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March 20, 2005


Paul Stankus

The Casimir coincidence is indeed wild, and reminds me that it's been a long time since I've had a good steak-frites.

An interesting question about Casimir forces: If you let the two plates move together under this attractive interaction, then they will gain kinetic energy, ie the Casimir force can do mechanical work. Where does this energy come from? It must somehow come "out of the vacuum," from something like the zero-point energy of the EM field. The reality of EM Casimir forces, which as you said have actually been measured experimentally (though why did it take until 1996?), in turn implies the reality of zero-point EM field energy, which in turn is very important for the question of dark energy.

Another way to ask this question is, if you exert a force and do work to pull the two plates apart against the attractive force, where does your expended energy go? There are no static, Maxwellian EM fields to store the energy, so it must go "into the vacuum" somehow. Homework question: could you make a "Casimir storage battery" this way?

And, anyone who might doubt the reality of the energy in EM field fluctuations might be interested to read this paper: http://prola.aps.org/abstract/PRL/v55/i21/p2246_1


Paul - Good points. And just in time to look like yet another coincidence: Bob Jaffe just put out a paper on the Casimir effect - http://xxx.lanl.gov/abs/hep-th/0503158


Though having little knowledge of the vacuum, I would like to suggest a perspective. The lower the mass of a particle, the more likely it is to appear in the vacuum.
Would this not mean that most of the vacuum's energy takes the form of extremely long wavelength photons?
And if so, maybe these photons are the vacuum, reinforcing eachother at certain points to have enough energy to allow the particle-antiparticle pairs.

I think the attempts to extract vacuum energy are doomed to failure as they all try to work with vacuum equilibrium. It's like trying to get a steam generator to work with steam but no coolant of any kind.

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