Monopoles and Magnetricity 67
szotz writes "Although there was once a hint from a cosmic ray experiment (on Valentine's Day, no less), no one's found any solid evidence of monopoles (unpaired north and south magnets) flying around the cosmos. But physicists did find monopole-like quasiparticles in some exotic crystals in 2009. One of the discoverers has an article this month in IEEE Spectrum that looks at how the particles were found and what's happened since. They might seem like a wacky curiosity, but the author says we shouldn't write them off — they might one day make useful new 'magnetronic' devices."
I thought... (Score:4, Funny)
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Wasn't it that he started to get into it in a phone interview, but that was when Kripke pranked him and filled his office with helium?
So he never got to finish explaining it.
Or is my episodic memory incorrect?
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Wasn't it that he started to get into it in a phone interview, but that was when Kripke pranked him and filled his office with helium?
So he never got to finish explaining it.
Or is my episodic memory incorrect?
I couldn't tell if he stopped talking, or if his voice just shifted up beyond my range...
Was there something about a "nozzle" involved in monopoles?
i know of one (Score:1)
Microsoft is a convicted monopole, aren't they?
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*golf clap*
Read Niven... (Score:1)
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Monopole Magnets (Score:3, Funny)
Requires Superstring Theory, Silksteel Alloys
Leads to Nanominiaturization, Unified Field Theory
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Re:Monopole Magnets (Score:5, Informative)
Re:Monopole Magnets (Score:5, Informative)
So monopoles actually only require Maxwell's equations and would lead to an explanation of why charge is quantized.
Not, not really. Maxwell's equations, in the known form, do not allow for magnetic monopoles. They are explicitly forbidden by "div B = 0". However, they could very easily be changed (symmetrized - so they would look the same for electric and magnetic fields) to account for them.
So just from Maxwell's equation you can't disprove the existence of monopoles, but you can't prove them either.
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Maxwell's equations, in the known form, do not allow for magnetic monopoles.
Adding the possibility for a non-zero magnetic charge into Maxwell's equations does not stop them being Maxwell's equations anymore than changing the value of the permittivity of free space due to a more accurate measurement would stop them being Maxwell's equations. The zero in 'div B = 0' is an experimentally observed number and not fundamental to the theory in the same way that the CP violating term in QCD is experimentally observed to be zero or the right handed coupling of the weak force is observed t
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And permits building magtubes, don't forget that.
Magnetism = relativistic electricity? (Score:5, Interesting)
Question for any physicists in the audience: I have long heard that magnetic forces can be described as relativistic effects of classical electricity (here, for instance [wikipedia.org]). How do magnetic monopoles fit into this? Are they are purely quantum mechanics/QFT concept, or is there some way to describe them classically that makes it clear why so many people are expecting to find them?
Re:Magnetism = relativistic electricity? (Score:5, Interesting)
According to special relativity, magnetic and electric fields can be "mixed" by Lorentz boosts (i.e. moving from one inertial reference frame to another that is moving with respect to the first one.) As a result, some say that a magnetic field is nothing more than an electric field as viewed by a moving observer. That isn't quite correct. The quantity E^2-B^2 (the square of the electric field minus the square of the magnetic field) is a Lorentz invariant. It is the same according to all observers. That means that if the magnitude of the electric (or magnetic) field is greater than the magnitude of the magnetic (or electric) field in one frame of reference, it is in all frames of reference. So a purely magnetic field can never be described as a purely electric field as seen by a moving observer.
In particular, Maxwell's equations, if valid in one inertial frame of reference, are valid in all frames. One of Maxwell's equations is div B = 0, which says there are no magnetic monopoles. A violation of this equation in one reference frame would be seen as a violation in all frames. That is a magnetic monopole in one frame of reference would be seen as a magnetic monopole in all frames of reference, despite the fact that in frames in which it is moving, it will generate an electric, as well as magnetic field, just as an electric charge, when moving, produces a magnetic field as well as an electric field.
Modswell's Demon (Score:2, Informative)
How can you know that downmods are coming from homosexuals? It could be from your observance frame as a mono-sexual [urbandictionary.com] that all higher order sexual behaviors appear different but similar in relation to one another and thus appear to be homogenous when they are, in fact, not.
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I think the parent was talking about quantum theory applied to electromagnetism (weak nuclear forces are combined too) and what you describe are the classical/relativistic equations of Maxwell.
I seem to remember that there actually is a reason why monopoles should exist with a unified theory of electromagnetism/weak force/quantum menchanics/relativity to describe a particular phenominon to the greatest degree of numerical accuracy, but unfortunately I just can't remember what that is. I seem to remember tha
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Vile, just vile.
Reproducing? The filthy things were proliferating as maggots upon a piece of rotten meat.
Humans! Ugh.
Loathe them or despise them, you just can't like them.
Monopoles and quantized charge (Score:4, Interesting)
As a followup to the excellent relativistic answer above...
As one of my professors put it: "if there is one monopole anywhere, then charge is quantized everywhere". This was at the end of a fairly straightforward derivation, first done by Paul Dirac IIRC.
We see by experiment that charge is quantized everywhere, but this doesn't prove the existence of monopoles. It's a tantalizing clue to why things may be the way they are in our universe.
Monopoles are predicted by some of the unified theories, so if they exist how come we don't see any?
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Because our compasses can't point to them. They just spin and spin...
Actually, no. Our compasses would point to them, the same way a water molecule, which has no electric charge but does have an electric dipole moment, tends to align itself to the electric field generated by ions in a solution.
Energy Scale (Score:3)
Monopoles are predicted by some of the unified theories, so if they exist how come we don't see any?
For example proton decay might be possible through hypothesized X and Y bosons which hav
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Monopoles are predicted by some of the unified theories, so if they exist how come we don't see any?
I think the standard explanation for this is cosmic inflation [wikipedia.org] combined with a high monopole mass.
Inflation, which is hypothesized to have happened very early in the history of the universe, makes the universe expand extremely quickly in a very short period of time, which has the effect of diluting all the particle content in the universe prior to inflation into insignificance. At the end of inflation, the energy that drove the expansion is converted into particles, re-populating the universe with matter.
But
Charge Quantization (Score:3)
How do magnetic monopoles fit into this?
Magnetic monopoles could be the mechanism by which charge is quantized. Dirac showed in 1931 that if monopoles exist then charge, quite naturally [wikipedia.org] becomes quantized through the fact that angular momentum is quantized. Unfortunately Dirac's mechanism puts no mass limits on real monopoles (i.e. not the condensed matter faked kind) but there is an experiment (MoEDAL) [web.cern.ch] being run by a colleague of mine which is searching for evidence of monopole production at the LHC. However, if they exist, they could lie anywhe
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Electromagnetism as described by Maxwell's equations and special (not general) relativity are equivalent, you can derive one from the other.
Maxwell's equations forbid monopoles, one of the interconnected equations says magnetic fields have no sources or sinks. So classically we expect NOT to find them.
These "quasi-monopoles" found in condensed matter physics are not the same nor are they related to true particle monopoles.the quasi-monopoles really are a type of dipole.
The true monopoles are predicted by
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no, the equations came from direct scientific observations and robust experiments. 150 years later still no exceptions observed to facts that electric charge has sources and sinks, and magnetic field lines in closed loops with no sources and sinks.
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please provide source that maxwell had them there originally. Rather it was Pierre Curie in 1894 that hypothesized them and made modified equations. Dirac with QED showed a monopole solution *consistent* with maxwell's equations with dipole tubes acting as monopoles
It was the can opener. (Score:1)
No news.
Monopole Magnets (Score:1)
With sufficient enlightenment we can give substance to any
distinction: mind without body, north without south, pleasure
without pain. Remember, enlightenment is a function of willpower,
not of physical strength.
—Chairman Sheng-ji Yang,
“Essays on Mind and Matter”
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Good for you sir, for laying down the SM:AC talk!
Define "useful" (Score:4, Informative)
Edward Leedskalnin (Score:1)
Falling Up (Score:2)
We must stop this dangerous research before hoards of roaming bandits start falling up! It's unconstitutional and immoral, I'm telling ya.
But (Score:1)