![]() ![]() The method could also work to block sound waves - like the cone of silence on the "Get Smart" TV show, but not as silly. 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. "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. 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. There'd be plenty of applications in the civilian world as well, even for rudimentary cloaking devices. Such a technology would be "far superior to stealth," he said. "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. The radar application is of great interest to military outfits such as the Defense Advanced Research Projects Agency, which funded Pendry's team. It's far easier to create radar invisibility, Pendry said: "You're talking millimeters" - that is, thousandths of a meter. 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. The tiny structures embedded in the metamaterial would have to be smaller than the wavelength of the electromagnetic rays you wanted to bend.Moving the material around would spoil the effect. ![]() The cloak could be made to cover a volume of any shape, but "you can't flap your cloak," Pendry said."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 invisibility effect would work only for a specific range of wavelengths.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. 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.Of course, there are some scientific catches that the tale-tellers never had to worry about: Maybe these Harry Potter novels were ahead of their time," Pendry said, half-jokingly. "Fiction has predicted the course of science for some time. "Metamaterials are very interesting products." "There are recipes for controlling metamaterials," explained University of Pennsylvania electrical engineer Nader Engheta, who published his own invisibility recipe last year. The most exotic technologies involve "metamaterials," blends of polymers and tiny coils or wires that twist the paths of electromagnetic radiation. 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 two papers lay out different theoretical methods for creating invisibility, not only for radar but potentially for optical wavelengths as well. 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. "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. ![]()
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