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Thread: Mono Pole Position

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    Mono Pole Position

    Can someone explain the basics of magnetic monopoles to me? The Wiki entry made my eyes cross. Please dumb it way down.

    All I got was that they are particles, and have "one north or south pole each". The rest is noise.
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    Well, you can start with that they almost certainly don't exist and can't exist...
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

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    Quote Originally Posted by Trebuchet View Post
    Well, you can start with that they almost certainly don't exist and can't exist...
    OK? Why do you say that?
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    Because I also read the Wikipedia article.
    Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.

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    Quote Originally Posted by Trebuchet View Post
    Because I also read the Wikipedia article.
    Then can you explain it? It's mostly alien to me.
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  6. #6
    According to Maxwell's equations a magnetic field is created by a rotating or moving electric field and always create a north and south poles. Even in materials that have a magnetic field to them they always have a north and south. So if a monopole exists then it might led to a discovery that will change some of the laws of physics.
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    So, any description or explanation of the theory(s) of monopoles themselves? Or are they too speculative?
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    It's a magnet with only one pole. And, according to experts, impossible. If you take a bar magnet, N on one end and S on the other, and cut it in half, you won't end up with an N and an S, you'll just have two smaller magnets, each with N on one end and S on the other.
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    Quote Originally Posted by Trebuchet View Post
    It's a magnet with only one pole. And, according to experts, impossible. If you take a bar magnet, N on one end and S on the other, and cut it in half, you won't end up with an N and an S, you'll just have two smaller magnets, each with N on one end and S on the other.
    Well, yes.

    I'm trying to comprehend it in a little bit of detail, about their theoretical formation and nature. That's what I can't wrap my head around.
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    Quote Originally Posted by Noclevername View Post
    Can someone explain the basics of magnetic monopoles to me? The Wiki entry made my eyes cross. Please dumb it way down.

    All I got was that they are particles, and have "one north or south pole each". The rest is noise.
    This page, I assume: https://en.wikipedia.org/wiki/Magnetic_monopole

    The introductory paragraphs seem reasonably clear to me (right up until it starts getting all mathematical with Maxwell's equations and beyond). Where do you come unstuck?

    Basically, magnetic monopoles would be the magnetic equivalent of electrically charged particles, which are electric monopoles: they have either a +ve or a -ve charge. Similarly, a monopole would have either a N or S charge, but not both.

    The electrical equivalent of a bar magnetic would be a dipole: an object that is positively charged at one end and negatively charged at the other. (These exist and are important in chemistry and various areas of physics.)

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    Quote Originally Posted by Strange View Post

    The introductory paragraphs seem reasonably clear to me (right up until it starts getting all mathematical with Maxwell's equations and beyond). Where do you come unstuck?
    Right about there. Everything from Maxwell on down. The numbers are a blur, but I'm used to that. The words in between however, are (collectively) semantically null to me.
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    I'll rephrase the question. What aside from mathematics, would you tell a young science student if you were told to give them an introductory speech on monopoles?

    ADDED: I don't mean to be so demanding. I'm not asking for a free lecture or anything, just a few hints to help me "get" how such a thing might exist.
    Last edited by Noclevername; 2019-May-21 at 03:12 PM.
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    Stackexchange physics article on magnetic monopoles, existing and not existing, but mainly what they might be good for if they do exist.

    https://physics.stackexchange.com/qu...particles-cant

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    Quote Originally Posted by Roger E. Moore View Post
    Stackexchange physics article on magnetic monopoles, existing and not existing, but mainly what they might be good for if they do exist.

    https://physics.stackexchange.com/qu...particles-cant
    Thank you.
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    I would want to ask a few non-mathematical questions.

    Supposing that there are magnetic monopoles, are they particles analogous to electrically charged particles? How would they interact with other forces. Do they have the variety of other properties that leptons and quarks do? Do they annihilate if they encounter the opposite pole? Do they form short (or even long) lived pairs like positronium? How is magnetic charge quantised?

    The answers may or may not be implied by the sea of maths in the Wiki article, which like others I find impenetrable.

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    Quote Originally Posted by agingjb View Post
    Supposing that there are magnetic monopoles, are they particles analogous to electrically charged particles?
    Yes, presumably.

    Quote Originally Posted by agingjb View Post
    How would they interact with other forces.
    Like other particles do. They could be subject to the strong or weak forces, or they might not be.

    Quote Originally Posted by agingjb View Post
    Do they have the variety of other properties that leptons and quarks do?
    Presumably yes. They could in principle be massive or massless, and they could have spin and other properties like other particles (and I don't think there's any reason why a particle couldn't have both electric and magnetic charge, at least in principle).

    Quote Originally Posted by agingjb View Post
    Do they annihilate if they encounter the opposite pole?
    Could be either way. The north monopole could be the antiparticle of the south monopole, so that they would annihilate like electrons and positrons. But there could also be two particles that are both matter, one of which has north magnetic charge and the other of which has south magnetic charge, so more like the electron and the proton, and in this case they would not annihilate. In the latter case, each of those could possibly have its own antiparticle, which might or might not have opposite magnetic charge.

    Quote Originally Posted by agingjb View Post
    Do they form short (or even long) lived pairs like positronium?
    They should probably be able to.

    Quote Originally Posted by agingjb View Post
    How is magnetic charge quantised?
    Here's an interesting bit. Dirac showed that having electric monopoles (like electrons) in the universe means that magnetic charge would have to be quantised, and that conversely, if magnetic monopoles exist, then electric charge has to be quantised. So it's kind of interesting that electric charge is quantised, even though we've never detected a magnetic monopole.
    Conserve energy. Commute with the Hamiltonian.

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    Quote Originally Posted by Grey View Post
    Here's an interesting bit. Dirac showed that having electric monopoles (like electrons) in the universe means that magnetic charge would have to be quantised, and that conversely, if magnetic monopoles exist, then electric charge has to be quantised. So it's kind of interesting that electric charge is quantised, even though we've never detected a magnetic monopole.
    Maybe they are all down in planetary cores. That's one of the hypotheses I read, anyway.
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    If we suppose that monopoles do not have the predominance of particles over antiparticles of other matter, then when a north encounters a south they will either annihilate or bond. Either way, free monopoles will be rare.

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    The key is the symmetry of Maxwell equations, and of electromagnetic waves in free space empty of electric monopole charges and electric currents.

    A changing magnetic field induces an electromotive field - electric field that gives energy to a charge over a closed circuit.
    A changing electric field acts as "displacement current" and creates a magnetic field just like an actual current does.

    The one difference is that there are also electric charges and electric currents.
    "Magnetic monopoles" are a hypothesis that the symmetry is actually full and we simply happen to live in a region where electric monopoles are common but magnetic monopoles are so rare we have not actually seen any yet.
    One magnetic monopole may have been seen on Valentine's Day, 1982, or it may have been a hoax.

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    So paired antiparticle monopoles would be indistinguishable from a regular magnet? A pole at either end.
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    Quote Originally Posted by Noclevername View Post
    So paired antiparticle monopoles would be indistinguishable from a regular magnet? A pole at either end.
    I donít know if that necessarily follows. If you think of an atom, for example, the individual protons and electrons have a charge, but the electrons are distributed around the nucleus, so you get an essentially chargeless atom. Iím not sure how it would work with magnetic monopoles though.


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    Quote Originally Posted by Jens View Post
    I don’t know if that necessarily follows. If you think of an atom, for example, the individual protons and electrons have a charge, but the electrons are distributed around the nucleus, so you get an essentially chargeless atom. I’m not sure how it would work with magnetic monopoles though.


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    Yeah but protons and electrons are not antiparticles.
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    Quote Originally Posted by Noclevername View Post
    Yeah but protons and electrons are not antiparticles.
    Oops, sorry, I didn't notice the word "antiparticle" when I read the post.
    As above, so below

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    Quote Originally Posted by Noclevername View Post
    So paired antiparticle monopoles would be indistinguishable from a regular magnet? A pole at either end.
    Well, except that the two ends could annihilate each other, so it would probably have a short lifetime, like positronium does.
    Conserve energy. Commute with the Hamiltonian.

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    Quote Originally Posted by Grey View Post
    Well, except that the two ends could annihilate each other, so it would probably have a short lifetime, like positronium does.
    What kind of annihilation products would we be looking at? Anything distinctive (IE detectable)?
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    No requirement for monopole annihilation to produce anything distinctive.
    So: if you have a composite particle with a magnetic dipole moment, how do you ascertain whether the moment is produced by the dipole consisting of magnetic monopoples, or by containing rotating electric charges?

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    Quote Originally Posted by chornedsnorkack View Post
    So: if you have a composite particle with a magnetic dipole moment, how do you ascertain whether the moment is produced by the dipole consisting of magnetic monopoples, or by containing rotating electric charges?
    That's the big question, isn't it? Have we already seen monopole pairs without recognizing them?
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    Quote Originally Posted by Noclevername View Post
    That's the big question, isn't it? Have we already seen monopole pairs without recognizing them?
    I doubt it, because if that chance existed, then surely somebody would write something that would be published in PRL. Believe me, they really are into publishing that kind of stuff...


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    I think part of the reason for people looking for magnetic monopoles is that they are permitted by the standard model, and some of these people feel that "permitted" is synonymous with "required."

    Since spinning charges can produce magnetic fields, magnetic monopoles aren't needed. I'll believe in magnetic monopoles when somebody finds one. I'm not holding my breath.
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    Quote Originally Posted by swampyankee View Post
    I think part of the reason for people looking for magnetic monopoles is that they are permitted by the standard model, and some of these people feel that "permitted" is synonymous with "required."

    Since spinning charges can produce magnetic fields, magnetic monopoles aren't needed. I'll believe in magnetic monopoles when somebody finds one. I'm not holding my breath.
    We can't find one if we don't look. Looking can be motivated by curiosity too. Wanting to find out IF they're real.
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