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Earthquake-squelching, sonar-invisible 'active cloak' unfurled

Will you just shut up about f*ing Harry Potter, pleads prof

Boffins in America have violated every rule of Invisibility Club by stating that their astounding new "active cloaking" research has nothing to do with Harry Potter or Star Trek.

"It's a brand new method of cloaking," says Utah Uni maths prof Graeme Milton.

"Real objects could be cloaked. It's called active cloaking, which means it uses devices that actively generate electromagnetic fields rather than being composed of 'metamaterials' [exotic metallic substances] that passively shield objects from passing electromagnetic waves."

Evidently worried about being lumped in with attention-seeking metamaterials boffins, university spokespersons testily (and probably futilely) insist that "This is not a 'Star Trek' or 'Harry Potter' story". They also provide this rather nifty vid showing how the "active cloak" functions.

According to Milton, the method isn't applicable to visible light as it requires the use of unfeasibly small active emitters. Even if these could be built, it would only be possible to cloak very very small things.

"It is very difficult to build antennas the size of light waves," says the prof. "We're so far from cloaking real-sized objects to visible light that it's incredible."

However, he says that with longer wavelengths the technique becomes practical. Microwave active cloaks could hide things from radar; sonic ones could make submarines disappear from active sonar. Destructive ocean waves could perhaps be nullified, even - Milton thinks - to the extent of squelching tsunamis before they hit the beach.

"It would be wonderful if you could cloak buildings against earthquakes," Milton adds. "That's on the borderline of what's possible ... even if it's not going to result in a 'Harry Potter' cloak, it will have spinoffs in other directions."

As ever, there are a few little issues to sort out before the kit goes mainstream. For one, the cloaking machinery would need to know all about the incoming waves before it could nullify them, probably requiring some kind of remote sensors in the case of the tsunamis, earthquakes and so on.

Meanwhile there are scholarly papers for those interested, in the journals Optics Express and Physical Review Letters. ®

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