define nuclear fission and nuclear fusion

In an intellectual chain reaction, scientists began to realize the possibilities of fission. This self-sustaining reaction is known as 'criticality.'Ī mushroom cloud rising from the first atomic explosion, which was detonated Jnear Alamagordo, New Mexico as part of the Manhattan Project. 2, 1942, in a basement in Chicago, according to Argonne National Laboratory. Fermi would ultimately create the first self-sustaining nuclear fission reactor on Dec. Italian physicist Enrico Fermi had also produced fission earlier in 1934, but had not realized it, according to the Atomic Archive. A single impact could jumpstart a chain reaction, driving the release of still more energy. Ultimately, other physicists realized that each newly freed neutron could go on to cause two separate reactions, each of which could cause at least two more. Working on the problem, she established that fission yielded a minimum of two neutrons for each neutron that sparked a collision. Previous efforts by physicists had resulted in only very small slivers being cut off of an atom, so the pair was puzzled by the unexpected results.Īustrian-born physicist Lise Meitner, who had fled to Sweden following Hitler's invasion of her country, realized that the split had also released energy. In a surprising twist, they wound up splitting the atom into the elements of barium and krypton, both significantly smaller than the uranium that the pair started out with.

In 1938, German physicists Otto Hahn and Fritz Strassman bombarded a uranium atom with neutrons in an attempt to make heavy elements, according to the Atomic Archive.

Define nuclear fission and nuclear fusion