Slashdot Mirror
"Overwhelming" Evidence For Magnetic Monopoles
Thorfinn.au sends along big physics news: magnetic monopoles have been detected at low temperatures in "Dirac strings" within a single crystal of Dysprosium Titanate. Two papers are being published today in the journal Science and two more on arXiv.org, as yet unpublished, provide further evidence. "Theoretical work had shown that monopoles probably exist, and they have been measured indirectly. But the Science papers are the first direct experiments to record the monopole's effects on the spin-ice material. The papers use neutrons to detect atoms in the crystal aligned into long daisy chains. These daisy chains tie each north and south monopole together. Known as 'Dirac strings,' the chains, as well as the existence of monopoles, were predicted in the 1930s by the British theoretical physicist Paul Dirac. Heat measurements in one paper also support the monopole argument. The two, as yet unpublished, papers on arXiv add to the evidence. The first provides additional observations, and the second uses a new technique to determine the magnetic charge of each monopole to be 4.6x10-13 joules per tesla metre. All together, the evidence for magnetic monopoles 'is now overwhelming,' says Steve Bramwell, a materials scientist at University College London and author on one of the Science papers and one of the arXiv papers."
I think this is at least one of the Science articles to which the post (almost) refers.
It's only against the law to use your monopole to extort the market.
Kwisatz Haderach
Sell the spice to CHOAM
This Mahdi took Shaddam's Throne
Damn! Anonymous Coward has thought of something none of the scientists have even considered. Give this guy a research position ASAP.
Surely if they are two monopoles tied by a dirac string then they actually make a dipole. I was under the impression a monopole would create a dirac string (a discontinuity in the field) that extends to infinity. Interestingly by allowing the dirac string to extend first in one direction, then in the other and joining the two resultant fields gives a fully continuous description of the monopole without the need for a dirac string.
I think what the summary is refering too is similar to the creation of a electron and hole pair in a semiconductor rather than a fundamental monopole particle. So they are in fact creating both poles but that inside the spin glass they are not confined with respect to each other so each one appears as a monopole in the material.
is it possible to create pepetium mobiles now? ;)
most of the the 'free energy' designs are based around non-existing monopoles, and tricks to 'emulate' monopoles.
Isn't this just in time for the new season of the show Big Bang Theory, where Sheldon is on an expedition to find magnetic monopoles? :)
Yea like that electric charge nonsense, you can't have a particle with a single electric charge! that'd be crazy whatever it is will allways have another side with the oposite charge!
All my coins are shaped like mobius strips.
That tells me nothing. How many beard seconds is that?
A magnetic monopole is to a magnetic field what an electron is to an electric field.
This will, amongst other things, mean that Maxwell's equations become more symmetrical.
div D = rho; div B = 0
Will become
div D = rho_e; div B = rho_m
And there will be a magnetic current term for curl H.
It's long been known that if a magnetic monopole exists then charge must be quantized.
I've not looked at any of the papers but I'm interested to find out if they've got a mass estimate for them. Last I remember reading about this they were expected to be heavy (uranium nucleus sort of heavy) but I don't recall if that was an extrapolation from their non-detection or whether there was a more fundamental reason for them needing to be so massive.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
Are there any applications for it within our understanding of physics?
The existence of monopoles is a possible "explanation" for the quantization of electric charge. Maxwell's Equations are only self-consistent if:
1. magnetic monopoles don't exist, and charge is not quantized;
OR
2. magnetic monopoles do exist (at least one, somewhere), and charge is quantized.
As charge is quantized, it has always been a strong argument for monopoles' existence. Of course, perhaps Maxwell's Equations aren't applicable at the quantum level, but so far they've done a damned good job of being consistent and predicting and explaining things.
I think the stupidity is yours. Magnets are not just atoms lined up, atoms themselves have magnetic poles. In fact, the components of atoms (such as electrons) have magnetic poles as well.
It's perfectly conceivable to think of a point source of just North or South where the field lines radiate outwards in all directions. They would arc toward the nearest magnetic pole of opposite polarity. The diagrams are simple to draw and have been accepted by just giants in the field as Dirac for eighty years. The only question is: do they actually occur?
I know what magnetism is, I also know what a magnetic monopole is, hell I even know what a dirac string is and what a spin glass is. Honestly your argument about coins made no sense at all.
I was attempting to point out that electric charge also has field lines but that they do not have two sides like a coin, the entire point of the discovery of a magnetic monopole is that it doesn't have two sides in the way that all the other magnetic dipoles we are used to have.
I'm sorry, but you're going to have to provide your credentials if you want me to accept that you know more about magnetism than four separate physics research teams, two with articles in Science and two more with draft articles on arXiv.org, all of which show evidence of the existence of magnetic monopoles.
Christ, not to mention Paul fucking Dirac.
circletimessquare, you have one again exceeded yourself at demonstrating your truly incredible arrogance and stupidity.
Now I've scanned one of the papers I see that they're not detecting the sort of magnetic monopole I was thinking of (i.e. a new sub-atomic particle)
Instead they've detected the equivalent of a charged molecule.
They give an analogy of the disassociation of water into H3O+ and OH-. They claim to have done the same thing with magnets - ending up with a disassociated north and south pole.
So their work doesn't appear to give any clue to the mass of a magnetic monopole particle. But AFAICT they have still created a type of magnetic monopole, exactly the same way as a proton is an electric monopole even though it has an internal structure.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
(Disclosure: I'm a physicist)
You could just as well ask: "how can an electric field line just stop somewhere?", and thereby conclude that there can be no such thing as an "electric monopole" (a positively- or negatively-charged particle). As long as the universe has no net electric or magnetic charge, all lines will terminate somewhere. If the universe did have a net charge the point is subtle, but that's irrelevant: the paper talks above pairs of opposite-pole monopoles created together, like a particle and its antiparticle. So this argument doesn't hold water.
Monopoles aren't impossible in principle (it would just be an extra term in Maxwell's equations) and are predicted in some theories, but fundamental-particle monopoles have never been observed. The summaries of this paper are confusing a lot of people: the authors are describing a crystal system with excitations that look like monopoles. They are NOT describing discovery of a new fundamental particle, but rather a new kind of solid-state phenomenon.
Having read at least one of the arxiv articles, it is clear to me that the authors have NOT detected magnetic monopoles, and don't actually claim that they have. They claim that a certain type of ordering in a very specific crystal at very low temperatures BEHAVES AS IF it was a magnetic monopole - it's an analogy at best. The energy required to trigger the effect is minute, so they can "see" lots of MMAs (magnetic monopole analogs [my terminology]), and hence study what would happen if lots of REAL MMs existed in some other situation. They confirm that setting up Maxwell's equations to include a monopole shows the same sorts of behavior as what they see. But a real, isolated magnetic monopole? Not this time......
I'm glad you provided the episode number, because the description didn't narrow it down much.
If you were blocking sigs, you wouldn't have to read this.
As I have stated in response to circletimessquare elsewhere in this discussion, there are a few good reasons to believe magnetic monopoles might exist. I remember circletimessquare's sig, and remember him or her making good posts in the past, but it's clear that he or she does not understand electricity and magnetism very well.
Classical electric and magnetic fields vary in a coordinated way between different Lorentzian reference frames. So where one observer might only observe an electric field with no magnetic field, an observer in a different reference frame moving at a constant velocity with respect to the first observer's frame might see a combination of electric and magnetic fields. Electricity and magnetism are different aspects of a single force, believed to be one of the four "fundamental" forces. It is called, shockingly enough, the electromagnetic force. That's one reason to believe that since electric "monopoles" (charges) exist, magnetic monopoles might too.
There are electric dipoles, which are made of opposing electric "monopoles" (charges). Why couldn't magnetic dipoles also be made of opposing magnetic monopoles? That's another reason to believe magnetic monopoles might exist.
Dirac didn't just think magnetic monopoles might exist for no reason. He discovered in his calculations that the existence of magnetic monopoles would automatically lead to the quantization of electric charge. Since all electric charge observed in nature is quantized (in integer multiples of the electron charge for free particles and, we believe, in integer multiples of 1/3 of the electron charge if we include particles that are not observed "free"), we have yet another reason to believe there might be magnetic monopoles.
Very smart folks with Ph.D.s in physics have been looking for magnetic monopoles in creative ways for a very long time. In another post in this discussion, I mentioned Professor Henry Frisch of the University of Chicago. These people aren't just looking for magnetic monopoles to do something crazy. They're doing it because their deep understanding of the theory and the experimental data leads them to believe magnetic monopoles might exist.
"It is nice to know that the computer understands the problem. But I would like to understand it too." --Eugene Wigner
Unending magnetic field lines and a particle with a net magnetic charge does not result in "perpetual motion", where that term always means "perpetual motion in the face of friction or other counteracting forces", because minus that "perpetual motion" is just Newton's 1st Law and completely uninteresting.
In the case of a magnetic monopole, it's actually little different than electricity (I know you think otherwise but you're wrong, look at the force equation), and in the case of electric fields, a charged particle in that field has a certain amount of potential energy, and that potential energy may be converted into kinetic, and that kinetic energy may be enough to reach escape velocity for the universe, but it isn't perpetual motion.
I know it's pointless explaining this to the deliberately dumb troll, since even if you wanted to understand it'd require you knowing some of the actual theory and math behind the physics you only understand through inaccurate analogy, but it's entertaining anyway.
P.S. Yes you're insane and yes you're stupid.
The enemies of Democracy are
I have to take exception to this:
For 30 years, physicists have believed that the universe is made up of tiny vibrating dimensional strings which only they are clever enough to understand. A fine idea, except it turns out not even they are clever enough after all. Nevertheless, they persist in this belief because the mathematics is beautiful.
It is incorrect to say "physicists have believed." It would be correct if you were to say "some physicists," or even better, "a small minority of physicists." String theorists certainly put a lot of stock in string theory; but even among that group of physicists, not all of them believe it's right so much as they think it's an idea worth working on. And at any rate, string theorists make up a tiny fraction of the community of physicists. Outside of that community, there's a lot of physicists who think it's hogwash, a lot of physicists who think it's uninteresting as long as it's so far divorced from the experimental realm (including myself), and a lot of physicists who simply don't care one way or the other because their work is in so separate a domain that they don't have a dog in that hunt.
I mention this because the overall premise of your post -- that physics (or, more accurately, physics research) is becoming more and more divorced from experiment -- is not borne out by my experience as a professional working physicist. Even among string theorists, of which I've known a fair number, I've never met any physicist who thinks there's virtue in untestable conjecture. They simply believe that if they work hard enough and are clever enough, they'll come up with effective ways to test string theories that are reachable by experiment or observation. They may be wrong about that (and whether they are or they aren't wrong, until they do come up with some way to test it, I'm not interested); but all the string theorists I've known understand quite well the importance of experiment and observation. They aren't simply believers. And at any rate, string theorists make up a small fraction of the community of research physicists.
These are simply sets of atoms that, together, act like monopoles. What has been discovered is not a single particle with one pole. It is a place inside a material that acts like a monopole. Real 'Dirac strings' connecting real monopoles are not long chains of molecules, these long chains of molecules simply act like Dirac strings. Please. This is the most misleading title and summary I've ever read here, and that is saying A LOT.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton