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Thread: INVISIBILITY

  1. #1 INVISIBILITY 
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    Hai,In my lower classes i was taught that we are able to see due to the reflection of light from a particular body,If that is the case cane we appreciably experience invisibility if we concenrate some harmess rays (whose wavelength is beyound the visible region) on an object?


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    Universal Mind John Galt's Avatar
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    Everything you see around you is bathed in harmless infra red waves. It hasn't made anything invisible.

    Fish approach invisibility by reflecting different wavelengths of light from different layers in their scales, so that they merge into the diffuse light pattern of their environment.

    Jellyfish approach it by having transparent bodies with almost the same refractive index as water.


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    invisability can be obtained by bending the light around your body
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    Forum Professor wallaby's Avatar
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    i guess the real goal would be having cloaking armor like out of those delightful predator movies.
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    Forum Sophomore NimaRahnemoon's Avatar
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    Hmm, I haven't thought of invisibility much... something that is green takes in all light and only reflects green light. So is it possible to take in white light (all visible lights) at the right ratios; will that make you "invisible"? :?
    Last edited by NimaRahnemoon; August 8th, 2013 at 12:51 AM. Reason: Spelling
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    Quote Originally Posted by Nima Rahnemoon
    Hmm, I haven't thought of invisability much... something that is green takes in all light and only reflects green light. So is it possible to take in white light (all visible lights); will that make you "invisible"? :?
    It will make you black :?

    Indeed, invisibility can only be achieved if you can bend incident light rays from any direction around you, and send them out in the exact opposite direction.
    Mmm.. maybe if you make a sort of armor with both light sensors and wave emittors, you could make an invisible object... If a light ray is detected on the armour, the angle of incidence, wavelength etc is detected, and a similar ray is emitted on the opposite side. But there would be a delay in time, so it isn't perfect invisibility..

    Difficult :?
    Stop looking - Start seeing
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    Forum Junior Cuete's Avatar
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    Quote Originally Posted by Ophiolite
    Jellyfish approach it by having transparent bodies with almost the same refractive index as water.
    This technique seems to be better. We need to have air's refractive index then...

    How to obtain such thing is the tough part... any ideas?
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    How to obtain such thing is the tough part... any ideas?
    Yes. A suit of liquid crystal or maybe even crushed quartz might do the trick. Clear quartz crystals with no other mineral inclusions and no veils, walls or fractures is a good example of invisibility. Many large quartz points like that will have several smaller crystals growing inside of them that cannot be seen with normal vision or normal light until they emerge diagonally out of the side of the parent crystal. The only way you can see the invisible smaller crystals in the interior of the large point is by directing magnified bright light into it at specific angles, the light reflections off the sides of the interior crystals allow you to measure the sizes and shapes of the interior crystals. But you can't actually see the crystals, only the reflected white light.

    Just a thought - anyone else got any better ideas?

    :wink:
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    Quote Originally Posted by rocky
    A suit of liquid crystal or maybe even crushed quartz might do the trick. Clear quartz crystals with no other mineral inclusions and no veils, walls or fractures is a good example of invisibility. Many large quartz points like that will have several smaller crystals growing inside of them that cannot be seen with normal vision or normal light until they emerge diagonally out of the side of the parent crystal. The only way you can see the invisible smaller crystals in the interior of the large point is by directing magnified bright light into it at specific angles, the light reflections off the sides of the interior crystals allow you to measure the sizes and shapes of the interior crystals. But you can't actually see the crystals, only the reflected white light.
    But in this case the observer would only see a composed image of the surroundings and some light effects, this won't make the observer actually "see through you". For me, the deal of being invisible is something like the movies...

    Maybe if we projected in this liquid crystal (LCD) an image captured by a CCD in the opposed size of the suit? (every side)
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    If you were invisible and in broad daylight would you cast a shadow?

    Not trying to be a smartass but the complete absence of light will do more to make one invisible than anything I know. We are all invisible to a blind person.

    Perfect camouflage would do it. An octopus is a near perfect example. If an octopus' brain can make the necessary adjustments to its background, very complicated as they may be, then a suit designed with a built in computer to accomplish the same thing should do it. Or in some twisted way we genetically alter someone, using Octopus DNA, so the necessary chemical changes within their skin can be made in order to blend in with their background. Or it might make a good sci-fi story.
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    Quote Originally Posted by Cuete
    Maybe if we projected in this liquid crystal (LCD) an image captured by a CCD in the opposed size of the suit? (every side)
    The problem is that this wouldn't have any depth. It wouldn't fool people for the same reason that you don't mistake a television image for a real object; your brain can tell whether it's looking at a three-dimensional object or a flat image of an object. It would be closer to great camouflage than invisibility.
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    In order to be invisible, a object must avoid the ways we view objects: refraction, reflection and obstruction. We see things with a different refraction index, or that reflect light, or that block light (cast a shadow).

    Of this three devices, the only that can be worked around si refraction index -a subtance may have the same refaction index as another, and so it will be very hard to see when sumerged into the other substance (that's why a quartz microcrystal is so hard to see when it is inside of, well, quartz).

    So invisibility is impossible. What is possible, is to use light in order to cheat light detectors.

    It's like with stealth airplanes. They are "illuminated" with a electromagnetic radiation, and then absorb it and reflect it in a different angle, so the device that dettects such kind of radiation gets no echo. ITOH, if radar radiaitn was flaling form all over the sky, the stealth plane would cast a shadow and would be easier to pick. And that's what happen with visible light, simply there's a lot of it coming from everywhere.

    ITOH, a object that casts light can be merged into a luminous backgroud, if it is seen from far enough and the detector is looking in he direction from which light is emitted. Theorethically, it should be possible to create an array which picked light in one direction and emitted a similar amount of light in a direction 180º opposed to the incoming one. The problem sio that objects are getting light from every direction, and so every emitter would be linked to a different receiver... yet it still could only emit one type of light. If there was just one beholder, he could be cheated, but a second beholder would need a different line of sight and so wouldn't be cheated. And not to mention, there would be necessary a location device that detected which line of sight could possibly have the beholder...

    No matter how cool, the Predator's camouflage wouldn't work in real world, unless from a distance that avoided perspective problems, or against a 2D background (this is what chameleons do, as from a distance they're effectively a 2D silhouettte against a 2D background).

    Think of this: the "Predator" is being viewed by 2 beholder, one right in front of him and the other to his front and elft (45º). Beholder A is seeing the Predator against a Red container, and Beholder B is seeing it against a Green container to the side of the red one. So, what would do the Predator's camouflage? It would turn red to cheat beholder A, but then beholder B would see a red Predator against a green container. The only workaround would be to use coherent & focused light emitted in different directions -lasers of different colors, each one separated enough from the other as to not interfere. Yet then, coherent light has got a serious problem with particles, and of course the Predator would be emitting light in every possible direction, casting a sort of "diapositive" or "motion picture" on the background... weird at least. And as soon as you used ordinary light, then each beholder would also pick the light being emitted towards each other beholder... It's a Catch-22; omnidirectional light can be seen by everyone, focused light will cast on evey surface, not just the beholder's eyes...
    “If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin.” -Charles Darwin
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  14. #13 taking in all white light to be invisaile 
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    Quote Originally Posted by Nima Rahnemoon
    Hmm, I haven't thought of invisability much... something that is green takes in all light and only reflects green light. So is it possible to take in white light (all visible lights); will that make you "invisible"? :?
    i would think that if you took in all white light that there would be a blank black space, like a 3D shadow, in your place
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    i would think that if you had some sort of LCD (liquid crystal display) to take in light, than eject it the other way, you could be invisible. if it worked both ways that would be an added bonus. Think: an invisible mouse ball adapted for humans.
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    Quote Originally Posted by chamilton333
    i would think that if you had some sort of LCD (liquid crystal display) to take in light, than eject it the other way, you could be invisible. if it worked both ways that would be an added bonus. Think: an invisible mouse ball adapted for humans.
    I think you missed my post...?

    It would have perspective problems. Two different behodlers would need to see two different thyigns, but there's no way to do such as ominidirecitonal light would cast two different backrounds, both visible to both beholdrs, and focused light would project on everything, not just the beholder's eyes (so a beholder could see the light being projected towards the other beholder). :wink:
    “If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin.” -Charles Darwin
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    Quote Originally Posted by Lucifer
    Quote Originally Posted by chamilton333
    i would think that if you had some sort of LCD (liquid crystal display) to take in light, than eject it the other way, you could be invisible. if it worked both ways that would be an added bonus. Think: an invisible mouse ball adapted for humans.
    I think you missed my post...?

    It would have perspective problems. Two different behodlers would need to see two different thyigns, but there's no way to do such as ominidirecitonal light would cast two different backrounds, both visible to both beholdrs, and focused light would project on everything, not just the beholder's eyes (so a beholder could see the light being projected towards the other beholder). :wink:
    you cannot see light that is not coming into your retinas , so you would not see the other light. if you could, you could see all sides of any object.
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  18. #17  
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    Quote Originally Posted by chamilton333
    Quote Originally Posted by Lucifer
    Quote Originally Posted by chamilton333
    i would think that if you had some sort of LCD (liquid crystal display) to take in light, than eject it the other way, you could be invisible. if it worked both ways that would be an added bonus. Think: an invisible mouse ball adapted for humans.
    I think you missed my post...?

    It would have perspective problems. Two different behodlers would need to see two different thyigns, but there's no way to do such as ominidirecitonal light would cast two different backrounds, both visible to both beholdrs, and focused light would project on everything, not just the beholder's eyes (so a beholder could see the light being projected towards the other beholder). :wink:
    you cannot see light that is not coming into your retinas , so you would not see the other light. if you could, you could see all sides of any object.
    Ein?

    As I already said, if the camouflage focused the light right into the retina, anythign could block it and then the light would be reflected, so other beholders would see it... focused light will reflect on ANYTHING. You don't need to have a cinema projector shining right into your eye, you just see the light reflected from the silverscreen. Also light would disperse if it hit mist or dust.

    And in any case, if you had such precise and effective location & targeting device as to project a false image right into the retina of multiple beholders... why not just send a simple little laser beam which dazzled them?

    AS I said, we can view things which refract, reflect or absorb light in a way diferent than the background. But of course, the easiest way to become invisible is to just dazzle or blind the enemy... the ages-old trick of charging with the sun on your back. :wink:
    “If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin.” -Charles Darwin
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  19. #18  
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    Quote Originally Posted by Lucifer
    Quote Originally Posted by chamilton333
    Quote Originally Posted by Lucifer
    Quote Originally Posted by chamilton333
    i would think that if you had some sort of LCD (liquid crystal display) to take in light, than eject it the other way, you could be invisible. if it worked both ways that would be an added bonus. Think: an invisible mouse ball adapted for humans.
    I think you missed my post...?

    It would have perspective problems. Two different behodlers would need to see two different thyigns, but there's no way to do such as ominidirecitonal light would cast two different backrounds, both visible to both beholdrs, and focused light would project on everything, not just the beholder's eyes (so a beholder could see the light being projected towards the other beholder). :wink:
    you cannot see light that is not coming into your retinas , so you would not see the other light. if you could, you could see all sides of any object.
    Ein?

    As I already said, if the camouflage focused the light right into the retina, anythign could block it and then the light would be reflected, so other beholders would see it... focused light will reflect on ANYTHING. You don't need to have a cinema projector shining right into your eye, you just see the light reflected from the silverscreen. Also light would disperse if it hit mist or dust.

    And in any case, if you had such precise and effective location & targeting device as to project a false image right into the retina of multiple beholders... why not just send a simple little laser beam which dazzled them?

    AS I said, we can view things which refract, reflect or absorb light in a way diferent than the background. But of course, the easiest way to become invisible is to just dazzle or blind the enemy... the ages-old trick of charging with the sun on your back. :wink:
    i never said project directly into the retina. all it would have to do is send out the light the same way it came in. light coming into the retina doesnt exactly mean that it would have to be artificially profected.
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  20. #19  
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    Quote Originally Posted by chamilton333
    i never said project directly into the retina. all it would have to do is send out the light the same way it came in. light coming into the retina doesnt exactly mean that it would have to be artificially profected.
    And what you do with perspective? We're talking of a 3D object blocking the light that coems form behind. Just emitting the light won't do anyhting, as the beams of light exitting the object must not show the gap that the object has left in their path... but then, each ebam hits the object in oen point but the exit point will depend upont he beholder, there will be two exit points to two different beholders, and each beholder will see the light form the exit point aimed at the other beholder.

    Damm, that's difficult to explain without a drawing. I'll try to draw one tomorrow, now it's time to go to sleep.

    Meanwhile think of this: why, when you look at a thick glass, you can notice the glass's width? Maybe because light beams are entering it through a 2D surface and exittign through another 2D surface... and there is a gap in between both surfaces?
    “If the misery of the poor be caused not by the laws of nature, but by our institutions, great is our sin.” -Charles Darwin
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