Gravity waves and a disapprearing sun.

  • #26
rbj
2,226
7
But it's so easy to say that c is the speed of light, since it is :)

About your statement of gravity lies in the speed of 20% of c...
just to be sure, i meant to say that the result of this one experiment is that the speed of propagation of gravity is within ±20% of c or, between (0.8)c and (1.2)c. not (0.2)c.

What do they define gravity as? Curved Spacetime or particles? I would like to see the explanation of this statement. Because i find it hard to believe that geometrical curving can be that slow. ( I was surprised of that gravity didn't happen instantly (if for example the sun disappeared) )
i dunno that they define gravity in this experiment. they were measuring some tangible effect, no matter how they define it. i think when GRists think about gravity, they think of it as a curving of spacetime that is caused by masses and that changes in that curvature also propagate at c. if gravity happened instantaneously, then that would mean that instantaneous communication could conceivably be done over vast distances by somehow creating a gravitational disturbance (like blowing up a star) that would be detected before a change in light from that star was detected.
 
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  • #27
disregardthat
Science Advisor
1,854
33
I understand now. Since it is between 0.8c and 1.2c you would naturally believe that it is excactly 1c, well, that is what i believe. I wonder what it would have looked like when an object appeared if you could see the 2 dimensional geometrical net curving as the object is presented. Maybe would the "ground" fall into it's position square after another, what do i know. It is difficult to imagine how the gravity works as it moves. But then again, couldn't you say it happened instantly if the gravity moved at c? Because if you rode the gravity wave time would be staning still.
 

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