Is science sometimes in danger of getting tunnel vision? Recently published ebook author, Ian Miller, looks at other possible theories arising from data that we think we understand. Can looking problems in a different light give scientists a different perspective?

Virtual Photons

What is science about? Having a comfortable research area, churning out papers in a very narrow niche, and thus securing further funding? Or taking a risk, getting out of the comfort zone and trying to understand? I am going to propose an experiment that chemists could do that could verify (or not, as the case may be) a major issue in physics. My question is, has anyone got the nerve? First, some background.


When James Clerk Maxwell applied his fundamental equations of electrodynamics to  consider a pulse of electric field in a transverse wave form, his equations required a similar wave of magnetic field be generated at right angles, with a phase delay, and that wave, then proceeded to generate a new electric field wave. Further, with a little mathematics he showed that the speed of this composite wave depended on the reciprocal of the square root of the product of the permeability and permittivity of space, which was close to the speed of light as then measured. He therefore concluded that light was an electromagnetic wave. This was one of the great unification moments in our understanding of reality. Unfortunately, within about two decades, evidence indicated particle properties, and the photon was "born". Now everybody thinks they know what a photon is.

In Maxwell’s electrodynamics, the electromagnetic fields are short-range, that is, they behave as if a charged particle is continually sending out messages at the speed of light, thus making other charged particles aware that they are there. As far as I can make out, current thinking is that the charged particle sends out pulses of “field”, which then behave as above, i.e. the messenger for the electric field is the photon, but since we do not see it, it is a virtual photon. Quantum electrodynamics describes how the virtual particle is supposed to behave, and is outside the scope of this blog, but it accounts for a very restricted set of observations with incredible accuracy.

But does that mean the "virtual photon" is a genuine intermediate? What would provide a means of deciding? After all, the value of the scientific method must lie in determining an answer, not reciting accounts of that with which we have become comfortable. What appears to be required is an experiment that gives a result that requires the virtual photon, and cannot be readily explained by some other means. To devise such an experiment we need to define the properties of such a virtual photon. Either the virtual photon is equivalent in most ways to a real photon, or it is not. If it is not, we know nothing about its real nature and the name gives misleading comfort.  Theory is useless if any term can take any value "on demand" as it explains everything and predicts nothing. 

 What do we require?  It carries momentum (which leads to the force), it carries energy (because the field itself carries energy), and it interacts in the same way a real photon does. It is postulated to be transmitted because it has oscillating electromagnetic fields. One possible difference involves where the oscillations occur. If real photons oscillate in the x, y dimensions, it has been proposed that virtual ones oscillate in the z,t dimensions.

An oscillation in the z dimension involves motion exceeding the velocity of light, while oscillations in time permit negative momentum as the photon travels backwards in time, thus permitting attractive forces. To me, leaving aside the minor problem that length and time are dimensionally different, this has an element of desperation about it, nevertheless quantum electrodynamics has had remarkable success. However, there are further options that do not seem to have been investigated, such as the use of additional dimensions. The question now is, what helps us devise an experiment to demonstrate their existence?

We know that electric fields are attenuated by intervening materials; we describe the degree of attenuation as the dielectric constant, and this should indicate that the virtual photons are absorbed, for if they were not, they should progress and deliver the expected force without the intervening medium. This would appear to give a possible method for detecting them. Set up two plates in parallel and with equal electric charge (to avoid a potential gradient), and insert a solution with a molecule that fluoresces. The concept is, the virtual photon should have a certain probability of exciting the molecule, but when the absorber's excited state relaxes via fluorescence, it will emit a real photon, which is detectable.

A positive result is a triumph, however the negative one is more problematical, after all, there may be many reasons why a set is empty. Thus if the virtual photons have the wrong frequency, there is no excited state, and the theory does not specify their frequency. If frequency represents the number of photons in a ray, then adjusting the voltage should alter the frequency so there are, in principle possible variations. 

Understanding implies that when presented with a new situation, you can predict the outcome. Can you predict the outcome of this? If the experiment gives a positive result, a number of experiments follow that allow a good understanding of virtual photons, and probably fame and fortune result. The question is, what do you do with a negative result? My guess is, that will prevent anybody from trying, but if you could do it, and you cannot explain why it would not work under any circumstances before doing the experiment, do you really and truly believe in virtual photons? Of don't you care one way or the other?

Posted by Ian Miller on Feb 21, 2012 9:13 PM Europe/London

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