According to Einstein's theory of relativity, even the smallest bit of matter is equivalent to a tremendous amount of energy. For instance, two pounds of matter, if converted completely into energy, would produce energy equivalent to the explosive force of 22 megatons of high explosives. In 1939, based on German experiments that successfully split the uranium atom, physicists were able to explain the process of nuclear fission. When a large, unstable atomic nucleus splits (fissions) it results in two or more smaller, more stable nuclei accompanied by the release of tremendous amounts of energy and lingering, deadly radioactivity. The first application of this powerful technology was in warfare. A top-secret research effort in the U.S. known as the Manhattan Project studied the fission proc