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Boltonian
04 May 06,, 13:34
'Cloaking device' idea proposed that could have potential military uses.

By Paul Rincon
BBC News science reporter


http://newsimg.bbc.co.uk/media/images/41631000/jpg/_41631964_spaceship_spl_203l.jpg
The work brings science fiction closer to science fact - just a little


The cloaking devices that are used to render spacecraft invisible in Star Trek might just work in reality, two mathematicians have claimed.

They have outlined their concept in a research paper published in one of the UK Royal Society's scientific journals.

Nicolae Nicorovici and Graeme Milton propose that placing certain objects close to a material called a superlens could make them appear to vanish.

It would rely on an effect known as "anomalous localised resonance".

However, the authors have so far only done the maths to verify that the concept could work. Building such a device would undoubtedly pose a significant challenge.

Starting small

Cloaking devices are a form of stealth technology much favoured by Star Trek baddies such as the Romulans and Klingons.

The complex mathematical phenomenon outlined by Milton and Nicorovici closes the gap a little between science fiction and fact.

The phenomenon is analogous to a tuning fork (which rings with a single sound frequency) being placed next to a wine glass. The wine glass will start to ring with the same frequency; it resonates.

The cloaking effect would exploit a resonance with light waves rather than sound waves.

The concept is at such a primitive stage that the scientists talk only at the moment of being able to cloak particles of dust - not spaceships.

In this example, an illuminated speck of dust would scatter light at frequencies that induce a strong, finely tuned resonance in a cloaking material placed very close by.

The resonance effectively cancels out the light bouncing off the speck of dust, rendering the dust particle invisible.

One way to construct a cloaking device is to use a superlens, made of recently discovered materials that force light to behave in unusual ways.

Vanishing point

Professor Sir John Pendry, of Imperial College London, who helped pioneer superlenses, said: "If the speck of dust is close enough it induces a very aggressive response in the cloaking material which essentially acts back on the speck of dust and forces it to stop shining.

"Even though light is hitting the speck of dust, scattering of the light is prevented by the cloak which is in close proximity," he told the BBC News website.

The authors of the paper argue that the cloak needn't just work with a speck of dust, but could also apply to larger objects.

But they admit the cloaking effect works only at certain frequencies of light, so that some objects placed near the cloak might only partially disappear.

"I believe their claims about the speck of dust and a certain class of objects. In the paper, they do give an instance about a particular shape of material they can't cloak. So they can't cloak everything," said Professor Pendry.

"Nevertheless, it's a very neat idea to get this aggressive response from the material to stop tiny things emitting light."

The Imperial College physicist agreed this particular concept had potential military uses: "Providing the specks of dust are within the cloaked area, the effect will happen. A cloak that only fits one particular set of circumstances is very restrictive - you can't redesign the furniture without redesigning the cloak."

Details are published in Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.

Paul.Rincon-INTERNET@bbc.co.uk

http://news.bbc.co.uk/2/hi/science/nature/4968338.stm

canoe
05 May 06,, 00:31
Interesting science, but where hundreads of years (at least) from being able to use any of it for practical applications.

RustyBattleship
05 May 06,, 01:03
Isn't this the erroneous and fictitious "Philadelphia Experiment" all over again?

ArmchairGeneral
19 May 06,, 01:48
Even if it's true, it seems to me that preventing an object from emitting light wouldn't make it invisible. It would just leave a black spot. The problem isn't preventing emission of light, the problem is emitting the proper light, i.e. what you would see if the object wasn't there.

2DREZQ
25 May 06,, 23:58
Anyone who doesn't believe in invisibility has never ridden a motorcycle in heavy traffic.

Bill
26 May 06,, 03:44
Anyone who doesn't believe in invisibility has never ridden a motorcycle in heavy traffic.

LOL........OR a German Supercar.

I had some FREAKING MORON in his SUV just SWERVE(his idea of a lane change i think) into my lane today- into airspace that i was currently occupying- on the phone, didn't bother looking, didnt wave or acknowledge his mistake afterwards.

I JUST barely stopped and swerved out of the way in time.

Thank god for a near 1G skid pad rating and the most awesome braking system i have ever experienced in my life.... ;)

RustyBattleship
27 May 06,, 00:24
Maybe there's something to this after all. This just appeared in this morning's edition of the Long Beach Press-Telegram. Sort of reminds me of the early 90's when I was the project leader on a Stealth program for the Navy. It was written as a Shipalt and later as an Installation Procedure on a very accessible Sun computer. I hid the texts in various other projects and titled the Shipalt as "Klingon" and the Installation as "Romulan".

Article Launched: 05/26/2006 12:00:00 AM PDT

Future of invisibility becoming clear
By Andrew Bridges, Associated Press

WASHINGTON The key to creating a Harry Potter-like invisibility cloak lies in man-made materials unlike any in nature or the Hogwarts School of Witchcraft and Wizardry, researchers say.
They're laying out a blueprint for turning science fiction into reality. And they say that, in theory, nothing's stopping them from making such a cloak.

Well, almost nothing: They still need to perfect the manufacture of those exotic materials with an ability to steer light and other forms of electromagnetic radiation around a cloaked object, rendering it as invisible as something tucked into a hole in space.

"Is it science fiction? Well, it's theory and that already is not science fiction. It's theoretically possible to do all these Harry Potter things, but what's standing in the way is our engineering capabilities," said John Pendry, a physicist at the Imperial College London. Details of the study, which Pendry co-wrote, appear in Thursday's online edition of the journal Science.

Scientists not involved in the work said it presents a solid case for making invisibility an attainable goal.

"This is very interesting science and a very interesting idea and it is supported on a great mathematical and physical basis," said Nader Engheta, a professor of electrical and systems engineering at the University of Pennsylvania. Engheta has done his own work on invisibility using novel materials called metamaterials.

Pendry and his co-authors also propose using metamaterials because they can be tuned to bend electromagnetic radiation radio waves and visible light, for example in any direction.

A cloak made of those materials, with a structure designed down to the submicroscopic scale, would neither reflect light nor cast a shadow.

Instead, like a river streaming around a smooth boulder, light and all other forms of electromagnetic radiation would strike the cloak and simply flow around it, continuing on as if it never bumped up against an obstacle. That would give an onlooker the apparent ability to peer right through the cloak, with everything tucked inside concealed from view.

"Yes, you could actually make someone invisible as long as someone wears a cloak made of this material," said Patanjali Parimi, a Northeastern University physicist and design engineer at Chelton Microwave Corp. in Bolton, Mass. Parimi was not involved in the research.

Such a cloak does not exist, but early versions that could mask microwaves and other forms of electromagnetic radiation could be as close as 18 months away, Pendry said. He said the study was "an invitation to come and play with these new ideas."

"We will have a cloak after not too long," he said.

The Pentagon's Defense Advanced Research Projects Agency supported the research, given the obvious military applications of such stealthy technology.

While Harry Potter could wear his cloak to skulk around Hogwarts, a real-world version probably would not be something just to be thrown on, Pendry said.

"To be realistic, it's going to be fairly thick. Cloak is a misnomer. 'Shield' might be more appropriate," he said.

ArmchairGeneral
27 May 06,, 00:43
Now that sounds more like it. If you can get the light from one side to come out the other side in the same direction, it should work. Sweet.

Bill
27 May 06,, 10:43
I would've killed for that cloak in my former profession.

What am i saying...i'd kill for it in my current profession.

LOL.

2DREZQ
27 May 06,, 18:18
Ha! You can be invisible now! Ever stood in line at the DMV right before lunch?

The Chap
28 May 06,, 04:43
Well, good to see that I am not the only old sod that appreciates good cartoons!

Steath can, and I gather, has, been achieved with radioactve coatings. That being purely for radar. The earliest, of course, were WWII exp with transparent aircraft and those with flashlamps over the Atlantic. I'd stll take an armoured airship any day. But That is because I'm probably senile. :biggrin:

ArmchairGeneral
28 May 06,, 05:23
Hey Chap, where you been? It seems like you're some sort of migratory internet beast, just comes over the horizon one day, stops and eats, then disappears over the other horizon. Where to? Nobody knows. :biggrin:

RustyBattleship
28 May 06,, 18:33
Steath can, and I gather, has, been achieved with radioactve coatings. That being purely for radar. The earliest, of course, were WWII exp with transparent aircraft and those with flashlamps over the Atlantic. I'd stll take an armoured airship any day. But That is because I'm probably senile. :biggrin:
Stealth (on ships) is not done with "radioactive coatings". I wrote the Shipalt and installation instructions for Stealth of a certain class of warships and know that the material is not radioactive. Otherwise I wouldn't have a sample of it in my desk drawer right now.

I believe "transparent" aircraft was experimented with in the FIRST World War but the "transparent" material reflected more light than just painted fabric coatings.

Flash lamps was a form of counter lighting to eliminate the shadows of aircraft. But it was soon discarded as it interfered with the aerodynamics of the planes as well as adding weight and requiring more electrical power. Plus it was difficult for the crew to adjust the intensity of the lights depending upon atmospheric conditions. They worked best on Hazy Days.
Which is also why Navy ships are painted "Haze Gray" instead of loading up the topsides with variable intensity counter lights and extra generators to power them.

It was more economical to paint all sides of a ship Haze Gray with the undersides of platforms and major overhangs an off-white to reduce shadowing. Since it was actually the Hornet that launched Doolittle's B-25's and NOT the Shangrilla (as announced by Roosevelt though it didn't exist then) we also found a neat trick by painting the same hull number of ships of the same class to confuse German U-boats just off our East Coast. So they wouldn't know if, say an Escort Destroyer with the number 173, was in Philly, Norfolk or in the Bahamas.

Simullacrum
30 May 06,, 16:00
Researchers say they are rapidly closing in on new types of materials that can throw a cloak of invisibility around objects, fulfilling a fantasy that is as old as ancient myths and as young as "Star Trek" and the Harry Potter novels.

Unlike those tales of fictional invisibility, the real-life technologies usually have a catch. Nevertheless, limited forms of invisibility might be available to the military sooner than you think.

"We're very confident that at radar frequencies, these materials can be implemented on a time scale of 18 months or so," John Pendry of Imperial College London told MSNBC.com.

Pendry's research team is one of two groups whose results were posted Thursday on the journal Science's Web site in advance of print publication. The two papers lay out different theoretical methods for creating invisibility, not only for radar but potentially for optical wavelengths as well.

Still more teams are out there with ideas to make things invisible using methods ranging from superlenses that cancel out the light from nearby objects to actual cloaks onto which video can be projected as a moving camouflage. The most exotic technologies involve "metamaterials," blends of polymers and tiny coils or wires that twist the paths of electromagnetic radiation.

"There are recipes for controlling metamaterials," explained University of Pennsylvania electrical engineer Nader Engheta, who published his own invisibility recipe last year. "Metamaterials are very interesting products."

The latest research papers describe how metamaterial could be fabricated to bend light in carefully curved paths around the object to be hidden, so that an observer would see right through it or more accurately, right around it to the other side.

"The cloak would act like you've opened up a hole in space," Duke University's David Smith, one of Pendry's co-authors, explained in a news release. "All light or other electromagnetic waves are swept around the area, guided by the metamaterial to emerge on the other side as if they had passed through an empty volume of space."

Pendry told MSNBC.com that the cloak wouldn't reflect any light, and wouldn't cast a shadow either. "It would be like Peter Pan had lost his shadow," he said, referring to the fictional character who had to have his shadow stitched back on.

Dreams come true, with a few catches
Theoretically at least, the metamaterial could work like the helmet of invisibility celebrated in Greek myth, or the cloaking device that hid Romulan and Klingon vessels in the "Star Trek" series, or the invisibility cloak that came in so handy for Harry Potter in J.K. Rowlings' novels.

"Fiction has predicted the course of science for some time. ... Maybe these Harry Potter novels were ahead of their time," Pendry said, half-jokingly.

Of course, there are some scientific catches that the tale-tellers never had to worry about:

* For a total invisibility effect, the waves passing closest to the cloaked object would have to be bent in such a way that they would appear to exceed relativity's light speed limit. Fortunately, there's a loophole in Albert Einstein's rules of the road that allows smooth pulses of light to undergo just such a phase shift.
* The invisibility effect would work only for a specific range of wavelengths. "There is a price to be paid if you want a thin cloak, in that it operates only over a narrow range of frequencies," Pendry said.
* The cloak could be made to cover a volume of any shape, but "you can't flap your cloak," Pendry said. Moving the material around would spoil the effect.
* The tiny structures embedded in the metamaterial would have to be smaller than the wavelength of the electromagnetic rays you wanted to bend. That's a tall order for optical invisibility, because the structures would have to be on the scale of nanometers, or billionths of a meter. It's far easier to create radar invisibility, Pendry said: "You're talking millimeters" that is, thousandths of a meter.

The radar application is of great interest to military outfits such as the Defense Advanced Research Projects Agency, which funded Pendry's team. "Radar is a defense technology, and if you wish to hide from it, this sort of cloak would be a good way of doing it," he said. Such a technology would be "far superior to stealth," he said.

If optical cloaks could be designed, that would be of interest to the military as well. "One obvious thing would be that you could construct a hutch in which you could hide a tank, and the hutch would make it appear as though the tank wasn't there. ... You could also think of weightier things, like submarines or battleships, where you might want to put some of this stuff," Pendry said.

Civilian applications, too
There'd be plenty of applications in the civilian world as well, even for rudimentary cloaking devices. For example, you could create receptacles to shield sensitive medical devices from disruption by MRI scanners, or build cloaks to route cellphone signals around obstacles. "You may wish to put a cloak over the refinery that is blocking your view of the bay," Duke University's David Schurig, another of Pendry's co-authors, was quoted as saying.

While Pendry's team proposed constructing all-over cloaking devices, the other research paper published Thursday describes a simpler method that would involve shaping the metamaterials into cylindrical cloaking devices. The method could also work to block sound waves like the cone of silence on the "Get Smart" TV show, but not as silly.

The catch here is that the invisibility effect would work only if you were on the same plane as the hidden object. "You could look on top of it, and look inside the cloak," said the paper's author, Ulf Leonhardt of the University of St. Andrews in Scotland.

Leonhardt told MSNBC.com that "potentially a mixture of the two schemes will lead to a practical design." He said the paper from Pendry's team gave him some additional ideas to work with.

"I read it for the first time just last Friday, and I've come up already with something new," he said.

The Chap
04 Jun 06,, 00:18
Hey Chap, where you been? It seems like you're some sort of migratory internet beast, just comes over the horizon one day, stops and eats, then disappears over the other horizon. Where to? Nobody knows. :biggrin:

Working! Nice to know someone cares though! :)

The Chap
18 Aug 06,, 16:29
And now just back from South Africa. Not working. ;)

The Chap
22 Sep 06,, 09:29
I reckon that for a few million bucks I could make anything visible. Hmm?

Aldrich bloody Aims:rolleyes:

SnowLeopard
22 Sep 06,, 10:52
Ahhh, the stuff of science fiction ............ and it wasn't used in just Star Trek either.

But generally, whereever it was used, it usually had vast energy requirements and vast storage requirements. Assuming that one had it, could they get past those sci fi requirements?

Actually, the best one I liked and one that showed something of practical applications was the invisibility of the Vipers in Galactica 1980. It was all a nice trick when they hid them on the ground, but real clincher of something like that was when they hit the cloak and broke the radar missile lock of the F-15's on their tails.

It's not quite Star Trek cloaking ......... but it is a cloaking of a type and that point, one isn't really worried about what kind of "hole" they are leaving in the sky just as long as there isn't anything there for weapons to lock on to and home in on.
--------------------------------------------------
(The 'Em Falcon' has just buzzed the bridge of the Star Destroyer Avenger. "Track him in case he comes around for another pass!"--Captain Needa
"Sir, the vessel no longer appears on our scopes!"--officer in the pit
"They can't have disappeared! No ship that small can have a cloaking device.", (w,stte), "The Empire Strikes Back")

Low-tech
25 Sep 06,, 12:39
living near boston, ive seen articles in the local papers about MIT research on this stuff.

if MIT is on it, there may be some validity to the science.the crazy theoretical stuff.

Repatriated Canuck
26 Sep 06,, 13:00
Anyone who doesn't believe in invisibility has never ridden a motorcycle in heavy traffic.

Even on a big ass Gold Wing no one sees you. :rolleyes:

SnowLeopard
26 Sep 06,, 13:27
Anyone who doesn't believe in invisibility has never ridden a motorcycle in heavy traffic.

Or hidden in a shadow during hide & seek. I did that as a teen once, we were playing at the compound's beach facility and I hid in the shadow of a wall on the sand. People came very close to me but never saw me ....... got chewed up by sand fleas, though.

That's one of the things about a cloaking device in space. Conceptually, if one hid in the shadow of a large body, they would be invisible. That's what the 'em Falcon' essentially did in the '2nd' SW's movie and it is basically realistic. They got inside the minimal range of the destroyer's sensors and there, they couldn't be seen. They were invisible.

There is true invisibility and there is practical invisibility. Magicians do the latter all the time. They accomplish their tricks because the actual feat is invisible ...... because people aren't looking at that particular area. Or their perception of that area is incorrect, such as with an optical illusion.

Romulian cloaking device? Well, it's definetly hardcore, the top of the mark ....... but there are lots of little tricks one can do to accomplish a short term purpose.
----------------------------------------------
(Hovercraft, they were going to strafe him, he'd be dead before he'd knew he was dying. And then they just raced past him, landed on the island he had just departed, and went searching. Hardin couldn't believe it but he understood it. The (Shah's) Iranians were focused on their radar searching for him but the Swan was fiberglass, invisible to radar. They had their eyes glued to the screen that they never looked up, never saw the sailboat, and just completely missed him.--(wtte), Book: The Shipkiller by Justin Scott)

highsea
20 Oct 06,, 18:42
Well, they are making good progress...

Researchers Create First Working Invisibility Cloak

By Imperial College, London and Duke University, USA, Scientists have demonstrated the first ever working 'invisibility cloak', reports Science Express today. The team of researchers from Duke University, USA, worked with Professor Sir John Pendry New Window of Imperial College London to create a prototype 'cloak' based on a new design theory proposed by the same team earlier this year. Using a new design theory, researchers at Duke University's Pratt School of Engineering and Imperial College London have developed the blueprint for invisibility cloak. Once devised, the cloak could have numerous uses, from defense applications to wireless communications, the researchers said.

The cloak deflects microwave beams as they flow around an object hidden inside it, in the same way that water in a river flows around a stick. The Duke scientists have proven that the object inside the cloak is rendered invisible to microwaves, which could, in the long run, have a variety of applications for radar and communications technologies. The group's design methodology also may find a variety of uses other than cloaking, the scientists said. With appropriately fine-tuned metamaterials, electromagnetic radiation at frequencies ranging from visible light to electricity could be redirected at will for virtually any application. For example, the theory could lead to the development of metamaterials that focus light to provide a more perfect lens.

The researchers at Duke University used theoretical designs published in an earlier Science paper to build a small cloak, less than five inches across, which would provide invisibility in two dimensions. The cloak was built using specially-manufactured 'metamaterials' which 'grab' light heading towards the cloak and make it flow smoothly around the cloak instead of striking it.

To test the prototype cloak, the researchers aimed a microwave beam at it inside a test chamber between two metal plates, and then measured the electromagnetic fields both inside and outside the cloak. Their measurements showed that the electromagnetic waves separated and flowed around the centre of the cloak, as predicted by theory.

Sir John said: "Our first paper developed the concept of a cloak but there remained the huge challenge of making this a reality. We knew that no naturally occurring materials would do the job, but the new class of metamaterials which owe their properties to their internal structure rather than their chemistry, have proved yet again that they can meet some of the most extreme challenges."

Sir John and his collaborators at Duke are concentrating on perfecting their cloaking technology for microwaves, and are hoping to develop a three-dimensional cloak for invisibility to microwaves.

The metamaterials used to build the cloak are fashioned into concentric two-dimensional rings, which interact with magnetic waves in a very specific way. The precise variations in the shape of the copper element used determine the cloak’s electromagnetic properties. The cloak is thought to be one of the most complex metamaterial structures ever made, as it has a unique circular geometry and it’s electromagnetic properties vary across its surface.

Such a cloak could hide any object so well that observers would be totally unaware of its presence, according to the researchers. In principle, their invisibility cloak could be realized with exotic artificial composite materials called "metamaterials," they said.

"The cloak would act like you've opened up a hole in space," said David R. Smith, Augustine Scholar and professor of electrical and computer engineering at Duke's Pratt School. "All light or other electromagnetic waves are swept around the area, guided by the metamaterial to emerge on the other side as if they had passed through an empty volume of space."

Electromagnetic waves would flow around an object hidden inside the metamaterial cloak just as water in a river flows virtually undisturbed around a smooth rock, Smith said.
The research team, which also includes David Schurig of Duke's Pratt School and John Pendry of Imperial College London, reported its findings on May 25, 2006, in Science Express, the online advance publication of the journal Science. The work was supported by the Defense Advanced Research Projects Agency.

First demonstrated by Smith and his colleagues in 2000, metamaterials can be made to interact with light or other electromagnetic waves in very precise ways. Although the theoretical cloak now reported has yet to be created, the Duke researchers are on their way to producing metamaterials with suitable properties, Smith said.
"There are several possible goals one may have for cloaking an object,” said Schurig, a research associate in electrical and computer engineering. "One goal would be to conceal an object from discovery by agents using probing or environmental radiation."

"Another would be to allow electromagnetic fields to essentially pass through a potentially obstructing object," he said. "For example, you may wish to put a cloak over the refinery that is blocking your view of the bay."

By eliminating the effects of obstructions, such cloaking also could improve wireless communications, Schurig said. Along the same principles, an acoustic cloak could serve as a protective shield, preventing the penetration of vibrations, sound or seismic waves.

"To exploit electromagnetism, engineers use materials to control and direct the field: a glass lens in a camera, a metal cage to screen sensitive equipment, 'black bodies' of various forms to prevent unwanted reflections," the researchers said in their article. "Using the previous generation of materials, design is largely a matter of choosing the interface between two materials." In the case of a camera, for example, this means optimizing the shape of the lens.

The recent advent of metamaterials opens up a new range of possibilities by providing electromagnetic properties that are "impossible to find in nature," the researchers said.

Their design theory provides the precise mathematical function describing a metamaterial with structural details that would allow its interaction with electromagnetic radiation in the manner desired. That function could then guide the fabrication of metamaterials with those precise characteristics, Smith explained.

The theory itself is simple, Smith said. "It's nothing that couldn't have been done 50 or even 100 years ago," he said.

"However, natural materials display only a limited palette of possible electromagnetic properties," he added. "The theory has only now become relevant because we can make metamaterials with the properties we are looking for."

"This new design paradigm, which can provide a recipe to fit virtually any electromagnetic application, leads to material specifications that could be implemented only with metamaterials," Schurig added.

The team's next major goal is an experimental verification of invisibility to electromagnetic waves at microwave frequencies, the scientists said. Such a cloak, they said, would have utility for wireless communications, among other applications.

- The research team, which also includes David Schurig of Duke's Pratt School and John Pendry of Imperial College London, reported its findings on May 25, 2006, in Science Express, the online advance publication of the journal Science.

www.ee.duke.edu/~drsmith

ArmchairGeneral
20 Oct 06,, 19:04
Now that is pretty dang sweet. Even if they can only get it to work in the microwave or radiowave frequencies, it would be very nice. The ultimate in stealth. I wonder how perfect it is? Would there be distortions, like in Predator?