Ciencias

ANNALS OF SCIENCE Vol. 62, No. 3, July 2005, 281–308

The Absolute and Its Measurement: William Thomson on Temperature
HASOK CHANG
Department of Science and Technology Studies, University College London, Gower Street, London WC1E 6BT, UK

and SANG WOOK YI
Hanyang University

Received 18 September 2003. Revised paper accepted 15 April 2004 Summary
In this paper we give a full account ofthe work of William Thomson (Lord Kelvin) on absolute temperature, which to this day provides the theoretical underpinnings for the most rigorous measurements of temperature. When Thomson fashioned his concepts of ‘absolute’ temperature, his main concern was to make the definition of temperature independent of the properties of particular thermometric substances (rather than to count temperaturefrom an absolute zero). He tried out a succession of definitions based on the thermodynamics of ideal heat engines; most notably, in 1854 he gave the ratio of two temperatures as the ratio of quantities of heat taken in and given out at those temperatures in a Carnot cycle. But there were difficulties with using such definitions for experimental work, since it was not possible even to approximatean ideal Carnot engine in reality. More generally, it is not trivial to connect an abstract concept with concrete operations in order to make physical measurements possible. In the end, Thomson argued that an ideal gas thermometer would indicate his absolute temperature, and that the deviation of actual gas thermometers from the ideal could be estimated by means of the JouleThomson effect. However,the measurement of the Joule-Thomson effect itself required measurements of temperature, so there was a problem of circularity.

Contents
1. 2. 3. 4. 5. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thomson’s quest for the absolute . . . . . . . . . . . . . . . . . . . . . . . . . Measurement: how the concrete was smuggled into the abstract . . .. Absolute temperature in the climate of energy conservation . . . . . . . The Joule-Thomson effect and the operationalization of Thomson’s second absolute temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6. Thomson’s re-formulation of the second definition of absolute temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 283 286 290296 303

1. Introduction William Thomson (1824–1907), better known to posterity as Lord Kelvin, made pioneering efforts to create the modern concept of absolute (thermodynamic) temperature, counted in ‘degrees Kelvin’ in his honour. Aside from its commonly recognized importance, Thomson’s work is particularly interesting because it was driven by an apparently paradoxical impulse. On the onehand, he insisted that the
Annals of Science ISSN 0003-3790 print/ISSN 1464-505X online # 2005 Taylor & Francis Group Ltd http://www.tandf.co.uk/journals DOI: 10.1080/00033790410001712246

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Hasok Chang and Sang Wook Yi

concept of absolute temperature should make no reference whatsoever to any properties of any particular material substances; on the other hand, he demanded that absolutetemperature should be a physically measurable quantity, with a clear correspondence to actual thermometer readings. What kind of procedure enabled Thomson to render an entirely abstract concept measurable by concrete physical instruments? The principal aim of this paper is to give a full and detailed account of Thomson’s work on absolute temperature and its measurement. To the best of ourknowledge, such an account is not available anywhere. Curiously, the story of absolute temperature is treated only in a brief and desultory fashion even in the exhaustive accounts of Thomson’s life and work by Silvanus P. Thompson, and by Crosbie Smith and Norton Wise; the same is true of the briefer yet insightful biography by Harold I. Sharlin.1 We have put together our account primarily on the basis...