Physics / Science / Space

Gravitational waves or no gravitational waves?

New Scientist have just posted an exclusive (but not very exclusive, since the same info appears plenty of other places) article about a group who have criticised the results found at LIGO, the gravitational wave detector. There’s a fair amount of back and forth going round if you Google: some people think it’s blown out of all proportion, some people think there’s a valid criticism, etc, etc. Now I’m not a physicist, but I do have some alarm bells ringing.

Namely, some of the data (and the methods of analysis) have been kept secret. If that’s true, their results are unfalsifiable (and unconfirmable) because they use in-house techniques which they haven’t fully published and explained. That’s really, really bad science: if your discovery is genuine, you want people to be able to go through exactly the same steps and come up with the same (or at least very similar) answers. Ideally, anybody with access to the same apparatus and information should be able to do so, not just people in the know. Some data has been released, but apparently you need special training to understand how to handle it; I can’t find (on a casual Google, mind you!) anything about anyone having had the training and then confirming the result.

There’s not much doubt that gravitational waves exist, as far as I can tell: they’re predicted by theories that have so far stood the test of observation. But have they been detected and recorded, and was that detection precise and accurate? That seems to be awaiting full publication followed by independent confirmation. Looking at the consensus from scientists quoted in the articles, I’m going to guess the positive detection is going to be largely corroborated.

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5 thoughts on “Gravitational waves or no gravitational waves?

  1. The trouble with any criticism of LIGO’s detection of gratitational waves is that the latest one was completely independently confirmed by the VIRGO instrument in Italy (LIGO is in the USA); it detected a positive signal at the same time as the LIGO instrument. The chances of both of them producing a false positive from external sources (e.g. an earthquake) at the same instant are negligibly tiny and in any case such souces of fexternal false positive events are ruled out as far as possible before a detection is declared. Hence both labs must be making identical errors at exactly the same time for the results to be wrong. This looks like another New Scientist sensationalist piece of reporting, almost certainly wrong.

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    • Yeah, my remaining issue is that Virgo aren’t independent — they are collaborating with LIGO, and the two groups are analysing data jointly. If there’s a flaw in their methods, it’s very likely to be replicated at Virgo. From what I understand it’s an issue of working out what is signal and what is noise, right? The gravitational waves are really faint compared to everything happening on Earth, so the signal takes some extracting… if that method is flawed, the whole is flawed. Like I said, from what I’ve read, it sounds like the detection is real and the real question is about the precise analysis. Not worth New Scientist’s breathless article for sure!

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      • I can’t even really believe that this is a problem of the same nature as the ’90s gravitational detections of exoplanets where the noise reduction created false positives, because of the timing. I said above that LIGO and VIRGO made the detection “at the same time” but in fact there is a tiny discrepancy in the times that fits exactly with the predicted propagation speed of the waves. I can’t believe the noise is identical at both locations but phase shifted by by precisely the right amount…

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      • I haven’t said anywhere that I think it is a case of false positives, so I think you’re arguing with New Scientist still rather than me! I’ve been talking mostly about the bad practice of having no one else able to verify or falsify your results due to lack of publication, which is a continuing problem with LIGO. The technical details simply aren’t available, and the group themselves admit they still need to publish them. I admit I’m not a physicist, so maybe their standards are lower, but in biology we don’t take results on faith — we need replicability and we need to be able to see and critique methods, not just results.

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