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Thread: Photons and Magnetism

  1. #1
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    Photons and Magnetism

    Why do magnets, especially magnets repelling each other, not glow? I've read somewhere that the human eye is capable of detecting a single photon. Anybody whose ever done the iron filing thing with magnets knows there is a lot of force; they just really do NOT want to be pushed together. So, if there are so many photons, why can't we read by refrigerator magnets? Why are we able to stand upright outside on a sunny day? Surely the Sun puts out far more photons than any magnetic source most of us will come in contact with, day to day?

    *Clarification: I know nothing really of Faraday. He never held a concert in my*area.
    Last edited by Hypmotoad; 2017-May-19 at 01:26 AM.

  2. #2
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    I don't think that permanent magnets emit photons in the first place. I can't really explain why, though.
    As above, so below

  3. #3
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    A permanent magnet simply has "displaced charges". The individual molecules each have a charge displacement themselves. At one end of each molecule there is a slight positive charge. At the other end of the molecule there is a slight negative charge. When heated and aligned in unison by a strong exterior magnetic field and allowed to cool, the molecules are locked into place and are all aligned the same. The magnetic fields of each tiny magnetic molecule are additive and give the overall magnet a field.
    The field represents potential energy which would be converted into heat if dissipated by unlocking the crystal structure through heating.

    In a static situation such as sitting on a room temperature shelf, no tiny magnets change their position, no field changes occur, no energy is released. No photons are emitted.

    If you heat a magnetized crystal above the Curie point and the tiny magnets relax, the field will disappear and an equivalent amount of heat will be added to the mix. A few photons of infrared heat will be all that is left of a formerly 'permanent' magnetic field.

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    Quote Originally Posted by billslugg View Post
    In a static situation such as sitting on a room temperature shelf, no tiny magnets change their position, no field changes occur, no energy is released. No photons are emitted.
    Surely the OP is asking about a dynamic system, where the magnets are moving relative to each other.

    I'm guessing that there might be some heat generated - i.e. photons in the IR range, but not sure.

  5. #5
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    Quote Originally Posted by DaveC426913 View Post
    Surely the OP is asking about a dynamic system, where the magnets are moving relative to each other.

    I'm guessing that there might be some heat generated - i.e. photons in the IR range, but not sure.
    I'm asking why, when pushing two magnets together, we don't see light becoming more intense as they get closer. Dull red up rough blue,e c.

    Also, thanks to billslugg, I have to ask if there is a such thing as "resting photons"?

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    Why do you think magnets emit photons?

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    Quote Originally Posted by John Mendenhall View Post
    Why do you think magnets emit photons?
    Because apparently, photons are the force carrier for magnetism. See billslug post #3

  8. #8
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    Quote Originally Posted by Hypmotoad View Post
    Because apparently, photons are the force carrier for magnetism. See billslug post #3
    That doesn't necessarily mean they have to be in the visible light range.

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    Quote Originally Posted by Hornblower View Post
    That doesn't necessarily mean they have to be in the visible light range.
    Thank you Hornblower. I've become aware of that, but if look carefully at post #5, you will see that the "WHY" of it is my question. I had thought the OP was clear though.

    Edit: Why do all photons NOT glow? Still not right, ok. Have you ever tried to hold to opposite poles of a magnet together? It's not easy and I cannot figure out WHY so much energy present yet no light?
    Last edited by Hypmotoad; 2017-May-19 at 03:18 AM.

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    Quote Originally Posted by Hypmotoad View Post
    Edit: Why do all photons NOT glow? Still not right, ok. Have you ever tried to hold to opposite poles of a magnet together? It's not easy and I cannot figure out WHY so much energy present yet no light?
    When you are talking about forces you are dealing with virtual photons. They represent quantised interactions between the underlying fields associated with the two magnets so in a sense the reason you cannot see them is because they are not available to be seen. They are one way to describe the field interaction between magnets. When we talk about people seeing a single photon what we are really talking about is seeing an interaction with a very weak but freely propagating excitation to the EM quantum field.

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    Quote Originally Posted by Hypmotoad View Post
    Because apparently, photons are the force carrier for magnetism. See billslug post #3
    This page has a good introduction to the concept of virtual particles:
    https://profmattstrassler.com/articl...what-are-they/
    The best way to approach this concept, I believe, is to forget you ever saw the word “particle” in the term. A virtual particle is not a particle at all. It refers precisely to a disturbance in a field that is not a particle.

  12. #12
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    i thought if you wiggle a magnet up and down then you will generate photons..... just very low frequency ones?
    is that not true?
    (i'm not talking about friction causing heat)

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    Virtual photons can be easily promoted into real photons if there is an energy source available. A real photon can be detected because of the energy that is put into it. This is easier to think about with regular electric forces, rather than magnetic ones. If you have two opposite charges, they will attract, so potential energy will be converted into kinetic energy if you release them. But there is no way to intercept that energy in transit, even though you can think of the charges exchanging virtual photons as the "reason" the charges accelerate toward each other. On the other hand, if you manually shake one of the charges, which involves doing work against the electromagnetic field, it will send out real photons that you could intercept on their way to the other charge. The work you are doing in effect promotes some of the virtual photons into real ones, and when the real photons move energy from one charge to the other, you can intercept that energy in transit, which is what we call a real photon rather than a virtual one. Bottom line, you can't see virtual photons because there is not energy in transit there.

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    I was also going to say virtual photons, but y'all beat me to it.

    Same with the electric force which attracts and repels. It's also mediated by virtual photons. Until lightning strikes, that is.

  15. #15
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    We should probably also mention Unruh radiation, which an accelerating observer interprets as being present and emanating from the "Rindler horizon," but the inertial observer does not observe because they do not register any such horizon. So even the issue of whether a photon is regarded as real or virtual appears to depend on reference frame, although it must be said that all combinations of relativity and quantum physics must be regarded as speculative given that there is no unified theory for both.

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    It looks like light can be affected by fields
    http://www.spacedaily.com/reports/Re...ields_999.html

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    Quote Originally Posted by publiusr View Post
    It looks like light can be affected by fields
    http://www.spacedaily.com/reports/Re...ields_999.html
    Not quite. What's happening there is that the electric field alters the behaviour of the material that light is passing through.

  18. #18
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    Why do magnet attracts or repels each other?

    This concept is one of the fundamental concept in electromagnetism.

    Before we go into the details of this question we must think that why the magnet has magnetism and why it exerts force. Then further we can think about attraction and repelling.

    Initially we learn the things about electromagnetic forces which is one of the fundamental forces.
    Last edited by tusenfem; 2020-Jan-08 at 08:29 PM. Reason: Link redacted by moderator

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