http://www.breitbart.com/news/2006/10/20/061020170453.em0doxnf.html
Scientists make Harry Potter-like 'cloak of invisibility'
Oct 20 1:04 PM US/Eastern
For fans of the fictional Harry Potter, US and British scientists
have demonstrated a working "invisibility cloak" that could, in
time, make wearers disappear.
Initial tests focused on making objects invisible to microwaves,
but the scientists said the same principles could theoretically
apply to visible frequencies, making a true invisibility cloak like
storybook hero Potter's possible.
Scientists at Duke University in North Carolina sought to put into
practice the design theory revealed earlier this year by Sir John
Pendry of Imperial College London.
They made a five-inch cloak (12.7 centimeters) from a complex
artificial composite, or metamaterial, of copper rings and wires
patterned onto fiberglass composite sheets.
The material is designed to distort space so that microwaves are
not reflected back, but are instead bent around the cloaked object,
whatever its shape, and allowed to flow on as if it didn't
exist.
The result is that the beams are deflected like water flowing
around a rock in a river, without noticeably interrupting the main
current.
"By incorporating complex material properties, our cloak allows a
concealed volume, plus the cloak, to appear to have properties
similar to free space when viewed externally," said Duke scientist
David Smith.
"The cloak reduces both an object's reflection and its shadow,
either of which would enable its detection."
The effect is different from, for instance, stealth technology
which protects US Air Force bombers from radar. That technology
simply deflects the radar in ways to disguise the jets, while not
making them invisible.
The invisibility cloak has potential applications in wireless
communications or radar -- preventing objects from blocking waves
or being disturbed by them or, for instance in military use, hiding
them from waves. Indeed, some of the funding for the research came
from the US Defense Department's high-tech research unit, the
Defense Advanced Research Projects Agency.
But the scientists said it's still a long leap to a real Harry
Potter-like cloak which would allow someone to walk around unseen.
It would take a much greater advance in engineering metamaterials
that do to the whole spectrum of visible wavelengths what the
existing cloak material now only does to microwaves.
"It's not yet clear that you're going to get the invisibility that
everyone thinks about with Harry Potter's cloak," said
Smith.