Speed of light in zero-index material or similar I've always thought that the maximum speed of light is achieved in vacuum. Now in some "popsci" news there are references as if there are mediums where light can go faster. Are these zero-index materials real? For example, could we have a fiber from Mars to Earth made of zero-index material and have near real-time communication?
Reference: http://www.nanowerk.com/nanotechnology-news/newsid=41635.php
 A: As the article states, only the phase of the light is being manipulated.  You cannot transfer energy (aka information) faster than $c$ no matter what you do.  The trick, so to speak, in these nanomaterials is to change the waveform, rather than wavelength, of the light.
A: The speed of light is not going to be faster than light in a vacuum. Even the article you mention says so. What it is saying is that the phase of the light waves will stay the same along the entire length of the conductor, resulting in less signal loss. The index of refraction is defined as the speed of light through a material: n = c/v, with c being the speed of light in a vacuum and v being the speed of light through a material. n is the index of refraction. If you change the equation to v = c/n you are solving for the speed of light through the material. If n = 0 the equation becomes v = c/0, which is undefined as in "Not a Number".In the article you mentioned, light still maintains some stately pace in the material described, but the amount of signal loss is very low because the light remains locked in phase and doesn't partially cancel itself out as it travels along.
