr., the director of the Manhattan Project, played by Matt Damon in Nolan's latest movie. He contributed to the project with modulated neutron initiators, and, as Oppenheimer was quoted saying:

"This device remained a stubborn puzzle but in early February 1945 Niels Bohr clarified what had to be done."

Played by Danny Deferrari, Enrico Fermi had led a team at the University of Chicago where the Chicago Pile-1, the first man-made self-sustaining nuclear chain reaction, was designed and built. The Trinity test, which took place on July 16, 1945, made use of his Fermi method to calculate the bomb's yield.

Jack Quaid plays Richard Feynman, the revolutionary physicist who was assigned to Hans Bethe's Theoretical (T) Division, where he and Bethe invented the Bethe–Feynman formula based on the previous works by Robert Serber. The formula is used to calculate the yield of a fission bomb.

On the same hand, Hans Bethe brought the concept of nuclear fusion to light and worked on the difference between fusion and fission. He suggested ways to fuse hydrogen nuclei with helium nuclei and helped to create the formula used to figure out the critical mass of uranium-235.

Robert Serber was part of Project Alberta under the Manhattan Project, which oversaw the delivery of the nuclear bombs to Hiroshima and Nagasaki for the bombing and he ended up being the only personnel from the project to enter the bombing sites to assess the aftermath.

Other notable scientists and physicists working with the Manhattan Project included Edward Teller, Frank Oppenheimer, Isidor Isaac Rabi, Klaus Fuchs, Vannevar Bush, Kenneth Bainbridge, Lilli Hornig, Patrick Blackett, Seth Neddermeyer, Luis Walter Alvarez, Giovanni Rossi Lomanitz, Werner Heisenberg, Philip Morrison, Donald Hornig, Edward Condon, George Kistiakowsky, Ward V. Evans, Kurt Gödel and Albert Einstein.