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stormwyrm [soylentnews.org] writes:

Gravitational waves were the most controversial and difficult to verify prediction of Albert Einstein's Theory of General Relativity, so much so that at one point even Einstein himself thought that they might just be an artefact of the mathematics. It wasn't until the 1970s that careful observations of binary pulsar systems [wikipedia.org] showed the indirect effects of gravitational waves, and not until 2016 that LIGO, an extremely sensitive instrument designed to detect gravitational waves directly, managed to detect the gravitational waves [soylentnews.org] from the merger of two black holes. It has made two more gravitational wave detections since. However, a new analysis [arxiv.org] of the LIGO data by an independent team led by Prof. Andrew D. Jackson at the Niels Bohr Institute in Copenhagen [nbi.ku.dk] has cast doubt on the detections, hinting that they might just be seeing patterns in the noise. Sabine Hossenfelder has an article [forbes.com] on this:

A team of five researchers — James Creswell, Sebastian von Hausegger, Andrew D. Jackson, Hao Liu, and Pavel Naselsky — from the Niels Bohr Institute in Copenhagen, presented their own analysis of the openly available LIGO data. And, unlike the LIGO collaboration itself, they come to a disturbing conclusion: that these gravitational waves might not be signals at all, but rather patterns in the noise that have hoodwinked even the best scientists working on this puzzle.

The LIGO gravitational wave observatory consists of two experimental sites – one in Livingston, Louisiana and one in Hanford, Washington – each of which is a laser interferometer with arms that are several kilometers in length. Even for these super-sensitive detectors, however, gravitational waves are difficult to measure. The problem isn’t so much the absolute weakness of the waves, the problem is that there are many other disturbances that also wiggle the interferometer. The challenge, thus, is to tell the signal from the noise.

[...]The Danish group found, however, that the noise at both detector sites — and puzzlingly, between the two supposedly independent detectors — is also correlated. And worse, the correlation time is similar to the time-lag between the recorded signals, for each of the three so-far confirmed events. According to Andrew Jackson, the leader of the Danish group,

“If the correlation properties of signal and the noise are similar, how is one to know precisely what is signal and what is noise?”

That's a really important realization. A correlation in the noise would not affect the individual signals at each of the sites. But in order to achieve a highly significant signal between the detectors, the LIGO collaboration takes into account how both signals are correlated. If this correlation were not reliable, because (for example) there was the possibility that noise correlations contaminated their data, the statistical significance of the detection would be reduced. In other words, what appears to be a signal might actually be caused merely by fluctuations. How much the statistical significance would be affected, however, the Danish researchers have not quantified.

Original Submission