Studies into the behaviour of light have delivered a blueprint for a new type of cloaking device that could be used to make objects and, potentially, people invisible. The researchers, some based at Imperial College London, have even created a prototype material capable of cloaking objects against radar waves as proof of their theory.

Sir John Pendry, professor of theoretical physics at Imperial, has compared such materials with the “invisibility cloak” seen in the Harry Potter films and suggests that the first could be created in the next decade. “Just as in Harry Potter, nobody would be able to see an object if it was cloaked,” he said. “Our cloaking system would render anything inside it invisible.”

If Pendry is right, such technology could be used for a variety of purposes, from hiding military hardware the size of warships or other objects such as unsightly buildings.

Pendry, whose work was partly sponsored by the Pentagon, based his research on close analysis of how photons — the basic particles of light — behave when hitting the surface of an object.

Most materials are opaque to light because they absorb photons and convert them to heat. This is why sunlight feels warm on the skin. But a few materials, such as glass, are transparent. This is because their atoms are organised in such a way that the photons can pass between them.

What Pendry and two colleagues from Duke University in North Carolina have shown, in a paper published in Science, the journal, is that there is a third class of materials that can be made to “grab” photons without absorbing them or allowing them straight through.

Instead, the metallic materials would carry the photons within themselves and then emit them from the other side as if they had travelled in a straight line directly through.The researchers liken the behaviour of such light to water flowing around a stick in a stream and then continuing smoothly on behind the stick downstream.

Pendry suggested such a material could be coated onto warships and tanks to make them invisible — although their wakes and tracks might give them away once they moved. “We know cloaking can be done with radar waves. Light waves are another form of electromagnetic radiation, so making a material capable of cloaking against light should be possible within a decade,” he said.

Pendry’s project is one of several around the world experimenting with invisibility. Astronomers at St Andrews University last week published a similar theory to Pendry’s but one derived from different research originating in the study of black holes.

At Tokyo University, researchers have used a much more low-tech system involving cameras and projectors to collect images from behind an object and then project them onto its front.

The researchers have disguised people and objects but the system has limitations. One is that objects must first be shrouded in a reflective film. Another is that the invisibility is hard to maintain if the subject is moving. It also consumes a lot of energy. However, it could be used on fixed military installations.

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