Slashdot Log In
Tying Knots With Light
Posted by
Soulskill
on Sun Sep 14, 2008 09:08 AM
from the knot-easy dept.
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."
Related Stories
This discussion has been archived.
No new comments can be posted.
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.
Done in 1984 - Flux Capacitor (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.
Re: (Score:2)
Real technical vocabulary (Score:5, Funny)
Bouwmeester continued by saying that light is, "way cool" and the ability to tie knots with it would be, "totally freaking awesome".
Re: (Score:2)
Light sabers? (Score:5, Funny)
Re: (Score:2)
Yup, it is. But only if it's perfectly spherical and never touches anything.
(Disclaimer: No, I just made that up, but something quite like it is probably true. Might have to be toroidal.)
Re: (Score:2)
Shit! I hate it when my Schwartz gets twisted!
The summary misses the key point (Score:5, Insightful)
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)
Re: (Score:2)
> 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)
Re: (Score:3, 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 [iter.org] state that it will take until the 2050s until the first production fusion powerplant comes online.
Re: (Score:2)
Re:The summary misses the key point (Score:5, Informative)
Parent
The Real Question is.... (Score:3, Interesting)
The real question is was a silver hammer necessary?
It's just cool (though maybe unrealistic)! (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.
Re: (Score:2)
Whooooosh....
Re: (Score:2, Insightful)
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:2)
> 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?
Re: (Score:2)
The Electric Universe....
because Creationists need someone to mock on science.
-
Re: (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 [nobelprize.org]
And so far their successful predictions should at least be
Ok, questions (Score:4, 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?
Re:Ok, questions (Score:5, 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.
Parent
Re: (Score:2)
I don't think that magnetic fields can bend light.
Re: (Score:2)
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.
Re: (Score:2)
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
Re: (Score:2)
> Magnetic fields will bend light, which I believe is what this paper was based on.
Not true.
Re: (Score:2)
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.
Re: (Score:3, 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 fiel
Dr. Octavius? (Score:2, Funny)
I'm pretty sure this was already covered in Spiderman 3 - hopefully things turn out better this time around.
Re: (Score:3, Funny)
Don't cross the streams (Score:4, Funny)
Maxwell's Equations? (Score:2, Interesting)
Ball Lightning? (Score:2, Interesting)
Scientific papers (Score:2)
Why aren't they simply published on the internet, instead of some silly place that asks $18 for a pdf?
Re: (Score:2)
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.
Re: (Score:2)
The real question... (Score:2)
Ball lightning? (Score:2)
Stable loops of light in plasma. I wonder if this might be related to ball lightning?
Subscription required?? (Score:5, Insightful)
Parent
Re: (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.
Re: (Score:3, 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.
Re: (Score:3, 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 purchasi
Re: (Score:2)
In the US publicly funded research does have to be freely available after some period of time.
Just like anything, the issue is a little more complex than "why don't you just publish it yourself on the Internet?" For an entrenched industry the journal publishers actually seem to be responding to reality fairly well. For a comparison point, see the RIAA.
You are not denied access. ANY library should be able to get you a copy, for free (or possibly the cost of a library card), of any article you like. It mi
Re: (Score:2)
Because up until quite recently that was a reasonable system. It is in your interest for the journal you submit to to remain solvent.
The Internet has changed things, and the journal industry is trying to figure out how to deal with it. Like any big industry, they're pretty slow at it. They ARE figuring it out though. Science releases freely any article older than a year, and there are open access journals springing up all over the place. One of the problems that has yet to be worked out is that the ope
Re:Subscription required?? (Score:5, 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.
Parent
Re: (Score:2)
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.
At the time of writing, this only achieves 3, Insightful? Come on mods, be a little more generous...
Re: (Score:2)
That trick has long since stopped working. All these subscription sites with fake google result have switched to detecting the googlebot by IP.
Re: (Score:2)
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.
Not true. The only way to provide valid XHTML is to serve it as text/html to IE and application/xhtml+xml to modern browsers.
Re: (Score:2)
And the stated goal of these journals: to make research -more- available.