Scientists are boldly going where only fiction has gone before -- to develop a "Cloak of Invisibility."
It is not quite ready to hide a Romulan space ship from Captain James T. Kirk of Star Trek or to disguise Harry Potter. But it is a significant start and could show the way to more sophisticated designs.
In this first successful experiment, researchers from the US and Britain were able to cloak a copper cylinder.
It is like a mirage, where heat causes the bending of light rays and cloaks the road ahead behind an image of the sky.
"We have built an artificial mirage that can hide something from would-be observers in any direction," said cloak designer David Schurig, a research associate in Duke University's electrical and computer engineering department.
For their first attempt, the researchers designed a cloak that prevents microwaves from detecting objects. Like light and radar waves, microwaves usually bounce off objects, making them visible to instruments and creating a shadow that can be detected.
The cloaking uses special materials to deflect radar or light or other waves around an object like water flowing around a smooth rock in a stream. It differs from stealth technology, which does not make an aircraft invisible but reduces the cross-section available to radar, making it hard to track.
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, Schurig said in a telephone interview. But, he added, "From an engineering point of view it is very challenging."
The cloaking of a cylinder from microwaves comes just five months after Schurig and colleagues published their theory that it should be possible. Their work was reported in a paper in yesterday'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 Smith, also of Duke.
"We know how to make a much better one," he added.
The first working cloak was in only two dimensions and did cast a small shadow, Smith said.
The next step is to go for three dimensions and to eliminate any shadow.
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 its shadow, either of which would enable its detection," Smith said.
The cloak is made of metamaterials, which are mixtures of metal and circuit board materials such as ceramic, Teflon or fiber composite.
In an ideal situation, the cloak and the item it is hiding would be invisible. An observer would see whatever is beyond them, with no evidence that the cloaked item exists.
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