A property of a material that changes the speed of light, computed as the ratio of the speed of light in a vacuum to the speed of light through the material. When light travels at an angle between two ...

Now there is a conundrum we can struggle with in the dead of night. But it is one that Brian Greene is actually equipped to try to answer in his latest book, Until the End of Time. Greene, director of ...

Physicists at Harvard University in the US have built a silicon waveguide that exhibits a refractive index of, or close to, zero when operating at near-infrared telecom wavelengths. The waveguide can ...