Paul Ehrenfest

Paul Ehrenfest (January 18, 1880 – September 25, 1933) was an Austrian physicist and mathematician, who obtained Dutch citizenship on March 24, 1922. He made major contributions to the field of statistical mechanics and its relations with quantum mechanics, including the theory of phase transition and the Ehrenfest theorem.

Paul Ehrenfest (circa 1910)

Sourced

• Einstein, my upset stomach hates your theory — it almost hates you yourself ! How am I to provide for my students ? What am I to answer to the philosophers ?
  • about the theory of general relativity, in a letter dated November 24, 1919, to Albert Einstein.

Attributed

• You will get your difficulties with the point electron.
  • as quoted by Hendrik Casimir in an interview by Thomas Kuhn, Léon Rosenfeld, Aage Bohr and Erik Ruedinger at the Institute for Theoretical Physics, Copenhagen, 5 and 6 July, 1963.

Quotes about Ehrenfest

• In passing I have to mention a typical Ehrenfest anecdote, not such a nice one, perhaps. Lorentz lived in Haarlem and all these celebrities, Rutherford, Madame Curie, Bohr, Einstein and very many others travelled by train, a special train, from Leiden to Haarlem. And the week before one of those rare fatal train accidents had occurred and I said to Ehrenfest, "Wouldn't it be dreadful if that train had an accident?" And Ehrenfest replied: "Yes, that would be dreadful, but think of all the young physicists who then could get jobs .... ".
  • Samuel Goudsmit (as translated by J. H. van der Waals from Goudsmit's lecture given in April 1971): "Chapter A.1. The discovery of the electron spin". Foundations Of Modern EPR. 1998. pp. 1–12.  (quote from pp. 9–10)

• The way he taught statistical mechanics and electromagnetic theory, you got the feeling of a growing science that emerged out of conflict and debate. It was alive, like his lectures, which were full of personal references to men like Boltzmann, Klein, Ritz, Abraham, and Einstein. He told us at the beginning that we should teach ourselves vector analysis in a fortnight—no babying. Ehrenfest's students all acknowledge how much his method of exposition has influenced their own teaching.
  • Dirk Jan Struik: (1989). "Interview with Dirk Jan Struik by David E. Rowe". The Mathematical Intelligencer 11 (1): 14–26. (quote from p. 15)
• Ludwig Boltzmann, who spent much of his life studying statistical mechanics, died in 1906, by his own hand. Paul Ehrenfest, carrying on his work, died similarly in 1933. Now it is our turn to study statistical mechanics. Perhaps it will be wise to approach the subject cautiously.
  • David L. Goodstein, States of Matter (1974), p. 1.