Are photons energy? What is energy, anyway?

Discussion in 'Physics & Math' started by origin, Aug 19, 2019.

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  1. arfa brane call me arf Valued Senior Member

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    Almost correct. An excitation of a quantum field, is a matter-field; or it's a matter-wave.
    Since clearly the quantum field is not material until it "has" an excitation. Ok?
     
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  3. arfa brane call me arf Valued Senior Member

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    Here you both support the notion that the change in energy IS a photon. Why is there an electromagnetic field (like in electronics), and can there be such a field anywhere if there are no charged particles to generate it?
    Or are you going with the idea that photons have their own "independent" quantum field?
     
    Last edited: Sep 26, 2019
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  5. arfa brane call me arf Valued Senior Member

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    I say the argument comes down to this:

    On the one hand we have thermodynamics, "thermal" or "thermalised" states of matter, on the other theories that say everything is particles interacting with fields, then generally the particles ARE also fields.
    Supporting the latter theories is the partial unification of the weak interaction and the electromagnetic interaction. Both based on the idea that the interactions are symmetries of spacetime, some of them "acting" at much smaller distances, subatomic ones.

    So we have SU(2) x U(1). Field symmetries. Thermodynamic states are really distributions of "energy", per particle in a system of particles. You can "choose" that the particles are classical (so they don't act on each other "at a distance", like charged particles do).
     
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  7. Neddy Bate Valued Senior Member

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    To Arf, if you had to answer these questions with either "Yes" or "No", what would you answer?

    1. Can all photons be categorized as pure energy, and nothing else?

    2. Can all pure energy be categorized as photons, and nothing else?

    ----------------------

    To James R and/or exchemist, if you had to answer this question with either "Yes" or "No", what would you answer?

    1. Can all pure energy be categorized as pure energy, and nothing else?

    ----------------------

    Arf, I have tried my best to make the questions to both parties as fair as I possibly could. You have two questions because you are in the unfortunate position of claiming that photons are pure energy, and pure energy is photons. If you are not claiming both, then you are admitting they are not the same thing as each other. So you must answer "Yes" to both, otherwise your claim is virtually meaningless. (Other than perhaps to say that the closest thing we have to "pure energy" is photons, which is still very much debatable since kinetic energy and gravitational potential energy seem to be just as close to "pure energy".)

    The other side is only claiming that pure energy is pure energy, so there is only one question for them, to which they obviously must answer "Yes".
     
  8. arfa brane call me arf Valued Senior Member

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    I don't recall having anything to say about "pure" energy. I'm more in the group that says energy is a thing you can define, once you have an "interaction" defined.
    And that you don't need "pure" energy, energy of a field or of an interaction does the job already.

    Consider the modern-day answer to the question, why does light travel at c in a vacuum? Which is, it doesn't interact with the Higgs field.
     
    Last edited: Sep 27, 2019
  9. Neddy Bate Valued Senior Member

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    Perhaps you'd be more comfortable answering these less detailed versions of the questions then?

    1. Can all photons be categorized as energy?

    2. Can all energy be categorized as photons?



    Consider your words:

    You saying, "Energy of a field," makes energy a property of a field.

    You saying, "Energy of an interaction," makes energy a property of an interaction.

    This puts you on the same side as James R and exchemist, who are the ones saying that energy is a property.
     
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  10. arfa brane call me arf Valued Senior Member

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    Yeah, but only sort of. See if you can spot the difference between what they keep saying, and what I'm saying.

    My version, once again, is that particles have energy because they get it from interactions, but these interactions are also particles.
    Or conversely it seems but equivalently, fields have energy if they interact with other fields. Energy, whatever it really is, appears to conform to specifications as a physics tool. Is it real is the same question as does a pair of electrons really exchange a photon.

    Consider a universe containing a single electron in a normal spacetime. Then this electron has an electric field around it; if the electron accelerates, the local distortion in this field can propagate as "free" electron-field energy. QED (see also the lepton matter-field eqn of Dirac).
     
  11. James R Just this guy, you know? Staff Member

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    arfa brane:

    You don't read your own quotes, do you? Or else, you don't understand what they are saying.

    In this connection, physicists speak of matter fields, and speak of particles as "quantum excitations of a mode of the matter field"
    In other words, the particles are not fields, but excitations of fields. Like I said.

    Aug 20, 2015 - Atoms are made of protons, neutron, and electrons. ..... which in turn gives rise to different elementary parts (matter field and force field).
    This does not say that atoms, protons, neutrons or electrons are fields.

    The quantum mechanical wave function was taken to represent the field of the electron, i.e., a matter field.
    Field of the electron. Which implies that the field is something associated with the electron, not the electron itself.

    Apparently, I grasp the basics of QFT better than you do. I assure you, I've studied enough of it to be very far from thinking I understand it all.

    What you pay for, ultimately, is all that coal being burnt, and those generators and power lines and stuff being maintained for your benefit. Indirectly, the measure of the resources that were consumed to provide your house with electricity is the energy supplied to your house. Somebody moved a number from the "power station" column in the Energy table to the "arfa brane's house" column, and then they issued you will the appropriate bill. No "energy stuff" moved from the station to your house when you turned on your TV.

    I haven't leapt to the conclusion. I deduced it from your postings. Your confusion is clear to almost everybody reading this thread, apart from yourself. You're somehow still (after 350 posts) laboring under the delusion that energy is stuff.
     
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  12. James R Just this guy, you know? Staff Member

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    No.
     
  13. James R Just this guy, you know? Staff Member

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    Particles have energy. Which implies that particles are not energy.

    As for the statement that interactions are particles, that's another basic category error. You really are all at sea with this stuff.

    Fields have energy. Which implies that fields are not energy.

    Given your confusion, I don't see much point trying to talk to you about what "real" means, so I'm not touching this.

    Your statement makes no sense.

    You start by saying that the electron has an electric field. Okay. Then you talk about the field distorting. Okay. Then you talk about that distortion propagating. Okay. So let's take stock at this point: what is propagating is a distortion in a field. Right? But then you end with the non sequitur that the distortion in the field has somehow turned into "electron-field energy". How and when did that happen? How did a field turn into a number?
     
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  14. James R Just this guy, you know? Staff Member

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    I liked your first version better, and I also note in passing that arfa brane had no answer.

    As I understand his position, he thinks photons are "pure energy" and nothing else, because if he thought there was a "something else" that they were, then he would have conceded the point that photons are not pure energy by now.

    He blathers on about fields and QFT and stuff. It is possible that he thinks quantum fields (e.g. matter fields) are also "pure energy and nothing else".

    It's an unsustainable position, for reasons I first gave hundreds of posts ago.

    If a photon, or a QFT field, or whatever, is really nothing but "pure energy", then "pure energy" must necessarily have all of the properties that photons have, or that quantum fields have. Clearly, though, it has nothing of the kind.

    At this point in the discussion, I'm starting to think that arfa is just trolling to string the discussion along for his own amusement. It's either that or he lacks the ability to understand a logical argument.
     
  15. arfa brane call me arf Valued Senior Member

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    7,832
    Since I've said nothing about "pure energy", I can seriously dispute everything you say here. I can still assume then, that you don't know or understand a word of field or gauge theories? I kinda thought we were talking about photons and electromagnetic energy. About which you've said FA that amounts to a coherent argument.

    For instance, whether infrared photons raise or lower temperature; you made the obvious error of replacing the "stuff" that the photons interact with, with some molecules "colliding" like classical particles. I have answered that question he posted, you dick. I don't like repeating myself, but, it seems to be an inevitable conclusion that electromagnetic energy is a form of . . . energy! so is gravitational energy . . .

    And we've discussed the Doppler effect, so energy is relative because frequency is relative to a direction of propagation, from a fixed or moving point. So what IS electromagnetic energy relative to? It's relative to two charged particles, which may or may not be in relative motion.
     
    Last edited: Sep 27, 2019
  16. arfa brane call me arf Valued Senior Member

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    Explain why the Schrodinger eqn was developed to explain/predict electron orbitals in hydrogen? In its form as an electron (lepton) orbital or resonant state, it's a field equation, the field is the electron. Remember?

    The equation has "energy" eigenvalues for the electron field = matter field . . .

    Or, in your version the eigenvalues are "associated with" the electron orbitals, not with the electron "itself".
     
    Last edited: Sep 27, 2019
  17. arfa brane call me arf Valued Senior Member

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    7,832
    But somehow watching TV when it's off isn't that absorbing. Pun intended.
     
  18. arfa brane call me arf Valued Senior Member

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    I hope you've seen an electroscope. When there's a charge present you get some separation, it persists or doesn't "leak away" and the separation persists--a force pushes two objects apart because they are "charged".

    Ok, where does the energy come from that keeps the objects separated? What does it have to do with your understanding of a field, i.e. an electric field?
     
  19. James R Just this guy, you know? Staff Member

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    arfa brane:

    Okay then. You are now saying that photons are not just "energy", but they are "electromagnetic energy", which is somehow different from plain vanilla energy.

    So, does this "electromagnetic energy" of yours have all the properties that photons have, then? Does it have polarisation, and a wavefunction, and a frequency, and all that? If so, why do we just say things like "The photon's energy is 1.2 eV." Why do we never see statements like "the polarisation of the photon energy is vertical" or "The wavelength of the energy is 12 metres"?

    If you think that "electromagnetic energy" is different in kind from something like, say, "gravitational potential energy", then you'll be able to tell me, presumably, what properties gravitational potential energy has that are different from the properties that electromagnetic energy has. Moreover, you'll be able to explain how electromagnetic energy can somehow turn into gravitational potential energy, or vice versa (because, as we know, you can convert one to the other).

    I look forward to your clarification on these matters.

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    Assume whatever you like. You're the one who ends up looking like the fool.

    There was no error.

    The Schrodinger equation was developed because classical models could not explain things like the emission spectra of atoms, including hydrogen.

    The equation is a wave equation. It operates on wave functions. In the case of hydrogen, the wavefunction describes the atom, not just the electron.

    The eigenvalues (of energy) are associated with the total energy of the atom in various quantum states.

    You speak as if you know this stuff, but then you come out with misguided descriptions of how the SE applies to hydrogen. You say you're an expert on quantum field theory, but here you are getting the SE wrong. What's the story?

    No energy is required to keep the plates separated, provided no charge is leaking away.

    The energy to charge the plates in the first place usually comes from the electric field of a statically-charged object of some kind.

    But this electroscope stuff is just another attempt at diversion on your part, isn't it?
     
  20. arfa brane call me arf Valued Senior Member

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    I'm not wrong.

    The reason is, you consider the proton in the atom to be at rest, the electron then is in a potential well. The potential goes into the wave equation as . . . potential energy.
    It's what accounts for the boundary of the solution(s). What does it represent? It represents the energy in the matter-field of a proton, as the electron sees it. You say you understand this stuff.
     
    Last edited: Sep 27, 2019
  21. arfa brane call me arf Valued Senior Member

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    7,832
    You're saying here, the energy keeping the plates apart is in this field of charge . . .?
    And you agree that, the charge has to flow into something first? It does this quite passively once you have a "charged" object it can flow out of?
     
    Last edited: Sep 27, 2019
  22. James R Just this guy, you know? Staff Member

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    You keep saying that, but you keep making mistakes.

    Potential energy is a property of the system as a whole, i.e. the proton and the electron making up the atom. You said the wavefunction described the electron only. That was wrong.

    It is clear that one of us understands this stuff, while the other has - let us say - a somewhat confused partial understanding.

    Energy doesn't keep plates apart. Energy is not stuff that can keep stuff apart.

    What's wrong with you? You dance and skip around the central issue, over and over again. Why can't you face it head on?

    Sorry, I don't understand what you're saying there. For an electrically neutral object to become charged, charge has to either flow onto it or off it. Do you disagree?
     
  23. arfa brane call me arf Valued Senior Member

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    7,832
    For god's sake. You're quite sure electron orbitals are described by a two-particle equation? The equation has to account for the "frequency" of the proton as well as the electron?
     
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