> The speed of light is constant as measured from any observer. That is not true. The "speed of light" in vacuum is not constant for all observers in the _gene

> The speed of light is constant as measured from any observer. That is not true. The "speed of light" in vacuum is not constant for all observers in the _general_ relativity. It is constant only _locally_, Lorentz invariance is a local symmetry in GR. Special relativity thus simply becomes an edge case of GR, where the Lorentz invariance is also a global symmetry. That's how we get lensing, regions of space near a massive object are more "viscous" and the light moves slower through them.