Warren Nyer (1921-2016) was an American physicist.
Nyer was nineteen and studying physics at the University of Chicago when he was hired as a research assistant with the Office of Scientific Research and Development, an early part of the bomb-building program. Although he did not have an undergraduate degree, Nyer traveled the circuit of the Plutonium Project: Chicago; Oak Ridge; Hanford; Los Alamos; and Trinity.
Nyer worked on the construction of exponential piles with Enrico Fermi. These piles were an important step in the development of Chicago Pile-1, the first self-sustained and controlled nuclear reaction in history. Nyer was present when Chicago Pile-1 went critical on December 2, 1942.
After Chicago, Nyer worked on the construction of the X-10 Graphite Reactor in Oak Ridge for a year. He then moved to Hanford at the request of DuPont, where he helped prepare equipment and measure radioactivity levels at B Reactor.
With the B Reactor running in February 1945, Nyer decided it was time to move on. He told Arthur Compton that he wanted to go to Los Alamos. Compton called J. Robert Oppenheimer and arranged for Nyer to get a job in Los Alamos. In Los Alamos, Nyer conducted multiplication experiments on U-235 and plutonium in preparations for the Trinity Test. He conducted experiments in Alamogordo before the test and was part of a group of physicists responsible for measuring the blast.
After the war, Nyer headed a small, experimental physics group at the Materials Test Reactor at the National Reactor Testing Station (now called the Idaho National Laboratory). He later became a management consultant to electric utility firms.
Nyer died on February 4, 2016 at the age of 94. According to his son Michael, he was the last living member of the group that worked directly under Enrico Fermi at the Chicago Metallurgical Lab.