Do photons exist?

[Chronos]

Of course, one can argue that anything doesn’t really exist, and is just a mathematical artifact which simplifies the models. Given that you can make that argument just as well for anything at all, I prefer to simply say that mathematical artifacts which simplify the models are “things”.

[Pasta]

@Lumpy

I think he was claiming that there’s no such thing as one single photon by itself, only the abstraction called a quanta that comes out of the equations for a distribution of wave functions (if I’m saying that right).

If the worry is that a photon with a specified momentum exists only as an infinite plane wave, that just means a photon can be non-local – not that it doesn’t exist.

[Exapno_Mapcase]

@TriPolar

Based on these explanations, ‘spooky action at a distance’ doesn’t seem so spooky after all. It sounds like photons seperated by great distances seem to be in the same place. Kind of like photons being somewhere and everywhere at the same time.

I don’t think anybody else addressed this.

I’m guessing that by what you call “spooky action at a distance” you mean quantum entanglement.

That can involve any set of particles, not just photons. Photonic massless behavior is a different issue. Nor are photons “somewhere and everywhere at the same time,” unless you’re talking about something like Feynman’s “every possible path” summation. But that also applies to every particle, not just photons.

[TriPolar]

@Exapno_Mapcase

@TriPolar

Based on these explanations, ‘spooky action at a distance’ doesn’t seem so spooky after all. It sounds like photons seperated by great distances seem to be in the same place. Kind of like photons being somewhere and everywhere at the same time.

I don’t think anybody else addressed this.

I’m guessing that by what you call “spooky action at a distance” you mean quantum entanglement.

That can involve any set of particles, not just photons. Photonic massless behavior is a different issue. Nor are photons “somewhere and everywhere at the same time,” unless you’re talking about something like Feynman’s “every possible path” summation. But that also applies to every particle, not just photons.

Thanks. Somewhere and everywhere had no meaning, but I’ve wondered why entanglement seems so spooky. From my point of view, not immersed in physics, I see the phenomena described as all pretty amazing, so entanglement seems no stranger than so many other things. I talked to one person studying physics now, and he remarked that the description of entanglement as ‘counter-intuitive’ is mainly in the context of classic physics. He agreed that my description of ‘non-intuitive’ would be how it would look without that background.

Pasta reminded me about how attempting to measure distance in the direction of travel goes down to zero for everything. I still wonder what time means in the reference frame of a photon though. Pasta says an observed rate can be measured from with the photon’s reference frame, so I assume that would have to be an observation not in the direction of travel.

I guess is seems easy for you physics guys, it’s kind of harder here on the outside.

[Pasta]

@TriPolar

Pasta says an observed rate can be measured from with the photon’s reference frame…

I was saying that a rate can be defined and calculated for that frame. A rate can’t necessarily be measured from within the frame, though, since (1) no real observer can ever be in that frame, and (2) any actual measurement would require you to travel a distance that we (say, on Earth) would say is infinite. One can’t say anything terribly meaningful about what traveling across that span would imply.

(This is why it’s reasonable just to say that the frame doesn’t exist, if you wish. I’ve taken the approach here that the frame does exist in a mathematical sense, even though you can’t get to it and you couldn’t necessarily do anything useful if you got there anyway. But you can still calculate how quantities behave in the v → c limit, and a clock’s period, when observed by someone in the same frame as the clock, is always one second per second.)

[TriPolar]

@Pasta

I was saying that a rate can be defined and calculated for that frame. A rate can’t necessarily be measured from within the frame, though, since (1) no real observer can ever be in that frame, and (2) any actual measurement would require you to travel a distance that we (say, on Earth) would say is infinite. One can’t say anything terribly meaningful about what traveling across that span would imply.

(This is why it’s reasonable just to say that the frame doesn’t exist, if you wish. I’ve taken the approach here that the frame does exist in a mathematical sense, even though you can’t get to it and you couldn’t necessarily do anything useful if you got there anyway. But you can still calculate how quantities behave in the v → c limit, and a clock’s period, when observed by someone in the same frame as the clock, is always one second per second.)

Well that makes sense. I didn’t think anything could actually be observed, but as you say, calculated. Since my frame of reference is much slower than the speed of light, a clock is doing the job just fine right now. Thanks for the explanation.

[JWT_Kottekoe]

@JWT_Kottekoe

Sorry to be a pedant, but no, a photon does not exist.

I was making a rather narrow point just to be provocative; that’s why I warned you that I was being pedantic. All the quantum phenomena really exist and I am not in any way denying that.

I have a slight problem with the way elementary QM is presented. There is not enough emphasis given to superpositions of basis states. All the discussions of photons going hither and yon, should conjure images of wave packets of electromagnetic fields moving, not stationary states sitting there doing nothing. I also think people overuse the photon language, attributing classical effects like stimulated emission to quantum mechanics (it is spontaneous emission that requires quantum theory). These are minor pedagogical points, nothing more.