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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    Right, it's the radiation that ups the temperature (which isn't stuff). When you burn yourself it has nothing to do with temperature or heat energy, because they aren't stuff.
    I see. So if I build a receiving antenna, I shouldn't confuse the energy it gets from an EM broadcast signal with the signal itself.
     
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  3. arfa brane call me arf Valued Senior Member

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    So, you mean heat is really interactions between molecules; but these interactions must be quantum interactions, unless molecules are classical, not quantum systems?
    So the flow of heat is a flow of quantum interactions, which we can say are discrete transfers of energy/momentum?

    But I'm not as smart as you, maybe I don't really understand any physics.
     
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  5. arfa brane call me arf Valued Senior Member

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    Wow, physics 101 all over again!
    Well, 1) depends on a certain context I feel. But generally if the surface of the pond can be free of waves, then the waves aren't the pond.
    2) A propagating wave is a form of energy, if you can convert the wave energy into another form, like say an electric current. In support of this hypothesis, I submit the proposed wave energy systems that engineers would like to build to generate electric power.
    3) It has energy, it also has an energy wave in it which you can define rigorously.
    4) See 2. The question is confusing, do you mean can the energy in a wave not be energy? that's ridiculous.
     
    Last edited: Sep 28, 2019
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  7. arfa brane call me arf Valued Senior Member

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    Ok. What do you think a U(1) quantised field is? Or U(1) charge? This is standard QFT stuff.

    And yes, this is stuff I think you seriously misunderstand, Mr smart guy.
     
  8. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Thought it was suitable here looking at post # 388

    Care to say what I missed? or feel free to cut / correct / paste

    Not To Be R?

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  9. origin Heading towards oblivion Valued Senior Member

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    Not quite.
    Temperature is the measure of the relative amount of translational kinetic energy of a substance.
    Heat is the transfer of energy from a high temperature substance to a lower temperature substance.
     
  10. arfa brane call me arf Valued Senior Member

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    A photon is a quantised field, James. The vacuum is where virtual particles are created and annihilated; virtual particles with charge are what screens the bare charges of real electrons, positrons, and other particles with U(1) charge, James.
    A professor emeritus tells us the vacuum is the underlying quantum field for all the particles (forms of energy) that we know about; you disagree with him.

    You are wrong about fields; the field you make great pains to point out is "associated with" a photon, correcting me several times, is the photon.
     
  11. origin Heading towards oblivion Valued Senior Member

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    21 pages and over 400 post and you still think waves are energy. Astounding. This is getting embarrassing. At least paddo ran away when he realized he was wrong. You have taken the trumpian path and doubled down on your error. Weird.
     
  12. exchemist Valued Senior Member

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    Not only that but he also thinks a photon is both energy and a field. So that means he must think a field is energy. So now we have that not only is a field energy but that waves in the self-same field are energy too.
     
  13. arfa brane call me arf Valued Senior Member

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    No, I still think waves are a form of energy. See if you can spot the difference.
     
  14. arfa brane call me arf Valued Senior Member

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    A photon is a quantised field. A field has energy in it--see Einstein's papers. Waves in a field carry field energy from place to place.
     
  15. origin Heading towards oblivion Valued Senior Member

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    I don't spot the difference. As far as I know there are many forms of energy; kinetic, potential and heat for instance, all of those can be correctly called energy or a form of energy.
    How are waves a form of energy? Are they a form of energy but not energy? Please explain.
     
  16. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    So
    something has a temperature (translational kinetic energy) which when some leaves the substance to move to a substance with lower (translational kinetic energy)
    on the way over IT (the translational kinetic energy on the way over) is (called) heat
    OR
    the the transfer (the action) itself is called heat?

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  17. James R Just this guy, you know? Staff Member

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    arfa brane:

    I walked you through this before. Look, here's the electrical potential energy term for the hydrogen atom, which we put into the Schrodinger equation:
    $U = -\frac{e^2}{4\pi \epsilon_0 r}$
    See that $e^2$ term there? One of those $e$ factors is the charge on the proton, while the other $-e$ factor is the charge on the electron.

    Also, see that $r$ in there? That is the distance between the proton and the electron. The fact that there is an $r$ there tells you that this energy term is a configuration energy that has something to do with the interaction between the proton and the electron.

    If you pretend the proton isn't there, you can't write down that term, and if you can't write it down then you're no longer solving the SE for hydrogen.

    As for the "ideal situation" you refer to, at this point I have explained the approximation to you three times. If there's something you still don't understand, then a smart person in your position would ask some questions to try to fill that knowledge gap. But not you. Why is that?

    I pointed out exactly where you went wrong, in detail, in each case where you presented a quote and misinterpreted it.

    If there was residual disagreement after I pointed out your errors, you could (a) ask questions to try to resolve the disagreement, or (b) try to show why you were right and I was wrong. But you didn't do either of those things. Why not?

    How are those 20 questions coming along? Any progress yet?
     
    Last edited: Sep 29, 2019
  18. James R Just this guy, you know? Staff Member

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    arfa brane:

    That "nothing to do with" in that sentence is weasel words. Of course burning yourself has something to do with temperature and heat. My point, again, is that a mathematical abstraction like heat or temperature cannot cause a burn.

    Right! I'd like to think you're understanding something at last, but then in the following posts it becomes clear that you've made no progress.

    No. I explicitly and repeatedly said that heat is energy.

    What's wrong with you? Is your "arfa brane" name chosen because you actually have some kind of brain injury or impairment? If that is the
    case, I'll be very sorry to hear it, but I'd also say to you that this might be the reason you can't follow the discussion properly. Please let me know, because I don't want to go hard on you if your failure to follow the conversation thread is due to something beyond your control.

    A "flow" of heat is a "flow" of energy. Of course, energy, being a number, doesn't really flow; that's a metaphor.

    Don't be too hard on yourself. I think it's probably more a case that you know a little physics, but you've carried around a lot of basic misconceptions for a long time and you're finding it hard (or maybe impossible) to let them go.

    On the other hand, you could be right. Maybe you're not as smart as me. Like the sporting field, the intellectual playing field is not an even one.

    Also, we all have different skills, and we're all educated to different degrees in different things. You might be great at painting, or at analysing poetry, or at biology, due to natural talent combined with training and education. I happen to be good at physics, due to natural talent combined with training and education. Also, practice - lots of practice. There's that whole 10000 hours thing, and so on.

    I see you got as far as question 4. Did it get too hard after that? Or do you just need more time to answer the other 16 questions? I thought it wouldn't be hard.

    Interesting that you can't give a simple "yes/no" answer to whether a wave in a pond is the same as the pond. But it looks like you've almost grasped that there is a difference. What will it take to get you over the line?

    Lots of dancing around, but at the end of the day I don't think you answered the question, which was "2. Is a water wave a "form of energy", or is it water?"

    So, what's your answer? Is a water wave made out of energy, or is it made out of water?

    Okay, a water wave has energy, according to you. That was the lead-in question to the big one:

    "4. If a water wave has energy, does that mean that it can't be energy?"
    If I have eyes, does that mean I can't be eyes?
    If I have height, does that mean I can't be height?
    If a water wave has energy, does that mean a water wave can't be energy?

    What's confusing you?

    Nice try, but I refuse to go off on another irrelevant tangent. If you want to know what a U(1) quantised field is, go look it up. I have no interest in trying to teach you QFT.

    If you think this U(1) field stuff is relevant to the question of whether photons are energy, you need to make the link.

    We haven't discussed any of that, so I don't see how you reach the conclusion that I misunderstand it.

    Is a ripple in a pond the pond? Just above, you were inclined towards the idea that the ripple is not the pond. Have you changed your mind in the space of half a post?

    I would point out to the emeritus professor that a vacuum is a void, empty. Space is full of quantum fields of various kinds.

    Mind you, I am quite comfortable with the professor talking about the "energy of the vacuum" and "quantum fluctuations of the vacuum" and such things, because I understand that what he is really referring to in such cases is not the vacuum itself, but the fields in the vacuum. (Which, incidentally, makes the vacuum not a vacuum. A vacuum with stuff in it is not a vacuum. But language is flexible.) I'm willing to forgive the professor his language shortcuts in this instance.

    You keep saying this, but you never explain why I'm wrong. I have given you reasons why a photon is not a field. One obvious reason is that the field extends throughout space, whereas the photon is reasonably well localised. Another is that photons are excitations of a field, not the field itself. I have explained to you that the ripple is not the pond, over and over again, but you apparently find it hard to grasp the distinction.

    Have you any reason why you believe that a photon is a field?
     
  19. James R Just this guy, you know? Staff Member

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    Why play games?

    You are now making the silly claim that a "form of energy" is not "energy".

    Tell us why a form of energy is not energy, if you can. I dare you.
     
  20. arfa brane call me arf Valued Senior Member

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    Let's start with the assumption that if A is a form of energy, it can be converted into B which is a different form of energy.

    So if A is say, wind energy, it can be converted into electrical energy--you might have heard of wind turbines.
    If A is wave energy, like in ocean waves, it can also be converted into electrical energy.
    If A is energy in water flowing down a river, it can be converted into electrical energy, exhibit A the Hoover Dam. In this case the water is "converting" gravitational energy into a bulk flow of water, so there's a pressure transverse to the, ah, gravitational field.
     
  21. arfa brane call me arf Valued Senior Member

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    The motion or flow of heat has long been understood as the individual motions of molecules, atoms, ions, etc. Why does a wire heat up when electric current flows through it? It's called the conversion of electrical energy into heat energy, but what actually happens, how do electrons heat metal atoms? I'm pretty sure I understand what happens.
     
  22. arfa brane call me arf Valued Senior Member

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    And I explained to you before that it's necessary to fix the Coulomb potential, because you "work in" the Coulomb gauge, and fix the proton's charge (at an origin).
    Or it tells you there is a radial distance, in spherical coordinates, when the proton is . . . fixed. This is a gauge choice.
     
    Last edited: Sep 29, 2019
  23. arfa brane call me arf Valued Senior Member

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    I know what the U(1) field is, thanks. Why don't you go look it up, maybe while considering you possibly don't understand as much as you tell yourself you do?
    I still see no advantage in adapting the philosophy "energy isn't stuff, energy is a number". It has physical units. Work energy is force times distance. Forces and distances are not numbers; why does their product suddenly become "just a number"?
     
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