Tripping the Light-Fantastic

Invisibility is no longer confined to fiction. In a recent
experiment, microwaves were bent around a cylinder and returned to
their original trajectories, rendering the cylinder almost
invisible at those wavelengths. This doesn't mean that we're ready
for invisible humans (or spaceships), but by using Maxwell's
equations, which are partial differential equations fundamental to
electromagnetics, mathematicians have demonstrated that in some
simple cases not seeing is believing, too. Part of this successful
demonstration of invisibility is due to metamaterials
electromagnetic materials that can be made to have highly unusual
properties. Another ingredient is a mathematical transformation
that stretches a point into a ball, "cloaking" whatever is inside.
This transformation was discovered while researchers were pondering
how a tumor could escape detection. Their attempts to improve
visibility eventually led to the development of equations for
invisibility. A more recent transformation creates an optical
"wormhole," which tricks electromagnetic waves into behaving as if
the topology of space has changed. We'll finish with this: For More
Information: Metamaterial Electromagnetic Cloak at Microwave
Frequencies, D. Schurig et al, Science, November 10, 2006.