Almost all physicists and physics watchers accept that electricity is composed of electrons and light of photons, despite the conceptual problems this creates. A great many physicists go further, and seek fundamental explanations for all matter and energy in terms of particles.
We see this when the ‘Higgs boson’ is invoked as an explanation for mass, the graviton as a carrier of gravitational attraction, and supersymmetry (a parallel set of undiscovered particles) for a range of difficulties with the standard model.
Reflecting this, most alternative theories are also based on particle explanations, as seen here.
One of the most fascinating debates in science is about the ultimate nature of its smallest physical elements, and this argument has been going on for millennia.
Democritus is known for having suggested that there is a smallest indivisible particle. Today, we know it as the atom, and know that it is not indivisible at all.
Isaac Newton wrote of ‘corpuscular’ light , at the same time as Huygens was initiating an analysis of how waves worked. After the exceptional contributions of Fresnel and Young in particular, in the early eighteenth century, the matter was considered settled. Light had all of the properties of a wave, in all circumstances, and so light was a wave.
By the end of that century, Michelson had failed to observe the background medium for wave light, as have others since, and Maxwell had failed in his grand attempt to codify the nature of such a medium. Maxwell’s ‘luminiferous medium’, the ether, was abandoned, and light could not be a wave without it.
Planck showed that light was emitted and absorbed in discrete amounts at specific frequencies. This was used to draw a further conclusion, that light from a particular atomic transition was always emitted in the same amount, as a specific quantum of energy, and could therefore be considered a particle, with all or most of what that entailed. Einstein discussed this as a discrete physical reality in his consideration of photoelectricity in 1905.
Robert Millikan showed that electric charge, retained on a drop of oil, existed only in discrete multiples of a fundamental amount.
From this period onwards, light has commonly been discussed as a particle, the photon, and electricity as composed similarly of particles called electrons.
The fundamental problem for the view that everything is particulate, and specifically for the photon and electron, is that both light and electromagnetism are most effectively modelled for most of their distinctive properties as spread out: the light wave and the electromagnetic field.
Niels Bohr, one of the founders of the Copenhagen Interpretation of quantum mechanics, recognised the problem:
‘As is well known, the [quantum] hypothesis introduces insuperable difficulties when applied to the explanation of the phenomena of interference, which constitute our chief means of investigating the nature of radiation. We can even maintain that the picture, which lies at the foundation of the hypothesis of light-quanta excludes in principle the possibility of a rational definition of the conception of a frequency ν, which plays a principal part in this theory.’
Huygens’ explanation of how a wave works is entirely dependent on it being a spread-out effect in a background medium, as are Fresnel’s analyses of interference and diffraction. No one has ever come close to explaining these effects, or frequency itself, with a purely particle model.
One attempt is to postulate parallel universes, in which different versions of the same particle photon in different universes pass through different slits, and then somehow communicate subsequently to produce interference patterns. David Deutsch, an advocate of this view, was once interviewed about it on TV by Jim Al’Khalili, who struggled and failed to keep a straight face. This is a somewhat desperate idea to save the photon, and tends instead to bring it into further disrepute. It falls on almost all scientific criteria. That it continues to be discussed is one of the clearest indications of the crisis afflicting theoretical physics.
Maxwell’s equations of electromagnetism, one of the great achievements of mathematical modelling in science, treat the phenomenon as spread out, and so electromagnetism is just as difficult to explain solely with particles as is light.
The fundamental problem in quantum mechanics, therefore, is that light must be a wave because only a wave can produce wave effects, and at the same time it cannot be a wave because the background medium it requires, the ether, has been ruled out. Looked at from the other side, light must be a particle because wave light has been eliminated, and at the same time it cannot be a particle because there is no way that a particle can produce the distinctive and ubiquitous wave effects, specifically frequency, interference and diffraction.
The ‘solution’ to this is ‘duality’, but on this we can be definitive:
Calling duality a ‘model’ is fundamentally unscientific. It is a fudge, an obfuscation, a compromise that no one is happy with and no one treats with respect.
It is not a scientific model, because it lacks clarity, and fails on all scientific criteria. It runs counter to Occam’s razor by including all options, and in so doing it fails Popper’s test of falsifiability in that there appears to be no observation that could falsify it. It is also absurd, failing by reductio ad absurdum, since it encourages us to consider a single entity or effect as both localised and spread out at the same time, a clear contradiction and absurdity.
As evidence that no one respects it, we can look at the recent origins of ‘quantum cryptography’. The principle of this is that light is a particle and each encoded bit (binary or phase or polarisation orientation) is destroyed when intercepted and read by a spying observer, meaning that those parts of the message that have not been intercepted are known to be secure. Yet I am aware of no one in the whole of physics who stepped forward to invoke the wave part of duality to lend a cautionary note.
An excellent example of the profound confusion that exists in physics about the duality ‘model’ is entanglement. All reasoning in this area rests on the assumption that light is a particle and quite categorically not a wave.
There are well-studied emission events that are known to affect more than one receptor, and in ways that are predictably related. In the particle model, this must therefore involve the simultaneous emission of more than one particle, and that these particles are part of a single system, known as ‘entangled’. Two further assumptions are made that each particle only comes into existence when observed, and that their properties (such as angle of polarisation) are only determined at that point. These are a consequence of probabilism .
Under these assumptions, it is a mystery how the second particle detected ‘knows’ its properties, and much work has been done on this problem. None of this involves viewing the emission as a wave, for then all the mystery (and funding) would disappear.
The failure of the ether by 1900 ceded theoretical ground to particle explanations. I do not know of anyone in mainstream physics today who rejects the photon and electron.
Particle physics is a huge area. Virtually all pronouncements out of CERN are based upon descriptions of smashing incredibly tiny particles up into even smaller ones. For a time it looked as if all of physical reality could be described with a handful of particles, although this claim involved overlooking the objections detailed above .
The ‘standard model’ of physics was introduced, and this was very attractive when the number of fundamental particles was 8, and especially so when this was expressed as one of the simplest patterns in mathematics. Today, particle physicists talk less hopefully about a ‘particle zoo’.
Nevertheless, the popularity of the particle physics view that wave explanations are superficial and superfluous supports the rejection of duality in quantum cryptography and elsewhere.
The experimental side of particle physics is very valuable, if very expensive, and some of its group-theoretic mathematics may at some point provide some physical insight, but if the analysis of modern theories of physics tells us anything, it is that ‘explanations’ that ignore important aspects of the phenomena, while potentially seductive, impede progress more than facilitating it.
An alternative explanation of quanta
While it has proved impossible to explain wave and field phenomena in terms of particles, it is much easier to explain particle behaviour in terms of waves and fields. The Higgs ‘particle’, for example, is not really a particle at all, in the accepted sense. The ‘Higgs field’ is a more appropriate description for both the mathematical modelling and the observations made. Physicists at the Large Hadron Collider do not claim to have detected a particle as part of the debris from their collisions, rather they claim to see the effect of a field (or they might say field of particles) in the motion of those particles they do observe.
Milonni correctly observes that modern theory of the photoelectric effect ‘allows Einstein’s relation to be deduced without photons: Once electrons are described by the Schrödinger equation, it follows that a classical light wave of frequency ν can induce an electron to change its state…’i
Maxwell and Schrödinger have done the most in this area, but their work on explaining light, electromagnetism and other effects in terms of wave and fields and other background motion has been largely discarded and forgotten, and both are now solely remembered for other aspects of their work. Schrödinger’s work was almost entirely excellent, while Maxwell’s was not quite perfect. Maxwell’s equations and their physical interpretation are discussed here.
One of the central themes of this site is that physicists are all too ready to go gung ho for a conclusion arrived at prematurely, and ‘everything is a particle’ seems to be one of these. Special relativity, general relativity and quantum mechanics offered conceptual answers across physics, and so other possibilities were discarded, even when these ‘answers’ proved inadequate or contradictory. This appears to have been a gamble that has failed, as the problems identified at the outset, for example by Bohr (above), have never been resolved, and physics has been unscientifically reluctant to re-examine and re-evaluate these theories and potential alternatives.
As an example, take the founding observations by Planck and Millikan. The quantisation they observed could indeed be an indication that what they were observing were discrete particles, the photon and electron, but such ‘explanations’ only work in limited ways. That quantisation could equally be due to the natural properties of atoms, which we know more securely to be discrete, localised entities.
In this view, a particular atom emits specific frequencies and vibrates at a particular rate because that is its nature, and that nature is modified by motion or by a change in gravitational field. Its detailed nature, in this model, is largely unknown but could be investigated. It emits light in discrete events as it changes from one preferred state to another. We would not expect this change to take place instantly, as if releasing a lesser particle, but over a finite time, and we would expect eventually to be able to ‘see’ this event in detail via observed effects through a sufficiently elegant experiment.
This is precisely what we see in the work of Ferenc Krausz and colleagues in Austria and Germany who presented in 2002 what they call the ‘first ever photograph’ of a light wave.
If we are happy to continue to try to solve the problems of modern physics through the medium of existing theory, I suggest we must also look at these wave and field alternatives. They additionally offer a route to examining the structure of atoms in ways that are not available in particle physics.
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i. Peter W Milonni, Los Alamos National Laboratory, in Am. J. Phys. (January 1997) page 11