In "Frozen Light" an article written by Lene Vestegaard Hau, it talks about Lene's experiments with, literally, slowing down light by way of passing it through "ultra-cold clouds of atoms." The experiment was undertaken at Cambridge and Lene and a group of researchers were able to get light's speed down to 60 kilometers per hour. ~Einstein says that the speed of light is a universal constant. If all it takes is a temperature of near zero and a cluster of "frozen" atoms to slow light's speed, then how can light be a constant? Wouldn't that mean the cold regions, those reaching near zero temperatures, of space would constrict the speed of light and contradict Einstein’s theory of general relativity? And if light is not a constant, how can we be sure about the measurements of celestial bodies. Those are measured by the constant of light?