Editing Lord Kelvin (section)

== Other contributions ==
=== ''Treatise on Natural Philosophy'' ===
{{Main|Treatise on Natural Philosophy}}
Over the period 1855 to 1867, Thomson collaborated with [[Peter Guthrie Tait]] on a textbook that founded the study of [[mechanics]] first on the mathematics of [[kinematics]], the description of motion without regard to [[force]]. The text developed [[Classical mechanics|dynamics]] in various areas but with constant attention to energy as a unifying principle. A second edition appeared in 1879, expanded to two separately bound parts. The textbook set a standard for early education in [[mathematical physics]].

=== Atmospheric electricity ===
Thomson made significant contributions to [[atmospheric electricity]] for the relatively short time for which he worked on the subject, around 1859.<ref name=":1">{{Cite journal|last1=Aplin|first1=K. L.|last2=Harrison|first2=R. G.|date=3 September 2013|title=Lord Kelvin's atmospheric electricity measurements|journal=History of Geo- and Space Sciences|volume=4|issue=2|pages=83–95|doi=10.5194/hgss-4-83-2013|arxiv=1305.5347|bibcode=2013HGSS....4...83A|s2cid=9783512 |doi-access=free }}</ref> He developed several instruments for measuring the atmospheric electric field, using some of the electrometers he had initially developed for telegraph work, which he tested at Glasgow and whilst on holiday on Arran. His measurements on Arran were sufficiently rigorous and well-calibrated that they could be used to deduce air pollution from the Glasgow area, through its effects on the atmospheric electric field.<ref>{{Cite journal|last=Aplin|first=Karen L.|date=April 2012|title=Smoke emissions from industrial western Scotland in 1859 inferred from Lord Kelvin's atmospheric electricity measurements|journal=Atmospheric Environment|volume=50|pages=373–376|doi=10.1016/j.atmosenv.2011.12.053|bibcode=2012AtmEn..50..373A}}</ref> Thomson's water dropper electrometer was used for measuring the atmospheric electric field at [[King's Observatory|Kew Observatory]] and [[Eskdalemuir Observatory]] for many years,<ref>{{Cite journal|last=Harrison|first=R. G.|date=2003|title=Twentieth-century atmospheric electrical measurements at the observatories of Kew, Eskdalemuir and Lerwick|journal=Weather|volume=58|issue=1|pages=11–19|doi=10.1256/wea.239.01|bibcode=2003Wthr...58...11H|s2cid=122673748 }}</ref> and one was still in use operationally at the Kakioka Observatory in Japan<ref>{{Cite journal|last1=Takeda|first1=M.|last2=Yamauchi|first2=M.|last3=Makino|first3=M.|last4=Owada|first4=T.|date=2011|title=Initial effect of the Fukushima accident on atmospheric electricity|journal=Geophysical Research Letters|volume=38|issue=15|doi=10.1029/2011GL048511|bibcode=2011GeoRL..3815811T|s2cid=73530372 |doi-access=free}}</ref> until early 2021. Thomson may have unwittingly observed atmospheric electrical effects caused by the [[Carrington event]] (a significant geomagnetic storm) in early September 1859.<ref name=":1" />

=== Vortex theory of the atom ===
{{Main|Vortex theory of the atom}}

Between 1870 and 1890 the vortex atom theory, which purported that an [[atom]] was a [[vortex]] in the [[luminiferous aether|aether]], was popular among British physicists and mathematicians. Thomson pioneered the theory, which was distinct from the 17th century vortex theory of [[René Descartes]] in that Thomson was thinking in terms of a unitary continuum theory, whereas Descartes was thinking in terms of three different types of matter, each relating respectively to emission, transmission, and reflection of light.<ref name="Kragh">{{cite journal |last1=Kragh |first1=Helge |title=The Vortex Atom: A Victorian Theory of Everything |journal=Centaurus |date=2002 |volume=44 |issue=1–2 |pages=32–114 |url=https://www.academia.edu/4084776 |access-date=9 March 2019 |doi=10.1034/j.1600-0498.2002.440102.x }}</ref> About 60 scientific papers were written by approximately 25 scientists. Following the lead of Thomson and Tait,<ref>{{cite journal | last1 = Thomson | first1 = Wm. | year = 1867 | title = On Vortex Atoms | url = http://zapatopi.net/kelvin/papers/on_vortex_atoms.html | journal = Proceedings of the Royal Society of Edinburgh | volume = 6 | pages = 94–105 | doi = 10.1017/S0370164600045430 }}</ref> the branch of [[topology]] called [[knot theory]] was developed. Thomson's initiative in this complex study that continues to inspire new mathematics has led to persistence of the topic in [[history of science]].<ref>{{cite journal|author=Silliman, Robert H. |year=1963|title=William Thomson: Smoke Rings and Nineteenth-Century Atomism|journal=Isis|volume=54|issue=4|pages=461–474|doi=10.1086/349764 |jstor=228151|s2cid=144988108 }}</ref>

=== Marine ===
[[File:DSCN1739-thomson-tide-machine.jpg|thumb|right|upright|Thomson's [[tide-predicting machine]]]]
Thomson was an enthusiastic yachtsman, his interest in all things relating to the sea perhaps arising from, or fostered by, his experiences on the ''Agamemnon'' and the ''[[SS Great Eastern|Great Eastern]]''. Thomson introduced a [[Kelvite sounding machine|new method of deep-sea depth sounding]], in which a steel [[piano wire]] replaces the ordinary hand line. The wire glides so easily to the bottom that "flying soundings" can be taken while the ship is at full speed. Thomson added a pressure gauge to register the depth of the sinker.<ref>{{cite book |last1=Thompson |first1=Silvanus Phillips |author1-link=Silvanus P. Thompson |title=The life of William Thomson, Baron Kelvin of Largs |date=1910 |publisher=Macmillan |location=London |oclc=5894345318 |page= 723}}</ref> About the same time he revived the [[Sumner method]] of finding a ship's position, and calculated a set of tables for its ready application.

During the 1880s, Thomson worked to perfect the adjustable [[compass]] to correct errors arising from [[magnetic deviation]] owing to the increased use of iron in [[naval architecture]]. Thomson's design was a great improvement on the older instruments, being steadier and less hampered by friction. The deviation caused by the ship's magnetism was corrected by movable iron masses at the [[binnacle]]. Thomson's innovations involved much detailed work to develop principles identified by [[George Biddell Airy]] and others, but contributed little in terms of novel physical thinking. Thomson's energetic lobbying and networking proved effective in gaining acceptance of his instrument by [[The Admiralty]].

[[File:Sir Lord Kelvin Mariner's Compass with Sun Dial.jpg|thumb|right|Kelvin Mariner's Compass]]

{{blockquote | Scientific biographers of Thomson, if they have paid any attention at all to his compass innovations, have generally taken the matter to be a sorry saga of dim-witted naval administrators resisting marvellous innovations from a superlative scientific mind. Writers sympathetic to the Navy, on the other hand, portray Thomson as a man of undoubted talent and enthusiasm, with some genuine knowledge of the sea, who managed to parlay a handful of modest ideas in compass design into a commercial monopoly for his own manufacturing concern, using his reputation as a bludgeon in the law courts to beat down even small claims of originality from others, and persuading the Admiralty and the law to overlook both the deficiencies of his own design and the virtues of his competitors'.
<p>The truth, inevitably, seems to lie somewhere between the two extremes.<ref>[[#Lindley|Lindley]], p. 259</ref></p>}}

[[Charles Babbage]] had been among the first to suggest that a [[lighthouse]] might be made to signal a distinctive number by occultations of its light, but Thomson pointed out the merits of the [[Morse code]] for the purpose, and urged that the signals should consist of short and long flashes of the light to represent the dots and dashes.

=== Electrical standards ===
Thomson did more than any other electrician up to his time in introducing accurate methods and apparati for measuring electricity. As early as 1845 he pointed out that the experimental results of [[William Snow Harris]] were in accordance with the laws of [[Charles-Augustin de Coulomb|Coulomb]]. In the ''Memoirs of the Roman Academy of Sciences'' for 1857 he published a description of his divided ring [[electrometer]], based on the electroscope of [[Johann Gottlieb Friedrich von Bohnenberger]]. He introduced a chain or series of effective instruments, including the quadrant electrometer, which cover the entire field of electrostatic measurement. He invented the [[current balance]], also known as the ''Kelvin balance'' or ''Ampere balance'' (''SiC''), for the precise specification of the [[ampere]], the standard unit of [[electric current]]. From around 1880 he was aided by the electrical engineer [[Magnus Maclean]] [[FRSE]] in his electrical experiments.<ref>{{cite web|title=Maclean, Magnus, 1857–1937, electrical engineer |url=http://strathclyde.ica-atom.org/maclean-magnus-1857-1937-electrical-engineer |website=University of Strathclyde Archives |access-date=19 January 2018}}</ref>

In 1893, Thomson headed an international commission to decide on the design of the [[Niagara Falls]] [[power station]]. Despite his belief in the superiority of [[direct current]] [[electric power transmission]], he endorsed Westinghouse's [[alternating current]] system which had been demonstrated at the [[World's Columbian Exposition|Chicago World's Fair]] of that year. Even after Niagara Falls, Thomson still held to his belief that direct current was the superior system.<ref>[[#Lindley|Lindley]], p. 293</ref>

Acknowledging his contribution to electrical standardisation, the [[International Electrotechnical Commission]] elected Thomson as its first president at its preliminary meeting, held in London on 26–27 June 1906. "On the proposal of the President [Mr Alexander Siemens, Great Britain], secounded [sic] by Mr Mailloux [US Institute of Electrical Engineers] the Right Honorable Lord Kelvin, [[G.C.V.O.]], [[Order of Merit|O.M.]], was unanimously elected first President of the Commission", minutes of the Preliminary Meeting Report read.<ref>{{cite web | url=http://www.iec.ch/about/history/documents/pdf/IEC_Founding_Meeting_Report_1906.pdf | title=1906 Preliminary Meeting Report, pp 46–48 | website=The minutes from our first meeting | author=IEC | access-date=21 October 2012 | archive-date=2 May 2019 | archive-url=https://web.archive.org/web/20190502223234/https://www.iec.ch/about/history/documents/pdf/IEC_Founding_Meeting_Report_1906.pdf | url-status=dead }}</ref>

=== Age of Earth ===
[[File:Lord Kelvin Vanity Fair 1897-04-29.jpg|thumb|upright|Kelvin caricatured by [[Leslie Ward|Spy]] for ''[[Vanity Fair (British magazine)|Vanity Fair]]'', 1897]]
Kelvin made an early physics-based estimation of the [[age of Earth]]. Given his youthful work on the figure of Earth and his interest in heat conduction, it is no surprise that he chose to investigate Earth's cooling and to make historical inferences of Earth's age from his calculations. Thomson was a [[creationism|creationist]] in a broad sense, but he was not a '[[flood geology|flood geologist]]'<ref>[[#Sharlin|Sharlin]], p. 169.</ref> (a view that had [[Flood geology#Criticisms and retractions: the downfall of diluvialism|lost mainstream scientific support]] by the 1840s.)<ref>{{cite book| last1 = Imbrie| first1 = John| first2 = Katherine Palmer| last2 = Imbrie| title = Ice ages: solving the mystery| year = 1986| publisher = Harvard University Press| place = Cambridge, Mass.| isbn = 978-0-674-44075-3| page =40| url = https://archive.org/details/iceagessolvingmy0000imbr_w0f3/page/40}}</ref><ref>{{Cite book | last1 = Young | first1 = Davis A. | last2 = Stearley | first2 = Ralph F. | title = The Bible, rocks, and time : geological evidence for the age of the earth | year = 2008 | publisher = IVP Academic | location = Downers Grove, Ill. | isbn = 978-0-8308-2876-0|page=99}}</ref> He contended that the [[laws of thermodynamics]] operated from the birth of the universe and envisaged a dynamic process that saw the organisation and evolution of the [[Solar System]] and other structures, followed by a gradual "heat death". He developed the view that Earth had once been too hot to support life and contrasted this view with that of [[uniformitarianism]], that conditions had remained constant since the indefinite past. He contended that "This earth, certainly a moderate number of millions of years ago, was a red-hot globe ... ."<ref name=Burchfield />

After the publication of [[Charles Darwin]]'s ''[[On the Origin of Species]]'' in 1859, Thomson saw evidence of the relatively short habitable age of Earth as tending to contradict Darwin's gradualist explanation of slow [[natural selection]] bringing about [[biological diversity]]. Thomson's own views favoured a version of [[theistic evolution]] sped up by divine guidance.<ref>{{cite book |author=Bowler, Peter J. |author-link=Peter J. Bowler |title=The eclipse of Darwinism: anti-Darwinian evolution theories in the decades around 1900 |edition=paperback |publisher=Johns Hopkins University Press |location=Baltimore |year=1983 |pages=23–24 |isbn=978-0-8018-4391-4 }}</ref> His calculations showed that the Sun could not have possibly existed long enough to allow the slow incremental development by [[evolution]] - unless it was heated by an energy source beyond the knowledge of [[Victorian era]] science. He was soon drawn into public disagreement with geologists and with Darwin's supporters [[John Tyndall]] and [[T. H. Huxley]]. In his response to Huxley's address to the Geological Society of London (1868) he presented his address "Of Geological Dynamics" (1869)<ref>{{cite web |title="Of Geological Dynamics" excerpts |url=http://zapatopi.net/kelvin/papers/of_geological_dynamics.html |access-date=29 October 2011 |publisher=Zapatopi.net}}</ref> which, among his other writings, challenged the geologists' assertion that Earth must be vastly old, perhaps billions of years in age.<ref name="England et al 2007">Kelvin did pay off gentleman's bet with Strutt on the importance of radioactivity in the Earth. The Kelvin period does exist in the evolution of stars. They shine from gravitational energy for a while (correctly calculated by Kelvin) before fusion and the main sequence begins. Fusion was not understood until well after Kelvin's time.
 {{cite journal |author1=England, P. |author2=Molnar, P. |author3=Righter, F. |date=January 2007 |title=John Perry's neglected critique of Kelvin's age for the Earth: A missed opportunity in geodynamics |journal=GSA Today |volume=17 |issue=1 |pages=4–9 |doi=10.1130/GSAT01701A.1 |bibcode=2007GSAT...17R...4E |doi-access=free}}</ref>

Thomson's initial 1864 estimate of Earth's age was from 20 to 400 million years old. These wide limits were due to his uncertainty about the melting temperature of rock, to which he equated Earth's interior temperature,<ref>Tung, K. K. (2007) ''Topics in Mathematical Modeling''. Princeton University Press. {{ISBN|
9780691116426}}. pp. 243–251. In Thomson's theory the Earth's age is proportional to the ''square'' of the difference between interior temperature and surface temperature, so that the uncertainty in the former leads to an even larger relative uncertainty in the age.</ref><ref>{{Cite journal|last=Thomson|first=William|title=On the Secular Cooling of the Earth|journal=Transactions of the Royal Society of Edinburgh|volume=XXIII|pages=160–161|doi=10.1017/s0080456800018512|year=1862|s2cid=126038615 |url=https://zenodo.org/record/2202654}}</ref> as well as the uncertainty in thermal conductivities and specific heats of rocks. Over the years he refined his arguments and reduced the upper bound by a factor of ten, and in 1897 Thomson, now Lord Kelvin, ultimately settled on an estimate that Earth was 20–40&nbsp;million years old.<ref name=Burchfield>{{Cite book | last=Burchfield | first=Joe D. | title=Lord Kelvin and the Age of the Earth | year=1990 | publisher=University of Chicago Press | isbn=978-0-226-08043-7 | page=43 }}</ref><ref>{{Cite book | last=Hamblin | first=W. Kenneth | title=The Earth's Dynamic Systems 5th ed | year=1989 | publisher=Macmillan Publishing Company | isbn=978-0-02-349381-2 | page=[https://archive.org/details/earthsdynamicsys00hamb_1/page/135 135] | url=https://archive.org/details/earthsdynamicsys00hamb_1/page/135 }}</ref> In a letter published in Scientific American Supplement 1895 Kelvin criticized geologists' estimates of the age of rocks and the age of Earth, including the views published by Darwin, as "vaguely vast age".<ref>{{Cite journal|last=Heuel-Fabianek|first=Burkhard|title=Natürliche Radioisotope: die "Atomuhr" für die Bestimmung des absoluten Alters von Gesteinen und archäologischen Funden|url=https://www.researchgate.net/publication/315459191|journal=StrahlenschutzPraxis|volume=1/2017|pages=31–42}}</ref>

His exploration of this estimate can be found in his 1897 address to the [[Victoria Institute]], given at the request of the institute's president [[Sir George Stokes, 1st Baronet|George Stokes]],<ref>{{Cite journal|url=https://books.google.com/books?id=sSeKh7OWAcgC|page=1095|title=The life of Lord Kelvin|journal=American Journal of Physics|volume=45|issue=10|author=Thompson, Silvanus Phillips |isbn=978-0-8284-0292-7|date=January 1977|bibcode=1977AmJPh..45.1010T|doi=10.1119/1.10735}}</ref> as recorded in that institute's journal ''[[Science and Christian Belief|Transactions]]''.<ref>{{Cite journal|url=https://books.google.com/books?id=sSeKh7OWAcgC|page=998|title=The life of Lord Kelvin|journal=American Journal of Physics|volume=45|issue=10|author=Thompson, Silvanus Phillips |isbn=978-0-8284-0292-7|date=January 1977|bibcode=1977AmJPh..45.1010T|doi=10.1119/1.10735}}</ref> Although his former assistant [[John Perry (engineer)|John Perry]] published a paper in 1895 challenging Kelvin's assumption of low [[thermal conductivity]] inside Earth, and thus showing a much greater age,<ref>Perry, John (1895) "On the age of the earth," ''Nature'', '''51''' : [http://babel.hathitrust.org/cgi/pt?id=mdp.39015038750868;view=1up;seq=266 224–227], 341–342, 582–585. ([https://archive.org/stream/naturelo51londuoft#page/224/mode/2up 51:224], [https://archive.org/stream/naturelo51londuoft#page/340/mode/2up 51:341], [https://archive.org/stream/naturelo51londuoft#page/582/mode/2up 51:582] at Internet Archive)</ref> this had little immediate impact. The discovery in 1903 that [[radioactive decay]] releases heat led to Kelvin's estimate being challenged, and [[Ernest Rutherford]] famously made the argument in a 1904 lecture attended by Kelvin that this provided the unknown energy source Kelvin had suggested, but the estimate was not overturned until the development in 1907 of [[radiometric dating]] of rocks.<ref name="England et al 2007" />

The discovery of radioactivity largely invalidated Kelvin's estimate of the age of Earth. Although he eventually paid off a gentleman's bet with Strutt on the importance of radioactivity in Earth's geology, he never publicly acknowledged this because he thought he had a much stronger argument restricting the age of the Sun to no more than 20 million years. Without sunlight, there could be no explanation for the sediment record on Earth's surface. At the time, the only known source for solar energy was [[gravitational collapse]]. It was only when [[thermonuclear fusion]] was recognised in the 1930s that Kelvin's age paradox was truly resolved.<ref>{{cite journal|last1=Stacey|first1=Frank D.|journal=[[Journal of Geophysical Research]]|volume=105|pages=13155–13158|year=2000|issue=B6|doi=10.1029/2000JB900028|title=Kelvin's age of the Earth paradox revisited|bibcode = 2000JGR...10513155S |doi-access=free}}</ref> However, modern cosmology recognizes the Kelvin period in the early life of a star, during which it shines from gravitational energy (correctly calculated by Kelvin) before fusion and the main sequence begins.
[[File:Jubilee of Baron Kelvin. Photograph by Maclure, Macdonald & Wellcome V0028635 (cropped).jpg|thumb|Kelvin on a pleasure cruise on the [[River Clyde]] aboard the [[Clyde steamer|steamer]] ''Glen Sannox'' for his 17 June 1896 "[[jubilee]]" as Professor of Natural Philosophy at Glasgow ]]
[[File:No-nb bldsa k2a001.jpg|thumb|Lord Kelvin and Lady Kelvin hosting Norwegians [[Fridtjof Nansen]] and [[Eva Nansen]] visiting at their house in February 1897]]