Originally posted by Hamylde
Yeah... but it's probably not quite that easy. light shares both the nature of a wave and of a quantum object, now which other gas does that?
they weren't saying it was actually a liquid, more that it behaved like a liquid in the ways that normal light behaves a little like a gas - they're drawing a parallel, not saying it's an actual liquid.
also, they're using nonlinear materials, in which the speed of light is variable (speed of light varies in different materials, but is usually uniform throughout the materials), so it's most likely some kinda of relative thing. and it certainly doesn't defy the theory of relativity.
you couldn't have a glass of liquid light, for instance - the properties that are useful are outlined in the article, and that's probably all the ways that it'll noticably differ from normal light.