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

“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).
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!

13 thoughts on “How uncertain are LIGO’s first gravitational wave detections? (Synopsis)

  1. “Because the idea behind LIGO is straightforward and simple…”

    How could that be? The theory of black holes is so confused and uncertain that Einstein did not believe they existed, and neither do some contemporary scientists. Also, Einstein’s spacetime is so absurd that nowadays many theoreticians reject it, explicitly or implicitly. And yet LIGO conspirators managed to model black holes, their collision, the ripples in spacetime the collision produced, and the measurements gloriously matched their calculations?!? The world is gullible but not infinitely gullible.

  2. Is the big peak at 50-60Hz due to the electrical grid? That’s a big spike. If so, a bit strange that the whole thing is not shielded better.

  3. Vast signal to noise problems , computer filtering artifacts, problems with identifying a tenuous signal many times smaller than the background noise by using an imaginary signal template, and the ridiculous conviction you can screen out every possible signal source but that of gravity waves generated by previously undetected orbiting black holes on an instrument roughly two miles long located on the surface of the earth requiring the precision of less than the width of a proton… Hmm. Why does this all sound so familiar…oh yeah, I brought it up months ago and was shown the door. Identical to the reaction for questioning alternative causes for polarized dust. sigh.
    This is going the way of BICEP…fast…and for many of the same reasons. I don’t think they have a gravity wave signal at all, just over processed noise tortured until it screamed whatever they wanted to hear. They are just slow rolling the retraction of an actual discovery.
    Scientific skepticism is far more useful when you embrace it before you claim discovery than having to hide from it later on when it comes crashing down on your confirmation bias.

  4. What’s needed is a vastly higher, cleaner, more obvious signal to noise ratio. If it takes sophisticated statistical analysis just to tell if you’re looking at something real or random fog, your detector technology just isn’t good enough.

  5. Below Einstein defines deductive theory (“built up logically from a small number of fundamental assumptions, the so-called axioms”) and its antithesis – empirical compilation (and there is no third alternative!):

    Albert Einstein: “From a systematic theoretical point of view, we may imagine the process of evolution of an empirical science to be a continuous process of induction. Theories are evolved and are expressed in short compass as statements of a large number of individual observations in the form of empirical laws, from which the general laws can be ascertained by comparison. Regarded in this way, the development of a science bears some resemblance to the compilation of a classified catalogue. It is, as it were, a purely empirical enterprise. But this point of view by no means embraces the whole of the actual process ; for it slurs over the important part played by intuition and deductive thought in the development of an exact science. As soon as a science has emerged from its initial stages, theoretical advances are no longer achieved merely by a process of arrangement. Guided by empirical data, the investigator rather develops a system of thought which, in general, is built up logically from a small number of fundamental assumptions, the so-called axioms.”

    Einstein’s general relativity, unlike his special relativity, is an empirical compilation – a malleable combination of ad hoc equations and fudge factors allowing Einsteinians to predict anything they want. Accordingly, all its predictions, including the gravitational-wave prediction, are not even wrong.

  6. From Ethan’s article: “The ripples were so powerful, they stretched and compressed the entire Earth by the WIDTH OF A FEW ATOMS, allowing the LIGO apparatus to directly detect gravitational waves for the first time.”

    I think I’m with CFT’s #3 comment here.

  7. Can’t they detonate some explosives at both facilities at exactly the same time, or some electrical discharges, or a drill, to generate some test pulses that can be used as markers and check their analysis algo’s? For instance a blast at 100m, 500 m 1km, with each time different strengths. Isn’t there anything man made that could simulate a gravity wave?

  8. “Isn’t there anything man made that could simulate a gravity wave?”

    The gravitational wave itself is man made. LIGO conspirators did a lot of exercise and the dress rehearsal was in 2010 – then “a select few expert administrators” deceived everybody, misled astronomers into wasting time and money on the fake, and “this became particularly useful starting in September 2015”:

    Quote: “…a blind injection test where only a select few expert administrators are able to put a fake signal in the data, maintaining strict confidentiality. They did just that in the early morning hours of 16 September 2010. Automated data analyses alerted us to an extraordinary event within eight minutes of data collection, and within 45 minutes we had our astronomer colleagues with optical telescopes imaging the area we estimated the gravitational wave to have come from. Since it came from the direction of the Canis Major constellation, this event picked up the nickname of the “Big Dog Event”. For months we worked on vetting this candidate gravitational wave detection, extracting parameters that described the source, and even wrote a paper. Finally, at the next collaboration meeting, after all the work had been cataloged and we voted unanimously to publish the paper the next day. However, it was revealed immediately after the vote to be an injection and that our estimated parameters for the simulated source were accurate. Again, there was no detection, but we learned a great deal about our abilities to know when we detected a gravitational wave and that we can do science with the data. This became particularly useful starting in September 2015.”

  9. @elle

    in terms of gravity waves, no, nothing man made can simulate it. if we could, we wouldn’t need LIGO.

    but in terms of detector, they don’t need explosions. the detectors are highly sensitive as is, that’s the problem in the first place…even a truck passing by causes the beams to fluctuate.

    gravity wave has a certain signature of fluctuation (calculated from gr), and it’s different than let’s say a sonic boom from a jet passing by….also the delay for two detectors is different for something traveling at c then something traveling the speed of sound or some seizmological wave. that’s how they differentiate between actual grav wave and rest. problem is that this rest is so much “louder”, then gw.

    second problem is that if the danes are right, the correlation in their noise (some 7ns) is almost the same as the delay a grav wave would cause, thus making it even harder to say for certain if it’s a systematic noise or actual delay caused by gw

  10. What would be the possibility that the GW is carrying the noise of the actual event within the wave? We use similar techniques to transmit audio, for instance, on a carrier wave to convey to a receiver where the information is removed from that carrier.

  11. “What’s vital to understand is that no one is claiming LIGO is wrong

    Innocent until proven guilty. I shall wait for LISA to give us proof of proof.

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