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Science Technology

Repulsive Force Discovered In Light 176

Posted by kdawson
from the push-me-pull-you dept.
Aurispector writes in with news that the Yale team that recently discovered an attractive force between two light beams in waveguides has now found a corresponding repulsive force. "'This completes the picture,' [team lead Hong] Tang said. 'We've shown that this is indeed a bipolar light force with both an attractive and repulsive component.' The attractive and repulsive light forces Tang's team discovered are separate from the force created by light's radiation pressure, which pushes against an object as light shines on it. Instead, they push out or pull in sideways from the direction the light travels. Previously, the engineers used the attractive force they discovered to move components on the silicon chip in one direction, such as pulling on a nanoscale switch to open it, but were unable to push it in the opposite direction. Using both forces means they can now have complete control and can manipulate components in both directions. 'We've demonstrated that these are tunable forces we can engineer,' Tang said."
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Repulsive Force Discovered In Light

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  • by Anonymous Coward on Tuesday July 14, 2009 @11:57PM (#28699871)

    Sweet! Next up, how lightsabers don't work.

    • by erroneus (253617) on Wednesday July 15, 2009 @12:05AM (#28699929) Homepage

      I always thought lightsabers don't work so much on the notion of light as the convergence of energy and solid matter where energy becomes matter and matter becomes energy explaining why lightsabers cast a shadow and why training lightsabers don't cut. (And also why there are light bridges that are mentioned but never seen in star wars.) It just happens that light is given off in this mashup of state changes.

      • Re: (Score:3, Interesting)

        by TiberSeptm (889423)
        I always assumed it was a misnomer and they were just very skillfully manipulated plasma devices. We already have the technology to create "plasma windows" that can hold back atmosphere against a vacuum and plasma torches than can cut through cowboynelium. Why not bridges and swords of the highly charged fun-stuff?
        • by erroneus (253617) on Wednesday July 15, 2009 @12:41AM (#28700177) Homepage

          Because you can't "block" other lightsabers based on such technology. I recall seeing one lightsaber video where the humor of the video was based on that notion. They were successful in creating an effective lightsaber in that it had a definite end point and would cut through anything, but when they attempted to cross swords, they just passed through one another... and then one of the people cut through the other one with the lightsaber he had. You can probably find it on youtube or on theforce.net somewhere...

          • by Dracos (107777)

            Only hard core Star Wars nerds would attempt to cross swords.

            • Re: (Score:3, Funny)

              by LKM (227954)
              Don't cross the swords! It would lead to all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.
              • by Nickbou (1403667)

                Don't cross the swords! It would lead to all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light.

                Yeah, yeah, total protonic reversal. Please, this is not my first rodeo.

          • by nessus42 (230320) <doug&alum,mit,edu> on Wednesday July 15, 2009 @02:54AM (#28700743) Homepage Journal

            They were successful in creating an effective lightsaber in that it had a definite end point and would cut through anything, but when they attempted to cross swords, they just passed through one another... and then one of the people cut through the other one with the lightsaber he had. You can probably find it on youtube or on theforce.net somewhere...

            Indeed you can find it on YouTube. Here it is:

                      http://www.youtube.com/watch?v=dsZNiCSCLXw [youtube.com]

            |>ouglas

          • Re: (Score:2, Funny)

            by Zediker (885207)
            Considering the powerful magnetic fields involved in order to contain the "plasma blade" and due to the way similar poles repel eachother, I dont see why plasma-based "light sabres" couldnt block one-another, since it would all be magnetic field interactions. The only downside is that this would likely cause the plasma-blade part of the device to fail somehow, unless there was some sort of stability mechanism to counter the other blades magnetic interference. Otherwise you'd end up with something like the S
            • by bsane (148894)

              This also doesnt go into the folly that your handle-section would be likely pulled right into your enemies blade-section from 20+ feet away

              I think you just described 'The Force'.

        • by superdana (1211758) on Wednesday July 15, 2009 @09:28AM (#28702611)
          I always assumed it was a movie. ;)
      • by Anonymous Coward on Wednesday July 15, 2009 @12:31AM (#28700109)

        Actually, they cast a shadow because the actors are really holding flash gun handles with white sticks in them, and the blades are rotoscoped on later. Yup, they were just too lazy to get rid of the shadows/film at angles to avoid them.

        • Re: (Score:3, Funny)

          by icebike (68054)

          Or perhaps they started to remove than and said, you know what, let's leave them in, and let the slashdot crowd try to explain the technology. Its not their job to fill in every detail of every imaginary technology.

        • Re: (Score:3, Informative)

          by Skreems (598317)
          I swear I read somewhere when I was much younger that in the originals they actually had blades covered in colored glass beads, and blasted extremely bright stage lighting at them during the fight scenes. That's why Darth Vader shines like Yul Bryner's head during the fight scenes, but not so much other times.

          Might have been just the first movie, since the later ones had them using the things in darker settings as well.
          • Re: (Score:3, Informative)

            by DinDaddy (1168147)

            You are correct. For the first film, they were octagonal blades with rotating motors and scotchlite paint, which reflected light back to the camera from a large light shooting from just behind it.

            The effect was weak (see Vader's as he is walking towards the closing blast doors before they escape the deathstar) so they ended up animating over it in almost all the shots.

            The rotation motor is the reason Obi-wan's saber has a white electric cord coming out of the hilt and going into his sleeve in the shot wher

      • by Sensible Clod (771142) <dc-7&charter,net> on Wednesday July 15, 2009 @01:16AM (#28700359) Homepage
        Oh, really? I thought lightsabers don't work because of the impossibility of handheld gigawatt nuke reactors to control the several tesla magnetic field to confine the plasma at one meter wirelessly.
        • Re: (Score:2, Funny)

          by roger_pasky (1429241)
          Flash gun handles with white sticks in them... Yeah, right... and now you'll tell me tooth fairy does not exist.

          Thanks God we can still trust Santa Claus. Maybe next Christmas I'll ask for a real lightsaber with this technology.
          • by mcgrew (92797)

            I'm Santa Clause, the tooth fairy, AND the Easter bunny. Just ask my kids, they'll tell you. I never hid the truth from them and they never suffered from their lack of ignorance.

      • convergence of energy and solid matter where energy becomes matter and matter becomes energy explaining why lightsabers cast a shadow

        I think you'll find they cast a shadow because the actors had to wield a bright blue brush-shaft whilst filming, before the CG was put in ;)

      • Wrong, they don't work because they're the product of a work of fiction.
    • Now, data (or Data) can join the dark side, and display a tension-deficit disorder

  • This is why (Score:2, Funny)

    by masmullin (1479239)
    Ahhh finally a scientific explanation of why girls are repulsed by me! Its not my lude jokes... its light!
  • by OakDragon (885217) on Tuesday July 14, 2009 @11:58PM (#28699881) Journal

    ...a bipolar light force with both an attractive and repulsive component...

    Just like my ex-girlfriend!

  • by spacefiddle (620205) <{moc.liamg} {ta} {elddifecaps}> on Wednesday July 15, 2009 @12:00AM (#28699895) Homepage Journal
    is for an alcoholic millionaire to cram it into a suit of armor!
  • Finally... (Score:3, Funny)

    by mldi (1598123) on Wednesday July 15, 2009 @12:00AM (#28699897)
    ... an explanation as to why so many WoW geeks shriek when they leave their parents'.... errrmmm.... their basements during the day.
  • by sootman (158191) on Wednesday July 15, 2009 @12:03AM (#28699919) Homepage Journal

    "Repulsive Force Discovered In Light"--well DUH. Anyone who's ever been in a strip club at closing time has witnessed this phenomenon.

  • Angular momentum (Score:5, Interesting)

    by TiberSeptm (889423) on Wednesday July 15, 2009 @12:08AM (#28699951)
    Huh, I had always wondered how to resolve conservation of light's angular momentum during destructive interference of collinear laser pulses consisting of phtons of the same "handedness." I wonder if this can be used to explain that.
    • Re:Angular momentum (Score:5, Interesting)

      by TiberSeptm (889423) on Wednesday July 15, 2009 @12:14AM (#28699999)
      Sorry about the double post, but I was reading an old paper on the subject. Light has a lower angular momentum inside an dialectric than in air or vaccum. This means that it imparts a force upon entering a dialectric and upon exiting a dialectric. If it is combined out of phase within the dialectic, then destructive interference will mean that the entering and exiting force imparted by the light beams will be out of balance (as the intensity of the exiting beam will be lower without any radiation-pressure type interactions being required) and there will be a net repulsive force. I wonder if this is the same thing as what they are seeing in the article.
      • by tenco (773732)

        Light has a lower angular momentum inside an dialectric than in air or vaccum. This means that it imparts a force upon entering a dialectric and upon exiting a dialectric. If it is combined out of phase within the dialectic, then destructive interference will mean that the entering and exiting force imparted by the light beams will be out of balance (as the intensity of the exiting beam will be lower without any radiation-pressure type interactions being required) and there will be a net repulsive force.

        If the beam is exiting the dialectric with a lower intensity as it normally would, where goes all the energy?

    • by Angstroem (692547) on Wednesday July 15, 2009 @04:24AM (#28701015)

      I had always wondered how to resolve conservation of light's angular momentum during destructive interference of collinear laser pulses consisting of ph[o]tons of the same "handedness."

      Bingo, Sir.

    • Re: (Score:3, Funny)

      by Digital Vomit (891734)

      I had always wondered how to resolve conservation of light's angular momentum during destructive interference of collinear laser pulses consisting of phtons of the same "handedness."

      Ummm...yeah...me, too...

    • by steelfood (895457)

      during destructive interference of collinear laser pulses

      So having known for many years that we're not supposed to cross the beams, I guess now we know why.

  • Light has an attractive and repulsive component. Sounds like Star Trek deflector and tractor beams to me. Who knows what they will be able to do with this in a hundred years or so.

    • by Laxori666 (748529) on Wednesday July 15, 2009 @12:28AM (#28700087) Homepage
      Anything, as long as you divert enough power to the deflector dish.
      • Maybe hovercraft like the Nebuchadnezzar [starhtml.de].
      • No, no, no. That's only half of the problem. Don't forget the inevitable social side-story, where some kid's pet tribble has gotten into the jeffries tubes, and his mom will be angry if he doesn't get it out and safe the ship in the process.

      • by yabos (719499)
        You need a recursive algorithm to tie the warp core into the main deflector dish. Then you can use that to close the subspace anomaly. But make sure you reverse the polarity of the tachyon beam first.
    • by TiberSeptm (889423) on Wednesday July 15, 2009 @12:32AM (#28700127)
      Possibly, but this looks like the effect of light beams interacting inside of a target dialectric combined with the differences in light's angular momentum at the different speeds of c inside and outside the target. Aside from also cooking whatever you wanted to tractor, you might be able to accomplish this with very powerful laser pulses and "cloaking" metamaterials. Since the metamaterials bend the relevent light frequencey around a target you may be able to exert the force on the material, use a vastly powerful laser pulse, and not cook the target. This could impart enough force to be useful and could be used to maintain a cloud of such objects over vast distances using a web of laser pulses pushing and pulling the disparate objects into a desired position. Kind of a neat idea and a good intuitive leap to suggest tractor beams

      http://www.msnbc.msn.com/id/12961080/ [msn.com]
  • Nice. But. (Score:4, Interesting)

    by terbo (307578) on Wednesday July 15, 2009 @12:31AM (#28700111) Journal

    While discovering new properties of old phenomena is interesting,
    does anyone ever question the 'bravado' of the wording of such
    discoveries?

    Does it inhibit later discoveries, in creating artificial limitations
    through language and subsequently expectation?

    • by Hadlock (143607)

      Someone broke your
      Carrier Return

      • Someone broke your
        Carrier Return

        When you find the USS Nimitz, look aboard and check to see if any "carriage return" keys are missing.

        Hint: Think OLD typewriters... and get off my lawn!

        • Re: (Score:3, Funny)

          by Hadlock (143607)

          Everyone knows carriage returns were supplanted by carrier returns with the advent of aircraft carriers. They're looking at revising the term as Shuttle Return when the Space Shuttle Program is finally Shuttered.

          • But my military Linux does not use any frikkin' Carrier Returns. It only separates the lines using Maginot Line Feeds.
            • by tenco (773732)

              It only separates the lines using Maginot Line Feeds.

              That's handy. You only need a piece of paper to write a whole book on, this way.

          • 3 of the best things in life are a good aircraft landing, a good poop, and a good orgasm
            a night landing on a carrier is one of the few times you get to experience all three at the same time

        • That's odd. I thought there was
          NO CARRIER

    • Re: (Score:3, Informative)

      by domatic (1128127)

      Probably not. Things are worded this way to explain them to laymen. Physicists are going to describe these phenomena with systems of equations and words and the equations will suggest deeper intuitive meaning to those used to working with them.

  • Force source? (Score:2, Insightful)

    by aeve (741109)
    What the crap is an article about a newly found force that doesn't explain at least a theory as to the source of the force? Is it magnetic?
  • by InsertWittyNameHere (1438813) on Wednesday July 15, 2009 @12:33AM (#28700129)
    Now emits 100% attractive light. That's twice as much as the next leading brand!
  • Can anyone enlighten me? I thought there were only the strong and weak interaction, electromagnetism and gravity.

    Is this some effect of electromagnetism? Or of one of the other forces?

    Because if it were none of this forces, it would pretty much throw the whole standard model of quantum physics into a blender and force us to put it together again, wouldn't it?

    This is really really interesting to me!

    • by MillionthMonkey (240664) on Wednesday July 15, 2009 @04:34AM (#28701063)
      When light shines through a diffraction grating and spreads out into beams going right and left, we don't need to talk about some strange new "force" that pushed the rightward beams to the right and the leftward beams to the left, since it's still a manifestation of electromagnetism. But specifically quantum electrodynamics, not classical electromagnetism which isn't good at handling this stuff.

      In this case, the fundamental reality is, of course, that each photon splits up at the grating and its wave function takes all paths- interfering with itself everywhere in space. When the photon is discovered hitting a screen, it will strike in a place that reveals the least amount of information about the path it actually took, and there will be many such places, called "interference maxima". (It probably won't land in a place that makes it obvious how it got there- such places are interference minima.)

      The Casimir force [wikipedia.org] is another "force" like this. Underneath it's still quantum electrodynamics.

      If you find this stuff interesting you should read Feynman's QED... basically Quantum Electrodynamics For Dummies. What you'll find is interesting:
      • Light can go faster than light or slower than light- but only briefly
      • Light really doesn't care about surfaces between air and water and glass or whatever
      • Light doesn't really go in straight lines, that's just sort of how things turn out

      These guys are sending beams of IR photons down a channel that is 220nm x 220nm, smaller than their wavelength. So transverse wave motion isn't a consideration at all... the light can barely fit in there and its wavefunction inside has no longitudinal component. I think it can be totally described with two scalar functions along the waveguide. The photons have apparently been through a beamsplitter or something and are being recombined out of phase. It's too bad the article doesn't provide any further details on how the photons were polarized (circular, linear, what?) or how the quantum interference between the two photon states results in transverse forces on the waveguide.

      • In this case, the fundamental reality is, of course, that each photon splits up at the grating and its wave function takes all paths- interfering with itself everywhere in space. When the photon is discovered hitting a screen, it will strike in a place that reveals the least amount of information about the path it actually took

        Or the light wave propagates through the aether and this transversal force is simply bernoulli's principle.

        P.S. Michaelson&Morley didn't give a negative result, they found a result inconsistent with a FIXED aether, but fully consistent with a fluidic aether.

    • by GryMor (88799)

      Light, aka, the photon, is the force carrier for electromagnetism, so it's either electromagnetism or gravity due to energy density. Gravity can effectively be ignored at the scales they are talking about, so it must be electromagnatism. This is confirmed if you RTFA and see that it's caused by light in dielectric materials.

  • by TheWanderingHermit (513872) on Wednesday July 15, 2009 @12:52AM (#28700217)

    So Earth finally discovers the repulsive force from the ninth light ray that they've known about on the dying planet of Barsoom for millennia. Does that mean that soon we can have navies of huge floating ships like the Kingdom of Helium does? Or that soon we'll be able to see the two colors they know about on Barsoom that we've never seen on Earth?

    • I got this. Some moderator not only didn't get the reference, they didn't even bother to look it up.

      Reading stuff like this at a too early age helped get me into physics rather than law...my bank account hates science fiction.

  • I work IT. (Score:4, Funny)

    by eosp (885380) on Wednesday July 15, 2009 @01:05AM (#28700271) Homepage
    I already knew that light repelled me.
  • by carpefishus (1515573) on Wednesday July 15, 2009 @01:07AM (#28700295)
    This was previously demonstrated by cockroaches.
  • finally, they've found out what was missing from the promise of a low-energy, low-heat, ultra-fast future in optical computing: Moving parts!

  • by zekt (252634) on Wednesday July 15, 2009 @02:11AM (#28700597)

    As I understand it, current thinking is that light bends because of gravity, and this is how distant planets and other distant objects are found.

    Could it be that it is, instead, is just light being pulled or pushed against something that is being observed, rather than an observation of the gravity that the body has?
    The next effect is the same I guess.

    • Could it be that it is, instead, is just light being pulled or pushed against something that is being observed, rather than an observation of the gravity that the body has?

      Or maybe that's all gravity is. If light == energy == matter, then why not? Maybe gravity and this attraction are the same thing. Maybe we're "this" far from figuring out the notion of anti-gravity.

  • There are a lot of jokes as replies, I assume partially because the summary sets them up so well and partially because it is rather dense subject matter. But doesn't this stuff excite you? Years ago a friend and I used to talk about how there should be a way to make computers out of light and we should just try for that, because, well, there isn't much faster. Articles like this mean its closer to reality. Even if it never happens in my life time it still excites me to know we are headed there.

    I am sure s
    • I believe there is one serious thread all the rest are people demonstrating their lack of a sense of humour :(
    • by omnichad (1198475)

      I agree that it's fascinating but....electricity travels almost as fast as light. I hardly think that would be the reason to go for optical computing.

  • Sorry Wesley Crusher. We came up with the idea first.....

    But feel free to take credit for it when you save the Enterprise.

  • All I ever needed to create something repulsive with light was Google Image Search.
  • by ryanvm (247662) on Wednesday July 15, 2009 @08:04AM (#28701899)
    Ugh. That is so digusting.
  • about photons from images of fat people having sex.

  • An added benefit of using light rather than electricity is that it can be routed through a circuit with almost no interference in signal, and it eliminates the need to lay down large numbers of electrical wires.

    There's no interference from electrical signals, but there is interference from light. And rather than needing a large number of electrical wires, this requires large numbers of light waveguides.

  • Find anti-gravity already. I want my flying car!
  • Could this new-found force somehow be related to what is causing the universe to continue to expand? Or otherwise account for forces now attributed to "dark matter"?

You have a tendency to feel you are superior to most computers.

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