Photons: The Argument for their Existence?

[Positor]

Several contributors to this forum have argued that photons do not really exist, and that electromagnetic radiation is not present as a physical entity in the time and space between its emission and absorption. For example, Faradave argues that these two events have 'zero separation' in a correct 4-dimensional representation, and therefore involve 'contact'.

As far as I am aware, mainstream physics still adheres to the belief in the existence of photons. It would be interesting to hear a defence of the established view, with reasoned rebuttals of the specific arguments of revisionists.

Is there any way of conclusively proving or disproving the existence of photons as particles in motion?

Or are the two views somehow compatible?

[Faradave]

Happy to reply from my gut, there's a good chance the thread will be moved to Personal Theories. That's not inappropriate considering many physicists would think my ideas are BS. I'll give others a chance first.

[TheVat]

It's almost a candidate for Philosophy of Science as well, given that you're asking what sort of proof could establish a particle-LIKE interaction as necessitating an actual physical particle. It seems to require that we determine what the nature of proof is, vis-a-vis objects that can only be known indirectly and are often conjured as terms of convenience. Let's see where this goes. The question has the potential to be wide-ranging, eh?

[Pivot]

Using a crude electric light bulb we can test the electromagnetic credentials of light from source to absorption, and even test its transmission across a near perfect vacuum. The real question is ‘what is the physical form of that light travelling from A to B in a controlled environment (i.e. one in which we can carry out testing)?’

Assuming that light is not a continuous ‘wave’ from source to absorption, it must consist of one or more electromagnetic energy spurts, which we can call photons. Any such photonic spurt would have a finite length, but this tells us nothing about the form of the photon or how multiple photons travel together (are photons of different frequencies super-imposed on each other or do they have separate space?). And are there any guidelines as to the number of wavelengths accommodated in that length: is it frequency (and thus energy) dependent?

The form of a photon would also seem to change in its life cycle. The form of dispersed light, freshly released by an electron changing orbital level within the source atom, changes when it enters a transparent medium where it is refracted and possibly reflected and becomes partly to completely polarised. And what actually causes light to be reflected; is it the electromagnetic fields of electrons or is it the protons or neutrons within the nucleus?

So we know that a photon has a linear dimension in its direction of travel (let’s call that length), but does it have a finite cross-sectional area? If it is considered to be a particle then it should. The fact that photons are refracted when they encounter a transparent medium, and such refraction causes dispersion (frequency dependent differences in speed and angles of refraction of light) strongly suggests they do have a finite effective cross-sectional area.

Then there are all the different types of light forms: incoherent, coherent (including laser light), optic vortex light, and the various forms of polarised light: plane, partially circularly and elliptically. And before we get too carried away with light, there is the rest of the EMR spectrum outside the frequency of visible light to which all these variations assumedly also apply.

The concept that a photon has finite dimensions and consists of electromagnetic energy would seem a reasonable assumption from what we observe and know about light. What is needed is some idea as to the form that photons take in different situations, starting from the raw emissions from the orbitals of energised atoms to when they are modified by reflection and refraction.

[bangstrom]

Assuming that light is not a continuous ‘wave’ from source to absorption, it must consist of one or more electromagnetic energy spurts, which we can call photons.

OK. Now the next step is to assume that light is a continuous wave.

[Pivot]

To assume that 'light is a continuous wave' is to assume that light is connected to the source no matter how many times it is refracted and/or reflected. Could you please explain your rationale for assuming this to be the case.

[bangstrom]

To assume that 'light is a continuous wave' is to assume that light is connected to the source no matter how many times it is refracted and/or reflected. Could you please explain your rationale for assuming this to be the case.

By assuming that light is discontinuous, you have reached the conclusion that photons exist and given them properties not supported by observation without considering the alternative. Refraction, reflection, and interference are properties of continuous waves

[Faradave]

In QED, Feynman does a heroic (and Nobel winning) job of explaining refraction, reflection and interference in terms of photons. However, he unabashedly offloads the critical wave aspects to imaginary stopwatches. The spinning hand of the watch is probability amplitude which he denies understanding and which happens to vary with a cosine function.

"To determine the direction of each arrow [probability amplitude], let’s imagine a stopwatch…has a single hand that turns around very, very rapidly. …(about 36,000 times per inch for red light)" p.27

"…as time goes on the angle of the amplitude for a photon to be emitted by a source changes. …like a stopwatch hand. … The rate of turning depends on the color of the light:" p.102

And in The Character of Physical Law
"...we invent an 'a' which we call a probability amplitude, because we do not know what it means." p.137

"Probability amplitudes are very strange…" p.166

[Pivot]

Bangstrom wrote "By assuming that light is discontinuous, you have reached the conclusion that photons exist and given them properties not supported by observation "

As a defense I would suggest this is scant on detail and reaches a conclusion that I have reached a conclusion and then retrospectively given 'continuous' properties a particle bias. When considering Physics matters conclusions are rarely reached and we are dealing with feasible possibilities that best match observations.

Actually it would be easier to have light being a continuous waveform, but nature is not like that. I see more evidence of the discontinuous point of view in the photoelectric effect, in the different types of light (see earlier response), in refraction and the polarisation by reflection and refraction. Also when I look at a lighthouse with a revolving light (there are still a few in commission), if light were continuous from source (i.e. connected to the source) why isn't the light bent as the source moves and appear more like a Catherine wheel? Think about it.

Bangstrom wrote "Refraction, reflection, and interference are properties of continuous waves"

Wave do not need to be continuous for these phenomena to occur. Being continuous is not a pre-requisite.

Faradave wrote "Feynman does a heroic (and Nobel winning) job of explaining refraction, reflection and interference in terms of photons."

Freyman and his research group certainly did a great job and I don't think anyone has been able to produce further observation to prove his opinion relating to the photonic nature of light wrong or off the mark. And he had the knack of describing phenomena in detail without drawing early conclusions.

[bangstrom]

Also when I look at a lighthouse with a revolving light (there are still a few in commission), if light were continuous from source (i.e. connected to the source) why isn't the light bent as the source moves and appear more like a Catherine wheel? Think about it.

In theory a light beam does bend whether a wave or a particle but the propagation of light is too fast to observe the curvature.

[BurtJordaan]

In theory a light beam does bend whether a wave or a particle but the propagation of light is too fast to observe the curvature.

Well, this depends on how you define a light beam, how you observe it and from which coordinate system you watch it. I think that in free and clean space (no dust particles to reflect some part of the beam), it will only be 'curving' in the rotating reference frame of the light beacon. In the inertial frames of both lighthouse and observer, it will be gun-barrel straight.

[Faradave]

Yup. I think of paint drops flying straight off a spin art plate. There are no curved forces.

[bangstrom]

Well, this depends on how you define a light beam, how you observe it and from which coordinate system you watch it. I think that in free and clean space (no dust particles to reflect some part of the beam), it will only be 'curving' in the rotating reference frame of the light beacon. In the inertial frames of both lighthouse and observer, it will be gun-barrel straight.

It depends on how you define “observe”. A light beam with nothing to reflect its path can not be observed from any reference frame.

[BurtJordaan]

It depends on how you define “observe”. A light beam with nothing to reflect its path can not be observed from any reference frame.

I think a single item of semi-silvered optics halfway would be enough to show a straight path.

[BurtJordaan]

Yup. I think of paint drops flying straight off a spin art plate. There are no curved forces.

If you are an observer sitting on the axis and spinning with the plate, then in your rotating frame the paint drops will trace curves, just like light beams for a for a lighthouse observer turning with the reflector.

[Pivot]

BurtJordaan wrote...

'Faradave » 25 Oct 2019, 22:39 wrote:

'Yup. I think of paint drops flying straight off a spin art plate. There are no curved forces.'

If you are an observer sitting on the axis and spinning with the plate, then in your rotating frame the paint drops will trace curves, just like light beams for a for a lighthouse observer turning with the reflector.

Lets keep focused and stop going off-beam (excuse the double pun). We are not talking about centrifugal/centripetal forces and pretty paint spots. Nor are we (yet) talking about different reference frames and relativity for flying droplets of paint.

What I suggested to counter Bangstrom's claim that a light rays are continuous from source (i.e. connected to the source) to where it might be detected or absorbed (let's say by the eye of a beholder). For a spinning light source (e.g. lighthouse light) the moment that the ray leaves the filament its source would have moved on (i.e. be pointing in another direction). Thus the light ray would be immediately disconnected from its source and be photon-like UNLESS it becomes bent, which it doesn't.

It would be nice to move onto some real issues related to the nature and form of light without becoming bogged down and side-tracked with trivia.

[BurtJordaan]

Chat forums owe their very existence to being sidetracked into trivia... ;)

[Reg_Prescott]

As far as I am aware, mainstream physics still adheres to the belief in the existence of photons. It would be interesting to hear a defence of the established view, with reasoned rebuttals of the specific arguments of revisionists.

Is there any way of conclusively proving or disproving the existence of photons as particles in motion?

Hello Positor,

It seems to me, without even delving into the minutiae of photon theory (which I'd be incompetent to do anyway), the standard antirealist arguments for the status of unobservable entities posited in scientific theories apply, viz., we have very good reasons for believing that photons do not exist.

These are, specifically, (i) the underdetermination of theories by data, and (ii) the pessimistic induction.


The latter, in particular, rings particularly loudly in this case.

We were once told light consisted of corpuscles. Later, we were told that light is a wave of one kind or another. Most recently, the essence of light is claimed to be photons.

Should the track record of failed "going behind the phenomena" causal-explanatory theories alone not caution us to be somewhat wary about committing to a belief in the existence of photons?

A salutary reminder....


"Whatever difficulties we may have in forming a consistent idea of the constitution of the aether, there can be no doubt that the interplanetary and interstellar spaces are not empty, but are occupied by a material substance or body, which is certainly the largest, and probably the most uniform body of which we have any knowledge." -- J. C. Maxwell

[bangstrom]

What I suggested to counter Bangstrom's claim that a light rays are continuous from source (i.e. connected to the source) to where it might be detected or absorbed (let's say by the eye of a beholder). For a spinning light source (e.g. lighthouse light) the moment that the ray leaves the filament its source would have moved on (i.e. be pointing in another direction). Thus the light ray would be immediately disconnected from its source and be photon-like UNLESS it becomes bent, which it doesn't.

It would be nice to move onto some real issues related to the nature and form of light without becoming bogged down and side-tracked with trivia.

There is a confusing bit of semantics in the theories of light where a photon can be described as a particle or a photon can be described as a quantum of energy in a wave like exchange not involving particles. Classical photon theory considers the photon to be a particle at least part of the time while alternatives to the classical theory consider the photon to be “non real” as a particle never anything but a wave. It is important to keep these distinctions in mind.

In the old Wheeler-Feynman Absorber Theory (W-F AT) the photon is considered to be a particle but, in the John Cramer Transactional Interpretation of Quantum Mechanics (TIQM), the photon is considered to be a quantum of energy. Both of these particle and non-particle theories consider a two-way connection between a signal source and a receiver moving both forward and backward in time to be prerequisite to the emission of light so the connection between a signal and receiver is established even before the light is emitted.

A light signal can be blocked from emission by either blocking the signal moving forward in time or by blocking the signal moving backward in time. A light signal is possible only if a pathway is open in both directions prior to emission. There are several ways of blocking one signal but not the other to test the hypothesis. The simplest but least conclusive of these is the Dirac three polarizer experiment and the most definitive is the quantum eraser experiment and there are others such as the Afshar experiment in between. Light appears to travel as if prescient of its destination which suggests a two way connection in time.

https://video.search.yahoo.com/yhs/sear ... ction=view

[bangstrom]

Hello Positor,

It seems to me, without even delving into the minutiae of photon theory (which I'd be incompetent to do anyway), the standard antirealist arguments for the status of unobservable entities posited in scientific theories apply, viz., we have very good reasons for believing that photons do not exist.

A salutary reminder....


"Whatever difficulties we may have in forming a consistent idea of the constitution of the aether, there can be no doubt that the interplanetary and interstellar spaces are not empty, but are occupied by a material substance or body, which is certainly the largest, and probably the most uniform body of which we have any knowledge." -- J. C. Maxwell

It has been said that Einstein’s SR and the Michaelson Morley experiment MM-X did away with the old concept of the aether but Einstein replaced the aether with spacetime in his GR. The difference between the aether and Einstein’s spacetime is that the former causes photons to drift from their normal straight-line path but spacetime does not. The null result of the MM-X demonstrated that either the aether doesn’t exist or photons don’t exist since the aether can’t effect the path of a nonexistent particle.

The Wheeler-Feynman Absorber theory explains the phenomenon of light perfectly well as a photon theory and, when Einstein first attended one of Wheeler and Feynman’s introductory lectures, he told the pair that their Absorber theory resembled a little known but similar theory proposed by Hugo Tetrode that worked the same way but without the photon.

The W-F Absorber theory and Tetrode’s theory both involve a non-local, two-way connection between the emitter and receiver in a light signal before energy can be exchanged and Einstein couldn’t accept either theory because they both involved, “Spooky action at a distance”. Einstein and Bohr once tried to visit Tetrode in person to discuss his theory for light but he was too sick with TB to see visitors and he died shortly after so there was never a meeting of the minds about Tetrode’s theory.

[Reg_Prescott]

It has been said that Einstein’s SR and the Michaelson Morley experiment MM-X did away with the old concept of the aether but Einstein replaced the aether with spacetime in his GR. The difference between the aether and Einstein’s spacetime is that the former causes photons to drift from their normal straight-line path but spacetime does not. The null result of the MM-X demonstrated that either the aether doesn’t exist or photons don’t exist since the aether can’t effect the path of a nonexistent particle.

With all due respect, and noting that I'm not a physicist, on conceptual grounds alone this doesn't sound remotely plausible.

What you're telling us is that only two conclusions were logically possible following the surprising experimental result. It's the myth of the "crucial experiment", except that you're saying two, rather than one, conclusions necessarily resulted.

To summarize the Duhem-Quine thesis: when observation clashes with theory, all that can be logically concluded is something is wrong somewhere. It may be that the theory is false. On the other hand, it may be that the theory is just fine and the fault lies with the auxiliary hypotheses -- and there are an indefinite number of them!

Is it not logically possible that neither the aether nor photons exist? Ans: Of course it is.



As a side note on so-called crucial experiments, we often hear it claimed, for example, that the MM experiment definitively refuted the existence of the aether. History tells quite a different story...

As J. J. Thomson said as late as 1909, "The ether is not a fantastic creation of the speculative philosopher; it is as essential to us as the air we breathe. . . . The study of this all-pervading substance is perhaps the most fascinating and important duty of the physicists"
-- The Advancement of Science and its Burdens, Holton, p79

[TheVat]

Thomson, best known for establishing the electron as particulate (a "corpuscle") in nature, rather than an immaterial waveform.

:-)

[BurtJordaan]

As a side note on so-called crucial experiments, we often hear it claimed, for example, that the MM experiment definitively refuted the existence of the aether. History tells quite a different story...

It definitely refuted the original "luminiferous aether", but not necessarily Einstein's "new aether", i.e. https://en.wikipedia.org/wiki/Luminiferous_aether, last paragraph:

As historians such as John Stachel argue, Einstein's views on the "new aether" are not in conflict with his abandonment of the aether in 1905. As Einstein himself pointed out, no "substance" and no state of motion can be attributed to that new aether. Einstein's use of the word "aether" found little support in the scientific community, and played no role in the continuing development of modern physics.

[Reg_Prescott]

It definitely refuted the original "luminiferous aether", ]

No, it didn't. You're making up history, pal.

The aether continued to be defended well into the 20th century.

[Reg_Prescott]

Burt, with all due respect, you're telling us only one of two conclusions was possible: either the ether doesn't exist or photons don't exist. It's manifest drivel.

Show me your derivations, please.

Or I will.

[Pivot]

Taking another tack to the last couple of dialogues, I would like to ask some questions about the creation and form of EMR.

For the wave-form supporters: electron–positron annihilation occurs when an electron (e−) and a positron (e+) collide. In a majority of cases, the result of the collision is the annihilation of the electron and positron, and the creation of a pair of gamma rays with 0.511 MeV energy each, that shoot off in opposite directions. Assuming that you consider, as for all EMR, the gamma radiation to be a continuous wave, how do you visualise or explain the transformation at the point of impact?

For the photonic particle supporters, when photons are plane polarised by reflection and/or refraction are the photons squeezed to become thinner or do they just become more wave-like with their electric and magnetic components in orthogonal planes; and how do you visualise or explain the transformation?

[BurtJordaan]

Show me your derivations, please.
Or I will.

No, rather give us links to the reference papers supporting your claim, which seems to be off the mainstream.

[Faradave]

annihilation of the electron and positron, and the creation of a pair of gamma rays with 0.511 MeV energy each, that shoot off in opposite directions. Assuming that you consider, as for all EMR, the gamma radiation to be a continuous wave, how do you visualize or explain the transformation at the point of impact?

Physics is full of energy transformations. Mass (a.k.a. "rest mass") may be considered a form of potential energy by E=mc². Annihilation is a conversion of those potential energies of the positron and electron into a purely kinetic form as E=pc. Of course, a particle in motion would have both kinetic and potential components. Thus Einstein's complete energy equation, given as a vector sum.

Einstein's energy equation is easily accommodated by Euclidean interval-time coordinates.

That's as far as I can go without Personal Theory.

[Reg_Prescott]

Show me your derivations, please.
Or I will.

No, rather give us links to the reference papers supporting your claim, which seems to be off the mainstream.

You mean logic won't do it?


Here's the schema...

My theory & an indefinite number of auxiliary hypotheses predict that X will be observed

X is not observed

Conclusion: Houston, we have a problem

[Reg_Prescott]

It's not "off the mainstream", sir.

It's just Duhem and Quine.