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Math Science

Tying Knots With Light 125

Posted by Soulskill
from the knot-easy dept.
thedreadedwiccan points out a summary of a recently released physics paper about tying knots with light. A pair of researchers showed that a relatively new solution to Maxwell's equations allows light to be twisted into stable loops. They are designing experiments to test the theory now, and it could have a big impact on fusion technology. The paper's abstract is available at Nature, though a subscription is required to see the rest. Quoting: "In special situations, however, the loops might be stable, such as if light travels through plasma instead of through free space. One of the problems that has plagued experimental nuclear fusion reactors is that the plasma at the heart of them moves faster and faster and tends to escape. That motion can be controlled with magnetic fields, but current methods to generate those fields still don't do the job. If Irvine and Bouwmeester's discovery could be used to generate fields that would send the plasma in closed, non-expanding loops and help contain it, 'that would be extremely spectacular,' Bouwmeester says."
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Tying Knots With Light

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  • by Anonymous Coward on Sunday September 14, 2008 @10:14AM (#24997989)

    Anybody who is anybody saw the flux capacitor in what 1984 - this is old work. the flux capacitor had loops and curves etc.

    • Re: (Score:1, Funny)

      by Anonymous Coward
      At least one of them has a fucked up foreign-sounding last name like Bouwmeester, so I predict this will be a success! Seriously, when's the last time a scientific advancement was made by Cooper & Smith?
      • by lanc (762334)
        that doesn't mean that all of the strangely named ones are successful.
      • by Kelbear (870538)

        Damn, that is some bad-ass physics when the description reads like Laforge boosting the output of the warpcore drive...

    • by selvan (259068)

      Meh. I did this years ago - Take a fiber optic cable, tie a knot in it, shine light through one end and viola - tied knot with light. This research is clearly over-rated.

  • by Nuclear Elephant (700938) on Sunday September 14, 2008 @10:18AM (#24998015) Homepage
    If Irvine and Bouwmeester's discovery could be used to generate fields that would send the plasma in closed, non-expanding loops and help contain it, 'that would be extremely spectacular,' Bouwmeester says."

    Bouwmeester continued by saying that light is, "way cool" and the ability to tie knots with it would be, "totally freaking awesome".
  • Or maybe the scientists are running around in circles? The goal is to figure out a way to bottle up plasma (for fusion energy harvesting). Since the magnetic bottle has not proven to be viable.
  • by slapyslapslap (995769) on Sunday September 14, 2008 @10:28AM (#24998055)
    Please tell me this is getting me closer to owning a light saber. PLEASE!!!
  • by Kupfernigk (1190345) on Sunday September 14, 2008 @10:35AM (#24998093)
    The light knots are secondary, the key point is solutions to the equations in which the electric and magnetic fields form closed loops. Otherwise the submission makes no sense, because the plasma in fusion experiments consists of matter, not photons.

    Even so, why do I think this is not actually going to work? Because for the last fifty years, fusion power has been constantly just twenty years in the future, that's why. The authors don't claim a solution to fusion containment, they are talking about possible new ways of trapping photons or creating condensates.

    • Re: (Score:3, Interesting)

      by sedm1143 (1253596)
      Yes, but plasma consists of charged particles which can be trapped by electro-magnetic fields. Light (in the wave picture at least) is simply an electro-magnetic field, so if you can tie light in loops theoretically you can also trap the plasma too. Now I agree that applications are a long way off - this is a theoretical paper so presumably no one has (intentionally) done it yet. If this proves interesting someone would have to build/modify an existing experiment to create and detect the phenomenon, and th
      • > Yes, but plasma consists of charged particles which can be trapped by electro-magnetic
        > fields. Light (in the wave picture at least) is simply an electro-magnetic field, so if
        > you can tie light in loops theoretically you can also trap the plasma too.

        Also, plasma affects the propagation of light in such a way that it may help stabilize the light loop.

        Ball lightning?

      • Re: (Score:3, Interesting)

        by jd (1658)
        I read the summary as more of a better feedback system. The earlier you can detect abnormalities, the earlier you can correct them. If the loops are only stable when the plasma is correctly configured, then your feedback becomes almost instantaneous from the time the plasma begins to destabilize, rather than being a rather slow interpretation of data from sensors that will only spot a problem once it passes the error threshold for that sensor. It would be like using the interference pattern from a tuning fo
    • Re: (Score:3, Informative)

      by JaredOfEuropa (526365)

      Because for the last fifty years, fusion power has been constantly just twenty years in the future, that's why.

      No.

      The ITER guys [iter.org] state that it will take until the 2050s until the first production fusion powerplant comes online.

    • by Instine (963303)
      "It is impossible, therefore, that any arguments from experience can prove this resemblance of the past to the future,..." Hume [marxists.org]
    • Even so, why do I think this is not actually going to work? Because for the last fifty years, fusion power has been constantly just twenty years in the future, that's why.

      We have certainly made a lot of progress towards sustainable fusion power in the last 50 years. There's no need to dismiss advancements just because we haven't reached the final stage of sustainable fusion power.

    • by Anenome (1250374)
      These knots of light are called... matter. Stable loops of electro-magnetic energy are the definition of matter.
  • by cychem1 (942136) on Sunday September 14, 2008 @10:55AM (#24998211)

    The real question is was a silver hammer necessary?

  • by gardyloo (512791) on Sunday September 14, 2008 @10:56AM (#24998219)

    The (slashdot) summary really does miss some of the key points, and emphasize the "fusion containment" aspect, which I doubt anyone takes seriously as a use of this. One of the points that I think is key is the whole subject of homotopy groups (which I've really just learned about).

    Maxwell's equations (and the wave equation, the Helmholtz equation in momentum space, etc.) have a family of solutions characterized by various parameter values. When you first start learning physics, you typically only allow real-valued wavevectors, which leads to only propagating waves and so on. Later on, you start to realize (as did George Green around 150 years ago, and Newton realized experimentally) that allowing for complex wavenumbers is more appealing mathematically (because it allows for more complete solutions), and actually leads to physically realizable solutions that propagating waves just don't give you. The effect of passing from real to complex wavenumbers is, on the face of it, crazy, but easily understandable once the analysis is carried out, and simple to visualize on an Argand diagram.

    However, homotopy groups (if I understand it correctly) say that there may be other solutions to such equations (in nonlinear/dispersive media) which one can't get to from just simple replacements of real with complex numbers, and so forth---these divisions are the "families" of solutions. There just isn't a simple projection from one family of solutions to another, and the solutions of from one may bear no resemblance to the solutions from other famililes. This means that there may, in sufficiently complicated systems, be physically realizable behaviors which a system may fall in to, which aren't describable by the "usual" solutions of the equations. Of course, Maxwell's equations work wonderfully in all situations I've ever heard of (no concession to the "Electric Universe" wackos!), so perhaps nature, for some reason, won't allow other families of solutions to make themselves known on any scale I know of.

    • by mrops (927562)

      Whooooosh....

    • Re: (Score:2, Insightful)

      by Anonymous Coward

      no concession to the "Electric Universe" wackos!

      While there are undoubtedly wackos out there, it's important not to be too absolute and dogmatic about unsubstantiated explanations for physical phenomena, because wackoness is always judged relative to current models rather than relative to the full but unknowable truth.

      All it takes to turn a wacko into an annoying "I told you so" is some physicist doing some lateral thinking and coming out with a new theory or an extension to a current one which just turns o

      • Re: (Score:1, Insightful)

        by Anonymous Coward

        Take, as an example the Aristotle's "Luminiferous Ether" which was viable, then crazy after MichelsonMorley, and now - depending on the next 6 months at CERN, very similar concepts may not sound so crazy any more if physicists can observe Higgs... leading to a pervasive field in the universe that creates mass (not light... which the original idea was used to explain), but nonetheless kind of sort of very much like the (a)ether ideas.

    • > The (slashdot) summary really does miss some of the key points, and emphasize the
      > "fusion containment" aspect, which I doubt anyone takes seriously as a use of this.
      > ...
      > However, homotopy groups (if I understand it correctly) say that there may be other
      > solutions to such equations (in nonlinear/dispersive media)...

      Nonlinear/dispersive media such as, for example, plasmas?

    • by Alsee (515537)

      The Electric Universe....
      because Creationists need someone to mock on science.

      -

    • Please correct me if I'm wrong, but I have a basic understanding of homotopy.

      I guess you view a solution as a certain kind of map on R^3 that obeys Maxwell's equations and then use homotopy to deform one map into another, all the while respecting Maxwell. Then, one element of the homotopy group would correspond to one family of solutions which may all be transformed one into another via homotopy. Knowledge about the group formed (which has to come from the kind of topological space that Maxwell's equations

    • Re: (Score:2, Insightful)

      by Anonymous Coward

      We're actually using Maxwell-HEAVISIDE equations all over the world after Oliver Heaviside rewrote Maxwell's original equations from quaternion notation into a much simpler vector notation.. throwing out some interesting stuff along the way.

      Oh regarding those Electric Universe 'wackos':

      You do realize that you're also calling a winner of the Nobel Prize in Physics a wacko, right?

      http://nobelprize.org/nobel_prizes/physics/laureates/1970/alfven-bio.html [nobelprize.org]

      And so far their successful predictions should at least be

      • by spectecjr (31235)

        We're actually using Maxwell-HEAVISIDE equations all over the world after Oliver Heaviside rewrote Maxwell's original equations from quaternion notation into a much simpler vector notation.. throwing out some interesting stuff along the way

        What interesting stuff was thrown out? I once spent a weekend comparing both, and as far as I can tell they're directly equivalent.

        (I was looking to see if there was a term thrown away by mistake ... doesn't look like it)

  • Ok, questions (Score:4, Interesting)

    by Marrow (195242) on Sunday September 14, 2008 @10:57AM (#24998223)

    1. How do you bend light without passing it through matter or using a grav field that will crush the experiment?

    2. If they can bend light, why are we using electron beams for crt's?

    3. If you could build loops of light can they be modulated to store information and read it back again?

    • Re:Ok, questions (Score:5, Informative)

      by mhall119 (1035984) on Sunday September 14, 2008 @11:47AM (#24998529) Homepage Journal

      1. How do you bend light without passing it through matter or using a grav field that will crush the experiment?

      Magnetic fields will bend light, which I believe is what this paper was based on.

      2. If they can bend light, why are we using electron beams for crt's?

      Because it's easier to bend a stream of electrons than a stream of photons.

      3. If you could build loops of light can they be modulated to store information and read it back again?

      I suppose, in theory, but it wouldn't be the most efficient means of data storage.

      The reason, I think (IANAP), that this could be important to fusion reactions is that a photon loop within a plasma could heat the plasma to fusion-levels without the plasma trying to burn it's way through the outer walls of the reaction chamber. Current torus designs, I think (IANA nuclear scientist), run the plasma around the inside of a magnetic field, like cars on a racetrack, to get the energies necessary for fusion. This causes that super-hot plasma to push against the outer part of the magnetic field, which has to be extremely strong to contain it.

      • by Marrow (195242)

        I don't think that magnetic fields can bend light.

        • by mhall119 (1035984)

          Well, technically they'll bend space, just like gravity does, which will bend the light. However, magnetism is many orders of magnitude less effective at it.

          • by ceoyoyo (59147)

            Magnetic fields don't bend space. At least not the way you're thinking. In string theory there's the possibility that magnetic and electric forces can be described as geometrical distortions of some of the EXTRA dimensions, but not the three (or four) we're used to.

            Light in free space completely ignores magnetic and electric fields, for all intents and purposes. If you want to get technical, magnetic and electric fields, since they carry energy, do gravitate, but VERY slightly. You'd need a truly huge f

      • > Magnetic fields will bend light, which I believe is what this paper was based on.

        Not true.

        • by mhall119 (1035984)

          I could be wrong, but I seem to remember reading about the very minuscule distortions of space-time that are produce around pulsars and other cosmological objects with very intense magnetic fields.

          • by drerwk (695572)

            ...around pulsars and other cosmological objects with very intense magnetic fields...

            Given that the question you answered required not crushing the experiment, and presumably having to do with the terrestrial use of the field for fusion, the cosmological do not count...
            But in complete seriocity, post a reference. I think you may be right, and it may have to do with a field so strong that the extreme vacuum energy results in non-linear propagation of the electric field. But Maxwell is linear and would not allow, if I understand correctly.

            • by mhall119 (1035984)

              I remember is working in pretty much the same was a gravity according to relativity theory, not that the attractive properties of magnetism were distorting space-time, but the extreme amount of it did. This was nearly a decade ago, though, and I haven't been able to find anything on the internet that backs it up. Perhaps it was just an article in a physics magazine, and not something that was actually proven or observed.

      • Were do you get that magnetic fields bend light? Not with Maxwell, not in a vacuum. Any reference to the contrary will be read!
      • by sedm1143 (1253596)
        Light is composed (in the particle picture at least) of photons which are neutrally charged particles. As such they are not affected by magnetic fields (which only affect charges MOVING in said magnetic field), outside of weird scenarios like a couple of people above have mentioned.
      • Re: (Score:3, Informative)

        by mako1138 (837520)

        The reason, I think (IANAP), that this could be important to fusion reactions is that a photon loop within a plasma could heat the plasma to fusion-levels without the plasma trying to burn it's way through the outer walls of the reaction chamber. Current torus designs, I think (IANA nuclear scientist), run the plasma around the inside of a magnetic field, like cars on a racetrack, to get the energies necessary for fusion. This causes that super-hot plasma to push against the outer part of the magnetic field, which has to be extremely strong to contain it.

        Not quite. In a tokamak, the plasma isn't accelerated around the torus to heat it. The basic method is ohmic, or resistive heating, where a current is induced in the plasma with magnetic fields. The current across the plasma resistance generates heat. This is kinda like your concept, but not exactly.

        Ohmic heating is typically insufficient for reaching fusion energies. The other methods of heating rely on direct energy injection, either through RF or neutral ion beams.

        Regarding containment, the magnetic fiel

      • Magnetic fields will bend light, which I believe is what this paper was based on.

        That's not true. Maxwell's equations are linear, meaning that they obey superposition. So, the light you are trying to bend and any additional magnetic fields will just pass right through each other.

    • by ntipouan (870467)

      Q to 1.

      How can you use a gravitational field in any
      experiment? oO

      That is, if you don't mean the field of Earth,
      from which we can't really shield anything
      in our experiments totally (or can we?).

  • by MikeUW (999162)

    I'm pretty sure this was already covered in Spiderman 3 - hopefully things turn out better this time around.

    • Re: (Score:3, Funny)

      by Lord Fury (977501)
      Doc Oc was Spiderman 2. The villain in Spiderman 3 was conforming to societal pressures, security guards outside of Hot Topic, and running out of mascara and hair spray.
  • Because I don't need flying cars. I want Jedi weaponry in my lifetime.

  • by symbolset (646467) on Sunday September 14, 2008 @11:32AM (#24998429) Journal
    That is all.
  • Maxwell's Equations? (Score:2, Interesting)

    by Snowtred (1334453)
    Its been awhile since I've had anything with Vector Calculus, but doesn't a stable loop of light violate Maxwell's Equations in some way? Divergence of B = 0, Div of E = p/epsilon, Curl of E = dB/dt. Seems like a stable knot might not fit with that. Anyone more math savvy know?
    • by shrikel (535309)
      Easy. They're using New Math.

      ...a relatively new solution to Maxwell's equations...

  • Ball Lightning? (Score:2, Interesting)

    by PeterJFraser (572070)
    If it is possible it probably appears in nature.
  • Why aren't they simply published on the internet, instead of some silly place that asks $18 for a pdf?

    • by ceoyoyo (59147)

      Because somebody has to manage things such as peer review and maintaining stable, reliable, long term archives.

      Have you noticed that stuff "published on the Internet" can be unreliable?

      $18 is ridiculous for one article. If you're really interested you should be able to get it free through any library.

      • by RockDoctor (15477)

        The $18 is a "laughing price" ; they don't want anyone to pay them $18 to read one article. What they (Nature Publishing Group) want you, and lots of others, to do is pay approximately £145 (whatever that is in your currency) for a year-long subscription to the magazine (50 or 51 editions) plus unlimited access to their archives. It is, after all, a magazine, and while it's raw content is given to it by authors, it still has real costs in organising peer review, typesetting (ever tried laying out a pa

    • by jd (1658)
      More than a few are pre-published for free, but aren't peer-reviewed and can potentially therefore deviate substantially from what is actually published. Since an entire science journal doesn't usually cost $18, except perhaps for something truly arcane, and as most scientists can't afford to buy their own journals, relying on the University library to do it for them, the odds are extremely high that you'll find a cheaper version somewhere.
  • Unfortunately the figures, equations, and tables came out as "Unfortunately we are unable to provide accessible alternative text for this. If you require assistance to access this image, or to obtain a text description, please contact npg@nature.com".....if someone can suggest where I should upload the PDF, I'd do that too.

    ======

    Letter

    Nature Physics 4, 716 - 720 (2008)
    Published online: 31 August 2008 | doi:10.1038/nphys1056

    Linked and knotted beams of light

    William T. M. Irvine1,2 & Dirk Bouwmeest

  • When will Air Jordans have light-based shoelaces?
  • Stable loops of light in plasma. I wonder if this might be related to ball lightning?

  • Let's cut to the important question... Can this tech be applied to make better light saber toys??

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