Secret of 'invisibility cloak' is uncovered by student
Published 10/08/2011 | 05:00
A STUDENT has developed an optical sphere which could be used to create an "invisibility cloak".
Janos Perczel (22), an undergraduate student at St Andrews University in Fife, Scotland, said that by slowing down light by way of an optical illusion, the light can then be bent around an object to "conceal" it.
Attempts have already been made to create invisibility cloaks but efforts are limited because any cloak would only work against certain backgrounds. But by slowing down light, Mr Perczel says the cloak wearer can move around ever-changing backgrounds.
Mr Perczel, from Hungary, came up with the idea under the guidance of "invisibility expert" Professor Ulf Leonhardt, who teaches at the university's school of physics and astronomy. The student recognised the potential of the invisible sphere and spent eight months fine-tuning his project.
The key development lies in the ability of the sphere to slow light. According to Prof Leonhardt, all optical illusions can slow down rays of light and the sphere can be used to bend this illusion around an object, reflecting off it and making it appear to be invisible.
Mr Perczel added: "When the light is bent it engulfs the object, much like water covering a rock sitting in a river bed, and carries on its path, making it seem as if nothing is there.
"Light, however, can only be sped up to a speed faster than it would travel in space, under certain conditions, and this restricts invisibility cloaks to work in a limited part of the spectrum, essentially just one colour.
"This would be ideal if somebody was planning to stand still in camouflage. However, the moment they start to move, the scenery would begin to distort, revealing the person under the cloak. By slowing all of the light down with an invisible sphere, it does not need to be accelerated to such high speeds and can therefore work in all parts of the spectrum."