House Ehrenfest

Lore & Background

House Ehrenfest is one of the duchies in the Ascendance of a Bookworm series, known for its relatively low status among the nobility but its unique dedication to book culture and printing. The house plays a central role in the story, particularly through the efforts of its members to preserve and spread knowledge. Its internal politics and alliances shape much of the series' conflict.

Reader's Guide

Most of Ehrenfest's scientific papers deal primarily with fundamentals, and seek to clarify single sub-topics. His publications are renowned for their lucidity and directness, and for solving paradoxes by providing clearer descriptions. His method is best illustrated by what he wrote to Robert Oppenheimer in the summer of 1928, after Oppenheimer invited himself for an extended stay in Leiden: 'If you intend to mount heavy mathematical artillery again during your coming year in Europe, I would ask you not only not to come to Leiden, but if possible not even to Holland, and just because I am really so fond of you and want to keep it that way.

But if, on the contrary, you want to spend at least your first few months patiently, comfortably, and joyfully in discussions that keep coming back to the same few points, chatting about a few basic questions with me and our young people—and without thinking much about publishing (!!!)—why then I welcome you with open arms!!' Characteristically, he did not like the abstraction of the new quantum theory of Heisenberg and Dirac. Ehrenfest's most important contribution from 1912 to 1933 is the theory of adiabatic invariants.

It is a concept derived from classical mechanics that can serve to refine certain methods of Niels Bohr's model of the atom (although initially Ehrenfest did not accept Bohr's ideas), and also creates an association between atomic mechanics and statistical mechanics. He made major contributions to quantum physics, including the theory of phase transitions and the Ehrenfest theorem, which states that expectation values of a quantum system conform to classical mechanics.

His name is also given to the Ehrenfest paradox, an apparent paradox of relativity still discussed, to the Ehrenfest model, and to Ehrenfest time, the time characterizing the difference of quantum dynamics for observables from classical dynamics. Ehrenfest was also interested in developing mathematical theories for economics. This interest was stimulated by his notion that there should be an analogy between thermodynamics and economic processes. While this did not result in publications, he did encourage his graduate student Jan Tinbergen to research this.

Tinbergen's thesis was devoted to problems from both physics and economics, and he later became an economist and was awarded the first Nobel Memorial Prize in Economic Sciences in 1969.