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The Military Science Technology

How To See Through an Invisibility Cloak 201

AMESN writes "Ways to bend light around objects and render them invisible are becoming a major field of scientific study and gaining ground. While no actual invisibility cloak exists yet, researchers are also theorizing on how to beat the perfect cloak."
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How To See Through an Invisibility Cloak

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  • by JKDguy82 ( 692274 ) on Saturday December 05, 2009 @06:41PM (#30338954)
    turn it on?
  • rain (Score:5, Insightful)

    by wizardforce ( 1005805 ) on Saturday December 05, 2009 @06:41PM (#30338958) Journal

    No invisibility cloak can hide the fact that it's still a solid object. That or utilize various frequencies of EM as it would be extremely difficult to defeat radar + infared + visible + UV all at the same time.

    • Re:rain (Score:4, Insightful)

      by Penguinisto ( 415985 ) on Saturday December 05, 2009 @07:05PM (#30339168) Journal

      Exactly. Even the vaunted "stealth" technologies of the 1980's and '90s were engineered only towards a certain set of frequencies.

      This 'invisibility cloak' could be defeated as easily as using a video camera with "night shot" built in (basically, an infrared emitter on the camera body sends out IR, and the lens picks that up, making it a bit more active than simply taking in whatever it sees). The cloak blocks the IR, so it'll either shine with the reflected waves or will show up as a shadow.

      Other ways to defeat it? Talcum powder or other particulates (like rain ferinstance).

      'course, I doubt that they could make such a "cloak" anyway, at least insofar as it would still show movement. So unless their 'spy' is really good at standing still, he's still liable to be noticed.

      • Re:rain (Score:5, Funny)

        by thelamecamel ( 561865 ) on Saturday December 05, 2009 @07:35PM (#30339422)

        How would it show movement? AFAIK the cloak should be able to move around and this movement shouldn't be visible to you.

        Or do you mean they won't be able to make a flexible cloaking ninja suit that keeps cloaking the ninja as they walk, despite the suit bending? The solution to that, of course, is to roll around inside a giant hamster ball/zorb cloaking device! Watch out... i'll sneak up on you and ROLL YOU TO DEATH.

        • So I should Plan on using stairs in my bases to prevent the invisible ninja from attacking.

          besides cloaks like this are still usable if the person hiding is standing still. you move when no one is watching and let the patrols pass you by.

        • The solution to that, of course, is to roll around inside a giant hamster ball/zorb cloaking device! Watch out... i'll sneak up on you and ROLL YOU TO DEATH.

          Taking rick-rolling to a whole new level.

    • Yep, and even if you got a broadband cloak that worked at all those frequencies, you could still pick it up by a number of ways not mentioned in TFA. You could pick it up with sonar (I guess in principle it could also be an acoustic cloak to beat that too), but you could also change the refractive index of the room. The cloak is designed so that no matter what's in the cloaked region, it appears to have a refractive index of 1 (or whatever the cloak's surrounds are supposed to be). If you change the refr

      • The other downside of these cloaks, of course, is that you can't see out of them since no light interacts with your eyes.

        You could use a mechanism similar to the linux tee command to send light both to the eyes and the opposite side of the cloak (semi-silvered mirror, and a light amplifier). Besides, two pupil sized holes that can only be seen when the cloaked person is looking directly at you could easily be missed.
        • The eyehole part might work, but not the tee. A semi-silvered mirror would create a "dim" area where you are standing.
    • extremely difficult to defeat radar + infared + visible + UV all at the same time

      Would it even make sense to become invisible to electromagnetic radiation at so many wavelengths? If someone creates the perfect cloak, how can the person on the inside see whats around them? How do you communicate with anything that is cloaked?

      • by h4rm0ny ( 722443 )

        Oh dear gods, not this again? :) Make a couple of eye holes and a little radio antenna hole. Which is easiest to conceal? A soldier in full battle gear, or a pair of floating eyes and a little pointy wire? I think the US legal system has a lot to answer for - it's breeding a generation of people who see only either utter unfeasible success, or complete failure. If such a "cloak" can be created, and if somehow it were cost effective to deploy (and that's a whole other question), then it would be one useful
  • by JonC88 ( 1176057 ) on Saturday December 05, 2009 @06:43PM (#30338964)
    Just throw a stone at it.
  • flour? (Score:2, Interesting)

    by korney ( 1469497 )
    > While no actual invisibility cloak exists yet, researchers are also theorizing on how to beat the perfect cloak."

    How about flour and water? This reminds me of a joke...
  • by unitron ( 5733 ) on Saturday December 05, 2009 @06:50PM (#30339014) Homepage Journal

    If you can, it's not perfect.

    The real problem isn't detecting it. It's knowing that you need to be trying to detect it in the first place, and approximately when and in what area.

    • The real problem isn't detecting it. It's knowing that you need to be trying to detect it in the first place, and approximately when and in what area.

      Monitor for changes in the field of gravity (or magnetic field to use a more mature technology, although I don't know how well that would work in e.g. deep space where there isn't a planetary magnetic field). If there isn't a corresponding change in the visual (or thermal, etc.) appearance of the same area, throw an alert that there's probably a cloaked object

      • what if the invisibility cloak is actually the ability to manipulate ones subatomic particles (i.e. Higgs Boson) to completely disappear. Say not become antimatter, but flip the Higgs from one state to another putting you in a flux state (or dimension). You may not be able to interact with anything, and displace regular matter when you 're-appear' - so makes sure you do it in air rather than solid rock...
        • The question then is, how exactly are you supposed to breathe? If you're out of flux with everything else, where's your air supply gonna come from, unless you wore some kind of rebreather too...

          I've always wondered that in Star Trek episodes for example; a crew member gets sent into some slightly out of phase dimension but can still breathe. Where is all this out of phase oxygen coming from?!

          • I think breathing would be the least of your problem. If you're in this flux state then even the earth's gravitational field may have no effect. You'd essentially need a vehicle which contains all the relevant life support. Assuming it is manned.

            I'd imagine being able to push an unmanned combat aircraft or vehicle into flux to maneuverer to a position of advantage would be one of the most valuable applications.
    • by rossdee ( 243626 )

      If your invisiblity device is 'perfect' then You can't see out.

      • by sopssa ( 1498795 ) *

        Yes you can. You transfer the light after it has hit the person and is going back. So instead of catching the light ray when it hits the invisibility cloak, you catch it when it's leaving the invisibility cloak and transfer on the other side.

        • by sznupi ( 719324 )

          The "catcher" of light at the back of cloaked individual/machine would be visible from the other side.

          • by sopssa ( 1498795 ) *

            Why exactly? You do this on both sides of course.

            • by sznupi ( 719324 )

              Invisibility cloak depends on "bending" the light on the surface of the object. If something "disturbs" the path of light behind perfectly cloaked object, that something is visible (otherwise that wouldn't be an invisibility cloak!).

      • by sznupi ( 719324 )

        That's why we have things like inertial navigation. Used already in comparable scenarios, in submarines for example.

    • by hey! ( 33014 )

      Somebody has been watching too many reruns of "Kung Fu"...

    • You mean, no true Scotsman can beat the perfect cloak.

  • A laser pointer, the cheap red kind you can find at any corner store.

    • by Tynin ( 634655 )
      It likely wouldn't work, as it could be redirected around/through the target, though perhaps you might be able to tell due to the laser light diffusing from a crisp point. In any case, a well placed pebble should also work as it would bounce off in a very obvious way.
  • Ala Marilyn Monroe [teennick.com] in "The Seven Year Itch".

  • TFA (Score:4, Informative)

    by wizardforce ( 1005805 ) on Saturday December 05, 2009 @06:59PM (#30339098) Journal

    TFA mentions using charged particles and multiple wavelengths of EM to detect a clocked object. TFA suggests that they were measuring the actual effect on the path of the radiation its self although it should be pointed out that this is quite possibly unnecessary as high energy charged particle entering a solid material undergo an extremely high de-acceleration phase which causes charged particles to emit EM radiation. It's called Bremsstrahlung [wikipedia.org] radiation and could quite possibly be detected.

  • Why worry? (Score:4, Insightful)

    by gmuslera ( 3436 ) on Saturday December 05, 2009 @07:00PM (#30339114) Homepage Journal
    A perfect invisibility cloak is also a perfect blindness cloak. Unless you make i.e. missiles or bullets (dodge that, Neo!) with it, things with a predefined target, could be somewhat useless for most interesting uses. The imperfect are the useful ones.
    • > A perfect invisibility cloak is also a perfect blindness cloak.

      You switch off a small area fifty times a second or so to let your camera look out. A 2cm diameter black spot that is only present a few percent of the time is going to be very hard to spet.

    • Meh. Amplify and fork the incoming light -- some goes around to the back of the cloak and out, some reaches your eyes. It's all right there in the manual...

  • Invisibility (Score:5, Insightful)

    by NoobixCube ( 1133473 ) on Saturday December 05, 2009 @07:05PM (#30339164) Journal

    An "invisibility cloak" these days doesn't just necessarily apply to the visible light spectrum. The cloak could be a thermal or radar "invisibility" cloak, leaving an object perfectly visible to the naked eye, but invisible on other scans. Penetrating thermal invisibility cloaks might end up more important, because camouflage can take care of visible light from overhead, it's the thermal that's the giveaway.

  • by Antiocheian ( 859870 ) on Saturday December 05, 2009 @07:11PM (#30339224) Journal

    You can drink a blessed potion of see invisible or eat an invisible stalker's corpse while invisible.

  • A handful of flour - good and covering just about everything within a 10 yard radius!
  • ...only the blind shall see.

    I'm sure widespread use invisibility cloaks will lead to increased recruitment of blind people to the military. And that blind kid who does echolocation will be recruited to train a new elite force of super-soldiers.

  • A device designed to do one thing (bend light of certain wavelength) turns out cannot do another (bend other particle/wavelength). News at 11.
  • by RudeIota ( 1131331 ) on Saturday December 05, 2009 @07:53PM (#30339548) Homepage
    Everyone knows firing short, repeated bursts of tachyons between a 3 dimensional grid made up of Federation star ships is the most effective way to detect invisible, cloaked objects.
  • This has always been something that's bothered me about Star Trek. It's well-established that "cloaked" objects, including people, still exist as solid matter and therefore displace whatever space they're occupying. I would think a foolproof means of tracking cloaked objects would simply be to concentrate on whatever it is they're displacing, and look for the telltale starship/person-shaped contour of gaps of nothingness where displacement is occurring. Take the interior decks of a Federation starship for e

    • by Thing 1 ( 178996 )
      I like that your .sig ties in perfectly with the knowledge that you display in your post. :)
  • You could just get a magical eye like Mad-Eye Moody....
  • Hit it with something. Seriously, the obvious solution is to spam your environment with small projectiles, track them, see what bounces off something. Or blow on it it: tracking motion of air/turbulence as air movement in the environment is changed by the objects presence.

    Point is if you have a object perfectly cloaked to a good swathe of the electromagnetic spectrum there are still other ways it impinges on it's environment. Accoustics, sound waves (although they may be easy to cloak also) etc.
  • Presumably, sensors that can penetrate cloaking would be very useful for the operators of the cloaked vehicle, because if no one can see you, you can't see anyone either. In order to see something, light has to be absorbed by the sensors inside the cloak. Since a cloak bends light around the vehicle, the vehicle is flying blind.

    Not sure what the fuss is about--sonar should work fine.

  • Let's keep it real (Score:3, Insightful)

    by Ancient_Hacker ( 751168 ) on Saturday December 05, 2009 @08:26PM (#30339764)

    We're getting a bit too excited here. If you read TFA you'll realize how limited this thing is. Many of these designs can only work at one frequency, usually microwave, in one direction, over a very small area, in 2D, and with considerable scattering and attenuation.

    That's a heck of a long way from a usable cloaking device. The problems of scattering and attenuation are going to be particularly intractable.

    It's unlikely that every one of the many shortcomings can each be improved by the needed factor of 100 or so.

  • If the people who can see through your invisibility technology aren't the people you're warring with or hiding something from, then your invisibility solution doesn't need to be foolproof. A solution can be perfect for a given situation even if it's not academically or technically perfect.
  • Silly question (Score:4, Informative)

    by eyrieowl ( 881195 ) on Saturday December 05, 2009 @09:27PM (#30340172)

    Use a scrying spell, obviously.

    • The invisible person would run away the moment you put on your robe and wizard hat - so it won't work.

      But you can make listen checks.
  • How can you detect? put some yelling powder on the floor!

  • Just spray a firehose around the area, and watch the water bounce off the person or thing with the invisibility cloak? Obviously the water, unlike light, won't warp around the person or thing because it is matter and not photons.

    I remember D&D scenarios trying to find an invisible person or thing:

    #1 Look for footprints, spread some paint or dust around and let the person step in them and leave a trail.
    #2 Throw water, dust, or paint around the room and eventually it will hit the invisible person.
    #3 The p

  • Spychecking (Score:3, Informative)

    by VGPowerlord ( 621254 ) on Sunday December 06, 2009 @12:35AM (#30341094)

    Well, the easiest way is to have Pyros that Spycheck, or just bump into the Spy by accident.

    Wait, you don't mean in Team Fortress 2?

  • Spray and pray in the direction from which an invisible enemy might approach. Where there's a blood spray, shoot some more.

    Invisible this, bitch!

  • Detecting the presense of an invisibility "cloak" is quite simple in theory. Not much harder for limited areas, but would be difficult for large areas or in highly mobile applications.

    Simply put, it's a matter of timing.

    If light is being guided around an object then it's taking a longer path than normal. Therefor the amount of time for the light to travel to an item behind the cloaked object would be longer than the time required if the cloak is not there.

    As I said. Concept is quite simple.

    For limited a

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