Magnetic Monopoles

Discussion in 'Physics' started by Wendy, Mar 26, 2008.

  1. Wendy

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    One of the theoretical particals in physics that has yet to be discovered is a Magnetic Monopole. This a particle that has either a North or South pole, but not the other end.

    OK, someone has just given you unobtanium, and it is a unusual magnet indeed. It has a North pole, radiating in all directions. What what you use it for?

    If we could make an electromagnet version that could be aimed in a specific direction the uses would be immediately obvious, a tractor beam comes to mind for example. A magnetic field with the directionality of a laser, that could be turned on and off. I've never read anywhere where they defined what a monopole field would look like.
     
  2. Papabravo

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    Aside from the fact that they would violate Maxwell's Equation which restricts the divergence of the magnetic field to be identically zero; what makes you think that they either exist or could be created?
     
  3. Dave

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    There is the idea, stemming from work by Dirac, that magnetic monpoles do in fact exist giving rise to the idea of "magnetic charge" - with trillions upon trillions of electrons why wouldn't we have magnetic monopoles, they ask.

    Obviously, this would violate the current expression of Gauss' Law of Magnetism (Maxwell's Equations), however there is work to suggest that Maxwells Equations could be modified to allow for the existance of the magnetic monopole (only Gauss' Law of Magnetism and Faradays Laws would need modification to allow for flow of "magnetic charge") - essentially it would provided symmetry in Maxwells Equations, and we all know how much scientists love symmetry.

    Dave
     
  4. Wendy

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    A lot of classic equations turn out to be simplifications of more complex systems. Newton's Laws, for example, were a simplification of the equations Einstein later derived for gravity. They are not invalid, Newtonian gravitational physics was used to calculate the orbits of the Apollo moon landing program, for example, but it didn't adequately cover the orbit of Mercury either. There was a 2% deviation that drove physicists nuts until Einstein's equations came along and showed that the space Mercury orbits in is warped by the gravitational field of the sun, more so than any other planet.

    A lot of Einsteins equations have also been updated as work in quantum physics has left its mark. Einstein didn't like quantum physics, felt it was counterintuitive. This from a man who created special relativity.

    I'm not sure I believe in monopoles either, but for now they remain an open question. With nanotech here something I've thought about is why couldn't you have a sphere of magnetic domains with one pole on the outside, and one on the inside, be created. Not a monopole, but something similar, one pole being hidden. I suspect the field lines (another imaginary concept, but useful) would wrap around each domain, killing yet another lovely idea.
     
  5. Papabravo

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    Dirac was without a doubt a giant in theoretical physics. Is there experimental evidence for the existance of magnetic monopoles? Is this one of those things that requires experiments at energies beyond what can be achieved at CERN or Femilab? I thought the Higgs Boson was about the end of the line for elementary particles.

    I also see nothing in the works of Feynman, Dyson, or Ginzburg on Quantum Electro Dynamics that says anything about them. It has been a while so my memory may be a bit foggy. I'm also pretty sure that the string theorists don't have much to say on this one, but I could be wrong. So could they apparently(ROFL).
     
  6. Dave

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    Diracs work was on something called Dirac Quantisation Condition/Theory.

    The only research I am aware of is by Price et al (http://adsabs.harvard.edu/abs/1975PhRvL..35..487P) and Cabrera (http://prola.aps.org/abstract/PRL/v48/i20/p1378_1), neither of which proved anything conclusive.

    I honestly don't know the details of how this comes about, or how indeed scientists intend to prove it. From my understanding, scientists who really believe in magnetic monopoles do so because of an underlying symmetry in nature, and that quantum mechanics loosely predicts the existence of the magnetic monopole through the work of Dirac.

    Superstring theory (supersymmetry string theory) predicts the possibility of magnetic monopoles and magnetic charge.

    Many scientists, like us engineers, take the existing status-quo as given - Maxwell's Equations work so well, why wouldn't we? Magnetic Monopoles might be something trapped solely in the world of theoretical physics.

    The whole idea of having symmetric Maxwell's Equations with a "displacement magnetic current" is quite pleasing to the eye, but if it is a condition where magnetic_charge = 0 for all but theoretical applications, then it is a rather pointless as a practical exercise.

    Dave
     
  7. Wendy

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    If it were ever conclusively proved I suspect it would make big news. I'm kinda curious about possible applications, which may be way premature. I'm not even sure what such a particles field would look like. It's one of those things that have been around physics for a very long time.

    Such a particle, passing through a coil, would produce a DC pulse, which is a signature for it, while a conventional magnet produces an AC pulse.

    With nanoelectronics just starting to work on individual spins on electronics it is possible we aren't too far away from either making them on demand or disproving their possibility.
     
  8. Dave

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    I expect it would make news too. The magnetic monopole is (theoretically) analogous to electric charge, maybe that indicates behavioural characteristics and where the potential applications lie.

    Dave
     
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