In thermodynamics, Ernst Zermelo (1871-1953) was a German mathematician, an assistant to German physicist Max Planck, who is noted for his 1894 article “On a Theorem of Dynamics and the Mechanical Theory of Heat” in which he used the 1890 Poincaré recurrence theorem to argue that there was inconsistence between the dynamics of classical mechanics (William Hamilton), and the dynamics of the mechanical theory of heat (thermodynamics), in which processes are said to not be reversible; where in the middle was the kinetic theory of heat trying to reconcile the two. [1] This sparked a bit of a debate with Austrian physicist Ludwig Boltzmann in the Annalen der Physik in the years to follow. [2]

References
1. Zermelo, Ernst. (1894). “On a Theorem of Dynamics and the Mechanical Theory of Heat”, Annalen der Physik.
2. (a) Boltzmann, Ludwig. (1896). “Reply to Zermelo’s Remarks on the Theory of Heat”, Annalen der Physik. 57: 773-84.
(b) Zermelo, Ernst. (1896). “On the Mechanical explanation of Irreversible Processes”, Annalen der Physik. 59: 793-801.
(c) Boltzmann, Ludwig. (1897). “On Zermelo’s Paper: ‘On the Mechanical Explanation of Irreversible Processes’”, Annalen der Physik, 60: 392-98.

Further reading
●Ebbinghaus, Heinz-Dieter, and Peckhaus, Volker. (2007). Ernst Zermelo (section: “The Boltzmann Controversy”, pgs 15-26). Springer.

External links
● Ernst Zermelo – Wikipedia.