[ExI] Fw: UFO UpDate: Cloaking Throws An Electromagnetic Curveball
Terry Colvin
fortean1 at mindspring.com
Fri Jan 16 09:08:46 UTC 2009
-----Forwarded Message-----
>
>Source: ars technica.com - New York, New York, USA
>
> http://tinyurl.com/a6ufcv
>
>January 15, 2009
>
>
>New Cloaking Surface Throws An Electromagnetic Curveball
>By Tim De Chant
>
>For centuries, humans have dreamed of fading into the
>background. Hunters have long wished to vanish into their
>surroundings, and these days, awkward moments at parties can
>evoke similar desires. But the ability to truly disappear is
>still only found in tales spun by writers and filmmakers, as
>cloaking has remained the stuff of fantasy and science fiction.
>Thanks to some pioneering researchers, however, cloaking has
>moved one step closer to reality.
>
>Six scientists have built a sophisticated metamaterial that
>literally bends electromagnetic waves, according to a new paper
>published Thursday in the journal Science. Ruopeng Liu and
>Chunlin Li, researchers in David R. Smith's lab at Duke
>University, along with three other colleagues, assembled more
>than 10,000 specially designed pieces to form a mat 20 inches
>long and four inches wide. When finished, the yellow pad sucked
>microwaves in and spit them out-with a curve.
>
>To test their new invention, researchers first beamed microwaves
>at a flat, mirrored surface. The waves behaved as they should,
>bouncing off at a predictable angle. Next they shot it at a bump
>in a mirrored surface. The microwaves bounced and scattered,
>carefully obeying the laws of physics. Then the scientists laid
>their yellow mat over the bump. And the wave ignored the bump-or
>so it seemed. After reflecting off the curved surface, the
>radiation veered downward and continued along a flat surface-
>trajectory. The mat had cloaked the bump.
>
>[Graphic]
>
>Aside from starring in the Harry Potter series and countless
>Star Trek incarnations, cloaking has been a very serious and
>very active research area in the past few years. In May 2006,
>two scientists proposed active cloaking devices based on
>superlenses, but their contribution at the time was only
>theoretical. The reality of superlenses hasn't been as
>promising, but in October of that same year, Smith and his
>colleagues presented a cloaking breakthrough-the ability to
>cloak an object from a specific microwave frequency. More papers
>followed, and the science progressed rapidly. But then last
>December, a new theoretical study published gave researchers a
>harsh reality check-cloaking at multiple frequencies may very
>well be impossible, the authors said. As the number of cloaked
>frequencies increases, the efficacy of the device or material
>decreases. It's a classic tradeoff, they implied, and one not
>likely to be overcome.
>
>Liu and Li's new research, though, seems to poke a giant hole in
>that last paper. Their new metamaterial masks not one tiny slice
>of the microwave spectrum, but a relatively large swath of it,
>from 13 to 16 gigahertz. Liu and Li built off the results of
>Smith's 2006 paper to create the new cloak, but this time used
>more powerful algorithm to help them fabricate the metamaterial.
>The formula dictated where each of the over 10,000 pieces in the
>structure should be placed to achieve the desired effect.
>
>"The difference between the original device and the latest model
>is like night and day," Smith said in a press release. While the
>earlier, more limited device took Smith and his team four months
>to build, the new, more capable cloak was ready in only nine
>days.
>
>Smith compares the mat's cloaking effect to a mirage. "You see
>what looks like water hovering over the road, but it is in
>reality a reflection from the sky," he said. "The mirage you see
>is cloaking the road below."
>
>While you won't be able to don a fancy blanket and duck out of
>work early any time soon, the new metamaterial proves that one
>surface can cloak many frequencies. Three gigahertz is certainly
>a far cry from the 350,000 GHz that make up the visible
>spectrum, but at least it's a step in the right direction.
>
>
>Science, 2008. DOI: http://dx.doi.org/10.1126/science.1166949
>
>
>[Thanks to Frank Fields for the lead]
Terry W. Colvin
Ladphrao (Bangkok), Thailand
Pran Buri (Hua Hin), Thailand
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