The Manhattan Project, Part One: Splitting the Atom
—Chrissie
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The concept of the atom goes back to Ancient Athens and the philosophy of Leucippus and Democritus, who theorized that everything was comprised of some basic building block that could not be further divided. The is the atomos, which means “uncuttable” or “unbreakable” or, if the translator was feeling particularly poetic, “indivisible.” This was a philosophical idea, of course, the fifth-century Athenians had no means to prove this scientifically. But, the idea remained over the thousands of years it took for natural philosophy to become science. It was not until the end of the eighteenth century and the beginning of the nineteenth that mathematical calculations corroborated the idea, and then experimental data confirmed it.
Through the nineteenth century, advances in chemistry allowed for better understanding of the atom. John Dalton began atomic theory in 1803 with the idea that each chemical element is comprised of a single type of chemically indestructible atom. Amedeo Avogadro added the means to estimate the atomic mass of elements and made a clear differentiation between molecules and atoms. J.J. Thompson discovered electrons in 1897, showing that atoms are not the smallest thing, but are themselves made up of smaller things called particles. Niels Bohr created the model for how an atom is comprised, with electrons moving around a nucleus like planets orbit a star, in 1913. In that same year, isotopes, atoms of the same element that weigh a different amount, were discovered by Frederick Soddy. The behavior of atoms was described by Werner Heisenberg, Louis de Broglie, Erwin Schrödinger, and others throughout the 1920s. This study of the subatomic came to be called Quantum Mechanics. And the reason for, and makeup of, isotopes was explained in 1932 when the newly-invented mass spectrometer revealed the neutron. Isotopes were now understood to be examples of the same element with a different number of neutrons.
All of this came together with the discovery of nuclear fission in 1938 by Otto Hahn and Fritz Strassman at the Kaiser Wilhelm Institute for Chemistry in Berlin, which was shortly afterward explained mathematically by Lise Meitner and Otto Frisch. In experimenting with irradiating various elements, they discovered that radioactive isotopes could be artificially produced. To be able to produce radiation and energy in this way meant that a nuclear chain reaction could be created, which opened the possibility not just for nuclear weapons but also nuclear energy. The fact that these discoveries were made by scientists in Germany prompted fear of the Nazis developing an atomic bomb.
This is the origin of the Manhattan Project, the effort by Allied scientists to figure out how to create an atomic bomb and to do it before the Nazis did. This work was primarily done in the United States, but included scientists from Britain, Canada, and Australia. The attention in the United States was directly prompted by a letter sent to President Franklin Roosevelt in the autumn of 1939 written by physicists Leo Szilard and Eugene Wagner, and supported by Albert Einstein, encouraging greater research into nuclear chain reactions and that the US begin to stockpile uranium. Roosevelt authorized the creation of the Advisory Committee on Uranium, headed by Lyman Briggs. They provided a $6000 grant to Columbia University, which was used by Szilard and mathematician Enrico Fermi to conduct their own tests about nuclear chain reactions and to begin designing prototype reactors.
At the same time, physicists in Britain, now including Otto Frisch, who had fled Nazi Germany, determined that a very small amount of enriched uranium was needed to begin a chain reaction; they estimated as little as a half kilogram could produce enough energy to be used as a bomb. Under agreements for the sharing of such information, the British report was provided to American scientists but the information (or its importance) was not properly communicated. It wasn’t until Australian physicist Mark Oliphant discussed it with Ernest Lawrence of University of California, Berkley, that American efforts were shifted toward work on a bomb rather than energy production. The recently created Office of Scientific Research Development (OSRD) absorbed the Uranium Committee, which now became known as S-1. The OSRD was headed by Vannevar Bush of the Massachusetts Institute of Technology (MIT) and the Carnegie Institute, who answered solely to President Roosevelt. The research into a nuclear bomb was put under the auspices of the US Army in October 1941, with a committee consisting of Secretary of War Henry Stimson, Army Chief of Staff General George Marshall, Vannevar Bush, chemist (and president of Harvard) James Conant, Vice President Henry Wallace, and President Roosevelt himself (though he was not directly involved). Their first meeting was planned for mid-December, meaning that when they did meet, it was with a very different mood than when they’d made the plans two months earlier.
Five different designs for the production of nuclear chain-reactions were being researched at the same time, for use both as weaponry and for energy production. All were to be funded by the OSRD until one or more proved to be the answer. One of these lines of research was headed by Arthur Compton at University of Chicago; he brought in colleagues from around the country to work on the calculations for fission, including J. Robert Oppenheimer of UC Berkeley. They also worked on designs for the bomb itself, the method by which the various parts would be brought together to begin the chain reaction.
By the autumn of 1942, the question of whether it was possible to build an atomic bomb had been answered and the logistics of actually doing so were at hand. The Manhattan Project had already begun under the leadership of Colonel James C. Marshall (it was the location of his office on Broadway that prompted the name “Manhattan” Project) in June. In September, it was passed to Brigadier General Leslie Groves of the Army Corps of Engineers. One of the first decisions for Groves was who would lead the bomb-building project (now known as Project Y); he chose Oppenheimer on the recommendation of Compton. Oppenheimer was not his first choice: while he did have the scientific knowledge, he did not have the administrative experience needed to run a project like this and he appeared to be a potential security risk because he had friends and family who were communists. But, after meeting with him, Groves and his colleague Kenneth Nichols found the man had a thorough understanding of what would be involved in making the bomb happen. On 20 July 1943, Groves signed off on Oppenheimer’s security clearance, making him head of the project to bring into being the most destructive force the world had ever known.
Read Part Two here: Building the Bomb