Editing Rudolf Clausius

{{short description|German physicist and mathematician (1822–1888)}}
{{Redirect|Clausius|the lunar crater|Clausius (crater)}}

{{Infobox scientist
|name              = Rudolf Clausius
|image             = Rudolf Clausius 01.jpg
|birth_name        = Rudolf Julius Emanuel Clausius
|birth_date        = {{birth date|1822|1|02|df=yes}}
|birth_place       = [[Koszalin|Köslin]], [[Province of Pomerania (1815–1945)|Province of Pomerania]], [[Kingdom of Prussia|Prussia]]<br/>{{small|(present-day Koszalin, Poland)}}
|death_date        = {{death date and age|1888|08|24|1822|1|02|df=yes}}
|death_place       = [[Bonn]], [[Rhine Province]], Prussia, [[German Empire]]
|nationality       = [[Germans|German]]
|ethnicity         = 
|field             = [[Physics]]
|work_institutions = 
|alma_mater        = 
|doctoral_advisor  = 
|doctoral_students = 
|known_for         = {{ubl|[[Chemical thermodynamics]]|[[First law of thermodynamics]]|[[Second law of thermodynamics]]|Originator of the concept of [[entropy]]|[[Entropy production]]|[[Disgregation]]|[[Ideal gas law]]|[[Kinetic theory of gases]]|[[Virial theorem]]|[[Real gas#Clausius model|Clausius model]]|[[Clausius theorem]]|[[Clausius–Mossotti relation]]|[[Clausius–Clapeyron relation]]|[[Clausius–Duhem inequality]]}}
|influences        = 
|influenced        = 
|prizes            ={{ubl|[[Poncelet Prize]] (1882)|[[Copley Medal]] (1879)|[[List of fellows of the Royal Society A, B, C|ForMemRS]] (1868)}}
|signature         = Rudolf Clausius signature.svg
}}

'''Rudolf Julius Emanuel Clausius''' ({{IPA|de|ˈʁuːdɔlf ˈklaʊzi̯ʊs}};<ref>{{cite book|author1=Dudenredaktion|last2=Kleiner|first2=Stefan|last3=Knöbl|first3=Ralf|year=2015|orig-year=First published 1962|title=Das Aussprachewörterbuch|trans-title=The Pronunciation Dictionary|url=https://books.google.com/books?id=T6vWCgAAQBAJ|language=de|edition=7th|location=Berlin|publisher=Dudenverlag|isbn=978-3-411-04067-4|pages=280, 744}}</ref><ref>{{cite book|last1=Krech|first1=Eva-Maria|last2=Stock|first2=Eberhard|last3=Hirschfeld|first3=Ursula|last4=Anders|first4=Lutz Christian|title=Deutsches Aussprachewörterbuch|trans-title=German Pronunciation Dictionary|url=https://books.google.com/books?id=E-1tr_oVkW4C&q=deutsches+ausspracheworterbuch|language=de|year=2009|publisher=Walter de Gruyter|location=Berlin|isbn=978-3-11-018202-6|pages=416, 884}}</ref> 2 January 1822 – 24 August 1888) was a German [[physicist]] and [[mathematician]] and is considered one of the central founding fathers of the science of [[thermodynamics]].<ref>{{Citation | author=Cardwell, D.S.L. | title=From Watt to Clausius: The Rise of Thermodynamics in the Early Industrial Age | location=London | publisher=Heinemann | year=1971 | isbn=978-0-435-54150-7}}</ref> By his restatement of [[Nicolas Léonard Sadi Carnot|Sadi Carnot]]'s principle known as the [[Carnot cycle]], he gave the [[theory of heat]] a truer and sounder basis. His most important paper, "On the Moving Force of Heat",<ref name="Theory of Heat"/> published in 1850, first stated the basic ideas of the [[second law of thermodynamics]]. In 1865 he introduced the concept of [[entropy]]. In 1870 he introduced the [[virial theorem]], which applied to [[heat]].<ref>{{cite journal | last = Clausius | first = RJE | year = 1870 | title = On a Mechanical Theorem Applicable to Heat | journal = Philosophical Magazine |series=4th Series | volume = 40 | pages = 122–127}}</ref>

==Life==
Clausius was born in [[Koszalin|Köslin]] (now [[Koszalin]], Poland) in the [[Province of Pomerania (1815–1945)|Province of Pomerania]] in [[Prussia]]. His father was a [[Protestant]] pastor and school inspector,<ref>Emilio Segrè (2012). ''From Falling Bodies to Radio Waves: Classical Physicists and Their Discoveries''. Courier Dover Publications. p. 228</ref> and Rudolf studied in the school of his father. In 1838, he went to the [[Gymnasium (school)|Gymnasium]] in [[Szczecin|Stettin]]. Clausius graduated from the [[University of Berlin]] in 1844 where he had studied mathematics and physics since 1840 with, among others, [[Heinrich Gustav Magnus|Gustav Magnus]], [[Peter Gustav Lejeune Dirichlet]], and [[Jakob Steiner]]. He also studied history with [[Leopold von Ranke]]. During 1848, he got his doctorate from the [[University of Halle]] on optical effects in Earth's atmosphere. In 1850 he became professor of physics at the [[TU Berlin|Royal Artillery and Engineering School in Berlin]] and Privatdozent at the Berlin University. In 1855 he became professor at the [[ETH Zürich]], the Swiss Federal Institute of Technology in [[Zürich]], where he stayed until 1867. During that year, he moved to [[University of Würzburg|Würzburg]] and two years later, in 1869 to [[University of Bonn|Bonn]].<ref>{{cite web |title=Rudolf Clausius, Prof. Dr. |url=https://www.physik.uzh.ch/de/institut/emeriti/RudolfClausius.html |website=physik.uzh.ch |publisher=Universität Zürich |access-date=18 June 2021 |language=de}}</ref>

In 1870 Clausius organized an ambulance corps in the [[Franco-Prussian War]]. He was wounded in battle, leaving him with a lasting disability. He was awarded the [[Iron Cross]] for his services.

His wife, Adelheid Rimpau died in 1875, leaving him to raise their six children. In 1886, he married Sophie Sack, and then had another child. Two years later, on 24 August 1888, he died in [[Bonn]], Germany.<ref name="Cropper2004">{{cite book|first=William H.|last=Cropper|title=Great Physicists: The Life and Times of Leading Physicists from Galileo to Hawking|chapter-url=https://books.google.com/books?id=UqbxZpELwHYC&pg=PA93|access-date=25 March 2014|year=2004|publisher=Oxford University Press|isbn=978-0-19-517324-6|pages=93–105|chapter=The Road to Entropy Rudolf Clausius}}</ref>

==Work==
Clausius's PhD thesis concerning the refraction of light proposed that we see a blue sky during the day, and various shades of red at sunrise and sunset (among other phenomena) due to reflection and refraction of light. Later, [[Lord Rayleigh]] would show that it was in fact due to the scattering of light.

His most famous paper, ''Ueber<!--[sic]--> die bewegende Kraft der Wärme'' ("On the Moving Force of Heat and the Laws of Heat which may be Deduced Therefrom")<ref>{{cite journal  | last=Clausius |first=R.  | title =Ueber die bewegende Kraft der Wärme und die Gesetze, welche sich daraus für die Wärmelehre selbst ableiten lassen |url=http://gallica.bnf.fr/ark:/12148/bpt6k15164w/f518.table  | journal =Annalen der Physik  | volume =79 |issue=4  | pages=368–397, 500–524| year =1850 | doi=10.1002/andp.18501550403|bibcode = 1850AnP...155..500C |hdl=2027/uc1.$b242250 | hdl-access=free}}. See English Translation: [https://archive.org/details/londonedinburghd02lond On the Moving Force of Heat, and the Laws regarding the Nature of Heat itself which are deducible therefrom]. Phil. Mag. (1851), series 4, '''2''', 1–21, 102–119.  Also available on [https://books.google.com/books?id=JbwdWbbM1KgC&pg=RA1-PA1 Google Books].</ref>
was published in 1850, and dealt with the mechanical theory of heat. In this paper, he showed there was a contradiction between [[Nicolas Léonard Sadi Carnot|Carnot]]'s principle and the concept of [[conservation of energy]]. Clausius restated the two [[laws of thermodynamics]] to overcome this contradiction. This paper made him famous among scientists. (The [[third law of thermodynamics|third law]] was developed by [[Walther Nernst]], during the years 1906–1912).

Clausius's most famous statement of the second law of thermodynamics was published in German in 1854,<ref>{{cite journal|last=Clausius|first=R.|title=Ueber eine veränderte Form des zweiten Hauptsatzes der mechanischen Wärmetheoriein|journal=[[Annalen der Physik|Annalen der Physik und Chemie]]|year=1854|volume=93|issue=12|pages=481–506|url=http://gallica.bnf.fr/ark:/12148/bpt6k15178k/f499.image|access-date=25 June 2012|doi=10.1002/andp.18541691202|bibcode=1854AnP...169..481C}}</ref> and in English in 1856.<ref>{{cite journal|last=Clausius|first=R.|title=On a Modified Form of the Second Fundamental Theorem in the Mechanical Theory of Heat|journal=[[Philosophical Magazine|Phil. Mag.]]|date=August 1856|volume=12|series=4|issue=77|pages=81–98|url=https://archive.org/stream/londonedinburghd12lond#page/80/mode/2up|access-date=25 June 2012|doi=10.1080/14786445608642141}}</ref> 
{{blockquote | Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time.}}

During 1857, Clausius contributed to the field of [[kinetic theory of gases|kinetic theory]] after refining [[August Krönig]]'s very simple gas-kinetic model to include translational, rotational and vibrational molecular motions. In this same work he introduced the concept of '[[Mean free path]]' of a particle.<ref>{{Citation  | author=Clausius, R.  | title =Über die Art der Bewegung, die wir Wärme nennen   | url =http://gallica.bnf.fr/ark:/12148/bpt6k15185v/f371.table  | journal =Annalen der Physik  | volume =100 | issue =3   | pages =353–379 | year =1857|doi=10.1002/andp.18571760302 |bibcode = 1857AnP...176..353C }}</ref><ref>{{Citation  | author=Clausius, R.  | title =Ueber<!--[sic]--> die Wärmeleitung gasförmiger Körper   | url =http://gallica.bnf.fr/ark:/12148/bpt6k15200x/f13.table  | journal =Annalen der Physik  | volume =115 | issue =1 | pages =1–57 | year =1862 |doi=10.1002/andp.18621910102 |bibcode = 1862AnP...191....1C }}</ref><ref>Clausius, R. (1864), [http://gallica.bnf.fr/notice?N=FRBNF37278069 ''Abhandlungen über die Mechanische Wärmetheorie'']. Electronic manuscript from the [[Bibliothèque nationale de France]].</ref>

Clausius deduced the [[Clausius–Clapeyron relation]] from thermodynamics. This relation, which is a way of characterizing the [[phase transition]] between two states of matter such as [[solid]] and [[liquid]], had originally been developed in 1834 by [[Émile Clapeyron]].<gallery>
File:Clausius-1-1.jpg|1864 edition of Clausius' ''Abhandlungen über die mechanische Wärmetheorie'', volume I
File:Clausius-1-2.jpg|Title page of an 1864 edition of Clausius' ''Abhandlungen über die mechanische Wärmetheorie'', volume I
File:Clausius-2-1.jpg|1879 English translation of Clausius' ''The Mechanical Theory of Heat''
File:Clausius-2-2.jpg|Title page of an 1879 English translation of Clausius' ''The Mechanical Theory of Heat''
</gallery>

===Entropy===
{{Main|History of entropy}}{{See also|History of thermodynamics#Rudolf Clausius}}
In 1865, Clausius gave the first mathematical version of the concept of [[entropy]], and also gave it its name.<ref name="Cropper2004"/>  Clausius chose the word because the meaning (from [[Ancient Greek|Greek]] ἐν ''en'' "in" and τροπή ''tropē'' "transformation") is "''content transformative''" or "''transformation content''" ("''Verwandlungsinhalt''").<ref name="Theory of Heat">{{cite book|last=Clausius|first=R.|title=The Mechanical Theory of Heat – with its Applications to the Steam Engine and to Physical Properties of Bodies|year=1867|publisher=John van Voorst|location=London|url=https://archive.org/details/mechanicaltheor04claugoog|quote=editions:PwR_Sbkwa8IC.|access-date=19 June 2012}} Contains English translations of many of his other works.</ref><ref>{{Citation  | author=Clausius, R.  | title =Ueber verschiedene für die Anwendung bequeme Formen der Hauptgleichungen der mechanischen Wärmetheorie | url =http://gallica.bnf.fr/ark:/12148/bpt6k152107/f369.table  | journal =Annalen der Physik  | volume =125 | issue =7 | pages =353–400 | year =1865 |doi=10.1002/andp.18652010702|bibcode = 1865AnP...201..353C }}</ref><ref name="Cooper">{{cite book|last1=Cooper|first1=Leon N.|title=An Introduction to the Meaning and Structure of Physics|date=1968|publisher=Harper|page=331}}</ref>{{Blockquote|text=I prefer going to the ancient languages for the names of important scientific quantities, so that they may mean the same thing in all living tongues. I propose, accordingly, to call S the entropy of a body, after the Greek word 'transformation'. I have designedly coined the word entropy to be similar to 'energy', for these two quantities are so analogous in their physical significance, that an analogy of denomination seemed to me helpful.|author=Rudolf Clausius|title=Ueber verschiedene für die Anwendung bequeme Formen der Hauptgleichungen der mechanischen Wärmetheorie}}He used the now abandoned unit 'Clausius' (symbol: '''Cl''') for entropy.<ref>{{Cite journal|last1=Huang|first1=Mei-Ling|last2=Hung|first2=Yung-Hsiang|last3=Chen|first3=Wei-Yu|date=2010-10-01|title=Neural Network Classifier with Entropy Based Feature Selection on Breast Cancer Diagnosis|journal=Journal of Medical Systems|language=en|volume=34|issue=5|pages=865–873|doi=10.1007/s10916-009-9301-x|pmid=20703622|s2cid=6658005|issn=1573-689X}}</ref>
:1 Clausius (Cl) = 1 [[calorie]]/[[degree Celsius]] (cal/°C) = 4.1868 [[joule]]s per [[kelvin]] (J/K)

The landmark 1865 paper in which he introduced the concept of entropy ends with the following summary of the first and second laws of thermodynamics:<ref name="Theory of Heat" />
{{blockquote |The energy of the universe is constant.<br />
The entropy of the universe tends to a maximum.}}

[[Leon Cooper]]<ref name="Cooper" /> added that in this way he succeeded in coining a word that meant the same thing to everybody: nothing.

==Tributes==
[[File:Prawa termodynamiki clausiusa pk.jpg|thumbnail|Memorial stone in front of [[Koszalin University of Technology]], with the laws of thermodynamics as formulated by Clausius]]
* Honorary Membership of the [[Institution of Engineers and Shipbuilders in Scotland]] in 1859.[http://www.iesis.org/honorary-fellows.html IESIS Institution of Engineers and Shipbuilders in Scotland]
* [[Iron Cross]] of 1870
* Fellow of the [[Royal Society of London]] in 1868 and received its [[Copley Medal]] in 1879.
* Member of the [[Royal Swedish Academy of Sciences]] in 1878.
* [[Huygens]] Medal in 1870.
* Foreign Member of the [[Accademia Nazionale dei Lincei]] in Rome in 1880
* Member of the [[German Academy of Sciences Leopoldina]] in 1880
* [[Poncelet Prize]] in 1883.
* Honorary doctorate from the [[University of Würzburg]] in 1882.
* Foreign Member of the [[Royal Netherlands Academy of Arts and Sciences]] in 1886.<ref>{{cite web|url=http://www.dwc.knaw.nl/biografie/pmknaw/?pagetype=authorDetail&aId=PE00004619 |title=R.J.E. Clausius (1822–1888) |publisher=Royal Netherlands Academy of Arts and Sciences |access-date=21 July 2015}}</ref>
* [[Pour le Mérite for Arts and Sciences]] in 1888
* The lunar crater [[Clausius (crater)|Clausius]] named in his honor.
* A memorial in his home town of [[Koszalin]] in 2009

==Publications==
* {{cite book|last=Clausius|first=R.|title=The Mechanical Theory of Heat – with its Applications to the Steam Engine and to Physical Properties of Bodies|year=1867|publisher=John van Voorst|location=London|url=https://archive.org/details/mechanicaltheor04claugoog|quote=editions:PwR_Sbkwa8IC.}} English translations of nine papers.
* {{Cite book|title=Abhandlungen über die Anwendung der mechanischen Wärmetheorie auf die elektrischen Erscheinungen, nebst einer Einleitung in die mathematische Behandlung der Elektricität |volume=2|publisher=Société belge d'éditions|location=Bruxelles|year=1898|language=fr|url=https://gutenberg.beic.it/webclient/DeliveryManager?pid=6830494}}

==See also==
*[[Hans Peter Jørgen Julius Thomsen]], one of the founders of the [[thermochemistry]].

==References==
{{Reflist}}

==External links==
{{wikiquote}}
{{Commons category|Rudolf Clausius}}
*[https://www.math.umd.edu/~lvrmr/History/Revival.html  Revival of Kinetic Theory by Clausius]
* {{MacTutor Biography|id= Clausius}}
*{{Cite EB1911|wstitle=Clausius, Rudolf Julius Emmanuel}}
* {{Gutenberg author | id=35970| name=Rudolf Clausius}}
* {{Internet Archive author |sname=Rudolf Clausius}}

{{Copley Medallists 1851–1900}}
{{Portal bar|History of science|Physics|Scotland|Germany}}
{{Authority control}}

{{DEFAULTSORT:Clausius, Rudolf}}
[[Category:1822 births]]
[[Category:1888 deaths]]
[[Category:People from Koszalin]]
[[Category:Academic staff of ETH Zurich]]
[[Category:Thermodynamicists]]
[[Category:German military personnel of the Franco-Prussian War]]
[[Category:19th-century German physicists]]
[[Category:German fluid dynamicists]]
[[Category:People from the Province of Pomerania]]
[[Category:Recipients of the Iron Cross (1870)]]
[[Category:Recipients of the Copley Medal]]
[[Category:Recipients of the Pour le Mérite (civil class)]]
[[Category:Humboldt University of Berlin alumni]]
[[Category:Academic staff of the University of Bonn]]
[[Category:Academic staff of the University of Würzburg]]
[[Category:Foreign members of the Royal Society]]
[[Category:Foreign associates of the National Academy of Sciences]]
[[Category:Members of the Royal Netherlands Academy of Arts and Sciences]]
[[Category:Members of the Royal Swedish Academy of Sciences]]
[[Category:German theoretical physicists]]
[[Category:Prussian Army personnel]]