"Electromagnetic Wormhole" Could Make Objects Invisible

Joab Jackson
for National Geographic News
October 23, 2007

An "electromagnetic wormhole" could make objects traveling through it invisible, scientists say.

A group of mathematicians, including Allan Greenleaf of the University of Rochester, recently thought up a way to build such a device.

It would not be what is commonly known as a wormhole—a theoretical bend in space and time that could serve as a shortcut for traveling over vast distances.

Instead, once something entered one end of the newly theorized tunnel, the object would be electromagnetically invisible to outside observation until it emerged from the other side, Greenleaf said.

"It would create a complete a disconnection between the outside world and stuff inside the cloaking region," Greenleaf said. "It's good for hiding things."

This tunnel would get its stealthiness through a coating of metamaterials, an experimental class of artificial substances with uniquely engineered properties, such as the ability to bend light in novel ways.

When light is bent around a surface, for instance, the surface itself effectively becomes invisible.

Scientists are already closing in such materials.

In October 2006, for instance, Duke University researchers led by David R. Smith, successfully demonstrated that a shield of metamaterials about 5 inches (13 centimeters) wide could become invisible.

It was not a true invisibility cloak, though, since it only worked in two dimensions and only at microwave frequencies. Humans and other animals see light at much higher frequencies.

Invisibility "Tunnel"

Greenleaf and his associates knew little about metamaterials. But upon hearing about the Duke work, the team quickly saw the similarities to their own mathematical computations.

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