   cold fusion is a hypothetical type of nuclear reaction that would occur at, or near, room temperature, compared with temperatures in the millions of degrees that are required for "hot" fusion, which takes place naturally within stars. there is currently no accepted theoretical model which would allow cold fusion to occur. in 1989 martin fleischmann (then one of the world's leading electrochemists) and stanley pons reported that their apparatus had produced anomalous heat ("excess heat"), of a magnitude they asserted would defy explanation except in terms of nuclear processes. they further reported measuring small amounts of nuclear reaction byproducts, including neutrons and tritium. ("it is inconceivable that this [amount of heat] could be due to anything but nuclear processes... we realise that the results reported here raise more questions than they provide answers...") the small tabletop experiment involved electrolysis of heavy water on the surface of a palladium (pd) electrode. the reported results received wide media attention, and raised hopes of a cheap and abundant source of energy. many scientists tried to replicate the experiment with the few details available. hopes fell with the large number of negative replications, the withdrawal of many positive replications, the discovery of flaws and sources of experimental error in the original experiment, and finally the discovery that fleischmann and pons had not actually detected nuclear reaction byproducts., , ,  by late 1989, most scientists considered cold fusion claims dead,, , ,  and cold fusion subsequently gained a reputation as pathological science. {{cite journal |ref=harv |separator=, |author= |date=2004-03-25 |title=us will give cold fusion a second look |url=http://query.nytimes.com/g
Cold_fusion Discovery_and_invention_controversies Electrolysis Fringe_physics Nuclear_fusion Nuclear_physics Palladium Pathological_science