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Tying Knots With Light

Posted by Soulskill on 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."

25 of 125 comments (clear)

  1. Done in 1984 - Flux Capacitor by Anonymous Coward · · Score: 4, Funny

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

  2. Real technical vocabulary by Nuclear+Elephant · · Score: 5, Funny

    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".

  3. Light sabers? by slapyslapslap · · Score: 5, Funny

    Please tell me this is getting me closer to owning a light saber. PLEASE!!!

  4. The summary misses the key point by Kupfernigk · · Score: 4, Insightful
    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.

    --
    From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
    1. Re:The summary misses the key point by quanminoan · · Score: 4, Informative

      Exactly - the magnetic confinement for a fusion torus is already completely closed. With a torus, as I understand, there are issues with plasma stability that limit the performance of the devices. However, there is no need for this light looping when you can just alter the magnetic field. Stellarators use a sort of 'helical' magnetic field twisting around a toroid to create a much more stable environment. See: http://www.physics.ucla.edu/icnsp/Html/spong/w7x_with_coils.JPG.

    2. Re:The summary misses the key point by sedm1143 · · Score: 3, Interesting

      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 then there's a long way from there to a practical device, assuming it actually proves technically feasible.

    3. Re:The summary misses the key point by JaredOfEuropa · · Score: 2, Informative

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

      No.

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

      --
      If construction was anything like programming, an incorrectly fitted lock would bring down the entire building...
    4. Re:The summary misses the key point by jd · · Score: 2, Interesting

      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 fork, rather than trying to copy the sound - the feedback loop becomes a part of the system.

      --
      It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
  5. The Real Question is.... by cychem1 · · Score: 3, Interesting

    The real question is was a silver hammer necessary?

  6. It's just cool (though maybe unrealistic)! by gardyloo · · Score: 5, Informative

    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.

    1. Re:It's just cool (though maybe unrealistic)! by Anonymous Coward · · Score: 2, Insightful

      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 out to be correct. And theoretical physicists have a habit of doing that.

      While the majority of wackos are inevitably going to be wrong, a few are just as inevitably going to be right. Let the scientific method decide.

    2. Re:It's just cool (though maybe unrealistic)! by Anonymous Coward · · Score: 2, Insightful

      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

      And so far their successful predictions should at least be called _interesting_ and not 'wacko' for anyone who follows the scientific approach with components like theory, predictions, verification, modification etc.

      http://thunderbolts.info/predictions.htm

      While the ideas of plasma cosmology seem radical. At this point to me they don't seem any more radical than the ideas put forth by standard cosmologists of multiple universes, dark matter, multiple dimensions, black holes, neutron stars spinning from 1.4ms(!!) to thirty seconds, strange matter, dark energy, etc..

  7. Ok, questions by Marrow · · Score: 3, Interesting

    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?

    1. Re:Ok, questions by mhall119 · · Score: 4, Informative

      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.

      --
      http://www.mhall119.com
    2. Re:Ok, questions by mako1138 · · Score: 2, Informative

      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 field in a torus is not like a hard wall; it only presents a permeable barrier that particles are still able to diffuse across. If you turn up the magnetic field, you slow down the diffusion, but turn it up too high and you risk plasma instabilities. The key is to control the energy leakage to a point where enough energy stays in the plasma long enough to sustain the reaction.

      I haven't read this new paper yet, so I can't comment on its applications to fusion.

  8. Dr. Octavius? by MikeUW · · Score: 2, Funny

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

    1. Re:Dr. Octavius? by Lord+Fury · · Score: 3, Funny

      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.

  9. Subscription required?? by linhares · · Score: 5, Insightful

    These science publishers are as evil or worse than the RIAA/MPAA with this paywall BS. To paraphrase, science is too important to be left to those that can pay 40 bucks per paper. I can't understand why Google, who wants to "organize the world's information", has not done anything to prevent the world's most valuable information from being inaccessible.

    1. Re:Subscription required?? by boto · · Score: 2, Insightful

      Google has already done it: the researchers just need to make their papers publicly available *anywhere* on the Web, and you'll find the articles on Google Search and Google Scholar Search.

      Google can't do much else if the authors aren't interested in making their works openly acessible.

    2. Re:Subscription required?? by ceoyoyo · · Score: 2, Interesting

      Most journals make you transfer copyright to them. Making your paper available is then illegal.

      It's changing, faster and faster. More journals are opening their archives after one or two years.

      Of course, you can always go to a library and get a paper for free. Even the local library in the town of 800 people I grew up in had a borrowing agreement with more than one university library.

    3. Re:Subscription required?? by causality · · Score: 4, Insightful

      Well, they could zero the pagerank on sites that show different stuff to googlebot vs ordinary mortals.

      If THAT'S all it is, then set your user agent to "Googlebot/2.1 (+http://www.google.com/bot.html)" and say fuck 'em. But you're right, Google should actively resist this sort of double standard because it's a detriment to the usefulness of the search engine. It doesn't matter how many great results you get with a search engine if you can't actually access the information in those results.

      You know, I still don't understand why there is even such a thing as a user agent string. That is, I can see why i.e. Microsoft would want such a thing but I do not see any way that it's in the interests of users. If we really want standards and we really want openness, having no way for a Web server to determine what the browser is can only advance this goal. Then the only concern is whether that browser is standards-compliant.

      --
      It is a miracle that curiosity survives formal education. - Einstein
    4. Re:Subscription required?? by causality · · Score: 2, Interesting

      Most journals make you transfer copyright to them. Making your paper available is then illegal.

      That's pure evil. Why do people keep submitting material to them? Journals that do that should lose their credibility.

      It's changing, faster and faster.

      I hope you are right.

      How about this: if you received any (one penny or more) public grants or public funds to perform your research, then that research must be available to the public free of charge. If you are wealthy and want to entirely fund your own research (for example), then you may do whatever you like with the results. The part that I consider bullshit is the idea that tax dollars are taken from me by force or threat of force under a confiscatory tax system and then I am denied access to what this money is purchasing.

      --
      It is a miracle that curiosity survives formal education. - Einstein
  10. Don't cross the streams by symbolset · · Score: 4, Funny

    That is all.

    --
    Help stamp out iliturcy.
  11. Maxwell's Equations? by Snowtred · · Score: 2, Interesting

    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?

  12. Ball Lightning? by PeterJFraser · · Score: 2, Interesting

    If it is possible it probably appears in nature.