The Invisibility Tunnel

The invisibility is descending from fiction and movies to reality. New measurements show how to build an electromagnetic "wormhole", an invisible tube from both sides, that allows the light to pass down the unseen center.

The idea is based on the technology of the spherical invisibility cloak proposed in 2006.

An invisibility cloak should be built of metamaterial, a thicket of metal rings or other elements that manipulate light. The hollow shell of metamaterial would direct light off its inner space without slowing down, making the hole invisible to an outside watcher. "But the invisibility cuts both ways. If light does not enter, then whatever is in the cloak cannot see outside," said mathematician Allan Greenleaf of the University of Rochester.

That's why Greenleaf came with an opposite idea. His team wants to manipulate light employing an open tube with flared ends. A straight-on view would render visible the cylinder.

But from a lateral view, the light would seen to emerge of nowhere, as from a detour to another dimension and back, like in a space wormhole connecting two distant points. "We're tricking the electromagnetic waves … into thinking that, actually, space has been changed," said Greenleaf. "It's a very nice twist on the spherical cloak," said physicist John Pendry of Imperial College London, one of the first promoters of the idea. "We can invent a secret connection between two parts of space, and that is interesting. Building an invisible tunnel should be as hard-or easy, depending on your level of optimism-as making a spherical cloak," said Greenleaf.

But the Duke University team that came with the idea of the invisibility cloak still struggles to the building of the metamaterials. Greenleaf's group speculates The Greenleaf's wormholes could be employed to pass metals into an MRI scanner or achieve a 3-D video display.