Haelfix said:It looks like there is a new standard candle source.
ohwilleke said:Yup. Although the margin of error on the Hubble measurement is big: 70 +12/-8, even though the mean value is right in the middle of the range of existing values and this measurement has the virtue of being completely independent of other methodologies and, almost, model independent.
The 1.7 second gap between the gravity wave detection and the first detection of an EM source (which could have happened slightly later or could have been detected midway through the first gamma ray arrival) at a distance of 130 million light years is also great direct proof that the speed of gravitational waves and the speed of light are the same. Another experimental test of GR checked off the list.
ohwilleke said:Yup. Although the margin of error on the Hubble measurement is big: 70 +12/-8, even though the mean value is right in the middle of the range of existing values and this measurement has the virtue of being completely independent of other methodologies and, almost, model independent.
The 1.7 second gap between the gravity wave detection and the first detection of an EM source (which could have happened slightly later or could have been detected midway through the first gamma ray arrival) at a distance of 130 million light years is also great direct proof that the speed of gravitational waves and the speed of light are the same. Another experimental test of GR checked off the list.
Sophrosyne said:It seems strange that this observation that light and gravity are behaving so similarly (forming waves that propogate at the same speed) can't somehow be used to show that gravitons belong in the standard model like photons. There has got to be a way.
Well the quantum ones have some "commuting" variable that circumvents the whole speed limit problem...ohwilleke said:The speed of propagation is something that the classical theories and quantum ones have in common, not a distinction.
The SM, by definition, doesn't include gravity. And just because both photons and hypothetical gravitons are massless doesn't mean the phenomena would be similar in any way. We know they are not, otherwise we would have a consistent theory of quantum gravity by now.Sophrosyne said:It seems strange that this observation that light and gravity are behaving so similarly (forming waves that propogate at the same speed) can't somehow be used to show that gravitons belong in the standard model like photons. There has got to be a way.
That was said by the scientists during the press conference.diogenesNY said:The matter of the observed collision was noted, followed by the comments (unsourced) that this resulted in the production of a large quantity of gold and platinum, and that consequently we now have a clear idea where heavy metals come from.
ohwilleke said:Gravitational waves in GR propagate at the speed of light and so do EM waves in Maxwell's classical EM equations. The speed of propagation is something that the classical theories and quantum ones have in common, not a distinction.
Sophrosyne said:Isn't there anything in these findings of observed gravitational waves that we can use to try to confirm or rule out some of the current proposals for a quantum theory of gravity, whether strings or quantum loop or whatever?
phyzguy said:So apparently the GW signal was too weak to get any information on the ring-down phase. At least I haven't seen it mentioned anywhere. Did I just miss it? Has anyone seen any information on a ring-down phase?
You underestimate the number of events we will get. Let's say conservatively 1 NS event in 1 year of running, ignoring that the sensitivity improved over time. In a year, with twice the sensitivity, we would expect 8 events per year. In ~3 years, with the full sensitivity, we might get something like 20-30 per year. Add KAGRA and the number will get even larger. Add INDIGO and we might get more than 100 events per year. And then we can build the Einstein telescope which will see these events routinely.
Of course we might have been extremely lucky with this NS event, but that is unlikely. For binary black hole mergers the situation is even better, with 4 events observed already we can be quite sure they are not extremely uncommon.
I believe physzguy kind of answered that in Borek's "splinter" thread:snorkack said:How long after merger did visual spectrum start to show lines (whether emission or absorption)?
phyzguy said:It took about 11 hours for the optical telescopes to start looking, mostly because they were waiting for it to get dark. As soon as they started looking, the optical radiation was there, but it shifted to longer wavelengths as the ejecta cooled off over time.
phyzguy said:The optical pictures you see are not resolved images of the merger. They just capture the total light emitted. Optical photos of distant stars are never resolved. The stars are just points of light.