10/22/2005

New Theory: How to Make Objects Invisible

High-tech cloaking machines could one day render very small objects nearly invisible and perhaps improve military stealth technology, scientists said Monday.

The idea is straight out of science fiction -- cloaking technology made Romulan spaceships disappear in Star Trek. A humble version of the device could become a reality, according to Nader Engheta and Andrea Alu of the University of Pennsylvania.

But don't expect to hide yourself or your spaceship anytime soon, at least not in the standard sense of invisible. In practical terms, the research is more likely to lead to improved technical and research devices, and even these applications are years away.

How it would work

The proposal involves using plasmons -- tiny electronic excitations on the surfaces of some metals -- to cancel out the visible light or other radiation coming from an object.

"A proper design … may induce a dramatic drop in the scattering cross-section, making the object nearly invisible to an observer," Nader and Alu write in a scientific paper that was made available to the public Feb. 14.

But cloaking ability would depend on an object's size, so that only with very small things -- items that are already microscopic or nearly so -- could the visible light be rendered null. A human could be made impossible to detect in longer-wavelength radiation such as microwaves, but not from visible light.

A spaceship might be made transparent to radio waves or some other long-wavelength detector.

The idea is in an infant stage but appears not to violate any laws of physics, according to an article Monday in news@nature.com, an online companion to the journal Nature, which provided advance copies of the story to reporters.

"The concept is an interesting one, with several important potential applications," John Pendry, a physicist at Imperial College in London in the UK, told the publication. "It could find uses in stealth technology and camouflage."

But Engheta, co-developer of the idea, said such applications can't even be considered yet.

New Theory: How to Make Objects Invisible

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