Friday, October 20, 2006

Invisibility Cloak Developed

Harry Potter and Captain Kirk would be proud. A team of British and American researchers has made a Cloak of Invisibility.
Before any perverts get their hopes up, it should be said that it's not perfect yet. But it is a start, since it did a pretty good job of hiding a copper cylinder. In this experiment, the scientists used microwaves to try to detect the cylinder. Like light and radar waves, microwaves bounce off objects making them visible and creating a shadow, though it has to be detected with instruments.
If you can hide something from microwaves, you can hide it from radar - a possibility that will fascinate the military. Cloaking differs from stealth technology, which doesn't make an aircraft invisible but reduces the cross-section available to radar, making it hard to track. Cloaking simply passes the radar or other waves around the object.
The new work points the way for an improved version that could hide people and objects from visible light. Conceptually, the chance of adapting the concept to visible light is good, cloak designer David Schurig, a research associate in Duke University's electrical and computer engineering department, said. But he added that from an engineering point of view it is very challenging.
Nonetheless, the cloaking of a cylinder from microwaves comes just five months after Schurig and colleagues published their theory that it should be possible. Their first success is reported in a paper in Friday's issue of the journal Science.
"We did this work very quickly and that led to a cloak that is not optimal," said co-author David R Smith, also of Duke. "We know how to make a much better one."
The first working cloak was in only two dimensions and did cast a small shadow, Smith acknowledged. The next step is to go for three dimensions and to eliminate any shadow.
Normally viewers can see things because objects scatter the light that strikes them, reflecting some of it back to the eye.
"The cloak reduces both, an object's reflection and it's shadow, either of which would enable it's detection," said Smith. In effect the device , made of meta-materials - engineered mixtures of metal and circuit board materials, which could include ceramic, Teflon or fibre composite materials - channels the microwaves around the object being hidden.
Just like when water flows around a rock, Smith explained, it recombines after it passes the rock and people looking at the water downstream would never know it had passed a rock.


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