@InertialObservr @LIGO By the almost simultaneous detections of gamma rays and gravitational waves from a very distant neutron star merger they were able to determine in 2017 that their speeds do not differ by more than a few parts in 10^-15! https://t.co/
5 (1199) GW170817 Multimessenger Astronomy https://t.co/kKZ79Lb3Jv [+1] 6 (1065) GW170817–GRB 170817A https://t.co/HapbYviEMZ [+2] 7 (1045) GW170814 Discovery https://t.co/C6hW7rNp7G [−2] 8 (810) The Advanced @LIGO Paper https://t.co/1Urs7wmo1U [−1]
5 (1138) GW170817 Multimessenger Astronomy https://t.co/kKZ79Lb3Jv [+4] 6 (1085) GW170814 Discovery https://t.co/C6hW7rNp7G [–] 7 (1048) GW170817–GRB 170817A [+3] https://t.co/HapbYviEMZ 8 (987) The Advanced @LIGO Paper https://t.co/1Urs7wmo1U [−3]
@tugbut @johncarlosbaez They do, as far as our experiments can discern. https://t.co/N0BYVbEH4a shows that "the difference between the speed of gravity and the speed of light to be between -3e-15 and 7e-16 times the speed of light", i.e. (1 - 3e-15 )c <