When the Soviet Union launched Sputnik in October 1957, the United States feared that nuclear missiles would soon follow. How could we stop them? In the Dr. Strangelove era, no idea was too absurd, and Nicholas Christofilos, an elevator engineer turned nuclear physicist, had a doozy. Christofilos had only undergraduate degrees in electrical and mechanical engineering, but he had become a top military scientist at California's Livermore Laboratory with a reputation for audacious creativity. He suggested that an atomic explosion in space could generate a vast flux of electrons, which would form a shell of energy over Earth, a phenomenon...