Editing Lord Kelvin (section)

== Early life and work ==
=== Family ===
[[File:Thomson family lineage.png|thumb|The Thomson family tree: [[James Thomson (mathematician)]], [[James Thomson (engineer)]], and William Thomson, were all professors at the [[University of Glasgow]], the latter two through their association with [[William Rankine]], another Glasgow professor, who worked to form one of the founding schools of [[thermodynamics]].]]

Thomson's father, [[James Thomson (mathematician)|James Thomson]], was a teacher of mathematics and engineering at the [[Royal Belfast Academical Institution]] and the son of an [[Ulster Scots people|Ulster Scots]] farmer. James Thomson married Margaret Gardner in 1817 and, of their children, four boys and two girls survived infancy. Margaret Thomson died in 1830 when William was six years old.<ref>{{cite web |url=http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Thomson_James.html |title=Biography of William Thomson's father |publisher=Groups.dcs.st-and.ac.uk |access-date=29 October 2011 |archive-date=2 May 2019 |archive-url=https://web.archive.org/web/20190502040147/http://www-groups.dcs.st-and.ac.uk/~history/Biographies/Thomson_James.html |url-status=dead }}</ref>

William and his elder brother [[James Thomson (engineer)|James]] were tutored at home by their father while the younger boys were tutored by their elder sisters. James was intended to benefit from the major share of his father's encouragement, affection and financial support and was prepared for a career in engineering.

In 1832, his father was appointed professor of mathematics at [[Glasgow]], and the family moved there in October 1833. The Thomson children were introduced to a broader cosmopolitan experience than their father's rural upbringing, spending mid-1839 in London, and the boys were tutored in French in Paris. Much of Thomson's life during the mid-1840s was spent in [[German Confederation|Germany]] and the [[Netherlands]]. Language study was given a high priority.

His sister, Anna Thomson, was the mother of physicist [[James Thomson Bottomley]] FRSE.<ref>{{Cite web |url=http://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp1.pdf |title=Former Fellows of The Royal Society of Edinburgh, 1783–2002 |access-date=30 April 2015 |archive-date=19 September 2015 |archive-url=https://web.archive.org/web/20150919152306/https://www.royalsoced.org.uk/cms/files/fellows/biographical_index/fells_indexp1.pdf |url-status=dead }}</ref>

=== Youth ===
 
[[File:PSM V72 D191 William thomson lord kelvin at the age of twenty two.png|thumb|left|upright|William Thomson, aged 22]]
[[File:University, Glasgow, Scotland, ca. 1895.jpg|thumb|The [[meander]] of the [[River Kelvin]] containing the [[Neo-Gothic]] Gilmorehill campus of the University of Glasgow designed by [[George Gilbert Scott]], to which the university moved in the 1870s (photograph 1890s)]]

Thomson attended the Royal Belfast Academical Institution, where his father was a professor of Mathematics in the university department.<ref>{{cite web |url=https://rbai.org.uk/house-system/kelvin-house/ |title=Kelvin House |author=<!--Not stated--> |date= |website=Royal Belfast Academical Institute |publisher= |access-date=January 15, 2025}}</ref> In 1834, aged 10, he began studying at the [[University of Glasgow]], not out of any precociousness; the university provided many of the facilities of an elementary school for able pupils, and this was a typical starting age. In school, he showed a keen interest in the classics along with his natural interest in the sciences. At age 12 he won a prize for translating [[Lucian]] of Samosata's ''Dialogues of the Gods'' from [[Ancient Greek]] to English.<ref>{{cite web |url=https://irvineburnsclub.org/assets/files/honorary16-1897-99.pdf |title=Honorary members of 1897-1899 |author=<!--Not stated--> |date= |website=Irvine Burns Club |publisher= |access-date=January 15, 2025}}</ref>

In the academic year 1839/1840, Thomson won the class prize in [[astronomy]] for his "Essay on the figure of the Earth" which showed an early facility for mathematical analysis and creativity.<ref>{{cite web |url=https://integratedcollegeglengormley.com/kelvin-house/ |title=Kelvin House|author=<!--Not stated--> |date= |website=Integrated College Glengormley |publisher= |access-date=January 15, 2025}}</ref> His physics tutor at this time was his namesake, [[David Thomson (physicist)|David Thomson]].<ref>{{cite web | url=https://homepages.abdn.ac.uk/npmuseum/article/Profs/ThomsonUni.shtml |title = David Thomson 17 Nov 1817 – 31st Jan 1880 | publisher=Aberdeen University}}</ref> Throughout his life, he would work on the problems raised in the essay as a [[coping]] strategy during times of personal stress. On the title page of this essay Thomson wrote the following lines from [[Alexander Pope]]'s "[[An Essay on Man]]". These lines inspired Thomson to understand the natural world using the power and method of science:

{{poemquote|
Go, wondrous creature! mount where Science guides;
Go, measure earth, weigh air, and state the tides;
Instruct the planets in what orbs to run,
Correct old Time, and regulate the sun; }}

Thomson became intrigued with [[Joseph Fourier|Joseph Fourier's]] ''Théorie analytique de la chaleur'' (''The Analytical Theory of Heat'').<ref>{{cite web |url=https://academic.oup.com/book/41694/chapter-abstract/353936888?redirectedFrom=fulltext |title=Joseph Fourier's Theory of Terrestrial Temperatures |last=Fleming |first=James R. |date=October 31, 1998 |website=Oxford University Press |publisher=Historical Perspectives on Climate Change, October 1998, page 55 |access-date=January 15, 2025}}</ref> He committed himself to study the "continental" mathematics resisted by a British establishment still working in the shadow of Sir [[Isaac Newton]]. Unsurprisingly, Fourier's work had been attacked by domestic mathematicians, [[Philip Kelland]] authoring a critical book. The book motivated Thomson to write his first published [[Scientific literature|scientific paper]]<ref>{{cite journal | author=P.Q.R. | year = 1841 | title = On Fourier's expansions of functions in trigonometric series | journal = Cambridge Mathematical Journal | volume = 2 | pages = 258–262 }}</ref> under the pseudonym ''P.Q.R.'', defending Fourier, which was submitted to ''[[The Quarterly Journal of Pure and Applied Mathematics|The Cambridge Mathematical Journal]]'' by his father. A second P.Q.R. paper followed almost immediately.<ref>{{cite journal | author=P.Q.R. | year = 1841 | title = Note on a passage in Fourier's 'Heat' | journal = Cambridge Mathematical Journal | volume = 3 | pages = 25–27 | url =https://en.wikisource.org/wiki/Note_on_a_Passage_in_Fourier%27s_Heat }}</ref>

While on holiday with his family in [[Lamlash]] in 1841, he wrote a third, more substantial P.Q.R. paper ''On the uniform motion of heat in homogeneous solid bodies, and its connection with the mathematical theory of electricity''.<ref>{{cite journal | author=P.Q.R. | year = 1842 | title = On the uniform motion of heat and its connection with the mathematical theory of electricity | doi =10.1017/CBO9780511996009.004 | journal = Cambridge Mathematical Journal | volume = 3 | pages = 71–84 }}</ref> In the paper he made remarkable connections between the mathematical theories of [[thermal conduction]] and [[electrostatics]], an analogy that [[James Clerk Maxwell]] was ultimately to describe as one of the most valuable science-forming ideas''.''<ref>{{cite book| editor=Niven, W.D. | title=The Scientific Papers of James Clerk Maxwell, 2 vols | location=New York | publisher=Dover | year=1965 | volume= 2|page=301 }}</ref>

=== Cambridge ===
William's father was able to make a generous provision for his favourite son's education and, in 1841, installed him, with extensive letters of introduction and ample accommodation, at [[Peterhouse, Cambridge]]. While at Cambridge, Thomson was active in sports, athletics and [[sculling]], winning the Colquhoun Sculls in 1843.<ref>{{cite book |last1=Mayer |first1=Roland |title=Peterhouse Boat Club 1828–1978 |year=1978 |publisher=Peterhouse Boat Club |isbn=0-9506181-0-1 |page=5}}</ref> He took a lively interest in the classics, music, and literature; but the real love of his intellectual life was the pursuit of science. The study of mathematics, physics, and in particular, of electricity, had captivated his imagination. In 1845 Thomson graduated as [[Wrangler (University of Cambridge)|second wrangler]].<ref>{{acad|id=THN841W|name=Thomson, William}}</ref> He also won the first [[Smith's Prize]], which, unlike the [[tripos]], is a test of original research. [[Robert Leslie Ellis]], one of the examiners, is said to have declared to another examiner "You and I are just about fit to mend his pens."<ref>{{cite book|last=Thompson|first=Silvanus |title=The Life of William Thomson, Baron Kelvin of Largs|volume= 1|year=1910|publisher=MacMillan and Co., Limited |page=98|url=https://archive.org/details/b31360403_0001}}</ref>

In 1845, he gave the first mathematical development of [[Michael Faraday]]'s idea that electric induction takes place through an intervening medium, or "[[dielectric]]", and not by some incomprehensible "action at a distance". He also devised the mathematical technique of electrical images, which became a powerful agent in solving problems of [[electrostatics]], the science which deals with the forces between electrically charged bodies at rest. It was partly in response to his encouragement that Faraday undertook the research in September 1845 that led to the discovery of the [[Faraday effect]], which established that light and magnetic (and thus electric) phenomena were related.

He was elected a fellow of St. Peter's (as Peterhouse was often called at the time) in June 1845.<ref name="physicsworld">{{cite news|first=Mark|last=McCartney|title=William Thomson: king of Victorian physics|work=[[Physics World]]|url=http://physicsworld.com/cws/article/print/16484|date=1 December 2002|access-date=16 July 2008|archive-date=15 July 2008|archive-url=https://web.archive.org/web/20080715173557/http://physicsworld.com/cws/article/print/16484|url-status=dead}}</ref> On gaining the fellowship, he spent some time in the laboratory of the celebrated [[Henri Victor Regnault]], at Paris; but in 1846 he was appointed to the [[Professor of Natural Philosophy, Glasgow|chair of natural philosophy]] in the University of Glasgow. At age 22 he found himself wearing the gown of a professor in one of the oldest universities in the country and lecturing to the class of which he was a first year student a few years before.

=== Thermodynamics ===
By 1847, Thomson had already gained a reputation as a precocious and maverick scientist when he attended the [[British Association for the Advancement of Science]] annual meeting in [[Oxford]]. At that meeting, he heard [[James Prescott Joule]] making yet another of his, so far, ineffective attempts to discredit the [[caloric theory]] of heat and the theory of the [[heat engine]] built upon it by [[Nicolas Léonard Sadi Carnot|Sadi Carnot]] and [[Émile Clapeyron]]. Joule argued for the mutual convertibility of heat and [[mechanical work]] and for their mechanical equivalence.

Thomson was intrigued but sceptical. Though he felt that Joule's results demanded theoretical explanation, he retreated into an even deeper commitment to the Carnot–Clapeyron school. He predicted that the [[melting point]] of ice must fall with [[pressure]], otherwise its expansion on freezing could be exploited in a ''[[perpetual motion|perpetuum mobile]]''. Experimental confirmation in his laboratory did much to bolster his beliefs.

In 1848, he extended the Carnot–Clapeyron theory further through his dissatisfaction that the [[gas thermometer]] provided only an [[operational definition]] of temperature. He proposed an ''[[absolute temperature]] scale''<ref>{{cite book | author=Chang, H. | title=Inventing Temperature: Measurement and Scientific Progress | publisher=Oxford University Press | year=2004 | isbn=978-0-19-517127-3|chapter =4 }}</ref> in which "a unit of heat descending from a body A at the temperature ''T''° of this scale, to a body B at the temperature (''T''−1)°, would give out the same mechanical effect ''[work]'', whatever be the number ''T''." Such a scale would be "quite independent of the physical properties of any specific substance."<ref>{{cite book | title=Mathematical and Physical Papers | chapter=On an Absolute Thermometric Scale founded on Carnot's Theory of the Motive Power of Heat, and calculated from Regnault's observations | publisher=Cambridge University Press | date=1848 | doi=10.1017/cbo9780511996009.040 | pages=100–106 | author = Thomson, W.| isbn=978-1-108-02898-1 }}</ref> By employing such a "waterfall", Thomson postulated that a point would be reached at which no further heat (caloric) could be transferred, the point of ''[[absolute zero]]'' about which [[Guillaume Amontons]] had speculated in 1702. "Reflections on the Motive Power of Heat", published by Carnot in French in 1824, the year of Lord Kelvin's birth, used −267 as an estimate of the absolute zero temperature. Thomson used data published by Regnault to [[calibration|calibrate]] his scale against established measurements.

In his publication, Thomson wrote:

{{Blockquote|... The conversion of heat (or ''caloric'') into mechanical effect is probably impossible, certainly undiscovered}}—But a footnote signalled his first doubts about the caloric theory, referring to Joule's ''very remarkable discoveries''. Surprisingly, Thomson did not send Joule a copy of his paper, but when Joule eventually read it he wrote to Thomson on 6 October, claiming that his studies had demonstrated conversion of heat into work but that he was planning further experiments. Thomson replied on 27 October, revealing that he was planning his own experiments and hoping for a reconciliation of their two sides.

Thomson returned to critique Carnot's original publication and read his analysis to the [[Royal Society of Edinburgh]] in January 1849,<ref>{{cite book | title=Mathematical and Physical Papers | chapter=An Account of Carnot's Theory of the Motive Power of Heat; with Numerical Results deduced from Regnault's Experiments on Steam | publisher=Cambridge University Press | date=1849 | doi=10.1017/cbo9780511996009.042 | pages=113–164 | author = Thomson, W.| isbn=978-1-108-02898-1 | url=https://zenodo.org/record/1634618 }}</ref> still convinced that the theory was fundamentally sound. However, though Thomson conducted no new experiments, over the next two years he became increasingly dissatisfied with Carnot's theory and convinced of Joule's. In February 1851 he sat down to articulate his new thinking. He was uncertain of how to frame his theory, and the paper went through several drafts before he settled on an attempt to reconcile Carnot and Joule. During his rewriting, he seems to have considered ideas that would subsequently give rise to the [[second law of thermodynamics]]. In Carnot's theory, lost heat was ''absolutely lost,'' but Thomson contended that it was "''lost to man'' irrecoverably; but not lost in the material world". Moreover, his [[theology|theological]] beliefs led Thomson to [[Extrapolation|extrapolate]] the second law to the cosmos, originating the idea of [[heat death of the universe|universal heat death]].

{{Blockquote|I believe the tendency in the material world is for motion to become diffused, and that as a whole the reverse of concentration is gradually going on – I believe that no physical action can ever restore the heat emitted from the Sun, and that this source is not inexhaustible; also that the motions of the Earth and other planets are losing ''[[vis viva]]'' which is converted into heat; and that although some ''vis viva'' may be restored for instance to the earth by heat received from the sun, or by other means, that the loss cannot be ''precisely'' compensated and I think it probable that it is under-compensated.<ref name="Sharlin 1979">[[#Sharlin|Sharlin]], p. 112.</ref>}}

Compensation would require ''a creative act or an act possessing similar power'',<ref name="Sharlin 1979" /> resulting in a ''rejuvenating universe'' (as Thomson had previously compared universal heat death to a clock running slower and slower, although he was unsure whether it would eventually reach [[thermodynamic equilibrium]] and ''stop for ever'').<ref>{{cite magazine |last1=Otis |first1=Laura |year=2002 |title=Literature and Science in the Nineteenth Century: An Anthology |url= https://oxfordworldsclassics.com/view/10.1093/owc/9780199554652.001.0001/isbn-9780199554652 |magazine=OUP Oxford |volume=1 |pages=60–67}}</ref> Thomson also formulated the [[heat death paradox]] (Kelvin's paradox) in 1862, which uses the second law of thermodynamics to disprove the possibility of an infinitely old universe; this paradox was later extended by [[William Rankine]].<ref>{{cite magazine |last1=Thomson |first1=William |year=1862 |title=On the Age of the Sun's Heat |url=https://zapatopi.net/kelvin/papers/on_the_age_of_the_suns_heat.html |magazine=Macmillan's Magazine |volume=5 |pages=388–393}}</ref>

In final publication, Thomson retreated from a radical departure and declared "the whole theory of the motive power of heat is founded on ... two ... propositions, due respectively to Joule, and to Carnot and Clausius."<ref>{{cite book | title=Mathematical and Physical Papers | chapter=On the dynamical theory of heat; with numerical results deduced from Mr. Joule's equivalent of a thermal unit and M. Regnault's observations on steam | publisher=Cambridge University Press | date=1852 | author = Thomson, W. | doi=10.1017/cbo9780511996009.049 | pages=174–332| isbn=978-1-108-02898-1 }}</ref> Thomson went on to state a form of the second law:

{{Blockquote|It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects.<ref>{{cite journal|last=Thomson|first=W.|title=On the Dynamical Theory of Heat, with numerical results deduced from Mr Joule's equivalent of a Thermal Unit, and M. Regnault's Observations on Steam|journal=Transactions of the Royal Society of Edinburgh|date=March 1851|volume=XX|issue=part II|pages=261–268; 289–298}} Also published in {{cite journal|last=Thomson|first=W.|title=On the Dynamical Theory of Heat, with numerical results deduced from Mr Joule's equivalent of a Thermal Unit, and M. Regnault's Observations on Steam|journal=Phil. Mag. |date=December 1852 |volume=IV |series=4 |issue=22 |pages=8–21 |url=https://archive.org/details/londonedinburghp04maga }}</ref>}}

In the paper, Thomson supports the theory that heat was a form of motion but admits that he had been influenced only by the thought of Sir [[Humphry Davy]] and the experiments of Joule and [[Julius Robert von Mayer]], maintaining that experimental demonstration of the conversion of heat into work was still outstanding.<ref>Thomson, W. (1851) ''p.''183</ref> As soon as Joule read the paper he wrote to Thomson with his comments and questions. Thus began a fruitful, though largely epistolary, collaboration between the two men, Joule conducting experiments, Thomson analysing the results and suggesting further experiments. The collaboration lasted from 1852 to 1856, its discoveries including the [[Joule–Thomson effect]], sometimes called the Kelvin–Joule effect, and the published results<ref>{{cite book | title=Mathematical and Physical Papers | chapter=On the thermal effects of fluids in motion | publisher=Cambridge University Press | date=30 June 2011 | doi=10.1017/cbo9780511996009.050 | pages=333–455| author1 = Joule, J. P. | author2 = Thomson, W.}}</ref> did much to bring about general acceptance of Joule's work and the [[kinetic theory of gases|kinetic theory]].

Thomson published more than 650 scientific papers<ref name="britannica.com" /> and applied for 70 patents (not all were issued). Regarding science, Thomson wrote the following:

{{Blockquote|In physical science a first essential step in the direction of learning any subject is to find principles of numerical reckoning and practicable methods for measuring some quality connected with it. I often say that when you can measure what you are speaking about and express it in numbers you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of ''science'', whatever the matter may be.<ref>{{cite book|last=Thomson|first=W.|title=Popular Lectures and Addresses, Vol. I|year=1891|publisher=MacMillan|location=London|page=80|isbn=978-0-598-77599-3|url=https://books.google.com/books?id=JcMKAAAAIAAJ|access-date=25 June 2012}}</ref> }}