Having read the recent thread on gravity waves, I was intrigued by the question of speed. This question has always bothered me when thinking about gravity, although this is probably because I'm not much of a physicist! Firstly, the speed of gravity, as discussed in the previous thread. If the sun did vanish, would we continue to orbit it for 8 minutes? Or, if gravity is "instantaneous" would we shoot off in a straight line immediately despite still being able to see the sun for a further 8 minutes? Secondly, assuming gravity propagates at the speed of light, this does suggest some kind of symmetry between light and gravity as Quasar2287 suggested in the previous thread. If so, does that mean all massive objects "emit" gravity? in the same way that all radiative objects "emit" photons? I'm confusing myself as I write this, so I'll throw open the floor to your comments!