Manhattan Project

American physicist J. Robert Oppenheimer directed the scientific research of the Manhattan Project.

Born out of a small research programme in 1939, the Manhattan Project's roots lay in the United States’ fears that, since the 1930s, Nazi Germany had been trying to develop nuclear weapons. Efforts towards upgrading this project moved forward in 1942, when it was transferred to the authority of the United States Army as the “Manhattan Project”. Formally designated as the Manhattan Engineer District (MED), this project ran from 1941–1946 under the control of the United States Army Corps of Engineers administered by General Leslie R. Groves. The scientific research was directed by American physicist J. Robert Oppenheimer.

Eventually, the Manhattan Project employed more than 130,000 people and cost nearly US$ 2 billion (equivalent to US$ 23 billion in 2007 dollars).
Various US sites important to the Manhattan Project

Eventually, the Manhattan Project employed more than 130,000 people and cost nearly US$ 2 billion (equivalent to US$ 23 billion in 2007 dollars). It created multiple secret production and research sites, the three primary ones being: the plutonium-production facility at what is now the Hanford Site (Washington state); uranium-enrichment facilities at Oak Ridge, Tennessee; and the weapons research and design laboratory, now known as Los Alamos National Laboratory in New Mexico. Project research took place at over 30 different sites across the United States, Canada and the United Kingdom. The Manhattan Project maintained control over United States’ weapons production until formation of the US Atomic Energy Commission in January 1947.

Josef Rotblat left the Manhattan Project after Nazi-Germany surrendered in May 1945.

One noteworthy “defection” from the Manhattan Project was that of Polish-born scientist, Josef Rotblat, who protested the completion of the Manhattan project after it had become clear that a nuclear programme did not exist in Nazi-Germany.  He left for moral reasons after Germany surrendered in May 1945. He was one of the nine scientists to sign the Russell-Einstein Manifesto. He also helped to found, and later became President of, the annual Pugwash Conferences on Science and World Affairs and received the Nobel Peace Prize in 1995.

Developing the bomb

Meanwhile, working out of the top-secret laboratories at Los Alamos, New Mexico, Oppenheimer and his scientific teams, in conjunction with such notable scientists as L. Szilárd, Enrico Fermi, and Niels Bohr, dedicated themselves to the challenge of developing the bomb. Finally, in 1945, two designs were proposed: one utilizing enriched uranium and the other its newly discovered derivative, plutonium.

Witnessing the strength of the first ever nuclear explosion, Oppenheimer later recalled reflecting on a passage in the Hindu scripture, Bhagavad Gita: “Now, I am become Death, the destroyer of worlds.”

Testing the “gadget”

The first plutonium bomb, "The Gadget", was developed in 1945.

Due to uncertainties about its capabilities, General Groves and Oppenheimer decided to test the military usability of a plutonium bomb nicknamed the “gadget”. The plutonium-based bomb was detonated at the Trinity site on 16 July 1945 at 5:29 AM local time.

The result was an explosion equivalent to 19 kilotons of TNT. It created a crater 10 feet deep and over 1,000 feet wide. According to an account by Steve Sagarra (“Making the Atomic Bomb”), the blast “illuminated the surrounding landscape brighter than daylight for a few brief seconds. The mushroom cloud caused by the explosion extended nearly eight miles into the sky; the resulting shock wave traveled as far as 100 miles. Noting the accomplishment, Oppenheimer stated simply, “It worked.” He would later recall reflecting privately on a passage in the Hindu scripture, Bhagavad Gita: Now, I am become Death, the destroyer of worlds.’”