Science reveals secrets of invisibility
8/9/06

(CNN) -- Invisibility has long been a fantastical ability exclusively
enjoyed by teenage wizards, super heroes and the ultra-advanced
civilisations of science fiction.
But more pragmatic-minded scientists and engineers now believe that
invisibility-enabling technology may be within reach of lesser mortals
as well.

The key to that possibility is the development of increasingly complex
metamaterials -- manmade composites engineered on a nano scale with
properties entirely different to anything found in nature.
Doctor Ulf Leonhardt, a physicist at Scotland's St. Andrews University
who has recently published two papers on the theory behind invisibility
technology, said the key was developing a transparent material capable
of bending light around an object concealed behind it.
"What you want to do is to surround yourself with a transparent material
that is not only transparent but bends the light around you," Leonhardt
told CNN.

Leonhardt said the underlying principle was inspired by natural
phenomena when light is bent to create optical illusions such as the
refraction of a spoon in water or a mirage in the desert or on hot
tarmac.
"There are many examples of ways a transparent material like water glass
or air can bend light," said Leonhardt. "The reason that is possible is
because light will always take the shortest route, which is not always a
straight line. All you need is a transparent material that bends light
around an object like water moving around a stone."
Work on metamaterials that could ultimately make invisibility a reality
is already underway at Duke University in the U.S., where a team led by
Professor David R. Smith is experimenting with the design of materials
to shield objects from other electromagnetic waves such as microwaves.

Leonhardt said that once that technology had been developed it would
merely need to be replicated on a smaller scale to work for light waves
as well.
"The essential idea is that all you have to do is make things smaller.
Visible light has a significantly smaller wavelength than microwaves or
radio waves but you could take the same building blocks and make them
very small. Thanks to nanotechnology there is a chance that can be
done."

One problem that engineers would face would be in creating a
metamaterial covering the full range of the optical spectrum rather than
a single color or light frequency. Currently researchers are only
working on developing materials with the ability to channel waves of a
specific frequency.
But Leonhardt said he believed the issue was surmountable: "There will
be advances on both the technological and theoretical sides which will
make invisibility happen in the not too distant future. This is not
completely beyond the range of present technology and theoretical
ideas."

While there may ultimately be practical, ethical and security
considerations to be considered for invisibility technology, initial
applications are likely to focus on microwave shielding, protecting
electrical devices from electromagnetic interference, and applications
to enable more effective wireless communications, Leonhardt said.
"What these new ideas give you is a new set of tools to guide microwave
radiation in a controlled and precisely adjusted way. Generally anything
connected with wireless technology would benefit from these new design
ideas."

Ironically, the method by which invisibility might be achieved is not
dissimilar to the way in which one comic book hero already achieves her
special powers. The Invisible Woman, one of Marvel's "Fantastic Four,"
hides behind a forcefield which guides light around her.
"This really is the underlying principle of these devices. You mimic
with a material an effect that would occur with a field like a curved
space," said Leonhardt. "That's the closest example to what people could
perhaps do with modern technology."

But the Invisible Woman and Harry Potter, armed with his invisibility
cloak, may still have an advantage over anything technology is capable
of. In the real world, anything or anyone concealed from view would also
be trapped in darkness.
"You would see black, of course ," said Leonhardt. "You are completely
cut off from light as it is guided around you -- so you wouldn't see
anything."