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"Overwhelming" Evidence For Magnetic Monopoles 256

Posted by kdawson
from the go-north-young-man-and-keep-on-going dept.
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 Two papers are being published today in the journal Science and two more on arXiv.org, as yet unpublished, provide further evidence.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 The two, as yet unpublished, papers on arXiv add to the evidence.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."
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"Overwhelming" Evidence For Magnetic Monopoles

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  • Missing Link (Score:5, Informative)

    by dtmos (447842) * on Friday September 04, 2009 @08:56AM (#29310485)

    I think this [sciencemag.org] is at least one of the Science articles to which the post (almost) refers.

    • Re: (Score:3, Informative)

      by biryokumaru (822262) *
      I believe this [nature.com] is the article that is quoted. I submitted it to the editor, but who knows if it'll get up there. Science articles listed therein are cited from print form.
      • Re:Missing Link (Score:5, Informative)

        by internic (453511) on Friday September 04, 2009 @11:31AM (#29312577)

        Thanks for posting this, though I realize a lot of people don't have access.

        The abstract of the article in Science actually makes matters quite clear:

        While sources of magnetic fields--magnetic monopoles--have so far proven elusive as elementary particles, several scenarios have been proposed recently in condensed matter physics of emergent quasiparticles resembling monopoles. A particularly simple proposition pertains to spin ice...well-described by networks of aligned dipoles resembling solenoidal tubes--classical, and observable, versions of a Dirac string. Where these tubes end, the resulting defect looks like a magnetic monopole. [emphasis mine]

        This makes it clear that they have not discovered a fundamental particle that is a monopole, which people have been searching for for a while. What they've discovered is a material where under certain conditions you can model the behavior as though there were monopoles present, but it's an imaginary construction, not an actual particle; that's what they mean by quasi-particle. As someone else mentioned, this is similar to how you can describe as hole, where an electron is missing in a semiconductor, as though it were a positive charged particle moving around in the material. In this case, they have a long series of aligned dipoles that they're saying is similar to a very long solenoid. If you're outside the solenoid near one of the ends it just looks like a monopole (because all the magnetic flux going the other day is confined to the narrow region inside the solenoid).

    • by julesh (229690)

      I think this is at least one of the Science articles to which the post (almost) refers.

      Useful. Because, you know, I'm really going to go and pay $15 to read a single article online, when I could alternatively just buy the magazine for $10.

    • by spun (1352) <loverevolutionary&yahoo,com> on Friday September 04, 2009 @11:38AM (#29312679) Journal

      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.

  • by jollyreaper (513215) on Friday September 04, 2009 @08:56AM (#29310493)

    It's only against the law to use your monopole to extort the market.

  • by Drakkenmensch (1255800) on Friday September 04, 2009 @08:59AM (#29310515)
    Uncle Pennybags purchases Acme's Magnet making division to create magnetic monopoly.
  • by Arancaytar (966377) <arancaytar.ilyaran@gmail.com> on Friday September 04, 2009 @09:06AM (#29310605) Homepage

    "...that yin-yang dualism can be overcome. 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

    So, can haz magtube now plz?

  • by anarchyboy (720565) on Friday September 04, 2009 @09:09AM (#29310649)
    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.
    • by Dr. Zowie (109983) <slashdot@@@deforest...org> on Friday September 04, 2009 @11:09AM (#29312269)

      Classic case of science journalists overblowing a mundane result. Yes, connected quasi-monopoles are interesting. they are visible in any conducting medium. But there's a HUGE difference between a quasi-monopole that is at the end of a finite-length, shielded dipole and a true monopole that actually violates the magnetic divergence-free condition.

      In solar physics we call such things "unipoles" to distinguish them from the infinitely harder-to-find "monopoles". Unipoles are all over the surface of the Sun, because the conductive interior hides the field lines that connect opposing unipoles.

      It is disingenuous at best and downright deceptive at worst to call the HZB result "evidence for magnetic monopoles", because it ain't.

      The only plausible true magnetic monopole detection ever was still in Blas Cabrera's instrument at Stanford in the 1980s. It was never replicated, so it is unknown whether they exist but are extremely rare (and Cabrera was just lucky) or whether his detector glitched.

  • by psy0rz (666238) on Friday September 04, 2009 @09:11AM (#29310679) Homepage
    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.
    • Re: (Score:3, Insightful)

      by John Hasler (414242)

      > is it possible to create pepetium mobiles now?

      No. The existence of magnetic monopoles does not imply perpetual motion.

      • Re: (Score:2, Insightful)

        by gurps_npc (621217)
        Actually it would, if they exist. Many of the so called perpetual motion machines would work if they had a monopole.

        This is why I agree with the others that laugh at this article with it's ridiculous claim that monopoles exist. A monopole connecting to another monopole is called a dipole, no matter how long the connection or what kind of item it is.

        • I disagree. Nothing about monopoles breaks the laws of thermodynamics. Even if they existed, there would still be constraints imposed by the rest of physics (eg. friction). Magnetic monopoles do not make that magically disappear.
        • Just because something exists at the microscopic level, doesn't mean it's useful at the macroscopic level. Example: Matter/Energy does just jump into existence in a vacuum. But as long as the particle and virtual particle don't live longer than Plank's constant/ their mass, conservation is preserved. Now, if you have a handy black hole, you could make a perpetual motion machine. (For sufficiently short definitions of perpetual)
        • > Actually it would, if they exist.

          Elucidate.

  • WTF.. (Score:3, Interesting)

    by Absolut187 (816431) on Friday September 04, 2009 @09:11AM (#29310695) Homepage

    ..is magnetic charge?

    >>
    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.
    >>

    And how is it different from electric charge?

  • Woo! (Score:4, Funny)

    by RenHoek (101570) on Friday September 04, 2009 @09:12AM (#29310697) Homepage

    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? :)

  • I thought we were talking about a Slashdot question that only had the CowboyNeal answer as a choice.

  • by olsmeister (1488789) on Friday September 04, 2009 @09:17AM (#29310765)
    That tells me nothing. How many beard seconds [wikipedia.org] is that?
  • by emeri1md (935883)
    Can someone translate this into English for us non-Physics geeks? What exactly does this mean? Will it lead to new applications of magnets (the closest analogy I can come up with from this brief description)?
    • by gurps_npc (621217)
      A monopole would be the north end of a magnet without a south end. A positive without a negative. Such a device, if it really existed, would enable us to build perpetual motion machines (see here [compsci.ca]. But the item described by this article is NOT a monopole. They are describing two monopoles connected by a dirac string (one dimenisional curve in space). If you connect two monopoles, that is a DIPOLE, it doesn't matter what connects them.
      • by ceoyoyo (59147)

        The "perpetual motion" machine you link to has some problems even if you could supply it with magnetic monopoles.

      • Re: (Score:3, Interesting)

        by locofungus (179280)

        I don't see why monopoles should imply perpetual motion.

        But the machine in the link you give doesn't make any sense at all. We could build it today, using electric charge instead of magnetic charge but it still won't work. Monopoles aren't some magic that mean the other laws of physics don't apply any more.

        At the very least to be plausible, any perpetual motion machine that depended on magnetic monopoles would also have to depend on electric monopoles otherwise you can build an equivalent machine using elec

  • Monopoles (Score:2, Funny)

    by Airdorn (1094879)
    ...therefore, God exists.
  • by 140Mandak262Jamuna (970587) on Friday September 04, 2009 @09:48AM (#29311147) Journal
    The whole crowd of people selling devices that use Zero Point Energy and magnetic suspension perpetual motion machines and people who write hundred page manuscripts in purple ink arguing why the Second Law of Thermodynamics must be repealed are going to come out of the wood work now.
  • Not this time..... (Score:5, Informative)

    by scradock (1420165) on Friday September 04, 2009 @09:49AM (#29311159)
    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......
  • by mdmkolbe (944892) on Friday September 04, 2009 @09:51AM (#29311193)

    What are the practical implications/applications of monopoles?

    I'm not dissing the theoretical impact. I'm just curious if anyone has a use in mind for them.

  • by Bootsy Collins (549938) on Friday September 04, 2009 @10:04AM (#29311309)

    Dirac's argument (and all the field-theoretic) arguments in favor of the existence of magnetic monopoles have had to do with an elementary particle exhibiting those characteristics. Sometimes this is phrased in the terms of a 0-dimensional topological defect, something that would be produced by certain kinds of symmetry breaking; and indeed one of the arguments in favor of cosmological inflation theories was the fact that we don't see fundamental-particle monopoles, and would expect to. Finding one of these guys would be amazing news.

    What these experiements seem to have done, however, is detected the effect of what condensed matter physicists like to refer to as a quasi-particle, akin to the phonon, which is a different thing entirely.

    Or am I missing something?

  • From one of the articles [sciencemag.org]:

    The spin ice state is argued to be well-described by networks of aligned dipoles resembling solenoidal tubesâ"classical, and observable, versions of a Dirac string. Where these tubes end, the resulting defect looks like a magnetic monopole.

    They've managed to create the microscopic equivalent of a long skinny magnet or a long bendy solenoid: a set of dipoles aligned end-to-end, which acts just like a string with two "monopoles" at the ends.

    While this is an interesting microscopic state of matter, from the "discovering monopoles" point of view it doesn't seem fundamentally different than the macroscopic description of magnet "poles" that has been well understood for over a century (and observed for a lot longer than that). I call hype.

  • 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. ...

    Even without directly seeing one, Bramwell says that he is certain that the monopoles are there. "I don't think anybody could question it after this flurry of papers," he says.

    This mentality is a good example of what Joel Spolsky calls fire and motion [joelonsoftware.com]. You just keep moving, keep publishing, keep innovating, and your opponent is so busy trying to catch up or deal with your earlier work that you gain huge momentum. Sometimes unstoppable momentum. People just can't deal with the information overload.

    When the crystals are chilled to near absolute zero, they seem to fill with tiny single points of north and south. The points are less than a nanometre apart, and cannot be measured directly. Nevertheless, Morris and other physicists believe they are there.

    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. Likewise, many physicists persist in their belief in magnetic monopoles because the concept is beautiful, or some other such rubbish. Look! It even makes Maxwell's equations symmetric. So what? What's so important about having symmetric equations. Unsymmetrical ones are so much more interesting!

    There's only one arbiter in physics, and science in general. It isn't a "flurry of papers". It isn't "beauty" or "symmetry" or "elegance" or "coolness". It isn't how many people agree with your viewpoint. It isn't how many journalists you can get to print words like "overwhealming evidence" in headlines. It isn't how much "supporting (online) material" you can find to back you.

    The one, only, and final arbiter is the experiment. An honest to gods experiment. It finds things. It separates truth from fiction. You can try to twist the meaning of the result this way and that, throw back the grenade and carry on with your fire and motion, but in the end the results of all those experiments will finally weigh down your dishonesty and halt your advance.

    There are no magnetic monopoles. You can try to separate north and south pole. You can even construct models of "magnetic charge" and dipoles if you like. But in the end, you can't get a north pole without having a corresponding south pole, very, very close by.

    Modern science, and worst of all physics, is in a deplorable state. Cargo cult scientists [lhup.edu],frauds [wikipedia.org], charlatans [timesonline.co.uk], fakes [bbc.co.uk], and deluded true believers [mit.edu](Yes I'm serious about that last link) have saturated certainly the media circuit, but I fear many physics departments as well. Sensationalism and media attention are now as never before, deciding what the "consensus"* in science should be. It's disheartening to see the world lose its faith in the method of observation, hypothesis, experiment and above all skepticism that has served it so well for so many centuries.

    P.S.
    *Before the cranks jump in; No, I do not in fact, doubt the reality of anthropogenic climate change.

    • by Bootsy Collins (549938) on Friday September 04, 2009 @11:18AM (#29312421)

      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.

    • Re: (Score:3, Insightful)

      by blueg3 (192743)

      There are no magnetic monopoles. You can try to separate north and south pole. You can even construct models of "magnetic charge" and dipoles if you like. But in the end, you can't get a north pole without having a corresponding south pole, very, very close by.

      Interesting. It seems if you properly understood experimentalism, you would say, "No experiment has shown the existence of a magnetic monopole, but no experiment has shown that they must not exist."

      You seem to be taking the approach that if an experiment does not show that A is true, then A must be false. Not only would a physicist criticize you (rightly) for this line of reasoning, so would any philosopher or logician.

  • by Anonymous Coward on Friday September 04, 2009 @10:32AM (#29311703)

    IAAP and I did do my PhD on this stuff, but it is a while ago now...

    The Dirac string is not real, but is really just a failure of the coordinate system. Coordinate systems are always failing: just stand at the North Pole and ask which direction is South. All directions are, and the coordinate system is broken at that point. That's fine, it works everywhere else and we jsut remember to be careful in the rare cases where we are asking for directions at the North Pole. There is no fundamental breakdown of space and/or time going on, it's just because we chose to impose a silly coordinate system onto the physical world. The fact the it breaks down at the North and South poles is also a red herring - we just chose to make the polar axis the same as the axis of rotation of the earth.

    The coordinate system used to simultaneously describe electric and magnetic charges is also broken, and the Dirac string is really just a way of fixing up this breakage. We imagine that one unit of magnetic flux arrived through a very narrow tube at the monopole and then spewed out in all directions (think toddlers or teenagers at this point). The tube is not real, it is just a way of patching up the failure of the coordinate system. In the same way that the Poles as points of failure is our choice, the direction that the tube arrives at the monopole is also an artifact of how we set up the coordinate system.
    We can change the direction that the tube arrives at the monopole from transparently using what is technically known as a gauge transformation, but let's not worry about that here.

    The tube is not real, so we must not be able to detect it. This leads to the concept of quantisation of electric charge. Normally, if you take a tube carrying g units of magnetic flux and then take an electrically charged particle round it in a circle, the wavefunction of the charged particle will change by a complex phase exp(i.theta) where theta is proportional to the product of q (its electric charge) and g. You can detect this phase using a quantum-mechanical interference experiment, if you feel the urge. If the Dirac string is to remain physically unobservable, no interference effects must be seen so the phase rotation must be a multiple of 2.pi, because exp(i.2.pi)=1.

    So, we know if there is one magnetic monopole anywhere in the universe then q.g = 2.pi.n (where n is some integer) so that the Dirac string (a mathematical fix for a choice of broken coordinate systems) remains just a theoretical trick and not observable physics. We must then have that the electric charge of every particle in the universe is some integer multiple of e = 2.pi/g, where g is the magnetic charge of that monopole.

    Whether you consider the smallest unit of electric charge to be the charge on the electron or the charge on a free quark (one third of this) doesn't matter. We do observe that electric charge is quantised (i.e. integer multiples of some base amount) and magnetic monopoles as fundamental particles provide a relatively elegant solution as to why this is true.

  • that's no monopole (Score:3, Informative)

    by jipn4 (1367823) on Friday September 04, 2009 @10:32AM (#29311705)

    A monopole is supposed to be an elementary particle with a magnetic charge. This is--as the abstract itself says--a "tractable analog" of a magnetic monopole.

    There are a lot of things in solid state physics that "behave like" some kind of elementary particle but aren't: phonons, holes, etc. This is just another instance.

  • 1. By softball sized foam ball at Hobby Lobby.
    2. By a couple hundred small neodymium magnets online.
    3. Get a hot glue gun and hot glue one pole facing towards the surface and the other pole away.
    4. Glue more magnets to the entire surface of the foam ball is covered in magnets.
    5. You now have your very own "Macro-Sized, Monopole analogue!"

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