I wonder if the current detection of gravitational wave at aLIGO has confirmed that gravity changes are moving with speed of light? If yes, then how?
I don't think the LIGO experiment explicitly addressed that, indirectly it did support that gravity propgàtes at c by cofiming the relativity prediction of gravity waves.
In a word - dispersion, or rather lack thereof: https://en.wikipedia.org/wiki/First..._waves_and_limit_on_possible_mass_of_graviton
You're welcome. Trying to 'directly' determine GW propagation speed via phase delay between the two aLIGO facilities is an obvious method but very crude owing to for instance currently irreducible uncertainties in GW incidence angle. As more facilities come on line, triangulation becomes effectual and directional uncertainty should dramatically reduce, but will still not allow any really accurate determination of GW speed. Whereas absence of detectable dispersion, to some extent model dependent but not dramatically so, over such huge distances provides a tight bound on any departure from c.
This is a good question, and the answer is Yes, it did prove . First let us consider the separation between two aLIGO facilities, it is around 3000 kms, so a wave travelling at light speed should not take more than 3000 kms/c time, that is 10 ms...the delay was 7 ms, suggesting some angle of incidence while speed at c, with two locations nothing much can be said, so as Qreeus suggested once we have more than 2 locations, we can get a real picture on this front. It will be make or break for GW detection. On the other front this detection says two BHs, 1.3 Bly away, 3 Solar Mass Energy released created this GW, how could they say that ? By creating a template that such and such cosmic event would make a GW which will travel at c, and will leave this kind of signature on aLIGO. So the light speed part is built into calculations.....
