I'm hoping some of the credentialed big guns on this board would be able to answer. I'm asking about the so-called "Casimir" force between two parallel closely-spaced conductive plates that is allegedly due to exclusion of certain virtual photons from the space between the plates.

My question is: does it matter, and if so how much, whether the plates are perfectly smooth vs. a little rough? Maybe if the roughness of the surface is less than a wavelength that is being excluded it doesn't matter? Also, what is the distance between the plates (a wavelength threshold) before the attractive force becomes noticeable on macro-scale?

Reason I'm asking, is because I'm thinking of a device that ought to be able to extract energy from the Casimir effect. Basically, one of the plates is not solid but consists of slivers that can slide along each other like scales on a fish. So, by sliding them over each other you turn the plate into a bunch of parallel metal strips, destroying (or at least halving) the Casimir force. Then you move this "folded" plate away from the other plate a little, then "unfold" it to make it a solid sheet of metal again. The plates attract, driving a generator, until they hit each other and the "folding" + withdrawal process repeats.

The device might be further optimized by making both plates foldable like that, but in such a manner that when folded they form a "checkerboard" pattern so that they no longer touch each other at any point (that should completely eliminate, as opposed to halve, the Casimir force.) Friction between the "scales" might be a problem, as would the inherent irregularity of the surfaces. Plus, I wonder about the magnitude of energy output (if any at all). What do you guys think, is this feasible?

The plates are merely a means of measuring the force to see if it exists. The casimir effect is all around you. A lot of scientists think there is about as much energy in a cc of empty space as a 50 000 <B>MT</B> bomb. That's an enormous amount of energy, and the reason you don't notice it is the same reason a boat sits still in perfectly still water, even though you know it's constantly being bombarded by particals (no, not cosmic rays, but water molecules) that statistics dictate will cancel each other out. The effect is the same only greater for the casimir effect, the field is SO uniform, you can only detect in one known way, with the plates (although there is much more theoretical, not experimental, evidence to support the casimir effect, such as the stability of atoms). This uniform energy (I THINK) is also known as a false vacuum, a metastable uniformity of energy.

About you're energy machine, I have pulled my hair out for the better part of a year trying to devise a casimir energy extraction device, the only problem is, unlike moving water molecules, where the smaller an object is, the more it get's bounced around by Brownian motion, even a single water molecule would be similar to a boat in a calm sea of casimir radiation, constantly bombarded by trillions of rays from every direction, that's how uniform it is. So, you can't boil water with it. As for your variable plates, it sounds really great, but imagine how it would work..

The plates would oscillate, right? But then, one way, weather opening or closing, you would have to fight the casimir effect it and it would take energy to open and close the "fish scale" plate, just like Maxwell's demon. The problem again is uniformity, there has to be a difference in pressure. So, it sounds great, but I don't think it would work. But go ahead, prove me wrong. You'd be rich and the world would be a lot better with infinite energy.

<I>Also, what is the distance between the
plates (a wavelength threshold) before the attractive force becomes noticeable on macro-scale?</I>

I don't really understand this, but the casimir effect is gradual, the wider the gap, the less powerful the effect. There is no limit or anything.

Thanks, um, huh? :D

I understand your concerns, and share them. And thanks for the more in-detail summary of the force.

I guess I feel it still ought to be possible to fold/unfold the fishscale plate without loosing too much energy since the "scales" won't be directly moving against the Casimir force but orthogonal to it. So you have to overcome friction between the plates that would squeeze them together where they overlap -- but perhaps one could design some sort of bearings that would make it much easier to slide the plates along (e.g. magnetic or electrostatic suspension?)

It's not like I have the resources or even the engineering savoir faire to build something like this, so I'm just playing with the idea. But the idea is that once you "fold" the plates the Casimir effect would be totally gone and it would be really easy to move the plates apart and unfold them again.

But the viability of the whole design rests on the kinds of energy that can be generated during the "collapse" once the plates are unfolded. IF there is enough work generated, then perhaps as much as 99.9999% of it can go toward folding, separating and unfolding the plates for the next round. Heck, I'd be happy to just get any energy, however little, out of the setup (even if only in the form of heat from the mechanisms.) Basically, if such a thing can be achieved then it would be proven that "free energy" can in fact be attained. From then on, it would be just a matter of optimization.

So the major concern is how strong the attractive force is depending on the distance between the plates. For example, if the distance between the plates is D and the area of a plate is A, what is the attractive force as a function of D? Can anyone characterize, or point toward an analytical characterization of this force?