Editing Cold fusion (section)

{{Short description|Hypothetical type of nuclear reaction}}
{{Hatnote group|{{About|the Fleischmann–Pons claims of nuclear fusion at room temperature, and subsequent research|the original use of the term "cold fusion"|muon-catalyzed fusion|all other definitions|Cold fusion (disambiguation)}}
{{Distinguish|cold welding}}
}}
{{Use dmy dates|date=March 2019}}
[[File:Cold-fusion-calorimeter-nhe-diagram.png|thumb|250px|Diagram of an open-type [[calorimeter]] used at the New Hydrogen Energy Institute in Japan]]

'''Cold fusion''' is a hypothesized type of [[nuclear reaction]] that would occur at, or near, [[room temperature]]. It would contrast starkly with the [[nuclear fusion|"hot" fusion]] that is known to take place naturally within [[Main sequence|stars]] and artificially in [[Thermonuclear weapon|hydrogen bombs]] and prototype [[Fusion power|fusion reactors]] under immense pressure and at temperatures of millions of degrees, and be distinguished from [[muon-catalyzed fusion]]. There is currently no accepted theoretical model that would allow cold fusion to occur.

In 1989, two [[electrochemistry|electrochemists]] at the University of Utah, [[Martin Fleischmann]] 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.<ref>{{cite web
 |mode        = cs2
 |title       = 60 Minutes: Once Considered Junk Science, Cold Fusion Gets A Second Look By Researchers
 |url         = https://www.cbsnews.com/news/cold-fusion-is-hot-again/
 |publisher   = [[CBS]]
 |date        = 17 April 2009
 |url-status  = live
 |archive-url  = https://web.archive.org/web/20120212001503/http://www.cbsnews.com/stories/2009/04/17/60minutes/main4952167.shtml
 |archive-date = 12 February 2012
}}</ref> They further reported measuring small amounts of nuclear reaction byproducts, including [[neutrons]] and [[tritium]].<ref name=FP1989>{{harvnb|Fleischmann|Pons|1989|p=301}} ("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...")</ref> The small tabletop experiment involved [[electrolysis]] of [[heavy water]] on the surface of a [[palladium]] (Pd) electrode.{{sfn|ps=|Voss|1999a}} The reported results received wide media attention{{sfn|ps=|Voss|1999a}} and raised hopes of a cheap and abundant source of energy.{{sfn|ps=|Browne|1989|loc=para. 1}}
Both neutrons and tritium are found in trace amounts from natural sources. They are produced in trace amounts from cosmic ray interactions and nuclear radioactive decays occurring in the atmosphere and in earth.

Many scientists tried to [[Reproducibility|replicate]] the experiment with the few details available. Expectations diminished as a result of numerous failed replications, the retraction of several previously reported positive replications, the identification of methodological flaws and experimental errors in the original study, and, ultimately, the confirmation that Fleischmann and Pons had not observed the expected nuclear reaction byproducts.<ref>{{harvnb|Browne|1989}}, {{harvnb|Close|1992}}, {{harvnb|Huizenga|1993}}, {{harvnb|Taubes|1993}}</ref> By late 1989, most scientists considered cold fusion claims dead,{{sfn|ps=|Browne|1989}}<ref name="most scientists">{{harvnb|Taubes|1993|pp=262, 265–266, 269–270, 273, 285, 289, 293, 313, 326, 340–344, 364, 366, 404–406}}, {{harvnb|Goodstein|1994}}, {{harvnb|Van Noorden|2007}}, {{harvnb|Kean|2010}}</ref> and cold fusion subsequently gained a reputation as [[pathological science]].<ref name="nytdoe">
{{cite news|mode=cs2
 |date=25 March 2004
 |title=US will give cold fusion a second look
 |url=https://www.nytimes.com/2004/03/25/us/us-will-give-cold-fusion-second-look-after-15-years.html
 |newspaper=The New York Times
 |access-date=8 February 2009
| first=Kenneth
| last=Chang
}}</ref><ref name="Ouellette">
{{cite web
 |mode        = cs2
 |date        = 23 December 2011
 |title       = Could Starships Use Cold Fusion Propulsion?
 |url         = http://news.discovery.com/space/could-interstellar-starships-use-cold-fusion-propulsion-111223.html
 |work = Discovery News
 |first       = Jennifer
 |last        = Ouellette
 |url-status     = live
 |archive-url  = https://web.archive.org/web/20120107185538/http://news.discovery.com/space/could-interstellar-starships-use-cold-fusion-propulsion-111223.html
 |archive-date = 7 January 2012
}}</ref> In 1989 the [[United States Department of Energy]] (DOE) concluded that the reported results of excess heat did not present convincing evidence of a useful source of energy and decided against allocating funding specifically for cold fusion. A second DOE review in 2004, which looked at new research, reached similar conclusions and did not result in DOE funding of cold fusion.<ref>{{harvnb|US DOE|2004}}, {{harvnb|Choi|2005}}, {{harvnb|Feder|2005}}</ref> Presently, since articles about cold fusion are rarely published in [[Peer-reviewed journal|peer-reviewed]] mainstream [[scientific journal]]s, they do not attract the level of scrutiny expected for mainstream [[scientific publications]].<ref>{{harvnb|Goodstein|1994}}, {{harvnb|Labinger|Weininger|2005|p=1919}}</ref>

Nevertheless, some interest in cold fusion has continued through the decades—for example, a Google-funded failed replication attempt was published in a 2019 issue of [[Nature (journal)|''Nature'']].<ref name=":0">{{Cite web|last=Koziol|first=Michael|date=22 March 2021|title=Whether Cold Fusion or Low-Energy Nuclear Reactions, U.S. Navy Researchers Reopen Case|url=https://spectrum.ieee.org/cold-fusion-or-low-energy-nuclear-reactions-us-navy-researchers-reopen-case|access-date=2021-03-23|website=IEEE Spectrum: Technology, Engineering, and Science News|language=en}}</ref><ref>{{cite journal | last1 = Berlinguette | first1 = C.P. | last2 = Chiang | first2 = YM. | last3 = Munday | first3 = J.N. | display-authors = etal | year = 2019| title = Revisiting the cold case of cold fusion | url = | journal = Nature | volume = 570 | issue = 7759| pages = 45–51 | doi = 10.1038/s41586-019-1256-6 | pmid = 31133686 | bibcode = 2019Natur.570...45B | s2cid = 167208748 }}</ref> A small community of researchers continues to investigate it,{{sfn|ps=|Browne|1989}}<ref name=Broad1989b/><ref name="small community">{{harvnb|Goodstein|1994}}, {{harvnb|Platt|1998}}, {{harvnb|Voss|1999a}}, {{harvnb|Beaudette|2002}}, {{harvnb|Feder|2005}}, {{harvnb|Adam|2005}} "Advocates insist that there is just too much evidence of unusual effects in the thousands of experiments since Pons and Fleischmann to be ignored", {{harvnb|Kruglinski|2006}}, {{harvnb|Van Noorden|2007}}, {{harvnb|Alfred|2009}}. {{harvnb|Daley|2004}} calculates between 100 and 200 researchers, with damage to their careers.</ref> often under the alternative designations '''low-energy nuclear reactions''' ('''LENR''') or '''condensed matter nuclear science''' ('''CMNS''').<ref name="ACS Press Release">
{{cite web
 |mode        = cs2
 |url         = http://www.eurekalert.org/pub_releases/2009-03/acs-fr031709.php
 |title       = 'Cold fusion' rebirth? New evidence for existence of controversial energy source
 | date=23 March 2009
 |publisher   = [[American Chemical Society]]
 |url-status     = dead
 |archive-url  = https://web.archive.org/web/20141221073942/http://www.eurekalert.org/pub_releases/2009-03/acs-fr031709.php
 |archive-date = 21 December 2014
}} Research presented at a meeting of the American Chemical Society.</ref>{{sfn|ps=|Hagelstein|McKubre|Nagel|Chubb|2004}}<ref>{{cite web |title=ICMNS FAQ |url=http://www.iscmns.org/FAQ.HTM#ref2 |publisher=International Society of Condensed Matter Nuclear Science |url-status=live |archive-url= https://web.archive.org/web/20151103020057/http://iscmns.org/FAQ.HTM#ref2 |archive-date=3 November 2015}}</ref>{{sfn|ps=|Biberian|2007}}<ref>{{cite web | title=Cold fusion may be a viable energy alternative to end reliance on fossil fuels| last1 = Josephson | first1 = Brian| author1-link=Brian Josephson|last2 = Nagel | first2 = David J| last3 = Smith | first3 = Alan| last4 = Biberian | first4 = Jean-Paul| last5 = Iwamura | first5 = Yasuhiro| publisher=The Guardian (letter)| date=28 January 2025 | url=https://www.theguardian.com/environment/2025/jan/28/cold-fusion-may-a-viable-energy-alternative-to-end-reliance-on-fossil-fuels}}</ref>