The First controlled nuclear chain reaction, achieved in Chicago on December 2, 1942, marked a scientific milestone that the book sets beside the hurried creation of the Manhattan Project’s weapons laboratory. Its significance in this account lies not only in the experiment itself, but also in the contrast it exposes: Chicago had the resources of a major city and an eminent university, while Los Alamos began as a remote site with almost none of the infrastructure experimental physics required.

The Chicago Milestone

On December 2, 1942, the Italian émigré physicist Enrico Fermi led a team in conducting the world’s first controlled nuclear chain reaction. The account introduces the achievement through John Manley, an experimental physicist whom J. Robert Oppenheimer had recruited as an assistant. Manley had just come from Chicago when he joined the effort to build a laboratory in New Mexico, carrying firsthand knowledge of the gulf between the two settings.

Chicago offered a large city, an eminent university, world-class libraries, and a deep pool of experienced machinists, glass-blowers, engineers, and other technicians. These were not incidental conveniences: Manley regarded experimental physics as work that depended heavily on practical equipment and skilled labor. The first controlled reaction thus appears as a scientific accomplishment embedded in a substantial institutional and technical environment.

Chicago and the Los Alamos Contrast

Oppenheimer had inspected prospective laboratory sites with Army officer John H. Dudley, and on November 16, 1942, the party visited Jemez Springs, northwest of Santa Fe. Oppenheimer knew the surrounding high country from horseback trips, and the eventual Los Alamos site offered the mountain view he wanted. General Leslie Groves, meanwhile, obtained the isolation he sought: access ran along a winding gravel road, with a single phone line connecting the site to the outside.

The physical setting that suited security made the scientific task harder. Construction crews put up inexpensive barracks and crude chemistry and physics laboratories, all painted Army green. Manley contrasted this makeshift beginning with Chicago’s concentration of libraries, equipment, and skilled workers. He imagined Los Alamos starting with little more than the Ranch School’s books and horseback-riding gear, neither of which could supply the equipment needed to produce neutrons. The contrast gives the Chicago achievement a practical dimension: controlled nuclear work depended not simply on ideas, but on the facilities and expertise that could make those ideas experimentally tractable.

The comparison also clarifies the scale of Oppenheimer’s undertaking. As director of the new weapons laboratory, he was expected to integrate the scattered work of the Manhattan Project and turn it quickly toward a usable weapon. The book describes this as a role that required him to acquire unfamiliar administrative skills and adjust to security practices alien to his previous life as a theoretical physicist. Chicago’s achievement preceded the arrival of the Los Alamos team, but the book does not present the two laboratories as interchangeable: the new site had to build, under severe time pressure, a working scientific community as well as its facilities.

Collaboration and Secrecy

At Los Alamos, the demand for coordinated work collided with military compartmentalization. Oppenheimer argued that scientists holding white badges needed opportunities to discuss the complicated project together. After Hans Bethe proposed a weekly open-ended colloquium, Oppenheimer agreed, despite Groves’s initial attempt to stop it. At the first meeting, held in the schoolboys’ library on April 15, 1943, Robert Serber briefed no more than forty scientists; Oppenheimer had him replace the word bomb with the more neutral gadget.

The laboratory’s working practices increasingly strained the rules intended to keep knowledge divided. Edward Teller warned Oppenheimer that excessive secrecy was a source of anxiety, and even senior scientists disregarded restrictions in discussion. The book describes the resulting compartmentalization as increasingly lax in practice, though it remained official policy. That tension places the Chicago milestone within a broader change in scientific work: nuclear research required collaboration across specialties, while its military purpose imposed controls that could obstruct the exchanges on which research depended.

The Wider Nuclear Stakes

The book’s later discussions show why the first controlled chain reaction belongs to a history extending beyond the laboratory. Niels Bohr argued that the danger of atomic weapons could not be managed through secrecy alone. He envisioned an open international order, with access to military and industrial facilities and information about scientific discoveries, and maintained that the Soviet Union should be invited into postwar atomic planning before the bomb became a reality. This was a proposed response to the security dilemmas surrounding atomic energy, not an outcome attributed to the Chicago experiment.

By 1949, debate had moved to the prospective Super. J. Robert Oppenheimer and the majority of the General Advisory Committee opposed producing a weapon whose possible yield and destructive reach, they warned, could make it a weapon of genocide. They also argued that a buildup of smaller tactical weapons, combined with conventional forces, might offer a more credible defense than an escalating stockpile of thermonuclear weapons. The book traces no direct line from Chicago’s experiment to these later policy positions; rather, it sets the controlled reaction at the beginning of a history in which scientific capability, military organization, secrecy, and the question of international control became inseparable.