The Physicist That History Forgot

If we were to judge Paul Ehrenfest by the company that he kept, he was surely a great scientist. Albert Einstein once called him “the best teacher in our profession whom I have ever known.” Niels Bohr, a pioneer of quantum physics, was his close friend and frequent houseguest. And Enrico Fermi and Robert Oppenheimer, both of whom were leaders of the Manhattan Project, trained as postdoctoral fellows in Ehrenfest's lab at Leiden University. Yet Ehrenfest's personal contributions were much more modest. Today, he's largely a forgotten figure, even among practicing physicists. Why, then, would he be considered a great scientist?