Harry Potter's Invisibility Cloak May Be Possible

Every kid has had the wish to put on a magic coat that would make him or her invisible. In the latest issue of the journal Science, scientists explain how it might actually be possible.

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STEVE INSKEEP, host:

Monday's business news focuses on technology, including some that's out of sight.

Finally, scientists are doing something really and truly useful. Physicists and engineers are tying to find out how to make things invisible. A report in the Journal of Science says they are getting closer, although of course they may have succeeded and just not noticed.

According to NPR's Christopher Joyce, there's more here than meets the eye.

CHRISTOPHER JOYCE reporting:

There's no big secret here. To be invisible you just have to make something that will bend electromagnetic radiation - like light - around you, and then continue on as if you weren't there.

That's the theory, and the authors of this paper explain how that's actually possible in a series of complicated equations.

The real trick is making the material that will do this. David Smith is an electrical engineer at Duke University. He says scientists are now making meta-materials, small lattice-work thingies that are covered with patterned circuits. These redistribute electromagnetic radiation that strikes them.

Mr. DAVID SMITH (Electrical Engineer): So if you imagine, for example, a stream, and you place a rock in the stream, the flow lines of the stream circle around the rock and that's essentially what's happening in this cloak. As light comes in it's directed around the object that you're looking to conceal.

JOYCE: But don't expect to see an invisibility cloak on the shopping channel just yet.

So far, the meta-materials can hide from microwave radiation. That could be useful in reducing interference to radio or telecommunications signals. Becoming visually invisible would require incredibly tiny circuitry, because lightwaves have very short wavelengths. Smith says it's theoretically possible. Apparently, though, if you wore an invisibility cloak of meta-materials, you couldn't do much.

So what you're saying is, to cloak something, make it invisible, it's got to stand still.

Mr. SMITH: Or it can't change its shape. It doesn't have to stand still but it can't change its shape. But if a person's moving around, and lifting their arms, and waving about, that becomes very difficult to cloak.

JOYCE: Still, you could learn a lot just sitting there someplace, invisibly. Except, there's another problem: there'd be no light in there. You couldn't see out.

Christopher Joyce, NPR News.

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