Casimir Effect (and duality of perspective)

Random interest article in this months New Scientist, basically saying the conclusions drawn from the Casimir experiments are unjustified.

The Casimir Effect is quite intriguing. First predicted in 1948 (by Hendrick BG Casimir), that placing two metallic plates close together in a vacuum will produce an attractive force between them. This effect was finally measured in 1997, not sure how many of you guys read the news about it then. =p Quick update now in 2005.

The traditionally accepted explanation and theory is that this force is caused by zero point quantum fluctuations. Virtual particle-antiparticle pairs continually form out of nothing and then vanish back into nothing. (energy and mass still conserved). The tiny space between the two plates restricts the range of wavelengths possible for these virtual particles : so there's lower energy density between the plates, creating a pressure difference compared to the outside that pushes both plates together.

The Casimir Effect is generally taken to be proof evidence of zero point energy, and hence leading the way to explaining dark energy and universe expansion.

Particle physicist Robert Jaffe published a paper recently essentially saying that we need not invoke vacuum fluctuations to explain the Casimir Force. He calls for a simpler explanation - the attractions between the particles making up the metal sheets.

Both methods differ in perspective : but they give the same answer. Both give mathematically close enough values for the expected force between the two metal plates.

The really ironic thing he points out is that the electron charge e is absent from Casimir's formula because he assumed perfect electrical conductance : but everyone convenient forgot this assumption... and when the experiments in 1997 confirmed Casimir's formula and theory, scientists assumed the Casimir Effect came out from the vacuum because there was no reference to metallic properties.

Robert Jaffe's doesn't disprove the existence of zero point energy in vacuum, but it does cast doubt over the use of the Casimir Effect to prove as evidence of zero point energy.

The trouble is, he suggests, physicists can't agree on what it means for something to be real - and Susskind has a radical solution in mind. "I would ban the word real from the physicist's vocabulary," he says.

My own thoughts triggered from this development :

It's all a matter of perspective. It's the same experiment, but two different schools of thought predict the same outcome. I've always assumed this is so in social science (where two people can predict two different motivations for a person to act) but for this to turn up in hard science is... slightly disturbing.

This is roughly similar to Fermat's Principle of Least Time : which I will not explain fully at this time, but basically it is used in optics. There are two ways of looking at optical refraction : the standard view most of us have (taught in high school science), of the action / reaction principle -> the light beam enters the glass block and is refracted to change direction.

Fermats Principle of Least Time dictates that the light ray always travels in a path that minimizes the time it takes to reach its destination. He states that optical path length is always extremal - either maximizing or minimizing the time taken.

This will mean that before the ray of light leaves the source, it has to know in advance its final destination and all the varying materials between it and its destination. Rather than an action/reaction type interpretation of light, this is a "purposeful" interpretation of light, where the light beam actively attempts to minimize its total path time.

My point : the same natural phenomenon can sometimes be explained by two completely valid theories, and that you can't really say which one is "real" or the "truth" : whether you're trying to explain attraction between two conductive plates or rays of light. Even in so called hard science there's a lot of subjectivity involved.

*edit* in case you think Fermat's principle of least time is some fanciful theory that doesn't really hold water, it's used to derive Snell's Law and is the basis of most optics calculations. there are quite a few extremal mathematical principles out there.