Not to be confused with ColdFusion , a software product, cold fusion is a hypothetical process in which hydrogen fusion supposedly occurs at room temperature. The topic is controversial, because the notion appears to defy the laws of physics. Some scientists believe that cold fusion represents a real phenomenon and that it will someday form the basis for an abundant, cheap source of energy. Others maintain that cold fusion, like perpetual motion, is impossible.
Hydrogen fusion as it is currently known is the process responsible for the energy output of the sun and most other stars. It does not ordinarily take place unless there is extreme heat (millions of degrees Celsius ) and extreme pressure. The only officially documented examples of human-generated fusion involve the explosions of hydrogen bombs. In the hydrogen fusion process, the nuclei of hydrogen atom s are driven together to form helium nuclei. It takes four hydrogen nuclei to ultimately produce a single helium nucleus . Energy, and certain subatomic particles, are emitted as byproducts.
After the first hydrogen bombs were successfully tested, scientists and engineers began searching for a way to control hydrogen fusion reactions and harness the energy in a constructive manner. Hydrogen fusion generates no dangerous nuclear waste, is far more efficient than the fission processes currently used in nuclear reactors, and has as its basis the most abundant element in the universe (hydrogen). In 1989, Stanley Pons and Martin Fleischmann of the University of Utah claimed to have produced hydrogen fusion in a controlled experiment at room temperature. The news created a stir among scientists, engineers, government agencies, and the public. It also caused a controversy among physicists that has been going on ever since.
The cold-fusion experiments conducted by Pons and Fleischmann involved deuterium, an isotope of helium in which the nucleus contains a neutron as well as a proton . (Ordinary hydrogen has a nucleus consisting of a single proton only.) The deuterium was packed into electrodes made of a metallic element known as palladium. Under certain conditions, it appeared that energy was produced along with helium nuclei at room temperature, in the same way, and according to the same mathematical formulae, as observed in hydrogen fusion at high temperatures. But these results have proven difficult to reproduce. Even in apparently successful cold-fusion experiments, no one has yet harnessed the energy and thereby built a functional reactor.