[PonyTailGuy]

That would sort of contradict the special theory of relativity, wouldn't it? I had the same reaction.

But read closely, it only says he SIMPLIFIED the calculations by computing from the Jupiter frame of reference.

Apparently the mathematics were considered intractable prior to this, and the fellow thought of a clever way around the problem.

In any event, just how central is the speed of gravity to the general theory of relativity? Is it in the hard core of the theory, is it a supporting assumption? a mathematical consequence? I'd be curious to know. I'm well versed in the special theory but only superficially knowledgeable of the general theory.

[RightWhale]

It is thought that Einstein said that nothing can exceed the speed of light. Gravity waves would therefore move no faster than c. However, I don't know that Einstein actually said that. Minkowski did say that, and much of the popular conception of special relativity is due to Minkowski. I don't see the problem, since we're talking about appearances of electromagnetic phenomena, not the reality behind them.

[AdmSmith]

In Einstein's General Theory of Gravity the speed of gravity is assumed to be equal to the speed of light. If it is found to be different then his theory must be changed for something better. That is evolution!

[RinaseaofDs]

This may be a completely uninformed question (I'm an EE, not a physicist), but gravity is a force, right? Light is a particle, right?

Or have we moved on, and discovered that gravity is now a particle, and so is light?

I already realize that there are no such thing as particles (part waveform, part particle).

Gravity, being a force is related to acceleration, not speed. mass times acceleration equals force.

Is this stupid? (Probably)

[wotan]

In any event, just how central is the speed of gravity to the general theory of relativity?

If the speed of gravity were infinite you could use gravitational effects to synchronize the clocks in two different frames. This leads to contradictions to the principle of relativity, even in special relativity.

For example, if spaceships pass each other moving in opposite directions, each appears to be contracted relative to the other.

However, by stationing observers at opposite ends of both ships with synchronized clocks, we could determine which ship was "really" contracted and which merely appeared contracted by observing the times at which observers on each ship passed their counterparties.