Physics Help Forum fields and photons?

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 Sep 16th 2019, 07:40 AM #21 Member   Join Date: Sep 2019 Location: Azores Posts: 32 I guess it boils down to :> All we can do is use the best tool for the job, to predict an outcome from a given set of circumstances. How the outcome happens is not so important. "Shut up and calculate" All things are quantum fluctuations in the vacuum of space. Even virtual particles. Thanks all the input and patience
Sep 16th 2019, 07:54 AM   #22
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 Originally Posted by topsquark I wanted to take this one out for a special comment. Magnetic fields are created by electric currents. Magnetic fields can change over time but they don't "travel" at all, much less in tight circles. Perhaps you are thinking of the trajectory of charged particles in a magnetic field, such as in a bubble chamber? -Dan
I was thinking of a permanent magnets field lines, down to single stationary electrons.

Thank you very much for the response.

"In QED a photon is the mediator of the EM field. This means that it "carries" the momentum between two distinct particles. (See diagram 1.)

How does that work with a simple dipole antennae. Maxwells equations use a polarized EM field, which induces a voltage in the antennae. A wave of photons might transfer momentum to the electrons in the antennae perhaps?

Sep 16th 2019, 08:06 AM   #23

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 Originally Posted by interested I was thinking of a permanent magnets field lines, down to single stationary electrons. Thank you very much for the response. "In QED a photon is the mediator of the EM field. This means that it "carries" the momentum between two distinct particles. (See diagram 1.) How does that work with a simple dipole antennae. Maxwells equations use a polarized EM field, which induces a voltage in the antennae. A wave of photons might transfer momentum to the electrons in the antennae perhaps?
It gets kind of weird for sure. There are two different ways to look at particles and fields and they give complimentary results. The antenna is best described by waves. It can be done with particles (in principle) but actually doing that is likely to be beyond me.

It boils down to this rather disturbing feature of QM: If you do an experiment to detect a wave, you'll get results that can be understood in terms of waves. If you do an experiment to detect a particle, you'll get results that can be understoon in terms of particles.

I don't understand why this should be. But I don't make 'em up, I just report 'em.

-Dan
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 Sep 16th 2019, 09:17 AM #24 Senior Member     Join Date: Jun 2016 Location: England Posts: 1,060 What Is It ? (3) I have to admit the "shut up and calculate" approach bugs me... The requirement of swapping of calculation methods for different circumstances seems to me to indicate the fundamental lack of understanding of the substance of the subatomic world. Swapping the calculation methods is not necessarily a problem, I do it all the time in practical situations where different approximations become appropriate in different circumstances. But I know where the approximations are and crucially why they work. What bugs me is that because we have a method that works (to incredible levels of accuracy) there seems to be a lack of urgency to understand "what is it". I know there are many physicists devising (and eventually discarding) very many possible ideas, I am just impatient. It also leads to great confusion (which we see almost daily on this forum) with talk of fields and particles and waves which don't seem to gel together into a consistent description, without the application of some particularly hairy mathematics. Is it that the words used are awkward analogues of what the maths describes? Or is the maths an awkward description of what it happening? (or both). topsquark, benit13, interested and 1 others like this. __________________ ~\o/~
 Sep 16th 2019, 12:10 PM #25 Member   Join Date: Sep 2019 Location: Azores Posts: 32 It seems we have singularities, wave particle dualities, and now what, a wave particle field trinities. The truth is out there somewhere! Maybe its will be SED in a deterministic way at some point in the future or maybe we could STRING along and find an answer there.
 Sep 16th 2019, 01:11 PM #26 Member   Join Date: Sep 2019 Location: Azores Posts: 32 After a bit of googling I cam up with this interesting link. https://www.researchgate.net/post/Is...the_QED_photon It seems Einsteins photon is definitely not the same as the Photon in QED, which might be the route cause of my difficulty. The Photon of QED has more degrees of freedom like a virtual photon. Are people using the term photon instead of virtual photon in QED. Has the term photon now been redefined. Here they use the term virtual photon as transmitting the electro magnetic forces https://www.researchgate.net/post/Ho...irtual_photon2 When talking about photons in QED should we specifically state virtual photon to make it clear we are not talking about Einsteins photons. donglebox likes this.
 Sep 28th 2019, 07:38 AM #27 Member   Join Date: Sep 2019 Location: Azores Posts: 32 A lingering question. The radio wave described by maxwells equations is a continuous polarized wave, this in QED is made up of photons. Photons are individual quanta with specific properties ie inertia frequency spin. Are radio waves actually made up of individual photons?? or is a radio wave a continuous field that conveniently can be mathematically modeled by individual photons?? But is not made up of individual photons????
 Sep 29th 2019, 03:36 PM #28 Senior Member     Join Date: Jun 2016 Location: England Posts: 1,060 While the concept seems strange, we can perhaps accept that ElectroMagnetic waves with tiny wavelengths (Light, X-rays, gamma-radiation) could be described as photons, however it does seem odd to similarly describe EM waves with substantial wavelengths (microwaves, radio-waves) as photons. But they are all variations of the same phenomena, so the same wave / photon duality must apply. interested likes this. __________________ ~\o/~
Sep 30th 2019, 01:43 AM   #29
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 Originally Posted by Woody While the concept seems strange, we can perhaps accept that ElectroMagnetic waves with tiny wavelengths (Light, X-rays, gamma-radiation) could be described as photons, however it does seem odd to similarly describe EM waves with substantial wavelengths (microwaves, radio-waves) as photons. But they are all variations of the same phenomena, so the same wave / photon duality must apply.
I was reading about QED again last night, references to different types of photons, photons being made up of virtual particles, photons having different properties and even radio waves being made up of virtual photons all add to my growing suspicion, that the word photon has expanded its meaning in the last 40 years. ie Einsteins simple photon E=pv is not the same beast as in QED, which it seems can have very flexible properties.

Are the models more mathematical than physical, as indicated in the links above to a research gate discussion.

Thanks for the response.

Sep 30th 2019, 07:36 AM   #30

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 Originally Posted by interested I was reading about QED again last night, references to different types of photons, photons being made up of virtual particles, photons having different properties and even radio waves being made up of virtual photons all add to my growing suspicion, that the word photon has expanded its meaning in the last 40 years. ie Einsteins simple photon E=pv is not the same beast as in QED, which it seems can have very flexible properties. Are the models more mathematical than physical, as indicated in the links above to a research gate discussion. Thanks for the response.
Just for my own clarity I'm not quite sure what you mean by "Einstein's photon" and QED's photon. Yes, Einstein had derived E = pc (v = c since we have a photon) and only used the energy and momentum properties, but what specifically do you mean by a QED photon?

-Dan
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