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Posted: November 2, 2009
The science of invisibility cloaks
(Nanowerk News) Whether it’s Harry Potter or Star Trek, Hollywood scriptwriters have recognised the storytelling appeal of the ‘invisibility cloak’. While most of us are simply happy with the thrill of special effects, one scientist has been inspired to try and make these cinematic fantasies real. Thanks to The Royal Society's Theo Murphy Blue Skies Award, Professor Ulf Leonhardt, who holds the Chair in Theoretical Physics at The University of St Andrews, will spend the next two years working on a blueprint for a cloaking device.
Bending of light
Leonhardt’s interest in this field goes back to his days studying at the University of Um in Germany, (coincidentally Einstein was born in Um) and wanted to teach a course on Special Relativity and General Relativity.
‘But I had never learned General Relativity myself,’ he explains, ‘I never attended a course, I learned by giving a course! I looked for connections between my research area which is Optics in general, and General Relativity, and this got me into this field.’
Leonhardt’s work approaches the idea of invisibility, through looking at optical illusions brought about by the bending of light. For example, in the desert, light rays from the sky are bent in the thin air above the sand, creating an apparent image of water. Another example of illusion created by the bending of light is when we see a fish in water. We don’t see exactly where the fish is, as the water surface refracts the light coming from the fish.
In 2002 Leonhardt found another part of the puzzle while attending a workshop at the Kavli Institute of Theoretical Physics in Santa Barbara, California.
‘There,’ he says, ‘I heard for the first time about metamaterials, and I felt immediately this is the answer to this.’
Metamaterials are sometimes described as designer atoms but according to Leonhardt the first metamaterial was actually invented by the Romans in the form of Ruby Glass. Scientists have shown that if you put an object into such a glass it will seem to disappear if you look at it through polarizing tinted glasses, it only works for one colour. The key to a functional ‘invisibility cloak’ is developing modern metamaterials. ‘What I like about it,’ says Leonhardt, ‘is that it can be imaginative research, it’s what I find fascinating about it.’