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Quote:Now you see it, now you don't: cloaking device is not just sci-fi
Ian Sample, science correspondent
Wednesday May 3, 2006
The Guardian
It's been the curse of the USS Enterprise and the Klingons' favoured weapon. But back on Earth, mathematicians claim to have worked out how to make a cloaking device to render objects invisible.
An outline for the device is described in a scientific paper published today in which the authors reveal how objects placed close to a material called a superlens appear to vanish.
Even in the world of science fiction, the technology is not perfect, and nor is the device proposed by Graeme Milton at Utah University and Nicolae-Alexandru Nicorovici at Sydney University of Technology. According to their calculations, the device would only work at certain frequencies of light, and only if the object is within close range of the superlens.
The cloaking device relies on recently discovered materials used to make superlenses that make light behave in a highly unusual way. Instead of having a positive refractive index - the property which makes light bend as it passes through a prism or water - the materials have a negative refractive index, which effectively makes light travel backwards. It's light, but not as we know it.
Prof Milton's team calculated that when certain objects are placed next to superlenses, the light bouncing off them is essentially erased by light reflecting off the superlens, making the object invisible.
The calculations show that while the device could be used to obscure almost any shape of object, it only works over a short range of wavelengths, so if used to hide objects from human vision, they might only partially disappear.
Sir John Pendry, a theoretical physicist at Imperial College London who invented superlenses, said: "Effectively, they are making a piece of space seem to disappear, at least as far as light is concerned."
The research appears in the journal Proceedings of the Royal Society today.
Prof Pendry said the technology has great potential for hiding objects from radar or cloaking electronic instruments so they can be used in strong electromagnetic fields, such as those produced by hospital MRI brain scanners. "The secret is having the cloak itself be invisible and if you can do that cheaply and efficiently and it doesn't need to be metres thick, it would be extremely valuable for stealth. Even if you could cloak a single frequency, it would be very useful. The military is extremely interested in this."
So far the researchers have only worked through the mathematics to prove that the device is plausible. The practicalities of making one have yet to be solved.
Guardian
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05-03-2006, 08:50 PM
(This post was last modified: 05-03-2006, 08:50 PM by Munkay.)
Alram,May 3 2006, 02:41 PM Wrote:Guardian
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The gap between mathematically proven and empirically proved is rather large. You won't see me worried about sneaky Hobbits or invisible Hogwarts wizards anytime soon.
Interesting article though, especially about the idea of negative refraction. It'll be interesting to see down the road how well they can make this work in real life.
Cheers,
Munk
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Alram,May 3 2006, 01:41 PM Wrote:Guardian
[right][snapback]108876[/snapback][/right] I am trying not to be seen.
*Boom*
So, it won't work all the time. Huzzah.
Next, I'd like a transporter to avoid the commute to work.
Occhi
Cry 'Havoc' and let slip the Men 'O War!
In War, the outcome is never final. --Carl von Clausewitz--
Igitur qui desiderat pacem, praeparet bellum
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To hell with all that, where's my damn bag of holding?
Enquiring minds want to know what the hell we've been doing with fractal technology all these years.
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When beset by doubt,
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Wave your arms and shout.
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Occhidiangela,May 3 2006, 03:51 PM Wrote:Next, I'd like a transporter to avoid the commute to work.
[right][snapback]108888[/snapback][/right]
Granted, but now a horde of door to door salesmen, girl scouts, mormons, and lobbyists can appear at your house every second. Additionally, you may never use the "I got stuck in traffic" excuse any longer in case your children want extra morning parent time with their last minute school projects.
It sounds like a mirror.
"the materials have a negative refractive index, which effectively makes light travel backwards"
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Actually, they have had a working invisibility cloak now for a couple of years at least.
A company in Japan made a fabric that is covered in tiny camera / LCD screens. I don't remember how small, but like tiny sequins.
The cameras send a composited image of what is on one side of the cloth over to the other side to display on the LCDs, and vise versa. The whole effect is that basically you see through somebody.
You wind up with a Preditor Effect. A slight shimmer as the fabric moves and the displayed images resequence themselves to the camera imput.
It's pretty cool stuff.
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Doc,May 3 2006, 10:41 PM Wrote:Actually, they have had a working invisibility cloak now for a couple of years at least.
I think you are referring to this
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Hi,
Doc,May 3 2006, 03:41 PM Wrote:The cameras send a composited image of what is on one side of the cloth over to the other side to display on the LCDs, and vise versa. The whole effect is that basically you see through somebody.
[right][snapback]108899[/snapback][/right] Doesn't work. Consider a simple case: one person wearing that suit, a barren plane (think semi desert) with one tree, and two observers. One observer, the person wearing the suit, and the tree are in a direct line. The other person is a few degrees off this line. The observer on the direct line would get the desired effect, but the other observe would see two trees, the real one, and the one projected from the suit at a small angle. It's just a simple case of parallax, and the further from the background, the worse it gets.
--Pete
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I'll believe it when I see it... er, or not. Not seeing is believing.
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The movie clip is cool, but I am not sure if that is it.
Pete, the technology is still in it's infancy. Give it a break. :D
The application of this effect is more for infiltration I believe. Last I heard anything about it, an American company that contracts out to the armed forces was working with the Japanese company. The idea is camo for urban assaults. When pressed up against a wall, the wall is projected over the front of the suit.
There were some pictures on the net a while back. I originally saw the link either on Slashdot or Fark. It was very, very difficult to spot the soldiers. One guy, you could barely make him out. You could even see the spraypainted image on the wall behind him. One guy was crouched down in some bushes, and you could not make him out at all.
It's not perfect yet. The worst drawback is you have to haul around like a 30 odd pound box holding a bunch of computer equipment to process and direct all of these images.
I remember reading they wanted to start trying it out on some tanks and armored rigs. Planes flying overhead would only see the ground and not the rig.
All alone, or in twos,
The ones who really love you
Walk up and down outside the wall.
Some hand in hand
And some gathered together in bands.
The bleeding hearts and artists
Make their stand.
And when they've given you their all
Some stagger and fall, after all it's not easy
Banging your heart against some mad buggers wall.
"Isn't this where...."
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Alram,May 3 2006, 07:41 PM Wrote:It's been the curse of the USS Enterprise and the Klingons' favoured weapon.
[right][snapback]108876[/snapback][/right]
Hrmm, I thought in the original series the cloaking device was used by the Romulans, not the Klingons.
-V
Cloak Room Attendant
The Forsaken Inn
Its not a matter of the technology being new Doc.
If you pay attention what Pete said its that you would see that. Its the same issue as the guy who paints realistic images in side walks. It only works for 1 specific veiwing location.
That said it is nifty idea and should make for some nice camoflauge, sort of like Predator.
With more consideration I suspect we have another examples of mathmiticians(spelling) getting lost in their work and fooling themselves.
In reading it it seems they are putting the cloak on the opposite side of of the obscured object from the veiwer. That just wont work unless they are actually warping space - highly unlikely.
If they are putting the cloak between the veiwer and the object then they basically have some sort of "translucent" mirror - not all that special.
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05-04-2006, 03:31 AM
(This post was last modified: 05-04-2006, 04:02 AM by Occhidiangela.)
Ghostiger,May 3 2006, 08:52 PM Wrote:Its not a matter of the technology being new Doc.
If you pay attention what Pete said its that you would see that. Its the same issue as the guy who paints realistic images in side walks. It only works for 1 specific veiwing location.
That said it is nifty idea and should make for some nice camoflauge, sort of like Predator.
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The military services have all spent some money, and some years, in perfecting digital camoflage utility uniforms. They don't make you invisible, but they are remarkably good at making you "low observable." No tricks needed, just some clever use of the visual spectrum and shading. The "digital" comes from the way the camo patterns are applied to the material. It looks a little bit like pixelated lines on a computer graphics drawing. If I remember the optical feature being used, the effect in most light conditions is to blend contrasts.
Batteries not included, nor required.
This cloaking device (yes, to Van, Romulan, you new winner of a +1 Mana ring! :D ) strikes me as being too dependent on the viewer cooperating, as was previously pointed out. For satellite defense against ground observation/targeting faciilties, it might have some utility. Don't know enough, and I suspect what they are working with is a bit raw at this point.
Occhi
Cry 'Havoc' and let slip the Men 'O War!
In War, the outcome is never final. --Carl von Clausewitz--
Igitur qui desiderat pacem, praeparet bellum
John 11:35 - consider why.
In Memory of Pete
Alram,May 3 2006, 10:11 PM Wrote:more here
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No thats completely different.
Its almost the old cliche "smoke and mirrors".
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Ghostiger,May 3 2006, 10:51 PM Wrote:No thats completely different.
Its almost the old cliche "smoke and mirrors".
[right][snapback]108922[/snapback][/right] It is different.
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Doc,May 3 2006, 08:37 PM Wrote:Pete, the technology is still in it's infancy. Give it a break. :D
Pete's point about parallax is not a criticism of early technology, but a real problem for this technology now and into the future. A parallax will occur, regardless of how well the image is shown (even if it was a 100% perfect projection). From two different vantage points it wouldn't line up.
Although it's not the best resource in the world, a good explianation of a parallax can be found on Wikipedia, linked here.
Thanks for bringing that up Pete, it hadn't crossed my mind until now.
Cheers,
Munk
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Munkay,May 4 2006, 08:55 AM Wrote:Pete's point about parallax is not a criticism of early technology, but a real problem for this technology now and into the future. A parallax will occur, regardless of how well the image is shown (even if it was a 100% perfect projection). From two different vantage points it wouldn't line up.
Although it's not the best resource in the world, a good explianation of a parallax can be found on Wikipedia, linked here.
Thanks for bringing that up Pete, it hadn't crossed my mind until now.
Cheers,
Munk
[right][snapback]108935[/snapback][/right] Parallax should have no effect on the technology described in the original post that began this thread--that is if it can indeed be made to work.
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