Magical material solves mystery of invisibility cloak

Invisibility cloaks are materials that bend light around an object so no light hits it, concealing its presence. A material that can make something else disappear clearly has military potential, but other uses have been suggested - ranging from wrinkle creams to transparent cockpit floors that could help pilots when landing aircraft by revealing the runaway and landing gear.

The trouble is, the laws of physics mean that the light would have to travel incredibly quickly round the disappearing object for the cloaking material to work - faster than the speed of light. Nothing - matter, energy, light - can travel this fast under most conditions.

Physicists have found the only solution so far has been to create the conditions where the speed of light can be exceeded - where there is superluminal propagation. This happens when the background of the object being made invisible does not change and only a limited number of wavelengths of light are sent towards the object rather than a broad spectrum. That works for a stationary object but not for a moving one.

"The way to get rid of these restrictions is to get rid of this requirement for superluminal propagation," says Janos Perczel, a 22-year-old Hungarian born physicist studying at the University of St. Andrews, UK.

Perczel's solution is to combine an invisibility cloak with another material capable of slowing light down.