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Engineers Devise Invisibility Shield 316

Posted by timothy
from the impossibly-large-yellow-somethings dept.
GerritHoll points out an article in Nature according to which "researchers at the University of Pennsylvania 'say that a "plasmonic cover" could render objects "nearly invisible to an observer.' Earlier attempts at invisibility worked by colouring a screen to match its background, like a chameleon. The described technique is new, because it works by the concept of reducing light scattering. It is not a 'magic cloak,' however, because it will not work for the full range of visible light and needs to be adjusted precisely for the shape of the object. However, the concept could find an application in stealth technology."
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Engineers Devise Invisibility Shield

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  • by kngthdn (820601) * on Tuesday March 01, 2005 @03:12AM (#11810462) Homepage
    It is not a 'magic cloak,' however.

    Like this [ananova.com]?

    Well, that actually requires a special viewfinder, so it's not quite as cool, but it sure *looks* awesome. Better than the "spot the spaceship" pic, anyway.

    How long til I can buy this stuff at Walmart?
  • by xsfo (604140) on Tuesday March 01, 2005 @03:15AM (#11810468)
    What sort of armor class do you get with that?
    • Yea, now it's a concealment of 50%, no AC modifier.

      Whatever. Engineers will be casting See Invisibility soon enough ;)
    • TFA doesn't say, but according to http://science.slashdot.org/comments.pl?sid=140954 &cid=11810480 [slashdot.org], you'll already have the the +100 size (subatomic) bonus to AC.
      • by Xaroth (67516) on Tuesday March 01, 2005 @11:46AM (#11812694) Homepage
        <pedantic class="geek" voice="nasal">

        First, it has to be a power of 2 in order to be a size-based AC modifier.

        Taking the medium size class to max out at 2 meters, microscopic would be about 16 size classes below medium (since each size class has a maximum of one half the height of the one above it; I'm taking ~30 micrometers max to be "microscopic". It is, of course, a DM's call as to what, exactly, would constitute microscopic - adjust accordingly.)

        This would give an AC bonus (and bonus to hit) of +32,768. Good luck finding a smith to craft armor or weapons for that size class, though.

        For contrast, the parent's "+100" size bonus would roughly correlate to the +128 bonus that's actually possible, and would exist for a creature no bigger than 7.8125mm - hardly subatomic. In fact, this would be the appropriate size class for many normal insects.

        Second, Invisibility grants a 50% miss chance due to total concealment, not an increase to AC.

        Of course, 2.5% of the time you'll still hit it anyway (what with the whole "a 20 always hits" rule + total concealment). So, if at first you don't succeed, try, try again. I'm sure your DM would allow you to take 20 on hitting something that poses so little threat to you (assuming you weren't otherwise potentially in peril).

        </pedantic>

        Oh, and smile. You know it's funny.
    • by Mr. Bad Example (31092) on Tuesday March 01, 2005 @04:37AM (#11810753) Homepage
      > What sort of armor class do you get with that?

      I'd tell you, but I can't find the fucking thing.
  • by Kiryat Malachi (177258) on Tuesday March 01, 2005 @03:15AM (#11810473) Journal
    Making something invisible is easy: all you have to do is generate a Somebody Else's Problem field of sufficient size.

    (Seriously, am I the only one who looked at this, saw the word 'plasmonic', and thought "Fucking Slashdot editors, its *March 1st*, not *April 1st*"?)
    • You also need a large can of pink paint or something else to make the object truly abnormal before a SEP field will work properly.

      Having a spaceship that looks like a small upended Italian bistro is a good start...
    • Invisible hell. One more drink past that and I can fly.
      • by Anonymous Coward
        Flying is a simpler problem. You just need to miss the ground.
    • by mcc (14761)
      (Seriously, am I the only one who looked at this, saw the word 'plasmonic', and thought "Fucking Slashdot editors, its *March 1st*, not *April 1st*"?)
      Correction: The Slashdot Editors have successfully convinced you it's March 1st, not April 1st.

      Best! April! Fools! Joke! Ever!
    • Re:Everybody knows (Score:4, Informative)

      by Anonymous Coward on Tuesday March 01, 2005 @06:00AM (#11810988)
      Plasmons are not science fiction or a hoax. They are electron waves in the surface of conducting materials. They also allow light to pass through holes very much smaller than the wavelength by converting the light to plasmons and back again on the other side. This was previously thought to be impossible and it has applications in optical microscopy.

      BTW plasmons are not my area of expertise but I am pretty sure that the above is correct in principle.
      • Re:Everybody knows (Score:5, Informative)

        by ShadeOfBlue (851882) on Tuesday March 01, 2005 @09:18AM (#11811616)
        Yeah, that's all basically correct. I did research on annealing these metal films to try to change their optical properties (we ran into some problems with grain structures in the metal growing during the annealing process).

        Most scientifically literate people probably haven't heard of plasmons because they only form when the surface of a metal is milled with a regular array of nanostructures. In this case you have an array of holes on the scale of tens to hundreds of nanometers in diameter. When there's some such repeating nanoscale structure it changes the electron energetics so that the energy to frequency ratio is similar to that of the electromagnetic spectrum, at which point light can couple with the surface electrons and form these longitudinal surface waves (I'm not a physicist yet, so some of this may be a bit shakey).

        As the parent said it's these waves that can then travel through the holes milled in the surface out onto the other side, where for some reason or another, they'll reemit the energy stored in them as light. It's pretty cool because they've done tests and the light doesn't just come out of the holes. It's as if the light passes straight through the metal film. Furthermore, they know the light's not simply passing through the film, because they've also measured it and found a very slight delay due to the formation, propagation, and reemission of the plasmons.

        The story I heard about the discovery of this phenomenon is kind of amusing. Apparently an English speaking chemist wanted an array of micro wells for some polymer reaction, asked a Chinese chemist if he could do make one. The Chinese chemist thought he was crazy and said it would take six months. Due to the language barrier, the "you're crazy" bit didn't make it through, and six months later the English speaker picked it up looked through it, and said, hey, there's nothing here.

        One use they're currently looking into is very specific optical filters which can be built for any wavelength. The grad student I worked with mentioned way down the line the possibility for essentially infinite resolution displays, although how that'd work isn't quite clear.
        • That's cool. I wasn't doubting the veracity of the story; but you have to admit, 'plasmons' sounds like ones of those words made up for bullshit Trek science.
    • by David Gould (4938) <david@dgould.org> on Tuesday March 01, 2005 @03:54PM (#11815405) Homepage

      Come on, guys! I can't be the first to notice... Okay, I'll spell it out for you -- the correct first reaction to this story is:
      How funny is it that this research is being done at the University of Pennsylvania, of all places?!

      (Have none of you kids ever heard of The Philadelphia Experiment [imdb.com]?)
  • obligatory (Score:5, Funny)

    by Anonymous Coward on Tuesday March 01, 2005 @03:16AM (#11810475)
    I didn't see that one coming.
  • by Vthornheart (745224) on Tuesday March 01, 2005 @03:17AM (#11810480)
    Those who read the article until the end will note that they save the kicker for the very end:


    This technology would only work for microscopic objects (as they must be the same size as the wavelength of light hitting it), and only a single wavelength. So in other words, for you to get a nice, new cloak of invisibility you'll need to be microscopic in size and constantly in environments with only one wavelength of visible light hitting you. =)


    Well, back to the drawing board.

    • This isn't as much of an issue as you might think. Imagine coating a stealth aircraft with very precisely made microscopic dust, and applying this technology to the particles. You'll end up with a macroscopic, radar invisible airplane.
      • by X0563511 (793323) * on Tuesday March 01, 2005 @06:01AM (#11810992) Homepage Journal
        This wouldn't work. The radar would pass through the molecules, only to reflect off of the aircraft skin, and pass back though the molecules.

        Now, if it could be set up so that the radar would pass through once, and bounce around between the skin and the coating before finding the right angle to escape, it would probably make the radar bounce off the plane at all kinds of weird angles (making the radar useless).

        The problem I'm wondering about is: What happens if the radar can't find a way out? Will it keep bouncing around, loosing energy all the while, heating up both the skin and the coating (this may become an issue)? Or would the time and energy it spent bouncing around untill it escaped be so trivial so as to not matter?
        • by bw_bur (634734) on Tuesday March 01, 2005 @06:37AM (#11811091)
          This wouldn't work. The radar would pass through the molecules, only to reflect off of the aircraft skin

          Exactly. Hopefully someone will mod you up...

          Now, if it could be set up so that the radar would pass through once, and bounce around between the skin and the coating before finding the right angle to escape, it would probably make the radar bounce off the plane at all kinds of weird angles (making the radar useless).

          The problem I'm wondering about is: What happens if the radar can't find a way out? Will it keep bouncing around, loosing energy all the while, heating up both the skin and the coating (this may become an issue)?

          These are the two conventional approaches to stealth: either deflect incoming waves anywhere but back towards the detector, or absorb as much as possible, in which case the coating inevitably heats up. I don't think this is much of an issue though: probably much more heat is generated simply by flying at high speeds.

    • by serutan (259622) <snoopdoug@g e e k a zon.com> on Tuesday March 01, 2005 @03:40AM (#11810572) Homepage
      This article is like going to a movie after seeing the really great preview, and finding out that the really great preview contains every single really great moment in the movie.
    • So in other words, for you to get a nice, new cloak of invisibility you'll need to be microscopic in size

      Not a problem. If you'll just step right over here to this shrinkometer....
    • by flakac (307921) on Tuesday March 01, 2005 @05:33AM (#11810901)
      Absolutely... if we can just get our weapons' size down to a few microns, and get (Al Quaida|Ruskies|Iraq|Iran|North Korea|Massachusetts) to limit their surveillance techniques to the proper wavelength, then this will be really breakthrough technology!
    • Another aspect to it that they don't point out is that this does is make things invisible, not transparent. We all think of transparency when we think of invisibility, but if something is invisible - no light from it strikes our eyes - then we can deduce it's presence from the black blob moving about in the front room.

      Which, since it only works on things too small to see, is not actually that big a deal I suppose...

      P.S. you've inspired me to a new trend; I'm going to mark anyone who actually reads the art
  • by ErichTheWebGuy (745925) on Tuesday March 01, 2005 @03:18AM (#11810481) Homepage
    ... to let me sneak undetected into a ladies locker room, then we'll talk.
  • invisible?? (Score:2, Interesting)

    by Awol411 (799294)
    the whole basis of this is to stop the scattering of light that the object emits. so if there was no scattering, then wouldnt the object still appear black. sooo. couldnt you just look for the object that's all black. might work well in space or night time, but at 2pm on a sunny afternoon, i think i'll be able to spot the large black body trying to hide.
    • that's only if the object absorbs the light, which this shielding apparenlty doesn't do. There's still the whole problem about it needing to be microscopic to work for visible light though.
  • by Anonymous Coward on Tuesday March 01, 2005 @03:18AM (#11810483)
    See, it hides my identity when I post on Slashdot!
  • Obvious Applications (Score:4, Interesting)

    by poopdeville (841677) on Tuesday March 01, 2005 @03:19AM (#11810488)
    I can think of a couple of obvious applications, especially if the technology can be adapted to scatter microwaves. Tanks and mechanized infantry are pretty obvious, but I think we want to avoid battleships unless we want a repeat of the Philadelpha Experiment and the crappy movie versions (though I loved the first one as a kid).

    But what about non-military uses? Perhaps a "coat" of plasma on windows to reduce cooling bills in the summer? Or another coat of plasma on TV's to reduce glare? I can't think of anything particularly inspiring.
  • This is awesome. Can I use this on my mother?
  • by jgardn (539054) <jgardn@alumni.washington.edu> on Tuesday March 01, 2005 @03:20AM (#11810494) Homepage Journal
    The object being hidden has to be less than the about the wavelength of the light. So, unless you are nanometers in size, you won't be hidden from visible light.

    And it only works on one frequency. Meaning, unless you are nanometers in size, and you are in a room with only red light, you won't be hidden.

    This isn't that great. I wouldn't read too much into it.
    • Whatever. *I* think its neat. When the telegraph was invented, no one could imagine a telephone... let alone an internet.
    • So, far example, you could use this technology to be invisible to light in the radio bands, which have wavelengths measured in meters?
    • You're right that it's not that special, but i think it's more obvious when you realize what's the current technology out there.

      It already is possible to create a 'stealth' type of shield by manipulating thin films (width exactly equal to 1/2 the wavelength of a particular light) to create destructive interference so nothing is reflected. Use multiple coats of differing thickness, and you can wipe out quite a bit of the spectrum. The theory behind this is well known and nothing more than undergrad physic
  • So they think they can eliminate light scattering. What about light absorption?
  • by MooseByte (751829) on Tuesday March 01, 2005 @03:22AM (#11810503)

    From the article: "And crucially, the effect only works when the wavelength of the light being scattered is roughly the same size as the object. So shielding from visible light would be possible only for microscopic objects."

    OK. So if I have this straight... "You see that thing you can't see because it's too small? Well we just made it invisible! Please send more grant funding. And a few burritos. We're like, totally hungry dude."

    Uh huh....

    • Minimizing scattering is no small feat. As they point
      out it could be very useful to me, since I would be
      very interested to use nanoscale probes near an
      object yet still see it in optical microscope with
      little to no distortion.
      This may also lead to cheap ways to probe the amount
      of light in fiber so you could instantly tell if a
      fiber cable is aging or if it was cut then where
      exactly. In short, this could be very useful, just
      not for hiding those spaceships.
  • This got me thinking:

    It is not a 'magic cloak,' however, because it will not work for the full range of visible light and needs to be adjusted precisely for the shape of the object. However, the concept could find an application in stealth technology.

    What kind of application would involve a fized object of known shape? How about a camera and it's controls/batteries/wireless? Use it as fake merchandise on a top shelf at a convenience store. Or books on a top shelf of an office. For that matter, a "invisibili

  • I, for one, welcome our invisible robo-army overlords.
  • by page275 (862917) on Tuesday March 01, 2005 @03:30AM (#11810525)
    Here is the technique let yourself invisible, try it yourself: http://www.sciforums.com/showthread.php?p=439508 [sciforums.com]
  • Also... (Score:5, Funny)

    by Create an Account (841457) on Tuesday March 01, 2005 @03:31AM (#11810531)
    From the article:
    ...it would be more like the shielding used by the Romulans in the Star Trek episode "Balance of Terror" in 1966, which hid their spaceships at the push of a button.

    ...it's called a "cloaking device", you insensitive clod!
  • by shannara256 (262093) on Tuesday March 01, 2005 @03:34AM (#11810553) Homepage
    the concept could find an application in stealth technology.

    Really? Invisibility could be used for tasks requiring stealth? No way, that's crazy talk.

  • What if this concept works for other EM waves, like radar, for instance? I don't remember the precise wavelength of most radar waves, but they are rather long (I'm thinking meters). Could an object smaller than the wavelength of a certain radar be stealthed by this "invisibility" shield?
    • You probably don't remember it because it doesn't exist. There are numerous radars using everything from millimeter waves (MMW) to multi meter long waves. Each type has its own specific uses, though I've heard that MMW radar is the most difficult technology to develop. But IANAEE (electrical engineer).
      • I did some research [aewa.org], and I found that VHF and UHF bands (about 6 to .3 meters wavelength) are used for long range serveiliance. So hiding a small object from long range radar may be possible...but other than that it's a long shot.
        • by digitalchinky (650880) <dtchky@gmail.com> on Tuesday March 01, 2005 @04:59AM (#11810814)
          It's not easily possible to hide from any good EW system. They use multiple frequencies, pulse modulation, frequency hopping, staggered pulses, and a hundred other techniques that provide some really fine grained resolution - right out to the MTUR.

          You also find RADAR on HF, it's annoying if your day job is to actually listen to the static, sounds a bit like a high pitched fart, transmissions are normally short duration though - less than 30 seconds then the frequency is changed - don't hear it again for a couple of minutes/hours.
    • RADAR transmissions are most common at the 9GHz band - india band navigation (boating/shipping) - the bane of many EW's existance.

      That said, the transmission can be on any part of the entire spectrum. You can find RADAR on most any frequency. Including light. It's all about duty cycle, dopplar, PRF etc... EW radars modulate the pulse so you get high target resolution and your transmitter pumps out much more effective power. millimetric band radar is mostly only useful in fire control systems - short range.
  • by mnemonic_ (164550) <jamec AT umich DOT edu> on Tuesday March 01, 2005 @03:40AM (#11810576) Homepage Journal
    U.S. Air Force scientists looked into generating a field of plasma around an aircraft to reduce aerodynamic drag. One unexpected effect was a reduction of RCS (radar cross section, a rough measure of radar visibility), though to my knowledge the research has not been pursued (it probably continues in classified state, just like the plasma toroid ABM system 7 years ago...). Of course, this is EM radiation in the radio portin of the specturm, not optical.

    Russian electrodynamicists are also infamously known for proposing "plasma stealth" devices, which have yet to be demonstrated veritably well. Every few months something pops up about how they've solved high power requirements, reduced weight of the devices, eliminated interferce with the aircraft's EM devices (radar and comm/nav, which critical to everything) and problem Y. And then, you see nothing of it in any journal or trade publication. Just claims, and it seems, nothing more.

    Notably, plasma radar stealth has an opposite effect of the optical stealth. The aircraft would glow like a lightbulb, and leave a trail of glowing plasma in its wake. Also notably, aircraft at high hypersonic speeds induce a local plasma air environment, due to the tremendous energy of the aerodynamics.
  • It was probably designed for RADAR avoidance technique, and visible light is more of a anomaly of the real thing. 2ndly. I'm just curious, what if we would have millions's of those small objects that are invisible to visible light, creating the aircraft frame. And any internal components would be painted black. So it would improve the camoflage of the aircraft, by making its wings invisible.
  • by SeaFox (739806) on Tuesday March 01, 2005 @03:44AM (#11810594)
    It's made me invisible to women for 10 years now.
    I wish I could turn it off.
  • Research abstract (Score:5, Informative)

    by FleaPlus (6935) on Tuesday March 01, 2005 @03:53AM (#11810635) Journal
    Here's an obligatory link to the pre-print research paper and the abstract:

    http://arxiv.org/abs/cond-mat/0502336 [arxiv.org]

    Achieving transparency with plasmonic coatings

    Andrea Alu, Nader Engheta [upenn.edu]

    The possibility of using plasmonic covers to drastically reduce the total scattering cross section of spherical and cylindrical objects is discussed. While it is intuitively expected that increasing the physical size of an object may lead to an increase in its overall scattering cross section, here we see how a proper design of these lossless metamaterial covers near their plasma resonance may induce a dramatic drop in the scattering cross section, making the object nearly invisible to an observer, a phenomenon with obvious applications for low observability and non invasive probe design. Physical insights into this phenomenon and some numerical results are provided.
  • Get everyone to wear blindfolds and then we can see what is going on and probably would all be happier

    Rus
  • The shadow effect (Score:5, Interesting)

    by Dikeman (620856) on Tuesday March 01, 2005 @04:02AM (#11810660) Homepage
    The article puts two techniques next to eachother, as if it were alternatives for the same problem. This is false.
    The proposed system with plasmonic covering reduces the scattering of light. The lightwaves pass by the object as were the object very small, smaller than it actually is. Hence it only works with objects that are allready very small, because otherwise the object would cast a shadow. (Light passes by, not through)
    The system with light detectors and emitters mimics the scene that is behind (bigger) objects with respect to the viewer. You could actualy say that it fills in the shadow cast by the object.

    So were the first system reduces the shadow effect, the second replaces the shadow alltogether. I could actualy see these two systems used along side eachother rather than instead of eachother.

  • by cfalcon (779563) on Tuesday March 01, 2005 @04:11AM (#11810687)
    "And crucially, the effect only works when the wavelength of the light being scattered is roughly the same size as the object."

    Visible light is around 400nm (violet) to 800nm (red). So, this is only effective for sufficiently tiny battleships.
  • Skeptical (Score:5, Funny)

    by ggvaidya (747058) on Tuesday March 01, 2005 @05:00AM (#11810816) Homepage Journal
    I won't believe this 'til I see it.
  • by TommydCat (791543) on Tuesday March 01, 2005 @05:04AM (#11810828) Homepage
    Move along...
  • by mykdavies (1369) on Tuesday March 01, 2005 @05:33AM (#11810902)

    the effect only works when the wavelength of the light being scattered is roughly the same size as the object

    This would make it the perfect for those awkward moments when your nanobots are being attacked by lasers (mounted on sharks?)

  • by vistic (556838) on Tuesday March 01, 2005 @06:33AM (#11811084)
    hmmm...

    I don't think these engineers devised any sort of "invisibility shield" ...maybe they're just really dull....

    host: With me now is Mr. Thomas Walters of West Hartlepool who is totally invisible. Good evening, Mr Walters. (turns to empty chair)

    walters: Over here, Hughie. (host turns to see boring, visible man)

    host: Mr. Walters, are you sure you're invisible?

    walters: Oh yes, most certainly.

    host: Well, Mr. Walters, what's it like being invisible?

    walters: Well, for a start, at the office where I work I can be sitting at my desk all day and the others totally ignore me. At home, even though we are in the same room, my wife does not speak to me for hours, people pass me by in the street without a glance in my direction, and I can walk into a room without...

    host: Well, whilst we've got interesting people, we met Mr. Oliver Cavendish who...

    walters: Even now you yourself, you do hardly notice me...
  • Chameleons (Score:5, Informative)

    by ndogg (158021) <the DOT rhorn AT gmail DOT com> on Tuesday March 01, 2005 @07:55AM (#11811270) Homepage Journal
    ...match its background, like a chameleon.

    Grrr...

    Chameleons don't change their colors for this reason. It's a myth. Stop spreading it.

    http://www.wsu.edu/DrUniverse/chamel.html [wsu.edu]
  • by thewiz (24994) * on Tuesday March 01, 2005 @09:07AM (#11811545)
    Why do engineers need to develop methods of invisibility? After all, most engineers are invisible to the female half of the population anyway.
  • by tod_miller (792541) on Tuesday March 01, 2005 @09:10AM (#11811563) Journal
    This technology is really invisibility in the sense that it stops light scattering, but for visible light would only work for microscopic items...

    Which must be working because right now I so not see many single microscopic items anyway...

    It can't be used to conceal guns from Xrays, which use 0.1nm-20nm wavelegths.

    Hiding missiles from radio based radar? Possible?

    So shielding from visible light would be possible only for microscopic objects; larger ones could be hidden only to long-wavelength radiation such as microwaves. This means that the technology could not be used to hide people or vehicles from human vision.

    Also the 'inventiveness' of the invisibility cloak [ananova.com] is much less than its engineering feat.

    We all have our own ideas about projecting the view behind your onto the front... from all angles... technically how to do it flexible, and stop illumination / shadow is very hard.

    Not impossible, with some very clever technology that can 'feel' its own shape, and sense light conditions, can absorb almost all light (be dark even in bright light, if a shadow is behind you), and shine as bright as the sun on a rock (if you are in the shade, but a bright rock is behind you, and you cannot use the sun on the material to compensate)

    This would require some l33t processing skills to handle the data.
  • Radio Silence (Score:3, Interesting)

    by Doc Ruby (173196) on Tuesday March 01, 2005 @10:43AM (#11812142) Homepage Journal
    "And of course the shielding would work fine for concealing large objects such as spaceships from sensors or telescopes that used long-wavelength radiation instead of visible light."

    Now we know how advanced alien civilizations have remained "off the radar", despite our sweeping radar telescope surveys of their space abodes. They're not that much more advanced than us. But they've concentrated on the important bits: privacy technology. We'll neve catch up at this pace.
  • This just in.... (Score:4, Insightful)

    by feloneous cat (564318) on Tuesday March 01, 2005 @12:13PM (#11812945)
    And crucially, the effect only works when the wavelength of the light being scattered is roughly the same size as the object. So shielding from visible light would be possible only for microscopic objects...

    Which are frikkin' microscopic and therefore don't need to be hidden?

    Or is it just me that can't see microscopic objects?

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