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Widow endows Casimir fund for interdisciplinary physics

This summer, the Casimir Research School celebrates its first lustrum. To mark the occasion and to commemorate the fact that Hendrik Casimir would be 100 this summer, his widow Josina Casimir-Jonker has endowed the Research School with a fund to support the activities of master's students.


Mrs Josina Casimir-Jonker. Photo: Frank de Ruiter.

The Casimir Research School is a partnership between Leiden and Delft. On Friday 26 June, in the presence of Mrs Casimir-Jonker, a cheque for the fund was presented at a location with which she has a particular bond. Eighty years ago she attended her first lecture in this same room in the Kamerlingh Onnes Building. Like her husband, after whom the Research School is named, she studied in Leiden. She graduated in 1934 in experimental physics. After graduating, the Casimirs maintained close links with Leiden.  


Hendrik Casimir with a diagram of the Casimir effect. 

Philips NatLab

After completing his study, Hendrik Casimir took the place of Professor Wander de Haas for a year. When the University closed during the war, he was offered a position with Philips NatLab, where he had prviously lectured. It turned out not to be the temporary position he had envisaged; he stayed with Philips until he retired, initially in a research position and later within the Board of Directors where he was responsible for national and international research. Casimir was professor of an endowed chair in Leiden and was president of the KNAW (Royal Netherlands Academy of Arts and Sciences) and editor of De Gids, a prominent Dutch literary and cultural journal. He is author of the classic work Het toeval van de werkelijkheid (The Coincidence of Reality).


Physical phenomenon

Mrs Casimir with her son and three of her four daughters. Photo: Frank de Ruiter.

As well as giving his name to the Research School, Casimir also has a natural phenomenon named after him, a phenomenon that he predicted in 1948 together with Dirk Polder: the Casimir effect, also known as the Casimir force. If two metal plates are placed very close together in a vacuum, they attract one another.  The force is exerted because only virtual particles of a particular wavelength pass between the two plates. The number of particles between the plates is smaller than the number outside and the plates are consequently pushed together. Casimir's prediction was not confirmed conclusively until 1997. The Casimir effect is represented symbolically in the logo of the Research School. It also represents the force of attraction between Leiden and Delft. 

(30 June 2009)

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