Thermodynamics began when caloric ended

A pivotal event in thermodynamic history occurred when Julius Robert Mayer and James Joule independently overthrew the caloric theory of heat, revealing heat and work as two forms of energy. In 1850 Rudolf Clausius used these findings to correct the single flaw in Sadi Carnot’s 1824 theoretical analysis of the steam engine and, in so doing, established the 1st Law of Thermodynamics. Surprisingly, around this same time period, scientists didn’t otherwise consider heat to be all that interesting.

Joseph Fourier – French mathematician and physicist

From 1790 to 1830 the science of heat was considered complete.  Or at least Joseph Fourier (1768-1830) suggested it was, writing in 1822 that “we have demonstrated all the principles of the theory of heat.”[1]

During this time, France led the scientific world, largely through the work of Pierre Simon Marquis de Laplace who used Newton’s work to bring many physical phenomena into the realm of mathematics, thus establishing “physics” as a standalone science.  The spread of this mathematized physics to other countries such as Britain helped foster the surge in Western science during the mid-1800s.  As part of this surge, Fourier’s Analytical Theory of Heat (1822)[2] did much to clarify the concept of heat and rates of heat transfer, bringing his powerful mathematics to “solve all the fundamental problems.”[3] 

But Fourier was indifferent to the fundamental nature of heat

But Fourier was indifferent to the fundamental nature of heat, not being interested in whether the caloric or mechanical theories were correct.[4] “Primary causes are unknown to us; but are subject to simple and constant laws, which may be discovered by observation, the study of them being the object of natural philosophy… The object of our work is to set forth the mathematical laws which [heat] obeys.”[5]  His predictive mathematics worked and that’s all that mattered.  However, the science of heat at this time was far from complete and awaited the efforts of Carnot, Mayer, Joule, Clausius, and many others to complete the job.

Explore more!

To appreciate the works of those involved with the creation of thermodynamics, one should first understand the history of heat. To capture the depth of the paradigm that needed to be overcome, I include this history in my book Block by Block – The Historical and Theoretical Foundations of Thermodynamics. Thank you for listening!

[1] Fourier, Joseph. 1952. “Theory of Heat.” In Great Books of the Western World.  45.  Lavoisier, Fourier, Faraday, 163–251. William Benton, Encyclopedia Britannica, Inc, p. 174.

[2] Fourier, 1952.

[3] Fourier, 1952, p. 174.

[4] In a 2017 email to the author, historian Robert Fox shared how striking it was that Fourier could do what he did without taking any position on the nature of heat, which suggests that the issue of the nature of heat was becoming irrelevant by the 1820s.

[5] Fourier, 1952, p. 169.