Nowadays we say that during the adiabatic expansion stage of the Carnot Cycle the internal energy due to the temperature of the gas gets transformed into work, but Carnot himself supported the caloric theory of heat, concieving that thermodynamic work could only be done by a "fall" of caloric from a body at one temperature to another body at a different temperature. How was adiabatic expansion seen from the caloric theory perspective? Thank you in advance for your time.

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    $\begingroup$ Why would we look at adiabatic expansion as seen from a now debunked theory? $\endgroup$
    – Bob D
    Commented Apr 16, 2022 at 15:36
  • $\begingroup$ You might try the History of Science and Mathematics Stack Exchange. $\endgroup$ Commented Apr 16, 2022 at 16:45
  • $\begingroup$ Oh, I see you've already posted there. $\endgroup$ Commented Apr 16, 2022 at 16:46
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    $\begingroup$ @Bob_D because there is a historically rational argument that Carnot understood the difference between entropy and heat, and he consistently used two different words to describe them: "calorique" for entropy and "chaleur" for heat. With that linguistic interpretation Carnot's theory is not debunked. $\endgroup$
    – hyportnex
    Commented Apr 16, 2022 at 21:04
  • $\begingroup$ @hyportnex I never said Carnot's theory is debunked. The caloric theory of heat is debunked. It is generally considered remarkable what Carnot achieved when heat was yet to be fully understood. $\endgroup$
    – Bob D
    Commented Apr 17, 2022 at 13:24

1 Answer 1


Some historians, e.g., La Mer, Truesdell, etc., argue that the word "calorique" as used by Carnot is to be distinguished from the word "chaleur"; the word chute is never used as "chute de chaleur" but always used as "chute de calorique" so that is not "drop of heat" but rather "drop of entropy", see La Mer: "Some Current Misinterpretations of N. L. Sadi Carnot's Memoir and Cycle.", https://doi.org/10.1119/1.1933908, and then it makes sense. Not all historians agree with this interpretation of the historical events, though; see Kuhn: Carnot's Version of "Carnot's Cycle" https://doi.org/10.1119/1.1933907 and the ensuing debate in the same Journal.

  • $\begingroup$ Very interesting. Thank you for the references. $\endgroup$
    – Metadani
    Commented Apr 16, 2022 at 21:29

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