Nuclear Weapons

Nuclear Weapons, explosive devices, designed to release nuclear energy on a large scale, used primarily in military applications. The first atomic bomb (or A-bomb), which was tested on July 16, 1945, near Alamogordo, New Mexico, represented a completely new type of artificial explosive. All explosives prior to that time derived their power from the rapid burning or decomposition of some chemical compound. Such chemical processes release only the energy of the outermost electrons in the atom.

Nuclear explosives, on the other hand, involve energy sources within the core, or nucleus, of the atom. The A-bomb gained its power from the splitting, or fission, of all the atomic nuclei in several kilograms of plutonium. A sphere about the size of a tennis ball produced an explosion equal to 20,000 tons of TNT. Nuclear weapons were the first true weapons of mass destruction and their first use in warfare, at the end of World War II, and their subsequent deployment, changed the nature of international relations for all time. This article focuses on how the weapons work, and their effects.
The first nuclear weapons were developed, constructed, and tested by the Manhattan Project, a massive United States enterprise that was established in August 1942 during World War II. Many prominent scientists, including the physicists Enrico Fermi, Richard Feynman, Isador Rabi, and Edward Teller, and the chemist Harold Urey, as well as scientists from Britain, were associated with what was, to date, the world's biggest scientific project, whose military head was US Army engineer Major General Leslie Groves. The scientific director of the project-which was based at Los Alamos, New Mexico-was physicist J. Robert Oppenheimer.

Work had already started during the Manhattan Project on even more powerful bombs, chiefly to tap the energy of light elements, such as hydrogen. In these bombs the source of energy is the fusion process, in which nuclei of the isotopes of hydrogen combine to form a heavier helium nucleus (see Thermonuclear, or Fusion, Weapons below).
This fusion research, begun largely by Edmund Teller, resulted in the production of bombs that range in power from a fraction of a kiloton (1,000 tons of TNT equivalent) to many megatons (1 million tons of TNT equivalent).