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Science Technology

How To Cloak Objects At a Distance 136

Posted by samzenpus
from the can-you-see-me-now dept.
KentuckyFC writes "All invisibility cloaks to date work by hiding an object embedded inside them. Now a group of physicists have worked out how to remotely cloak objects that sit outside a cloaking material. The trick is to make the cloaking material with optical properties that are exactly complementary to the space outside them. Complementary means that the material reverses the effect the space has on a plane wave of light passing through it. To an observer this space would appear to vanish. The scientists say that to cloak an object sitting outside the cloaking material, first measure its optical properties and then embed a "complementary image" of the object within the cloak. So a plane wave is first distorted by the object but then restored to a plane by the complementary image of the object within the cloak (abstract). An observer sees nothing. This method has another benefit. Objects hidden in conventional cloaks are blinded because no light enters the cloaked region. But objects that are remotely cloaked like this should still be able to see their surroundings."
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How To Cloak Objects At a Distance

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  • by Lumpy (12016) on Thursday November 06, 2008 @09:05AM (#25659705) Homepage

    "The trick is to make the cloaking material with optical properties that are exactly complementary to the space outside them. "

    So if you are hiding a tank in the desert, paint it desert colors?

    Oh wait more complex... desert != shiny...

    use flat paint.

    got it!

    • by discord5 (798235) on Thursday November 06, 2008 @09:12AM (#25659793)

      So if you are hiding a tank in the desert, paint it desert colors?

      We've actually gone one step further. We've actually built an entire tank made out of sand. Our prototype required very little materials other than that: a bucket, a shovel and a beach.

      It's still a prototype though since it breaks easily, but it does blend in with its surroundings, and it has been proven combat worthy by having our troops stomp over sandcastles.

      • by Arimus (198136)

        It's still a prototype though since it breaks easily,

        What do you mean prototype? that sounds almost ready for serious use - just look at most tanks ;)

      • by Cthefuture (665326) on Thursday November 06, 2008 @11:44AM (#25661763)

        Heh, you know to this day I'm still pissed about something that happened when I was in 2nd grade. We were doing some kind of group work thing and I got was this multiple choice question about what a telescope could be made out of. One of the possible answers was sand. I instantly came up with the design in my head. The question wasn't very specific so I wasn't sure if I would need to melt the sand to form the lenses but I knew I could use a glue/sand mixture for the body (shaped by a mold while it hardened).

        Naturally I got the answer "wrong" and nobody would listen to me. That episode basically represents how my entire life has gone when dealing with other people...

        • by psydeshow (154300) on Thursday November 06, 2008 @02:37PM (#25664533) Homepage

          Otherwise known as "Too smart for your own good." That happened to me all the time while I was growing up.

          Now people just think I'm a crank when I make non-linear associations like that.

          • by Artuir (1226648)

            People mod that up funny, but it's actually insightful as to how the school system doesn't work for everyone, and how thinking outside of the box is so frowned upon when everyone should do their utmost to encourage it.

            • Forget the box, think inside, outside, underneath, or on top of the box, just for fuck's sake use your damn brain.
            • People mod that up funny, but it's actually insightful as to how the school system doesn't work for everyone, and how thinking outside of the box is so frowned upon when everyone should do their utmost to encourage it.

              It's not just the school systems that frown upon non-standard answers, it's the majority of society. In many situations, propose an idea even slightly outside of the predominant group-think, and watch how many folks start to get offended/shoot it down without thought.

              For example - I had a bos

        • by Sethumme (1313479)
          I hate how all those elementary questions had an implicit "only pick the practical answers." That period is not the time to stymie children's creativity.
        • by Fluffeh (1273756)
          You should have replied in a /. friendly car analogy instead of using some mumbo jumbo about melting sand to make glass.

          Sheesh!
        • by nilbog (732352)

          I had this happen when I insisted that there was a reasonable argument that glass could be considered a viscous liquid, that objects of different weights fall at the same rate in a vacuum, and that the plural of "Ravioli" is "Ravioli" and not "Raviolies."

          Each time it was me alone against my friends, students, and teachers (including supposed science and english teachers!) and each time I was right. Schools are full of retarded people who can't think of anything better to do with their lives (well, higher e

    • by Emb3rz (1210286) on Thursday November 06, 2008 @09:15AM (#25659821) Homepage
      Think about it in terms of bitmasks...

      Background   = 00110000
      UncloakedObj = 11100000
      CloakedObj   = 00001100

      CloakShows   = 11110000
  • by vvaduva (859950) on Thursday November 06, 2008 @09:08AM (#25659747)

    The better question is, can they fire while cloaked? I hear the Klingons made substantial advances in that area.

    • Mmm not sure. I know Harry Potter couldn't.

  • by AltGrendel (175092) <ag-slashdot@ex[ ].us ['it0' in gap]> on Thursday November 06, 2008 @09:08AM (#25659751) Homepage
    ...this reminds me of that "X-Files" article from yesterday.

    "Gee, if we had enough money, we could make your troops invisible, Mr. General Sir."

  • Dougal, this cow is small.

    Those ones are far away.

    Small...far away.



    "That's nearly as mad as that thing you told me about the loaves and the fishes."
    • Re: (Score:2, Insightful)

      by andy19 (1250844)
      As much as I love the Father Ted reference, that really doesn't have anything to do with this article.
  • wait (Score:5, Funny)

    by jav1231 (539129) on Thursday November 06, 2008 @09:20AM (#25659861)
    Wouldn't pr0n constitute a complimentary image? Cuz I gotta tell ya with the right pr0n nearly everything around it disappears.
  • Jeez (Score:5, Funny)

    by Konster (252488) on Thursday November 06, 2008 @09:22AM (#25659875)

    Everyone knows that a tachyon sub-space burst from the main deflector dish invariates the sublimated inverse proportional fields that all cloaking devices use.

    Phase the array with multi-numinal values and any cloak in the perimeter will be dropped due to subversive nominal decay but only if you attune your tertiary sensing systems to compensate for the quadralinear flux.

    This is all so simple, and I have to wonder about the credentials of /. editors that would post such elementary issues on this website.

    I mean really, this is first trimester stuff that any recruit can do off the tops of their heads.

    • by jez9999 (618189)

      ... and, Mr. Data.

      Yes, sir? ... Nicely done!!!

    • That's the oldest trick in the book, and it only works against objects that are polaron neutral against the subspace background. And since most variations of phase-harmonic shields break polaron symmetry any military warp-capable ship is immune.

  • So we have the technology for an invisibility cloak. Now I just need an unbeatable wand and a funky "I see dead people" ring and I can be master of death. Suck on that, Voldemort!
  • by Notquitecajun (1073646) on Thursday November 06, 2008 @09:32AM (#25659977)
    Ummm...howzabout just hiding behind a tree or ducking...
    • by dkleinsc (563838) on Thursday November 06, 2008 @09:41AM (#25660069) Homepage

      Notquitecajun, will you stand up please. (gunshot)

      This demonstrates the value of not being seen.

    • by chord.wav (599850)

      I was thinking more like going one step further past the point where you are a tiny on the horizon to your enemy's eyes

  • This must only work with translucent objects. The other method works with any object.

  • This "cloak"-technology is just a re-adjustment of your mental reference framework:

    Soon, you'll get these kindof presentations:
    "This! is the best thing ever since the previous thing that was the best thing ever!" "Can I see?"
    "It's right here, it's cloaked.. You can see it but you cannot perceive it. But believe me, it's there."
    "If it's invisible, it must be good! *throws monnies*"
  • by Dunbal (464142) on Thursday November 06, 2008 @09:35AM (#25660027)

    This technology, if adopted by the military, will probably only be useful against civilians. Against another sophisticated military there will always be a way to detect what you're trying to hide through other means than visible light - magnetism/alterations in the earth's magnetic field (in the case of big chunks of metal, heat), RF emissions, overhead imaging, radar, sonar, etc.

    You won't be able to hide your tank like this, but the small laser turrets to keep the neighbor's cat off the lawn might work... now if only those sharks would stop swimming.

    • Re: (Score:3, Interesting)

      by Yvanhoe (564877)
      That is why it is important to maintain sophisticated technology in the civil society.
    • by JustinOpinion (1246824) on Thursday November 06, 2008 @10:58AM (#25661017)

      I'm not so sure about that. I mean, the military currently uses a whole bunch of stealth technology against their enemies: everything from simple paint color and camouflage, to radar-reflective stealth paint or ultra-quiet engines for submarines. None of these are perfect, but all are useful.

      You may not be able to make yourself 100% invisible to an enemy that has good tech, but as long as you can give yourself an advantage in hiding, it's worth using. The "advantage" could be increased survival (enemy hit accuracy is reduced), better range (you can get closer before being detected), or maybe just the cost to the enemy for them to launch all the overhead imaging and use all magnetic field sensing equipment you just mentioned.

      If cloaking became viable, it would definitely be used by the military against other high-tech enemies. In battle, every advantage counts.

    • by Culture20 (968837) on Thursday November 06, 2008 @11:01AM (#25661059)

      This technology, if adopted by the military, will probably only be useful against civilians.

      Or unsophisticated military. Against other sophisticated military, it's good to have the tech first because that allows research into counter-tech sooner. One way to beat the enemy is to force them to spend too much in resources keeping a stalemate.

    • The key point (Score:4, Interesting)

      by brunes69 (86786) <slashdot&keirstead,org> on Thursday November 06, 2008 @11:52AM (#25661905) Homepage

      ... in your argument is "against another sophisticated military".

      However this is rarely the case. Nowadays most engagements the US Military is involved in are against people with little more than 25-50 year old weapons. The problem the US Military has is the on the ground war against these kinds of insurgents - this tech. would be invaluable against them, you could approach a camp on foot without fear of being seen.

    • by dreamchaser (49529) on Thursday November 06, 2008 @03:06PM (#25664945) Homepage Journal

      You obviously haven't given it much thought. If your logic held true, there would also have been no reason to develop stealth technology for our aircraft. As someone else astutely pointed out in response to you, every advantage helps. There would be many, many applications for 'cloaking' technology against even high tech militaries.

      Of course, it's fashionable around here to say will really only be useful when used against civilians.

  • Wouldn't this method limit the cloaking mechanism to only work from one viewing angle? It seems to me the cloak would need to have hundreds of complementary images embedded in it to prevent someone from seeing it who took a step to the side. That, however, causes the problem of the complementary images distorting areas around the cloaked item, therefore making the cloaked item even more obvious. Is there something I'm missing?
  • All invisibility cloaks to date work by hiding an object embedded inside them.

    This conventional kind is enough for me. Where can I get one?

    • Re: (Score:2, Funny)

      by Anonymous Coward

      You do realize you will be blind, right?

      Unless you poke some holes in your cloak, and then people will just see eyes floating in the air.

      Actually, that seems like a fantastic idea.
      Sign me up!

  • In TFA it admits that the solution would only be 2D and on a single frequency. This leaves me with a few questions.

    1. Is the "cloak" effectiveness reduced as the observer gets closer to the object being cloaked?
    2. How would they overlay the new image of the item being cloaked, would they use some type of projected hologram, or another physical system - such as attaching the image to the object?
  • by Anonymous Coward
    I'm sure that "The Fast Show" covered this last century...
    • You aint seen me, right?
    • I'll get my cloak.
  • by indros (211103)

    I've been doing this for a long time. I simply hold my hand in front of my eyes. Viola! Object remotely cloaked.

    • We've had a hands free version for years, it's called a blindfold. It does kinda require the co-operation of whoever you're trying to cloak things from though.

  • Scientists: "We've made an invisibility cloak that will make your soldiers vanish!"
    General: "That's amazing, let's try these out."
    Scientists: "Right, Here is one you can try, but if you want more then we need money... a lot of money."
    General: "Sorry, the deals off, the soldiers say they can't see out of it when they're inside it."
    Scientists: "Give us a few minutes."
    [Obligatory view of shed with hammering and sawing noises]
    Scientists: "Okay, how about your troops just hide behind it?"
  • So, in plain English, they take a big photo of the background, put it in front of the object and make the object disappear from view. How incredibly ingenious.
    • by Comboman (895500) on Thursday November 06, 2008 @10:32AM (#25660663)
      Wile E. Coyote claims prior art.
    • Re: (Score:3, Interesting)

      by Keramos (1263560)

      Well, no, actually they take a photo of the subject, make a sort of translucent negative, and put it in front of the object and make the object disappear from view. Slightly more ingenious because the background can change.

      Not sure how they handle the "light behind the 'cloaked object' isn't shining through it" scenario. Presumably you could bend the light around the object and back into it's orignal path - but that's the 'embedded cloaking device' as far as I can tell.

  • ... has been doing this for years.
  • I remember reading about this somewhere, I think it's called an SEP Field... "An SEP is something we can't see, or don't see, or our brain doesn't let us see, because we think that it's somebody else's problem.... The brain just edits it out, it's like a blind spot. If you look at it directly you won't see it unless you know precisely what it is. Your only hope is to catch it by surprise out of the corner of your eye." -- Douglas Adams, HHGTG. In that series, a strange object can be effectively hidden from
  • seems to me that having a cloak showing a "complementary object" is only going to work if the original object doesn't destroy information about the background. If it does, the object is going to show via the distortion of the background.

  • wrong road (Score:4, Funny)

    by Patrik_AKA_RedX (624423) <patrik.vanostaeyenNO@SPAMgmail.com> on Thursday November 06, 2008 @01:07PM (#25663275) Journal
    Scientists are looking in the wrong direction in this matter. Like in so many other breakthroughs, they just have to watch how nature does it. What in nature can be totaly invisble without any kind of complex technology or huge power consumption? Easy: keys.
  • ... I can still uncloak them in my mind.

  • 1) Assume a cloaking material with optical properties that are exactly complementary to the space outside them.

    2) Become invisible using that material.

  • I am not a physicist, but it seems to me the proposed invisibility 'cloak' is just a mathematical trick, and its not clear to me that the mathematical model actually corresponds with the real physics of light/electromagnetic waves. And even if the model is sound, I don't believe materials with the desired properties can actually be made. Also, it seems, the method only works when the background light is uniform, i.e. monochromatic background light, i.e. no other objects are allowed anywhere in view, beside

  • it will then be ignored.

  • by shish (588640)
    Can we get some photos? I want to see this in action :-)
  • Object * (1/Object) = 1

    Why didn't we think of it before!

  • I expect someone else already pointed this out, but just in case... -Todd

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