Energy from Einstein’s Equation covers the harnessing of nuclear energy, from fission’s discovery through the end of World War II. The development of nuclear power is detailed, including careful explanations of needed terminology. Interactions of technology, politics, and economics are stressed in Admiral Rickover’s development of naval propulsion reactors and the consequential world-wide adaptation of water-cooled reactors for generating electricity. Diagrams explain pressurized water and boiling water reactors’ operations. The chapter’s final section examines the high capital costs of power reactors, their causes, and how they may be dramatically reduced.