Editing Heike Kamerlingh Onnes (section)

== Superconductivity ==

In 1911 Kamerlingh Onnes measured the electrical conductivity of pure metals ([[mercury (element)|mercury]], and later [[tin]] and [[lead]]) at very low temperatures. Some scientists, such as [[William Thomson, 1st Baron Kelvin|William Thomson]] (Lord Kelvin), believed that [[electron]]s flowing through a [[Electrical conductor|conductor]] would come to a complete halt or, in other words, metal resistivity would become infinitely large at absolute zero. Others, including Kamerlingh Onnes, felt that a conductor's electrical resistance would steadily decrease and drop to nil. [[Augustus Matthiessen]] said that when the temperature decreases, the metal conductivity usually improves or in other words, the electrical resistivity usually decreases with a decrease of temperature.<ref>{{Cite journal | doi = 10.1098/rstl.1862.0001| title = On the Influence of Temperature on the Electric Conducting Power of Metals| journal = Philosophical Transactions of the Royal Society of London| volume = 152| pages = 1–27| year = 1862| last1 = Matthiessen | first1 = A.| last2 = von Bose | first2 = M.| url = https://zenodo.org/record/1432436| doi-access = free}}</ref><ref>{{Cite journal | doi = 10.1098/rstl.1864.0004| title = On the Influence of Temperature on the Electric Conducting-Power of Alloys| journal = Philosophical Transactions of the Royal Society of London| volume = 154| pages = 167–200| year = 1864| last1 = Matthiessen | first1 = A.| last2 = Vogt | first2 = C.| doi-access = free}}</ref>

On 8 April 1911, Kamerlingh Onnes found that at 4.2 [[kelvin|K]] the resistance in a solid mercury wire immersed in liquid helium suddenly vanished. He immediately realized the significance of the discovery (as became clear when his notebook was deciphered a century later).<ref>{{cite journal|url=http://ilorentz.org/history/cold/DelftKes_HKO_PT.pdf |title=The Discovery of Superconductivity|author1=van Delft, Dirk |author2=Kes, Peter |date=September 2010|pages=38–43|journal=Physics Today|doi=10.1063/1.3490499|volume=63|issue=9|bibcode = 2010PhT....63i..38V |doi-access=free}}</ref> He reported that "Mercury has passed into a new state, which on account of its extraordinary electrical properties may be called the superconductive state". He published more articles about the phenomenon, initially referring to it as "supraconductivity" and, only later adopting the term "superconductivity".