Paul Ehrenfest - Academic Career

Academic Career

In October 1912 Ehrenfest arrived in Leiden, and December 4 he gave his inaugural lecture Zur Krise der Lichtaether-Hypothese (About the crises of the light-ether hypothesis). He remained in Leiden for the rest of his career. In order to stimulate interaction and exchange among physics students he organized a discussion group and a fraternity called De Leidsche Flesch. He maintained close contact with prominent physicists within the country and abroad, and invited them to visit to Leiden and give a presentation in his lecture series. Ehrenfest was an outstanding debater, quick to point out weaknesses and summarize the essentials.

In his lectures he would focus on simple models and examples to illustrate and clarify the underlying assumptions. His classes were small, and he made an effort to get to know students who made use of the reading room. Though few of them were accepted as majors in Theoretical Physics, he had long discussions with them almost on a daily basis. According to Einstein:

"He was not merely the best teacher in our profession whom I have ever known; he was also passionately preoccupied with the development and destiny of men, especially his students. To understand others, to gain their friendship and trust, to aid anyone embroiled in outer or inner struggles, to encourage youthful talent — all this was his real element, almost more than his immersion in scientific problems".

If Ehrenfest felt that there was little more he could teach his students, he would send them to other centers in Europe for more training. He would also encourage them to accept positions abroad.

Among his students were Johannes Burgers, Hendrik Kramers, Dirk Coster, George Uhlenbeck and Samuel Goudsmit, who became famous for jointly proposing the concept of electron spin, Jan Tinbergen, Arend Rutgers, Hendrik Casimir, Gerhard Dieke, Dirk Struik, and Gerard Kuiper. His assistants included Yuri Krutkov, Viktor Trkal, Adriaan Fokker, Paul Epstein, and Gregory Breit. Other young foreign scientists who spent an extended period in his laboratory included Gunnar Nordström, Enrico Fermi, Igor Tamm, Oskar Klein, Robert Oppenheimer, Walter Elsasser, Ralph Kronig, Werner Heisenberg, Paul Dirac, and David Dennison.