This is a picture of Calutron operators at their panels, in the Y-12 plant at Oak Ridge, Tennessee during World War II. The calutrons were used to refine uranium ore into fissile material. During the Manhattan Project effort to construct an atomic explosive, workers toiled in secrecy, most having no idea to what end their labors were directed. Gladys Owens, the woman seated in the foreground, didn’t understand the exact purpose of her job until she saw see this photo in a public tour of the facility fifty years later. (via Wikipedia)