Are photons energy? What is energy, anyway?

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

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

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    Look, this thread is not here for me to teach you quantum mechanics. We're supposed to be discussing your claim that photons are energy, are we not? Can we get to that at some stage?
     
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  3. arfa brane call me arf Valued Senior Member

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    What does "keep" the plates apart then, in your corner of the universe? Do you think it's the charge itself, the "stuff" that flowed into the electroscope?
     
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  5. James R Just this guy, you know? Staff Member

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    Like charges are observed to electrically repel one another. There is a force between the charges on the plates.

    Can we discuss whether photons are energy now?
     
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  7. arfa brane call me arf Valued Senior Member

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    What the hell are you asking me that for?? Isn't that what I said just a few posts ago? You say I'm trolling here . . . what the fuck are you doing then?
     
  8. arfa brane call me arf Valued Senior Member

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    Ah, I see. There's a force keeping the plates apart. Where does this force come from, does it do any work moving these plates apart?
     
  9. arfa brane call me arf Valued Senior Member

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    Don't avoid my question: does the SE need to formulate proton frequencies, or their energy eigenvalues? Are electron orbitals only explained by a system with two oscillators in it, i.e. a pair of coupled oscillators?

    Or not? Please don't assume I don't know the answer, this time, and answer the fucking question.
     
  10. James R Just this guy, you know? Staff Member

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    I couldn't tell what you were saying. So, I explicitly told you I didn't understand what you were getting at, and I asked for clarification.

    Did you actually have a point or a question? What is the relevance of all this stuff about electrons anyway? The question is "Are photons energy". If you think they are, how about you address my direct questions and objections to your contention? Why do you keep dancing around the topic, rather than engaging with it?
     
  11. arfa brane call me arf Valued Senior Member

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    Right now I'm waiting for some kind of answer to my direct question to you, which I think goes to the whole "what is a photon" thing. So please, let's hear about the 2-particle eqn for electron orbitals in elemental hydrogen.
     
  12. James R Just this guy, you know? Staff Member

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    arfa brane:

    Nothing you are asking me is relevant to the thread topic.

    The force comes from the electrical interaction between the charges on the plates.

    It does work as the plates charge up. Once they have a steady charge, movement stops and no further work is done.

    Don't you already know this stuff? We're talking electromagnetism 101 at this point (for some reason).

    When we solve the SE for the hydrogen atom, we are not concerned with the sub-atomic physics of the situation; we are concerned with the atomic physics, namely the electromagnetic interaction between the electron and the proton - at least for starters.

    Therefore, I don't know what you mean by proton frequencies. The energy of the atom is the total energy of the system, consisting of the electrical potential energy of the electron-proton system and the kinetic energy of the electron (assuming that we're working with the approximation that the proton does not move).

    The hydrogen atom has no oscillators in it - not in the simplest Schrodinger description. What falls out of the solution is the wavefunctions of the atom and the corresponding energies that relate to those wavefunctions.

    There. Does that answer your "fucking" question?

    Can we talk about your claim that photons are energy some time soon?
     
  13. exchemist Valued Senior Member

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    Neddy, my answer would be that your question to James and myself has no valid answer, because there is no such thing as "pure energy", any more than there is such a thing as pure momentum, or pure velocity - or pure length!

    What James, Origin and I have all maintained throughout is that energy is an attribute, not an entity. You cannot have a "pure" property existing on its own, fairly obviously.
     
    Last edited: Sep 27, 2019
  14. exchemist Valued Senior Member

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    EXACTLY!

    I begin to suspect Arfa has some sort of mild cognitive impairment. Several times in this thread he has quoted sources that say something different from what he maintains they are saying.
     
  15. exchemist Valued Senior Member

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    This about Schrödinger's equation is tangentially interesting, in a way.

    As most people who have experience of trying to solve problems in physics will know, one of the most powerful ways to analyse a physical system is by means of considering its energy. This is what Schrödinger did, in effect, using the Hamiltonian formulation. https://en.wikipedia.org/wiki/Hamiltonian_mechanics

    The power of this approach is that the eigenfunctions of his equation contain within them all the other information about the system, not just the energy. Just as solving a problem in classical mechanics by recourse to energy allows one to deduce, subsequently, all manner of other results about the system.
    Applying the appropriate operator to these eigenfunctions yields values for all observable properties of the system.

    The fact the eigenfunctions are derived from considering energy obviously does not mean they ARE energy, in some silly way, any more than a classical mechanical system IS energy. Considering energy is, like considering entropy or momentum, a method of problem solving.
     
  16. BdS Registered Senior Member

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    I don’t understand how you guys are defining energy. I find it really easy to understand like this.

    Energy = motion or Kinetic Energy

    Work = a change of motion or Kinetic Energy

    Potential Energy = Potential Kinetic Energy

    All physical forms of energy are fundamentally KE.

    End of story…

    ?
     
    Last edited: Sep 27, 2019
  17. exchemist Valued Senior Member

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    Apart from being off-topic, this is not a very useful way of looking at energy. There is no reason to think any one form of energy is more fundamental than another.

    In fact energy is commonly defined as "the ability to do work", which has the weakness of suggesting work is somehow more fundamental than other forms. But work has at least the benefit of being easily recognised and measured, whereas various forms of internal energy, (heat energy, chemical energy), potential energy, or even kinetic energy, can only be inferred indirectly from other measurements or by calculation.
     
  18. BdS Registered Senior Member

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    How can it be off topic when the tread title is "Are photons energy? What is energy, anyway?"


    There is only one form of energy... KE


    The work is caused by another object/mass transferring KE or momentum to the object/mass being worked.


    Both forms of KE,
    heat energy = motion or oscillation of molecules/atoms.
    chemical energy = motion of particles or systems being moved by field interactions.

     
    Last edited: Sep 27, 2019
  19. exchemist Valued Senior Member

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    Total ballocks.
     
  20. arfa brane call me arf Valued Senior Member

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    Ok, so electric fields 101 includes the lesson that a pair of objects which can hold or store some electric charge interact; in a simple metal foil electroscope, the pair of objects can be the two halves of a rectangular piece of thin metal foil. The interaction pushes the two halves apart because they have inertia, and they stay that way because the forces are equal.

    The work done is explained as a transfer of momentum, say, from the electric field to the matter field aka piece of foil. Equivalently the work is done on the foil by "converting" electrical energy into motion. Or did I miss a really important physics 101 lecture here?
     
  21. arfa brane call me arf Valued Senior Member

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    But you insisted earlier we're dealing with a solution that includes wavelengths for two quanta, deBroglie wavelengths, because the hydrogen atom is an electron plus a proton. Then you say
    . You're saying we consider solutions for the kinetic energy of the electron, for one of, not two of, the particles under consideration in the atom, as you insisted? How peculiar.
     
  22. arfa brane call me arf Valued Senior Member

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    Well, no. Can you give me an example of a simple Schrodinger description, with no oscillators, for the hydrogen atom? I haven't really heard that kind of thing before.
     
  23. arfa brane call me arf Valued Senior Member

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    Here is how I would say what the hydrogen atom's wavefunction is.
    .
    It uses the Coulomb potential as a gauge--a fixed boundary--for the kinetic energy eigenstates of the electron. It's nonrelativistic, you can't solve the Schrodinger field equation for the electron + proton without fixing the proton in space, at the origin, conceptually a pointlike positive charge. Even in just one dimension there are no solutions if you don't.

    You can't easily define a quantum harmonic oscillator without this idea of potential boundaries; I haven't seen any yet.
     
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