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Thread: If photons are the carriers of magnetism, then..

  1. #1 If photons are the carriers of magnetism, then.. 
    Time Lord
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    For a magnet, like say a rare Earth magnet, what kind of photon is it? Is it a really high frequency photon, low frequency, or is it a "virtual" photon with no frequency attribute at all?


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    Moderator Moderator Markus Hanke's Avatar
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    They are virtual photons, or rather a "cloud" of virtual photons around the magnet. At least that is my understanding of it...?


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    Forum Bachelors Degree Kerling's Avatar
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    In rare earth magents, magentism is (generally theorized to be ) governed by spins. The angular momentum is what is responsible for magnetism. Photon's aren't really the carrier of magnetism, or at least not more then electrons are the carrier of electricity.
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    I think you are off base when you think of magnetism as requiring a "carrier". Magnetic force is more like gravity. I think you are better advised to think in terms of a warping of space caused by the presence of magnetized mass.
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    Moderator Moderator Markus Hanke's Avatar
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    Quote Originally Posted by Sealeaf View Post
    I think you are off base when you think of magnetism as requiring a "carrier". Magnetic force is more like gravity. I think you are better advised to think in terms of a warping of space caused by the presence of magnetized mass.
    Err no, gravity and magnetism and distinct phenomena. While gravity is well described by space-time curvature, magnetism is not - it is based on Maxwell's Equations, and QED on a micro-level.
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    Quagma SpeedFreek's Avatar
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    I think perhaps Sealeaf was trying explain how both gravity and electromagnetism can be thought of as static fields.
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    Moderator Moderator Markus Hanke's Avatar
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    Quote Originally Posted by SpeedFreek View Post
    I think perhaps Sealeaf was trying explain how both gravity and electromagnetism can be thought of as static fields.
    Ok then, if that's the case then yes, they are both static fields. It's just that those fields are of a different nature and behave somewhat differently.
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    Forum Bachelors Degree Kerling's Avatar
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    Quote Originally Posted by SpeedFreek View Post
    I think perhaps Sealeaf was trying explain how both gravity and electromagnetism can be thought of as static fields.
    I can hardly call magentism in a rare earth garnet as static. Spin dynamics make up, well, more or less the entire field (of science). Solid state magnetism is governed by angular momentum. (that is both L and S) Their relation to light is therefore governed by the (more or less) Optical interactions, that are relevant till a certain order of size. And therefore the general behaviour between light and magnetism in rare earth garnets are rarely direct.
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    Quagma SpeedFreek's Avatar
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    All rare earth magnets produce static (electro)magnetic fields.
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    Forum Bachelors Degree Kerling's Avatar
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    Quote Originally Posted by SpeedFreek View Post
    All rare earth magnets produce static (electro)magnetic fields.
    But the process that macroscopically produce this field can hardly be called static!
    By the way how about anti-ferromagnetic materials.
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  12. #11  
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    Quote Originally Posted by Sealeaf View Post
    I think you are off base when you think of magnetism as requiring a "carrier". Magnetic force is more like gravity. I think you are better advised to think in terms of a warping of space caused by the presence of magnetized mass.
    A lot of physicists believe gravity is carried by some kind of "graviton" as its carrier. So if photons are the carriers of magnetic fields, then it makes you wonder how these special photons are capable of causing attraction, when all the other photons we observe in nature don't (or they only generate a very very small amount from their energy exerting gravitational attraction).

    So, I'd really like to understand how the theory works. Even if the theory isn't true. It would be nice to know why anyone believes it, and what the mechanics are that would make it work if it were true.
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    Moderator Moderator Janus's Avatar
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    Quote Originally Posted by kojax View Post
    Quote Originally Posted by Sealeaf View Post
    I think you are off base when you think of magnetism as requiring a "carrier". Magnetic force is more like gravity. I think you are better advised to think in terms of a warping of space caused by the presence of magnetized mass.
    A lot of physicists believe gravity is carried by some kind of "graviton" as its carrier. So if photons are the carriers of magnetic fields, then it makes you wonder how these special photons are capable of causing attraction, when all the other photons we observe in nature don't (or they only generate a very very small amount from their energy exerting gravitational attraction).

    So, I'd really like to understand how the theory works. Even if the theory isn't true. It would be nice to know why anyone believes it, and what the mechanics are that would make it work if it were true.
    Just like electromagnetic forces being mediated by virtual photons, gravity would be mediated by virtual gravitons in any quantum theory of gravity. The graviton itself is a quantum of gravitational radiation (gravity waves) while the photon is the quantum of electromagnetic radiation (e.g. Light).

    Quantum field theory deals with the electromagnetic force, we do not as of yet have a quantum theory for gravity.

    The reason that we expect that there should be a quantum theory for gravity is that otherwise it would be the only hold-out among the forces, and we hope that such theory could unite GR and QM.
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    I am admittedly an amature in physics, but it seems premature to talk of carriers of magnetism and of gravity without some independent evidence of their existence. That is evidence other than the fields we are seeking to explain. To talk of "photons" of magnetic force, that behave unlike any other sort of photons and whoes existence is only testified to by those un-photon like behaviors is theorising in the absense of evidence. The word "photon" is being used in advisedly unless you have evidense of the existence a discrete packet of energy that has the desired effects. To me this conversation is like " What kind of cat is it that likes to swim on the surface of ponds and will fly away if startled?" The obvious answer is," That is no kind of cat , that is a duck."
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    Forum Bachelors Degree Kerling's Avatar
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    Also I would like to remind everyone that Bohr once proved that according to classical physics (Maxwell etc.) ferromagnetism cannot exist! (from a random collection of charges)
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    Moderator Moderator Markus Hanke's Avatar
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    Quote Originally Posted by Sealeaf View Post
    I am admittedly an amature in physics, but it seems premature to talk of carriers of magnetism and of gravity without some independent evidence of their existence. That is evidence other than the fields we are seeking to explain. To talk of "photons" of magnetic force, that behave unlike any other sort of photons and whoes existence is only testified to by those un-photon like behaviors is theorising in the absense of evidence. The word "photon" is being used in advisedly unless you have evidense of the existence a discrete packet of energy that has the desired effects. To me this conversation is like " What kind of cat is it that likes to swim on the surface of ponds and will fly away if startled?" The obvious answer is," That is no kind of cat , that is a duck."
    I suggest you have a read here for starters, and then perhaps work your way through some of the references given at the end of that article :

    Virtual particle - Wikipedia, the free encyclopedia

    There is also quite a list of experimental and observational evidence for their existence.
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    Moderator Moderator Markus Hanke's Avatar
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    Quote Originally Posted by Kerling View Post
    Also I would like to remind everyone that Bohr once proved that according to classical physics (Maxwell etc.) ferromagnetism cannot exist! (from a random collection of charges)
    That's because he treated the electron as a classical particle, and didn't realize that it has an intrinsic magnetic moment due to its half-integer spin. He couldn't have known any better at the time.
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  18. #17  
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    Quote Originally Posted by Janus View Post
    Quote Originally Posted by kojax View Post
    Quote Originally Posted by Sealeaf View Post
    I think you are off base when you think of magnetism as requiring a "carrier". Magnetic force is more like gravity. I think you are better advised to think in terms of a warping of space caused by the presence of magnetized mass.
    A lot of physicists believe gravity is carried by some kind of "graviton" as its carrier. So if photons are the carriers of magnetic fields, then it makes you wonder how these special photons are capable of causing attraction, when all the other photons we observe in nature don't (or they only generate a very very small amount from their energy exerting gravitational attraction).

    So, I'd really like to understand how the theory works. Even if the theory isn't true. It would be nice to know why anyone believes it, and what the mechanics are that would make it work if it were true.
    Just like electromagnetic forces being mediated by virtual photons, gravity would be mediated by virtual gravitons in any quantum theory of gravity. The graviton itself is a quantum of gravitational radiation (gravity waves) while the photon is the quantum of electromagnetic radiation (e.g. Light).

    Quantum field theory deals with the electromagnetic force, we do not as of yet have a quantum theory for gravity.
    So, they are "virtual" photons? Not real photons? They don't have the properties of a normal photon, such as a frequency or related energy?

    I guess if you move toward or away from the field source of a magnetic field, then the field strength would change in your vicinity, and that would be kind of like getting hit by a photon of a frequency that corresponds with the amount of time it took the field to change.... Except of course it's only one half of the photon (only the positive or negative part.)

    I know you academic types hate me to go guessing about stuff like that, but I need to narrow the question somehow. And please don't ever think I don't appreciate your willingness to answer, or that I'm trying to compete with you or something.
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    Forum Bachelors Degree Kerling's Avatar
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    Quote Originally Posted by Markus Hanke View Post
    That's because he treated the electron as a classical particle, and didn't realize that it has an intrinsic magnetic moment due to its half-integer spin. He couldn't have known any better at the time.
    Exactly making magnetism an essential quantum mechanical effect.
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    Quote Originally Posted by kojax View Post
    So, they are "virtual" photons? Not real photons? They don't have the properties of a normal photon, such as a frequency or related energy?
    I guess if you move toward or away from the field source of a magnetic field, then the field strength would change in your vicinity, and that would be kind of like getting hit by a photon of a frequency that corresponds with the amount of time it took the field to change.... Except of course it's only one half of the photon (only the positive or negative part.)
    Correct, they are virtual photons, and as such do not have all ( only some ) of the same attributes as "real" ones. See here :

    Virtual particle - Wikipedia, the free encyclopedia
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