The author makes several assertions about the speed of gravity, arguing
primarily that it's effects are instantly transmitted. He claims certain
astronomical observations of pulsars as evidence.
I was under the impression that the effects of gravity propagate at c,
although no experiments had yet shown this. In particular, I believe that
the work at LIGO and other large interferometers was trying to test this
hypothesis.
Am I confused? What is the state of our knowledge?