What is the true nature of a photon?

[lightarrow]

The American Heritage Science Dictionary:

The subatomic particle that carries the electromagnetic force and is the quantum of electromagnetic radiation. The photon has a rest mass of zero, but has measurable momentum, exhibits deflection by a gravitational field, and can exert a force. It has no electric charge, has an indefinitely long lifetime, and is its own antiparticle.​

The word "particle" in this definition seems to trip a lot of people up including myself, which is one reason why I wanted to involve the FAQ's commentary on that word.

Infact the word "particle" doesn't necessarily imply "moving corpuscle", in my opinion. Furthermore, the fact a photon "exhibits deflection by a gravitational field" it's just a speculation, made on the fact that light is really gravitationally deflected but on the assumption that light is made of moving corpuscles which should be the photons.

Physics speaks of energy, waves, fields, force, etc., not just nuggets of matter as I think you'll agree, so I'm not sure what you meant by restricting to a physical entity. According to the above, the photon "is" the quantum of electromagnetic radiation.

I intended to refer to the fact that physics studies measurable entities (directly or through their properties) and not something else. So, this given, what does "the quantum of electromagnetic radiation" mean, in your opinion?

 

[kwestion]

the word "particle" doesn't necessarily imply "moving corpuscle", in my opinion.

Okay. Among the options are propogation and some other fun ideas. Do we agree though, that physicists speak of photons at least changing locations at speed c? This may be tricky since it'd be hard to prove sameness, but maybe that's where the statement about indefinitely long lifetime comes in. I think sameness from point A to point B is assumed. Am I on your wavelength?

what does "the quantum of electromagnetic radiation" mean, in your opinion?

Uhm, errh... I think it refers to the idea of the e/m , or its energy, being sort of packaged, and not loosely continuous, giving an all-or-nothing proposition--you get the whole quantity of energy or none of it. Beyond that, for me, there seems to be freedom in meaning, but without mass.

 

[lightarrow]

the word "particle" doesn't necessarily imply "moving corpuscle", in my opinion.

Okay. Among the options are propogation and some other fun ideas. Do we agree though, that physicists speak of photons at least changing locations at speed c? This may be tricky since it'd be hard to prove sameness, but maybe that's where the statement about indefinitely long lifetime comes in. I think sameness from point A to point B is assumed. Am I on your wavelength?

It indeed seems physicists talk about photons in those terms, yes. For what I understand, however, we can only say: "a photon was generated in A, after some time a photon is detected in B"; what happens in between is not clear to me.

what does "the quantum of electromagnetic radiation" mean, in your opinion?

Uhm, errh... I think it refers to the idea of the e/m , or its energy, being sort of packaged, and not loosely continuous, giving an all-or-nothing proposition--you get the whole quantity of energy or none of it. Beyond that, for me, there seems to be freedom in meaning, but without mass.

Yes, but how do you relate this concept to something measurable? Which is the quantization that you can measure? That of the EM field or that of the interaction between EM field and matter?

 

[kwestion]

It indeed seems physicists talk about photons in those terms, yes. For what I understand, however, we can only say: "a photon was generated in A, after some time a photon is detected in B"; what happens in between is not clear to me.?

Okay, it sounds like physicists speak in terms of a sort of travel, but you are leaving the possibilities between A and B wide open. Is that the jist?

Yes, but how do you relate this concept to something measurable? Which is the quantization that you can measure? That of the EM field or that of the interaction between EM field and matter?

I think your point is that we need an interaction with something to give us information. I'll go along with that.
I might point out that the interaction can also be with the photon's antiparticle, and it can be an interaction followed by a prolonged period of time "reacting" with empty space. So we at least have some clues/measurements that go beyond interaction with traditional matter alone.
I'm thinking I'm getting and accepting your point. I guess you're emphasizing that we only know what we measure, and I'm thinking that the measurements are only clues to what the pure thing is between the measurements. I don't necessarily see a conflict in the ideas so far.

 

[lightarrow]

It indeed seems physicists talk about photons in those terms, yes. For what I understand, however, we can only say: "a photon was generated in A, after some time a photon is detected in B"; what happens in between is not clear to me.

Okay, it sounds like physicists speak in terms of a sort of travel, but you are leaving the possibilities between A and B wide open. Is that the jist?

Sorry, don't understand "jist".

I think your point is that we need an interaction with something to give us information. I'll go along with that.
I might point out that the interaction can also be with the photon's antiparticle, and it can be an interaction followed by a prolonged period of time "reacting" with empty space. So we at least have some clues/measurements that go beyond interaction with traditional matter alone.

I'm lost, here.

I'm thinking I'm getting and accepting your point. I guess you're emphasizing that we only know what we measure, and I'm thinking that the measurements are only clues to what the pure thing is between the measurements. I don't necessarily see a conflict in the ideas so far.

Mmmh, I would talk about "clues to what the pure thing is between the measurements" if we could analyze the "pure thing" properties through another kind of measurement, otherwise, how would you prove that such a "pure thing" really exist and it's not a mere speculation?

 

[kwestion]

Sorry, don't understand "jist".

I meant "gist"

I'm lost, here.

I was mentioning that photon interaction with matter isn't the only tool that we have. We can add time and distance to the study. We can also add motion of the source and detector to the study. We can also try to study the effects of photon-photon interaction. Introducing these types of non-matter variables offers another kind of measurement as touched on below:

Mmmh, I would talk about "clues to what the pure thing is between the measurements" if we could analyze the "pure thing" properties through another kind of measurement, otherwise, how would you prove that such a "pure thing" really exist and it's not a mere speculation?

How would I prove that the pure thing, a photon, exists without speculation? I think the process is that we first observe effects a,b,c,d, then we notice a correlation among observations and assume that there was a cause for it. We then simply name the mystery cause a "photon".

As a bonus, nothing stops us from deriving plausible models of the photon that predict future findings. I think we agree that the existence of those extended models might be difficult to prove. I also have a beef with the layman's model which I think causes confusion in communication and perception, but I guess we have to start somewhere.

 

[Loren Booda]

At least one philosopher, Bas van Fraassen, believes that only things we can "perceive" with the unaided senses are real. I don't know if he would include our ability to "see" the photon in that category.

 

[lightarrow]

Sorry, don't understand "jist".

I meant "gist".

Ah, ok, then yes, that's the gist.

I was mentioning that photon interaction with matter isn't the only tool that we have. We can add time and distance to the study. We can also add motion of the source and detector to the study. We can also try to study the effects of photon-photon interaction.

The experimental prove of a quantized interaction between tho light beams, would infact convince me much more of the real existence of the EM field quantization.

Introducing these types of non-matter variables offers another kind of measurement as touched on below:

How would I prove that the pure thing, a photon,

No, the "pure thing" you have in mind, in my opinion, it's not the photon, it's the "moving corpuscle of light" carrying the quantized energy. The photon is the quantized interaction between EM field and matter and so not necessarily such a moving corpuscle.

exists without speculation? I think the process is that we first observe effects a,b,c,d, then we notice a correlation among observations and assume that there was a cause for it. We then simply name the mystery cause a "photon".

First, let's give, as I said, the correct name to this mystery cause you want to discuss: "moving corpuscle of light carrying the quantized energy". That said, why can't I say that there are no such moving corpuscle of light, but just an electromagnetic wave which interacts with matter in a way that the exchanged energy is quantized?

As a bonus, nothing stops us from deriving plausible models of the photon that predict future findings. I think we agree that the existence of those extended models might be difficult to prove. I also have a beef with the layman's model which I think causes confusion in communication and perception, but I guess we have to start somewhere.

 

[ValenceE]

Zapper,

can you really compare water with photons ?...


VE

 

[Yor_on]

Now here is where my headache starts :)

Is a photon a defined 'point' at all times traveling in spacetime.
Or is it just a probability, 'materializing' as we measure it.

That is, our sun 'throws' out photons and as i look up on it those will hit me in time.
Or the sun make it possible for photons to exist and my interaction with this probability according to my eyes orientation and existence allows the interaction to be.

I have to admit that I prefere the first myself.

 

[Shackleford]

Don't ever use Wikipedia. Grab some textbooks instead.

 

[Yor_on]

Shackleford?
If you're referring to my question :)
Didn't use no Wikipedia, does 'many paths' sound familiar to you?
Feynman?
//advancingphysics .i op . org/previous/wb/teacher/ManyPathsandEM.pdf

and this too perhaps
//www . overcomingbias . com/2008/04/feynman-paths.html

 

[kwestion]

the "pure thing" you have in mind, in my opinion, it's not the photon, it's the "moving corpuscle of light" carrying the quantized energy.

What I want to convey by the "pure thing" is the definition of photon posted in #31. If I stray from that, I want to reel myself back in. I really don't like summarizing it as a moving corpuscle. I think corpuscle gives imagery that just doesn't seem to work well.

The photon is the quantized interaction between EM field and matter and so not necessarily such a moving corpuscle. [...] That said, why can't I say that there are no such moving corpuscle of light, but just an electromagnetic wave which interacts with matter in a way that the exchanged energy is quantized?

I think this brings us back to an earlier topic. That stance is reasonable and I think it may have been examined in the BKS model. My limited understanding of that model is that it proposed that matter regulated the quantum effects of light. It was eventually ruled out in favor of the e/m itself having the quantum properties. I'm just addressing the quantization topic here.

It sounds like neither of us have much use for the imagery of a moving corpuscle. Heck, I don't even know what is meant by that. Do you understand it to be a requirement of a photon? The definition uses the word particle, but I'm all over the FAQ when it says its not your normal "particle". There's also a zero-ness to this particle that might not make it as challenging as the normal particle. I mean if it has zero (rest) mass and no discernable size, then that seems pretty close to a non-corpuscle to me. This seems to leave e/m, a scant particle, and some other properties.

 

[Yor_on]

Yes, but it has momentum and obeys gravity.
Doesn't that mean that there has to be something there?

And if we say that photons are some kind of 'probability focus' that change 'location' over 'time'
(Yeah, I know, a lot of ''''':)
Then what would 'time' be?

 

[lightarrow]

What I want to convey by the "pure thing" is the definition of photon posted in #31. If I stray from that, I want to reel myself back in. I really don't like summarizing it as a moving corpuscle. I think corpuscle gives imagery that just doesn't seem to work well.

In that definition:

"The subatomic particle that carries the electromagnetic force and is the quantum of electromagnetic radiation. The photon has a rest mass of zero, but has measurable momentum, exhibits deflection by a gravitational field, and can exert a force. It has no electric charge, has an indefinitely long lifetime, and is its own antiparticle."

something is missing: the photon's spin and the fact that "quantum of electromagnetic radiation" refers to quantization of the energy; furthermore, as I wrote, I don't think it's correct to state that the photon "exhibits deflection by a gravitational field"; to state something like that we shoude have a valid and accepted quantum theory of gravity, and we still don't have it.

I think this brings us back to an earlier topic. That stance is reasonable and I think it may have been examined in the BKS model. My limited understanding of that model is that it proposed that matter regulated the quantum effects of light. It was eventually ruled out in favor of the e/m itself having the quantum properties. I'm just addressing the quantization topic here.

Wikipedia says:

<<Nevertheless, all semiclassical theories were refuted definitively in the 1970s and 1980s by elegant photon-correlation experiments.[33] Hence, Einstein's hypothesis that quantization is a property of light itself is considered to be proven.>>

but I'm not sure if all physicists would agree on it.

It sounds like neither of us have much use for the imagery of a moving corpuscle. Heck, I don't even know what is meant by that. Do you understand it to be a requirement of a photon? The definition uses the word particle, but I'm all over the FAQ when it says its not your normal "particle". There's also a zero-ness to this particle that might not make it as challenging as the normal particle. I mean if it has zero (rest) mass and no discernable size, then that seems pretty close to a non-corpuscle to me. This seems to leave e/m, a scant particle, and some other properties.

I have the same concerns.
Some times ago I made a computation, sincerely don't know if it was really correct, about a simply elastic collision between two particles, one of which initially stationary with mass M and the other relativistic with mass m which I then made go to zero, because I was trying to understand if a photon could be thought of as an "ordinary" particle with negligible mass at least for what concern the Compton effect; the resultant energies were different from what results from the Compton Scattering. This is one of the reasons I stll have no idea of how photons can be thought of.