Gravitational Waves: the Picture Clarifies

In a recent post, I was leery of the claimed detection of gravitational waves. This was for a number of reasons–but mainly because 1) the entire announcement was based on only a single observation in five months, 2) the signal could not be localized, and 3) no corroborating signals were seen in any other instrumental mode (X-rays, etc.)

I felt and still feel that going public with such an immense and unhedged claim–on the strength of just a single observation (GW150914) made under rather odd circumstances–was a questionable decision, and deserved a considerably more guarded reception by the press than was universally the case.

That said, I’ve just seen a couple additional pieces of information I didn’t know about when I wrote the original post–and they leave me a lot more satisfied that gravitational waves have indeed been detected.

First, it looks like at least two additional likely gravitational wave events (named GW151012 and GW151226) were spotted by LIGO, in October and December 2015 respectively, although these results were subsequently erased from the LIGO web cache.

Second, there’s this paper, indicating that a strong gamma-ray spike occurred within a second of the GW150914 event, and that it came from the same general area of the sky as GW150914. Gamma-ray pulses could definitely be produced by the merger of black holes if there was even a tiny bit of matter floating around them.

The gamma-ray observation only is able to narrow the location of the source to about a quarter of the whole sky, and I guess the timing could also be coincidental–gamma ray bursts are not too rare–but at this point it’s looking silly to doubt.

So, if the additional events of 10/12 and 12/26 hold up, we’ve gotten the triplicate of observations I wanted and I hereby withdraw my quibbles. I do still wonder why the two other observations were not included in the original announcement and manuscript. Vicissitudes of the publication process? A decision that the media optics would be best going with the first signal alone while polishing up the data for the other two?

Hopefully more results will be fully vetted and out in the open very soon.


  1. My quibbles are the same as yours but not yet quelled.

    Why did the two other observations disappear from the Web cache?

    Only when LIGO publishes again, based on these or some completely new observation will that little niggling doubt fully be quashed. Then finally I shall be able to distance myself from the various conspiracy theorists who seem strangely offended by LIGO and for some reason desperate for it to fail.


  2. And there it is! The second observation – GW151226. Now, finally, it feels real and we can start looking forward over coming years to significant scientific advances from this new cosmological observatory.


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