[jeletonskelly]

Does gravity propagate at the speed of light? Like, if I were to plop down a planet somewhere in the solar system, would the gravitational effects be immediate or would it take effect at the speed of light? Because if it's immediate, then we should be able to transmit information through gravity waves if we could build a device to detect subtle enough changes.

[Tenoke]

Yes, gravity operates at c. There is nothing that we know of (or have a theory of) that can even in principle travel faster than c.

[minkzilla]

It might interest you that a couple of years ago was the first observation of gravitational waves. Here is a BBC article https://www.bbc.com/news/science-environment-35524440