HARRY POTTER and Captain Kirk would be proud. A team of American and British researchers has made a Cloak of Invisibility. Although not perfect yet, it is a start, and it did a 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, although 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 does not make an aircraft invisible but reduces the cross-section available to radar, making it difficult to track. Cloaking just passes the radar or other waves around the object as if it were not there.
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, said cloak designer David Schurig of Duke University. The cloaking comes five months after Schurig and colleagues published their theory that it should be possible. Their success is reported 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 said.
The next step is to go in for 3-D 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," said Smith.
The cloak is made of engineered mixtures of metal and circuit-board materials, which could include ceramic or fiber composite materials. AP