Lawrence Berkeley National Laboratory · Public domain

A theoretical physicist who explained the atomic bomb to the scientists who had to build it: at Los Alamos, his introductory lectures on the Manhattan Project's basic physics and goals were printed and given to every incoming staff member as "The Los Alamos Primer." The New York Times later called him the project's intellectual midwife, and he was portrayed by Michael Angarano in the 2023 film Oppenheimer.