Once it's invented, how will they find it?
ANNE MCILROY
Globe and Mail Update with Associated Press
It sounds like an idea lifted from Harry Potter or Star Trek – a cloak that would make someone or something invisible.
Researchers in Britain and the United States, however, have published a theoretical blueprint for how to construct a cloak made from revolutionary materials that could guide light around it. They say they might be able to build one within five years.
The cloak would be made from metamaterials, which are engineered with tiny physical structures – metal coils, or rods shaped like aerials. Scientists have been able to ”tune” them to bend electromagnetic waves, and effect that could be extremely important in military applications.
Researchers say the cloaks might be able to hide planes or ships from the radio waves used in radars.
Even more astounding – at least for the average person – would be the ability to wrap oneself in an invisibility cloak and disappear.
”The cloak would act like you've opened up a hole in space,” said David Smith, a professor of electrical and computer engineering at Duke University and a co-author of one of the papers on cloaking devices published this week in the on-line edition of the journal Science.
Hide an object in a metamaterial cloak, he said, and electromagnetic waves would flow around it as water flows virtually undisturbed around a smooth rock.
”Is it science fiction? Well, it's theory and that already is not science fiction. It's theoretically possible to do all these Harry Potter things, but what's standing in the way is our engineering capabilities,” said John Pendry, a physicist at the Imperial College London.
Scientists not involved in the work said it presents a solid case for making invisibility an attainable goal.
”This is very interesting science and a very interesting idea, and it is supported on a great mathematical and physical basis,” said Nader Engheta, a professor of electrical and systems engineering at the University of Pennsylvania. Mr. Engheta has done his own work on invisibility using novel materials called metamaterials.
Mr. Pendry and his co-authors also propose using metamaterials because they can be tuned to bend electromagnetic radiation – radio waves and visible light, for example – in any direction.
A cloak made of those materials, with a structure designed down to the submicroscopic scale, would neither reflect light nor cast a shadow.
Instead, like a river streaming around a smooth boulder, light and all other forms of electromagnetic radiation would strike the cloak and simply flow around it, continuing on as if it never bumped up against an obstacle. That would give an onlooker the apparent ability to peer right through the cloak, with everything tucked inside concealed from view.
”Yes, you could actually make someone invisible as long as someone wears a cloak made of this material,” said Patanjali Parimi, a Northeastern University physicist and design engineer at Chelton Microwave Corp. in Bolton, Mass. Mr. Parimi was not involved in the research.
Such a cloak does not exist, but early versions that could mask microwaves and other forms of electromagnetic radiation could be as close as 18 months away, Mr. Pendry said. He said the study was ”an invitation to come and play with these new ideas.”
”We will have a cloak after not too long,” he said.
The Pentagon's Defence Advanced Research Projects Agency supported the research, given the obvious military applications of such stealthy technology.
While Harry Potter could wear his cloak to skulk around his Hogwarts school, a real-world version probably would not be something just to be thrown on, Mr. Pendry said.
”To be realistic, it's going to be fairly thick. Cloak is a misnomer. ‘Shield' might be more appropriate,” he said.
