Physicists have drawn up blueprints for a cloaking device that could, in theory, render objects invisible.
Light normally bounces off an object鈥檚 surface making it visible to the human eye. But John Pendry and colleagues at Imperial College London, UK, have calculated that materials engineered to have abnormal optical properties, known as metamaterials, could make light pass around an object as so it appears as if it were not there at all.
Metamaterials are exotic composites made of electronic components such as wires and inductors that can be engineered to precisely control the way light travels through them.
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Pendry鈥檚 team has drawn up plans for a spherical metamaterial structure that would render an enclosed object invisible. 鈥淭he theory tells us the material properties we need at each point,鈥� says team member David Smith, from Duke University in North Carolina, US. 鈥淭he challenge is to match those theoretical requirements in the actual material, point-by-point.鈥�
Bad visibility
Other designs for invisibility cloaks have been drawn up in the past. One idea is to calculate exactly how an object scatters light and design a surrounding material to exactly cancel this out.
But such cloaking devices could not be used for more than one object. 鈥淯sing our method you can hide different objects under the same cloak, or move around within the cloak, and remain hidden,鈥� says Pendry.
However, Pendry鈥檚 team鈥檚 design could currently only work at wavelengths larger than visible light. Designing a cloaking device for visible wavelengths could be tricky as it would involve creating nanoscale metamaterials. 鈥淎t these levels it is far more difficult to control the metal鈥檚 properties,鈥� says Smith. Nonetheless, he believes that optical cloaking devices could be become a reality within the next decade.
Fun idea
Will Stewart, an independent optics expert at the University of Southampton, UK, is less convinced. He believes that it may prove too difficult to overcome these problems within such a timeframe. 鈥淚t鈥檚 great fun and a lovely idea, but I don鈥檛 think it can literally be taken and applied to make an optical cloak,鈥� he says.
But Stewart says the approach could work well with a narrow band of wavelengths and could, for example, shield an object from radar. Pendry鈥檚 team is, in fact, working on just such a device made from millimetre-sized metal units, which they hope to complete within a year.
鈥淚t looks like Star Trek was right,鈥� Stewart says, referring to the invisibility shield famously used by Klingon spaceships in the science fiction show.
Journal reference: Science (DOI: 10.1126/science.1125907)
