Evidence of Magnetic Monopoles Found? 66
TheMatt writes "As reported on PhysicsWeb and published in Science (subscription required), researchers at AIST and co-workers believe they have
found evidence of magnetic monopoles. They observed an anomalous Hall effect in a ferromagnetic crystal that they say can only be explained via magnetic monopoles. To refresh your memory, magnetic monopoles are the magnetic analogue of electrons and other charged particles--a "north" or "south" pole only.
Dirac in 1931 showed that the existence of a magnetic monopole naturally leads to the quantization of electric and magnetic charge. Thus, showing the existence of just one magnetic monopole would be quite profound for physics, but their mass (> 10^16 GeV) has made searches for them difficult."
There's monopolies on everything else... (Score:3, Funny)
Patents (Score:1)
Should this discovery check out, I wonder who will get the patents on inventions that arise from this discovery.
Re:There's monopolies on everything else... (Score:2)
Re:There's monopolies on everything else... (Score:2)
The incremental costs of posting to Slashdot are nil. The same is true for writing an editorial for the local newspaper.
It isn't money that prevents free speech, it's fear of imprisonment for conducting cutting-edge research or for finding flaws in government policies. One of the worst aspects of things like the PATRIOT Act or the DMCA aren't the laws themselves but the resulting chilling effect they cause. They are an example of the di
For non-physics geeks... (Score:4, Informative)
Relativity and quantum mechanics currently give physicists nightmares. As near as we can tell, both are fantastically accurate descriptions of the world, and both are fundamentally at odds with each other. If we could find a flaw in one or the other, that would potentially open the door to a new and better theory, one which might allow us to reconcile these differences without resorting to theology [*].
Now, when Einstein devised relativity, he based it very heavily on Maxwell's Laws. The Laws are a set of four equations which describe pretty much all electromagnetic phenomena out there. It was the world's first Grand Unified Theory (GUT), in that it unified electricity and magnetism into one package. And one of Maxwell's Laws ("the divergence of the magnetic field equals zero") has, as a direct consequence, an absolute law: NO MAGNETIC MONOPOLES EXIST. NO OPEN MAGNETIC FIELD LINES EXIST.
So if Maxwell's Laws are wrong and relativity is built heavily on Maxwell's Laws, then there's a tantalizing chance relativity is wrong.
Or if Maxwell's Laws are right and monopoles are conclusively proven not to exist, then there's a tantalizing chance quantum mechanics is wrong.
Either way, physics wins: no matter what happens, we get to see a flaw in our current theories. And seeing that flaw is the first step to coming up with better, more accurate theories.
What's the worst-case scenario? The worst-case scenario is these guys are wrong, just like every other monopole researcher before, and the "do magnetic monopoles exist?" question remains unresolved for the next few hundred years.
Warning: I'm not a professional physics geek. In fact, I may be stark barking mad wrong here.
[*] Theology, aka string theory. Sorry, but any theory which literally cannot be experimentally tested at any realistic energy level isn't a theory at all. It's an article of faith.
Re:For non-physics geeks... (Score:4, Interesting)
The equation can be stated "the divergence of the magnetic field equals the density of magnetic monopoles", but of course, in most situations, it's easier to say "zero" than "the density of magnetic monopoles", since there aren't any magnetic monopoles around.
Re:For non-physics geeks... (Score:2)
Re:For non-physics geeks... (Score:2)
NO OPEN MAGNETIC FIELD LINES EXIST.
You are wrong here; it is perfectly easy to get open field lines, using a current distribution.
Re:For non-physics geeks... (Score:2)
Nope, that creates closed field lines.
Re:For non-physics geeks... (Score:2)
No, you can get open field lines from infinite current sheets. I've encountered these in MHD simulations of winds from luminous, magnetic stars.
Re:For non-physics geeks... (Score:2)
Re:For non-physics geeks... (Score:3, Interesting)
You misunderstand; I have open field lines which terminate at the stellar surface (where the field is generated). Without the wind, the field is a dipole; however, the wind rips the field lines open and creates unterminated lines. In what way is this unrealistic? Stars have been observed which appear to be doing this.
Re:For non-physics geeks... (Score:2)
Check the data again, it is quite possible that field lines can appear to terminate, but on closer inspection they d
Re:For non-physics geeks... (Score:2)
Whoops, there I go again. What I meant to say was that, deep within the star, the field lines are those of a dipole. However, above the stellar surface, the wind pulls the lines into an open configuration. So, the field lines do not terminate at the stellar surface; they pass through the surface and assume a dipole form at small radii.
The point I am making, however, is that the field lines above the surface are ripped open by the wind. This is a counterexample of the assertion "magnetic monopoles are requ
Re:For non-physics geeks... (Score:2)
Re:For non-physics geeks... (Score:2)
No, they aren't making such an assumption (I know this for a fact, since I work with one of them); 6 stellar radii is just the outer boundary of their computational domain. More detailed calculations indicate that the field lines extend out to inifinity without meeting. Such behaviour is perfectly compatible with the fact that div B = 0; why are you insisting that it isn't?
Re:For non-physics geeks... (Score:2)
Re:For non-physics geeks... (Score:2)
You can consider what you want, but that won't make it true.
If you look back through my posts, you will see that I never set out to claim that I had terminating field lines (in your sense) without monopoles. I claimed that I had open field lines without monopoles, from a physically-realistic model. This contradicts what the original poster wrote: that open field lines are only realizable with magnetic monopoles. Please explain to me how I am wrong.
Re:For non-physics geeks... (Score:2)
You misunderstand; I have open field lines which terminate at the stellar surface (where the field is generated).
This certainly is a (later corrected) claim that you had terminating field lines in a circumstance which ought to be a magnetic monopole.
Field lines that 'terminate' at infinity do not produce a monopole because, of course, they do not actually 'terminate'. div B = 0 everywhere.
This is completely consistent with bcrowell's earlier comme
Re:For non-physics geeks... (Score:2)
In fact I cannot find anywhere in this entire thread where anyone claimed that open field lines imply monopoles
I quote diretly from a post by rjh, which began this thread: And one of Maxwell's Laws ("the divergence of the magnetic field equals zero") has, as a direct consequence, an absolute law: NO MAGNETIC MONOPOLES EXIST. NO OPEN MAGNETIC FIELD LINES EXIST. This is, at least a link between magnetic monopoles and open field lines.
My response to rjh's post was (I quote): You are wrong here; it is per
Re:For non-physics geeks... (Score:5, Informative)
And one of Maxwell's Laws ("the divergence of the magnetic field equals zero") has, as a direct consequence, an absolute law: NO MAGNETIC MONOPOLES EXIST. NO OPEN MAGNETIC FIELD LINES EXIST.
So if Maxwell's Laws are wrong and relativity is built heavily on Maxwell's Laws, then there's a tantalizing chance relativity is wrong.
Or if Maxwell's Laws are right and monopoles are conclusively proven not to exist, then there's a tantalizing chance quantum mechanics is wrong.
You have to be careful here. Your first paragraph is a correct statement of what's implied by one of the four Maxwell Equations. It's a bit misleading, though, to say that "relativity is built heavily on Maxwell's Laws." That seems to imply that relativity somehow depends upon Maxwell's Equations being true. That isn't correct. A better way of putting it is that Maxwell's Equations can be shown to incorporate special relativity within them, in the sense that the laws of electromagnetism stay the same ("Lorentz covariance") after changing relativistic reference frames (through a Lorentz transformation).
In fact, we already know that the Maxwell Equations are wrong. We know that they're wrong because they fail to explain behavior on the quantum scale. For that, we turn to quantum electrodynamics (QED), which, again, incorporates special relativity. Maxwell's Equations are thus seen as an excellent approximation on macroscopic scales. The failure of such an approximation to allow for magnetic monopoles doesn't seem like much of a failure.
That said, I've forgotten enough of my field theory that I don't remember how monopoles fit into QED. But I do know lots of field theorists, and most of them believe that monopoles are around (they'd be produced by the breaking of certain fundamental symmetries that many theorists expect to have been present in the early universe; although any inflationary epoch in the history of the Universe would be expected to make monopoles very very rare); and they don't seem to be stressing about the implications of monopoles for QED. So my suspicion is that QED is OK.
Oh, and just as a brief defense of string theorists . . .I don't much like string theory myself, and I echo your reluctance to take it seriously on the basis of the difficulty in making comparison to experiment. But I think most string theorists would take exception to your statement
that string theories "literally cannot be experimentally tested at any realistic energy level." To we who are not string theorists, that's what it looks like, yes; but a string theorist would simply reply that string theorists haven't yet been clever enough to figure out how to extract observable predictions. In other words, I don't think many string theorists would disagree with the principle that for a theory to be interesting, it must be testable. In fact, they would claim that that's their goal with string theory -- to figure out how to make realistically testable predictions -- and they just haven't yet been successful. The Planck scale is a long way from observable energy scales, to be sure. But people explore ideas that allow the examination of classes of models, e.g. the "one large dimension" stuff from a few years ago that would have had observable consequences.
Re:For non-physics geeks... (Score:5, Informative)
From the later parts of your post it's obvious that you're now talking about *special relativity*. It is not in any way at odds with quantum mechanics; in fact, the fusion of relativity and quantum mechanics (something called "quantum field theory") is *the most succesful theory of physics ever developed* (at least when success is measured by how well the theory fits with experiment).
What we don't have is a quantum theory of gravity. We have a very well working *classical* theory of gravity, called "general relativity", which is obviously as much at odds with quantum mechanics as any classical theory is.
Now, when Einstein devised relativity, he based it very heavily on Maxwell's Laws. The Laws are a set of four equations which describe pretty much all electromagnetic phenomena out there. It was the world's first Grand Unified Theory (GUT), in that it unified electricity and magnetism into one package.
That would not be a _GUT_.
And one of Maxwell's Laws ("the divergence of the magnetic field equals zero") has, as a direct consequence, an absolute law: NO MAGNETIC MONOPOLES EXIST.
This is certainly true, but it is trivial to fix this law to handle magnetic monopoles. Remember, you have one Maxwell equation basically stating that
div E = electric charge density
and another, the one that states that no magnetic monopoles exist,
div B = 0
(for the completely unprepared reader: here E and B are the electric and magnetic fields and "div" is a certain sort of an operator that acts on vectors) If you compare these two equations, you'll see *why* the divergence of B is zero: by analogy, div B should just equal the "magnetic charge density", but since there are no magnetic monopoles, the magnetic "charge" density is always zero and div B = 0. In other words, there is no *theoretical* reason why you couldn't write
div B = magnetic charge density
but since the *experiments* tell us that this is always zero, we don't usually bother talking about magnetic charges at all and just set this to zero. If the experiments ever tell us that magnetic monopoles exist, then we'll just have to include these magnetic charge/current terms (which are normally set to zero) in Maxwells equations as well.
So if Maxwell's Laws are wrong and relativity is built heavily on Maxwell's Laws, then there's a tantalizing chance relativity is wrong.
No, there isn't. First of all, including magnetic monopoles the way I outlined above won't make Maxwells theory of electromagnetism in any way incompatible with special relativity. This would be a very minor modification of electodynamics. Second of all, special relativity isn't *based* on electrodynamics at all - ED was an inspiration for Einstein (basically, Maxwells ED is at odds with Newtonian mechanics; Einstein saw this and decided to seek an alternative theory of mechanics that wouldn't be in conflict with it - and found one). If electodynamics ever turned out to be wrong, it wouldn't yet say anything at all about the validity of special relativity.
Warning: I'm not a professional physics geek.
Well, I am. Trust me, I know what I'm doing. :-)
Relativity not based on Maxwell's theories (Score:5, Informative)
Right. Just as a reminder to anyone reading this thread, the three axioms from which special relativity can be derived are:
The third is often not stated, as it's implicit in most of physics anyway. I wish I could remember the entire proof, but it's been a few years. It's not especially arcane or incomprehensible, though, and you don't need a degree in physics to understand it.
The fact that special relativity has so few dependencies, and is relatively simple, is part of its brilliance. It's also why theories that special relativity is flawed tend to be treated with extreme skepticism--it's hard to think of a theory that's more solid.
Maxwell's theory of electrodynamics supports the idea that the speed of light in a vacuum is a constant, but it's not the only evidence; there's the Michelson-Morley experiment, for starters. So Maxwell's theory falling over would not prove that the speed of light wasn't constant, and would not knock down special relativity.
If you want to knock down special relativity in favor of your own masterpiece, though, axiom #2 is certainly the one to go for... Throwing out either of the others tends to be a bit self-defeating. That's why most aether-theory crackpots [crank.net] claim that the Michelson-Morley experiment is flawed in some bizarre way.
Re:For non-physics geeks... (Score:3, Informative)
curl(B)-(1/c)(partial E/Partial t) = (4pi/c)J_e to get
curl(E)+(1/c)(partial B/partial t) = (4pi/c)J_b rather than 0.
Re:For non-physics geeks... (Score:1)
I didn't forget. Did you notice that part where I said that "...then we'll just have to include these magnetic charge/current terms (which are normally set to zero) in Maxwells equations as well."
Re:For non-physics geeks... (Score:2)
I have a question... (Score:1, Interesting)
Re:For non-physics geeks... (Score:1)
"""
talking about *special relativity*. It is not in any way at odds with quantum mechanics;
"""
and:
"""
"general relativity", which is obviously as much at odds with quantum mechanics as any classical theory is.
"""
So special relativity, being non-quantum, is also as much at odds with quantum mechanics as any classical theory too?
So it's not in any way at odds with quantum mechanics, and yet it's at odds with quantum mechanics.
Woh, deep!
"""
Trust me, I know what I'm doing
"""
Maybe, but your explanat
Re:For non-physics geeks... (Score:1)
So special relativity, being non-quantum, is also as much at odds with quantum mechanics as any classical theory too?
No.
Woh, deep!
Not really; this is just an issue with terminology. What's a classical theory and what's a quantum theory? Well, I don't want go into that much detail on a web forum, so lets just grab some simple example, like the point particle.
The classical (Newtonian or rela
Re:For non-physics geeks... (Score:1)
Re:For non-physics geeks... (Score:1)
Quantum field theory is very successful
Re:For non-physics geeks... (Score:1)
If I read you correctly, you'd want to assume that electromagnetism can be built on a single vector potential and then con
Re:For non-physics geeks... (Score:1)
Proceeding from the existence of the EM potential, A, is not begging the question; it is merely organizing the theory on a parsimonious basis, since writing the wave function of a test charge inherently requires the existence of A.
The existence of A also ties into unification with general relativity. Kaluza pointed out long ago that A becomes the addition to the metric tensor - the potential of gravity - wh
Re:For non-physics geeks... (Score:3, Informative)
Although people often state the principles of relativity using the word "light," e.g., describing c as the speed of light,
Re:For non-physics geeks... (Score:2)
Not really. The del dot B = 0 equation can easily be amended to del dot B = rho, where rho is the magnetic monpole density, and that makes it beautifully balanced with the del dot E equation, and there are no problems for relativity.
Well I feel dumb (Score:4, Funny)
Man I hope he doesn't find my email address.
Re:Well I feel dumb (Score:3, Funny)
You trepanned your friend?
that it was impossible to have one of those.
Yeah you find it impossible to have friends, what a surprise.
Man I hope he doesn't find my email address.
Well I for one am giving it to him if he asks, and I'm mailing Cowboy Neal to get him to release full details on you, you psychopath. Mind you, after drilling into his brain like that, he probably doesn't even know what day it is.
Re:Well I feel dumb (Score:2)
Burn!!
Good one!
Re:Well I feel dumb (Score:2, Informative)
Re:not front page? (Score:2)
I guess (Score:3, Funny)
Re:I guess (Score:2, Funny)
Re:I guess (Score:1)
Where is the one you call Jack Brennan?
Can "only" be explained? (Score:2)
Re:Can "only" be explained? (Score:1, Funny)
Re:Can "only" be explained? (Score:2, Funny)
Do you reckon there's cold fusion going on in those crystals instead, perhaps?
YAW.
burp! (Score:3, Funny)
They I ate all these yams, and damn do I have a hangover.
Re:burp! (Score:2)
Re:burp! (Score:1)
This is the end... (Score:2)
Re:OK we need to discover... (Score:1)
D: I'll pay you $10, but I need $5 of that in taxes
Who helps the poor?-- CodeGod@fark
okay, so i have to take exception to this
R: i'll pay you $6 but you owe me $5 with interest.
D: i'll pay you $10 but i need $5 back in taxes.
their mass; not in "real space"?? (Score:4, Informative)
This is an inaccurate representation of the article. The article says:
- Magnetic monopoles are also predicted by some theories that seek to unify the electroweak and strong interactions. However, the monopole masses that are predicted by these so-called grand unified theories are much too large - about 10^16 giga-electronvolts - to be detected in experiments.
They probably don't exist at all. Even if they do exist, it's only within the context of certain theoretical frameworks that this mass estimate could apply. If the mass is in the 10^16 GeV range, then there's no hope of creating them artificially with any forseeable technology; the only way to search for them would be to look for ones that occurred naturally soon after the big bang, and happen to cruise through your detector on a certain day.Instead of searching for magnetic monopoles in real space, Yoshinori Tokura of the National Institute of Advanced Industrial Science and Technology (AIST) in Tsukuba and co-workers turned to momentum space - the mathematical space in which condensed matter physicists construct Fermi surfaces, Brillouin zones and so on. The team was motivated by recent theoretical work which suggested that the behaviour of magnetic monopoles in momentum space is closely related to the anomalous Hall effect.
I'm not a condensed matter specialist, so I don't really understand what they're saying here, but it sounds like they may be saying they found something mathematically analogous to a magnetic monopole, not a real magnetic monopole. Unfortunately they don't seem to have posted preprints anywhere, but they certainly aren't creating 10^16 GeV particles in a condensed matter lab, nor does it sound like they claim to have captured natural ones.
Re:their mass; not in "real space"?? (Score:3, Interesting)
An electron hole is merely a pattern that mimics an anti-matter electron.
I think the crystal the
Re:their mass; not in "real space"?? (Score:1)
For those who don't have access to the article, these guys are making measurements on the anomalous Hall effect in a strontium ruthenate crystal. As far as I can tell, they are claiming that the fact that the transverse magnetoresistance is nonm
Re:their mass; not in "real space"?? (Score:2, Funny)
Dude!
I just had a STNG/Jordy flashback moment there...
(whoa...)
OldFart 8-)
Re:their mass; not in "real space"?? (Score:1)
Monopoles (Score:3, Funny)
from doimg their anti-competetive magnetic practices.
Ramblings (Score:3, Interesting)
In the case of "magnetic monopoles"... putting aside everything I've ever learned in my years as an electrical engineer... lets suppose that these actually exist.
The first pattern we see in nature is that matter exists in pairs... particles appear out of vacuum as matter and antimatter, we have electrostatic charge from protons and electrons, so I would think that you'd still have to have a "sink and source" arrangement when dealing with magnetic monopoles. Another law that we hate to break is the conservation of energy. Over a closed space, all exchange of energy nets to zero. So, I would think that for a field emitter to exist, there must be a field receiver... the only question is where does the energy go.
Tieing these two theories together, what's to say that a "monopole" in 3-space isn't really still a dipole in multidimensional space? In 3-space, we'd see a discontinuity, but over the whole space, we'd still have the continuity that Maxwell's classic equations require.... There really are "returning" field lines, they're just not directly observable because they don't interact with our form of matter; like dark matter in gravitic space, who's to say that similar objects can't exist in electromagnetic fields?