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Comment by DonGateley | Hacker News Reader

What has always puzzled me about this is why anyone would think that a local change in a gravitational field would not propagate as a wave. What the hell else could it do?

I do believe there are differential equations involved that make the field at one point dependent on the field at another point after a period of time and that's all that's required.

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It's not that simple, due to the gauge invariance of the theory (not all mathematical degrees of freedom correspond to physical ones) and the approximations involved in deriving wave solutions. The argument was finally settled by Feynman's "sticky beads": http://en.wikipedia.org/wiki/Sticky_bead_argument

>why anyone would think that a local change in a gravitational field would not propagate as a wave. What the hell else could it do?

propagate immediately. Wave is a propagation with finite speed (and the expectation is for gravitational waves to have the same "c" ). There wouldn't be "wave" in immediate propagation, i.e. with infinite speed.

Are their no other testable aspects of GR that would show gravity changes to have finite propagation speed?

The assumption for the past 100 years has been that gravity propagates as a wave -- as mentioned in the article, it's the last untested prediction of Einstein's general relativity. But conclusive evidence has not been discovered.

Untested, untested.. Directly observed is a better definition, the quasar observations are quite convincing.

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