Shining an appropriate light on such a wire from the outside would alter its refractive index (a measure of how fast light travelling inside the wire can move).

ECONOMIST: New-age crystals

Google has agreed to alter its search results in the light of a European investigation into whether it unfairly promoted its own services.

BBC: Google offers clearer search labels after EU probe

Now scientists - at the University of California, San Francisco, and Cincinnati Children's Hospital Medical Center - believe that body-penetrating light can alter the development of the eye, at least in mice.

BBC: Light in womb 'gives healthy eyes' - in mice