Rutherford, Ernest: Worked out the nature of radioactivity in 1902, discovered the nucleus of the atom in 1911, and split the first atom in 1919. Soddy, Frederic: Discovered isotopes in 1910. Urey, Harold: Discovered hydrogen's heavy isotope, deuterium, in 1932. GLOSSARY _AEC_ Atomic Energy Commission (U.S.) All atomic energy in the United States is under the control of the AEC. The Commission is in charge of the sources, manufacture, and uses of all fissionable materials. It has important programs of research, building, training, and information. _artificial_ A chemical element that does not exist in _element_ nature but which can be made in an atomic reactor. _atomic_ An atomic reactor. _furnace_ _canal_ A tank of water which is used to hold dangerously radioactive materials in order to protect workers. _coffin_ A thick metal box which is used to hold very radioactive material. _contaminated_ Anything that has accidentally become radioactive. _cool off_ To stop being radioactive. Some materials have to cool off before they can be handled safely. _critical size_ The smallest amount of atomic fuel that will allow a chain reaction to take place. _curie_ The unit used to measure radiation. It is equal to the amount of radiation given off by one gram of radium in one second. _Einstein_, (1879-1955), born in Germany, fled under _Albert_ Hitler, and became an American citizen in 1940. In 1955 he published a brilliant theory which became the basis for the discovery of atomic energy. The theory stated that neither matter nor energy can ever be destroyed, but that matter can be changed into energy. Einstein expressed this in the equation E = mc^2. It means that energy (E) is equal to mass (m) multiplied by the speed of light (c), multiplied by itself. Mass is the amount of material or matter in anything. The speed of light is 186,000 miles a second. _emit_ To give off. Radioactive substances emit rays. _enriched_ Ordinary uranium which has fissionable _uranium_ uranium added to it. _fissionable_ Usable as an atomic fuel. A material whose atoms will split. _fusion_ A source of atomic energy which is the opposite of fission. Instead of nuclei being split, they are forced together. The energy of the sun is released by fusion. _hot_ Radioactive.