Leiden University
How it all began...

The first institute for theoretical physics in The Netherlands began its activities in 1921 with a public lecture by Lorentz. The two-story building had rooms for professors Lorentz & Ehrenfest (1,7), a pair of lecture rooms (3,6), and a library with reading room (4,5). It was attached to the physics laboratory of Kamerlingh Onnes. Both the Kamerlingh Onnes Laboratory and the Instituut-Lorentz (as the laboratory and institute came to be called) moved out of downtown Leiden in 1998. The old laboratory still exists, the old institute was replaced by a bigger building in the 1960's.

Afdeeling voor theoretische Natuurkunde aan de Langebrug 111 in Leiden.

"Den 31sten Januari 1921 werd het nieuwe gebouwtje met een kleine plechtigheid, waarbij Prof. Onnes een toespraak hield, in gebruik genomen en daarna door een college van Prof. Lorentz in den waren zin des woords ingewijd."

Ehrenfest gathered with his students at the entrance to the institute on Langebrug. The sign above the door says "Leeskamer Bosscha" ("Bosscha reading room"), in honor of the Leiden physics alumnus Johannes Bosscha Jr.

A monument for Lorentz (by the sculptor Corinne Franzén-Heslenfeld) was erected above the entrance on 3 November 1933. (Here is its present location.) Ehrenfest had died a few months earlier, and would be succeeded by Hans Kramers. The name "Instituut-Lorentz" was introduced in 1953 by his successor Sybren de Groot.

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