Geometry and light: the science of invisibility
Invisible sphere. You can just about see the sphere that has nearly the same refractive index as its surroundings (water).
Invisibility has been a subject of fiction for millennia, from the myths of the ancient Greeks and Germans to modern novels and films.
Now fascinating new developments in optics have resulted in a new science of invisibility. Scientists have made the first prototypes of cloaking devices – although it will still be a long time before you can get a real invisibility cloak from your nearest shop.
How does it work?
The secret of invisibility is the connection between geometry and light. We are used to assuming that light always travels along straight lines, but in fact certain materials can curve light rays, and this can lead to optical illusions.
Invisibility is the ultimate illusion. Here the material of the cloaking device bends light rays around so that anything inside the device is hidden. Moreover, the rays exit the device as if it were not there at all. So not only does the device hide what is inside, but it also hides the fact that something is hidden.
How do scientists do this ? The blueprint for invisibility comes from geometry: as optical materials bend light they appear to transform the geometry of ordinary space. The cloaking device is designed to open a hole in space for light. As light never touches this hole its interior becomes invisible.
Videos below demonstrate some of the science displayed at this exhibit.