Posted on 11/02/2006 6:22:09 AM PST by Red Badger
It might not seem like much compared with Harry Potter's magic garment, but the first functional invisibility cloak has emerged from a North Carolina laboratory.
NOW YOU SEE IT. Microwaves bent by the concentric walls of this 1-centimeter-tall invisibility device circumvent the center area and emerge on their original paths as if nothing had been in the way. The copper hoop that was cloaked in the tests isn't pictured. Schurig et al./Science
The disk of concentric fiberglass-and-copper bands—about the size of a cocktail coaster—bends a narrow-frequency range of microwaves around a protected zone at its center. By then reorienting those electromagnetic rays so that they exit the disk on their original paths, as if undisturbed, the shield renders itself and whatever is in its protected zone almost invisible to a microwave detector downstream.
A team with members from Duke University in Durham, N.C., the Imperial College London, and the San Diego–based company SensorMetrix created the new device. Several of the scientists last spring proposed how to make such invisibility shields (SN: 7/15/06, p. 42: http://www.sciencenews.org/articles/20060715/bob9.asp).
In the latest experiments, the researchers placed a copper hoop in the path of microwaves and took readings with and without the novel cloak around the hoop. The measurements showed that the cloak eliminated nearly all the microwave disturbances that a naked hoop would cause.
The structure is "doing two things, not perfectly, [that] are the essence of cloaking" says Duke physicist David Schurig, who designed the device. "One is to reduce reflection, and the other is to reduce shadow." He and his colleagues describe the work in a report released Oct. 19 online by Science.
Physicist Oskar J. Painter of the California Institute of Technology in Pasadena calls the shield "a clear breakthrough that will have a ripple effect throughout the research-and-development community."
It's "a very big splash in the field," agrees mechanical engineer Xiang Zhang of the University of California, Berkeley. "Cloaking has been a dream for many years for many physicists and technologists."
Still, there was a noticeable shadow, notes theoretical physicist Costas M. Soukoulis of Iowa State University in Ames. "I was expecting the device to perform better," he says.
The new cloak's developers assembled the cloak from 10 narrow bands of fiberglass on which they had imprinted thousands of copper loops. The researchers arrayed the bands in concentric circles. The bands belong to a new class of building blocks, called metamaterials, that go into devices that manipulate electromagnetic waves in ways that were never before possible (SN: 3/25/00, p. 198: Available to subscribers at http://www.sciencenews.org/articles/20000325/fob5.asp).
To reduce the challenge of making and testing its prototype, the team gave the device a low profile, virtually eliminating the third dimension. They then exposed it to a thin layer of microwaves.
The flat shield has shown that cloaking is possible, but the device is probably not of much practical value, Schurig notes. Three-dimensional cloaks promise to be much more useful—for instance, to potentially thwart military radar.
The first demonstration of 3-D cloaking in microwaves is still at least a year or two away, estimates Duke physicist and team leader David R. Smith.
To be practical against radar, cloaks will have to work across a broad range of microwave frequencies, comments theoretical physicist Nathan Myhrvold, the former chief scientist of Microsoft. Now heading Intellectual Ventures in Bellevue, Wash., he does research on metamaterials and has collaborated with the cloak's inventors.
Cloaking at visible-light frequencies isn't yet feasible, Smith notes.
Hey, I haven't seen Sean Penn lately. Do you suppose ...
Except, if the cops can't see you, that means the moron changing lanes right into or pulling out in front of you can't see you either.
Paging Mr. Spock...
LOL!!!!........I knew it'd be you!.........
Kerry's already placed an order...
Turn it off! I can't see what you posted!........
Until some semi checks his mirror twice and comes into your lane.
We have a winner!
I'd use it only in the interstate and no cars in sight..........unless someone else had one.......
They had it first:
http://www.startrek.com/imageuploads/200303/tos-009-romulan-bird-of-prey/320x240.jpg
I had a buddy who used to work for some defense contractors on the west coast. Some of his friends had way too much money.
Don't know if this is true, but he told me that one of them had a Porsche that they painted with the then-experimental radar-absorbing paint used on some modern military aircraft. They'd put on a set of night-vision goggles, turn off their lights, and go speeding past a patrol car running radar on a deserted freeway for fun.
They weren't completely invisible, but at the rate of speed, and with the lights out at night, the patrolman wouldn't see them on the radar until they were very close, then the radar would suddenly register something travelling very fast just as they came wizzing by.
Again, he may have made it up, but this is something I wouldn't have put past him if he had the resources to do it.
I heard that when Predator came out some defense department officials saw the Predators suit and said "I want that!"
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