Editing Absolute zero (section)

===Lord Kelvin's work===
After [[James Prescott Joule]] had determined the mechanical equivalent of heat, [[William Thomson, 1st Baron Kelvin|Lord Kelvin]] approached the question from an entirely different point of view, and in 1848 devised a scale of absolute temperature that was independent of the properties of any particular substance and was based on [[Nicolas Léonard Sadi Carnot|Carnot]]'s theory of the Motive Power of Heat and data published by [[Henri Victor Regnault]].<ref>{{Cite journal |last=Thomson |first=William |author-link=Lord Kelvin |date=1848 |title=On an Absolute Thermometric Scale founded on Carnot's Theory of the Motive Power of Heat, and calculated from Regnault's observations. |url=https://www.biodiversitylibrary.org/item/87114#page/72/mode/2up |journal=Proceedings of the Cambridge Philosophical Society |volume=1 |pages=66–71}}</ref> It followed from the principles on which this scale was constructed that its zero was placed at −273&nbsp;°C, at almost precisely the same point as the zero of the air thermometer,<ref name="AS2016" /> where the air volume would reach "nothing". This value was not immediately accepted; values ranging from {{convert|-271.1|C}} to {{convert|-274.5|C}}, derived from laboratory measurements and observations of [[Atmospheric refraction#Astronomical refraction|astronomical refraction]], remained in use in the early 20th century.<ref>{{Citation |last=Newcomb |first=Simon |title=A Compendium of Spherical Astronomy |date=1906 |page=175 |place=New York |publisher=The Macmillan Company |oclc=64423127 |author-link=Simon Newcomb}}.</ref>