> We are not talking about coordinate speed here, we are talking about the light cone looking different, depending on which direction you go. Before you could

> We are not talking about coordinate speed here, we are talking about the light cone looking different, depending on which direction you go. Before you could even test for this, you would need to come up with a consistent mathematical model of it and show how it's different from the mathematical models in standard GR. Otherwise you won't even know what to test for. Note that in standard GR, models that do not have isotropy of space also do not necessarily have the "isotropy of light cones" that you describe, at least not once you go beyond a single local patch of spacetime that is small enough for curvature to be ignored. I'm not aware of any such mathematical model that is different from standard GR.