For anyone curious, There is an alternative formulation of GR (which is consistent with GR[0]) that drops the assumption that the speed of light is consistent:<p><a href="https://ui.adsabs.harvard.edu/abs/2009APS..NWS.C1024R/abstract" rel="nofollow noreferrer">https://ui.adsabs.harvard.edu/abs/2009APS..NWS.C1024R/abstra...</a><p>[0] except the math is harder. I hear that there are some strange nonlocal effects that also appear, if someone is interested, it might provide an avenue for reconciling GR with QM which also has nonlocal effects (Einstein GR does not have nonlocality iirc)<p>Last I checked tangherlini is alive and able to maybe teach someone a thing of two.