fission

fission, in physics: see nuclear energy and nucleus; see also atomic bomb.

Division of a heavy atomic nucleus into two fragments of roughly equal mass, accompanied by the release of a large amount of energy, the binding energy of the subatomic particles. The energy released in the fission of one uranium nucleus is about 50 million times greater than that released when a carbon atom combines with oxygen atoms in the burning of coal. The energy appears as kinetic energy of the fragments, which converts to thermal energy as the fragments collide in matter and slow down. Fission also releases two or three free neutrons. The free neutrons can bombard other nuclei, leading to a series of fissions called a chain reaction. The energy released from nuclear fission is used to generate electricity, to propel ships and submarines, and is a source of the vast destructive power of nuclear weapons.

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Method of determining the age of a mineral that utilizes the damage done by the spontaneous fission of uranium-238, the most abundant isotope of uranium. The fission results in radiation damage, or fission tracks, that can be made visible by preferential leaching (removal of material by solution) of the host substance with a suitable chemical reagent; the leaching process allows the etched fission-track pits to be viewed and counted under a microscope. The amount of uranium present can be determined by irradiation that produces thermal fission of uranium-235, which produces another population of tracks, related to the uranium concentration of the mineral. Thus, the ratio of naturally produced, spontaneous fission tracks to induced fission tracks is a measure of the age of the sample. See also dating.

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Fission is a splitting of something into two parts.

Fission may refer to:

• In physics, nuclear fission is a process where a large atomic nucleus (such as uranium) is split into two smaller nuclei
• In biology, binary fission is the mitosis process whereby a prokaryote reproduces by cell division
• In anthropology, fission is the process whereby a nation-state divides and becomes multiple states
• In geology, fissility is the property of mudstones to split along layers

Other uses:

• Fission (band), a Swedish melodic death metal band