Historical research guide · 0421 · 2009

Casimir Effect

Peter W. Milonni · Umar Mohideen

In one minute

This is the encyclopedia entry for the effect the rest of the site stands on. Milonni and Mohideen — one of them the author of the standard book on the quantum vacuum, the other the man who weighed the force with an atomic force microscope — write the short reference account of the Casimir effect for Springer’s Compendium of Quantum Physics. The physics is simple to state and hard to escape. Empty space is not inert: the electromagnetic field goes on fluctuating even with every photon removed. Put two mirrors close together and they exclude the longest of those fluctuations from the gap between them, so the field outside pushes harder than the field inside and the plates are pressed together. Casimir predicted the force in 1948; Lamoreaux weighed it in 1997 and Mohideen and Roy again in 1998 with a different instrument in a different laboratory. Two pages, two authors, one of the most consequential facts in physics: the vacuum has structure and you can measure it.

Connection

Chapter 2 needs one fact more than any other — that the vacuum is a real medium with real energy, not an absence — and this entry is where the physics community says so in its own reference works. Chapter 6 then follows the same force into hardware, because every vacuum-energy programme now on the bench is an attempt to make a Casimir geometry that does work rather than merely pull.

From the source

The Casimir effect has a settled place in the reference literature of quantum physics. It is written up as a standalone entry in Springer’s Compendium of Quantum Physics — Concepts, Experiments, History and Philosophy, alongside the entries for the other founding phenomena, by the author of the standard monograph on the quantum vacuum and by one of the two experimenters whose measurements established the force.Bibliographic record; Compendium of Quantum Physics, entry at pages 87 to 88
Hendrik Casimir predicted in 1948 that two parallel, perfectly conducting, uncharged plates in vacuum attract each other, with an energy per unit area of minus pi squared times h-bar c divided by 720 times the cube of the separation, and a pressure of minus pi squared times h-bar c divided by 240 times the fourth power of the separation. Only h-bar, the speed of light and the geometry appear — no property of the material, and no charge.Read from Casimir, Proc. K. Ned. Akad. Wet. 51, 793 (1948); stated as Eq. 2 in Rev. Mod. Phys. 81, 1827 (2009)
The force is real and has been weighed twice over, by different instruments in different laboratories. Lamoreaux’s 1997 torsion pendulum agreed with theory at the five to ten percent level near one micrometre; the atomic-force-microscope series begun by Mohideen and Roy in 1998 reached the one percent level at separations from about 0.1 to 0.9 micrometres.Read from Phys. Rev. Lett. 78, 5 (1997) and Phys. Rev. Lett. 81, 4549 (1998); summarised in Rev. Mod. Phys. 81, 1827 (2009), Sec. I.C
The origin of the force is a correlation in the vacuum field, not a substance. The quantized electric field at a point in empty space averages to zero, but the product of the field at two separated points does not; put real surfaces into that correlated field and the correlation shows up as a measurable pull. The Casimir force and the van der Waals force are the same phenomenon in two limits.Read from Rev. Mod. Phys. 81, 1827 (2009), Sec. I.A
Real mirrors are not ideal ones, and the accounting for that is complete. Lifshitz theory extends Casimir’s result to gold, to doped silicon and to an atom near glass, with finite conductivity, surface roughness and temperature all entering as measurable corrections rather than as unknowns.Read from Rev. Mod. Phys. 81, 1827 (2009), Sec. II
What follows from a settled attractive force is the open engineering question the site tracks: whether a geometry can be built in which the vacuum does net work rather than simply pulling two surfaces together. That is the common design behind the asymmetric optical and Casimir cavities now being built, and the measurement that would settle it is a cavity that delivers current or force continuously.Site framing; the entry itself reports the force, not a device

The way in

https://doi.org/10.1007/978-3-540-70626-7_26

Historical source-access record. This guide links to the original; it does not reproduce the paper text.

WHAT THIS IS. Not a research paper and not a review article: a short reference entry, indexed at pages 87 to 88, in the Compendium of Quantum Physics — Concepts, Experiments, History and Philosophy, edited by Daniel Greenberger, Klaus Hentschel and Friedel Weinert, Springer, Berlin and Heidelberg, 2009. The library’s working note calling it a review is corrected here. LICENCE AND TEXT. The Crossref record carries only Springer’s text-and-data-mining terms, which are not a licence to republish; OpenAlex and Unpaywall both report the entry closed with no repository copy, and Springer’s server answers automated requests with a client challenge rather than the page. The entry itself could not be opened, so this sheet carries no reproduced text and no quoted abstract, and the summary is written from the bibliographic record. SOURCES FOR THE CLAIMS. Because the entry could not be read, each claim below is read from the primary literature it summarises and its locator names that source rather than a page of the entry: Casimir’s 1948 note for the prediction, Lamoreaux 1997 and Mohideen and Roy 1998 for the measurements, and the Reviews of Modern Physics survey by Klimchitskaya, Mohideen and Mostepanenko for the real-materials theory. THE AUTHORS. Peter W. Milonni, of Los Alamos National Laboratory, wrote the standard monograph on the subject, The Quantum Vacuum: An Introduction to Quantum Electrodynamics, 1994; Umar Mohideen, of the University of California Riverside, made the atomic-force-microscope measurement of the Casimir force in 1998. Three fuller treatments in this library are linked below.

How to cite it

Peter W. Milonni, Umar Mohideen (2009) Casimir Effect doi:10.1007/978-3-540-70626-7_26

In one minute

From the source

The way in

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Where it sits in the curriculum