Ultima Thule

In ancient times the northernmost region of the habitable world - hence, any distant, unknown or mysterious land.

Sunday, May 28, 2006

Invisibility Through Nano

By Aussiegirl

Here's an interesting article about what looks like magic, but could really work -- making something invisible.

Invisibility Through Nano

by Charles Q. Choi
New York (UPI) May 26, 2006

Invisibility cloaks that bend light might develop using nanotechnology, experts tell UPI's Nano World. "There are probably quite a number of useful things you could do with stealth for the military," said researcher John Pendry, a physicist at Imperial College London.
More mundane applications also include hiding obstacles -- "for example, one may wish to put a cloak over the refinery that is blocking your view of the bay," said researcher David Schurig, a physicist at Duke University in Durham, N.C. Moreover, objects invisible to electromagnetic fields are isolated from them as well. "You may want to protect something from electromagnetic interference," he added. [....]

Light is often bent in nature. For instance, mirages form when desert sands heat air that goes on to bend light rays from up above, creating images of the sky that deceive thirsty wanderers as illusions of water, Schurig explained.

The cloaking devices a team of scientists at Imperial College London and Duke University conjectured, along with Leonhardt working independently, do not render items transparent, with light streaming through an object. Nor would these machines simply provide camouflage. Instead, the invisibility the scientists describe would smoothly guide rays of light completely around an item so they proceed along their original trajectory as if nothing were there, hiding the object from sight without producing reflections or shadows. These devices would not require power to work.

Imagine making a hole in space the right size to fit a desired object. "This hole is akin to one that can be opened up in a woven cloth by sticking a pointed object between the threads and compressing the fibers radially outward," Schurig explained. "In essence, the electromagnetic fields are confined to the 'threads of the cloth' and cannot reach an object placed in the 'hole.' Outside the compressed region the 'threads' and the fields are returned to their original paths, undisturbed."

The key ingredients for cloaking devices are compounds known as metamaterials. Metamaterials that deal with light are made of structures smaller than the length of a wave of light -- if the structures were larger, they would scatter the light instead of guide it. Red light has a wavelength of roughly 650 nanometers or billionths of a meter, while blue light has a wavelength of about 475 nanometers. Radio waves, microwaves and infrared waves have longer wavelengths than visible light while ultraviolet rays, X-rays and gamma rays have shorter ones. [....]


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