In Newtonian gravity, gravitational effects are assumed to propagate at infinite speed, so that for example the lunar tides correspond at any time to the position of the moon at the same instant. This...In Newtonian gravity, gravitational effects are assumed to propagate at infinite speed, so that for example the lunar tides correspond at any time to the position of the moon at the same instant. This clearly can’t be true in relativity, since simultaneity isn’t something that different observers even agree on. Not only should the “speed of gravity” be finite, but it seems implausible that it would be greater than c.
