3 ms·

The distincion you're making between isotropy of space and isotropy of the speed of light is important but I don't think the following is true: > The second co

The distincion you're making between isotropy of space and isotropy of the speed of light is important but I don't think the following is true: > The second concept, anisotropy of the one-way speed of light, is not an invariant concept or a geometric property: it's an artifact of your choice of coordinates. You can take a spacetime that is spatially isotropic, and choose coordinates on it that make it seem like the one-way speed of light varies by direction. We are not talking about coordinate speed here, we are talking about the light cone looking different, depending on which direction you go. This is (or would be) a geometric / invariant property.

pdonis 4y ago
> 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.