Invisibility has been an ingredient of myths, novels and films for millennia ? from Perseus versus Medusa in Greek legend to James Bond?s latest car and Harry Potter?s cloak. A new study published today by the Institute of Physics reveals that invisibility is closer than we think. The paper, Notes on conformal invisibility devices, published in the New Journal of Physics describes the physics of several theoretical devices that could create the ultimate illusion ? invisibility. ?Objects are visible because they reflect light rays? says author Dr Ulf Leonhardt at St Andrews University, Scotland. ?To be invisible, an object would have to let light pass through it, like H. G. Well?s Invisible Man. Alternatively light would have to bend around an object for it to be invisible. The ideas in this paper are based around devices that will bend light or radio waves around a hole inside the device. Any object placed inside the hole will become invisible. The light would flow round the hole like water around an obstacle.?
The bending of light is the cause of many optical illusions, such as mirages in the desert. Light bends in the hotter air near the ground in the desert and this causes a reflection of the sky on the ground ? a mirage. Dr Leonhardt went on to say ?The devices work by bending light, as in a mirage. However, a mirage involves the reflection of light which produces the shiny image that can be seen: an invisibility device bends light without producing an image. To do this, the devices must have carefully designed refractive index profiles. The paper explains the physics and mathematics behind the devices using images rather than complex equations: it visualizes invisibility.?