Starts With A Bang

How uncertain are LIGO’s first gravitational wave detections? (Synopsis)

The 30-ish solar mass binary black holes first observed by LIGO are likely from the merger of direct collapse black holes. But a new publication challenges the analysis of the LIGO collaboration, and the very existence of these mergers. Image credit: LIGO, NSF, A. Simonnet (SSU).

“We hope that interested people will repeat our calculations and will make up their own minds regarding the significance of the results. It is obvious that “belief” is never an alternative to “understanding” in physics.” -J. Creswell et al.

Three times now, the LIGO collaboration has produced very strong evidence that black hole pairs, from across the Universe, inspiraled and merged, producing gravitational waves. The twin LIGO detectors in Hanford, WA and Livingston, LA each detected these signals, and the signals were correlated between both detectors. For the first time ever (and the second, and the third), we had directly detected gravitational waves.

The masses of known binary black hole systems, including the three verified mergers and one merger candidate coming from LIGO. Image credit: LIGO/Caltech/Sonoma State (Aurore Simonnet).

But last month, a team of independent scientists from Denmark attempted to reproduce LIGO’s analysis, and noticed something that shouldn’t be there: noise correlations between the two detectors. Noise is supposed to be uncorrelated, and yet the noise correlations peaked at the moment of the inspiral-and-merger event. It doesn’t mean that gravitational waves aren’t real, but it does mean that LIGO, perhaps, has room for improvement.

Even with the analysis of the team from Denmark, a strong gravitational wave signal emerges from both LIGO detectors. But so does a large amount of correlated noise, which may mean a bit of signal-and-noise are being mixed up. Image credit: Comments on our paper, ‘On the time lags of the LIGO signals’, J. Creswell et al.

This has been a very controversial topic over the past few weeks; come learn where we are in this saga of science playing out in real-time!