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Researchers Discover "Magnetic Current"
fsouto writes "Researchers have discovered a magnetic equivalent to electricity. From the article, 'The phenomenon, dubbed "magnetricity," could be used in magnetic storage or in computing. Magnetic monopoles were first predicted to exist over a century ago, as a perfect analogue to electric charges. Although there are protons and electrons with net positive and negative electric charges, there were no particles in existence which carry magnetic charges. Rather, every magnet has a "north" and "south" pole.'"
If this is a discovery then why did I learn about this in my electromagnetics class I took a semester ago? And why did I have to work on problems with magnetic circuits if this phenomenom wasn't discovered yet?
I think so. It sounds more like "electron holes" in semiconductors. The spin ice contains tetrahedrons formed from ions. Because of this arrangement, adjacent ions must form a positive-negative pair, which then affects the way electrons spin and the resulting magnetic field. Bring in an external magnetic field and that runs the process in the opposite direction. That's where the storage idea comes from.
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No, they aren't. Maxwell's equations don't preclude magnetic monopoles or the movement of net magnetic 'charge' (aka 'current'). In fact it's always been a mystery why monopoles didn't appear to exist. There was no theoretical reason why they shouldn't, we have just never found a particle carrying a net magnetic charge. We still haven't exactly, just a crystal structure in which you can find discreet units of net magnetic charge, but that's effectively the same thing. And now we've seen that these units can move through a structure, so magnetic current exists.
In a way this must be a relief. Electricity and magnetism are symmetric in so many ways, it was odd that in this one way they weren't since they're ultimately aspects of the same force (electromagnetism).
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There was also no theoretical reason for monopoles _to_ exist. If charge exists, and moving electric charges create magnetic fields, who do you _need_ magnetic charges? Making the equations "symmetrical" for both electric and magnetic charges does not make them any more elegant or powerful, any more than not having "negative mass" makes Newton's equations any less valid.
"Discrete units of net magnetic charge" may be a quantum effect of aligned, moving electrical charges. I still see no need for monopoles.
Oh quasi-particles; on one hand you you think "well they're just mathematical constructs rather than physical things" but then you realize that regular particles fall into the same category. I heard of an interesting experiment where a Stern-Gerlach experiment was conducted on a dark-state polariton and resulted in the same effect as for nuclei. You can really only talk about how something behaves when a particular measurement is performed when treating it within whichever theory you're using, calling something a particle or a quasi-particle doesn't really matter.
So if this is the future...where's my jet pack?
Okay, yes, I almost replied to myself to point out that the one equation based on the lack of the observation of magnetic monopoles would change. But none of the rest of the theory would change, and as you point out Maxwell's theory perfectly accommodates this change, so yeah, Maxwell's equations(plural) aren't "crying", except maybe with joy that now the expected symmetry has been discovered.
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Would they though? Assume a negative mass which still has a positive volume. If you use the (probably way oversimplified) model of positive mass objects acting like a lead ball on a rubber sheet in space you'd wind up with negative mass objects pinching it and pulling it upwards.
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