LIGO gravitational wave announcement

[Samson]

The first detection was above the mass usually expected for stellar black holes - see On the Maximum Mass of Stellar Black Holes which has a limit of 30 solar masses in favorable conditions. So suggesting primordial black holes with a higher mass was plausible.

The second detection which the letter did not know about is closer to what we expect for stellar black holes. This is not hopeful for a "lot of 30-mass events".

The evidence against this is that we have looked for Massive Compact Halo Objects including black holes in the halo of the Milky Way and not found enough to explain all dark matter.

ETA: One thing I have not seen is an explanation about why the primordial black holes would have masses like ~30 solar masses. My expectation would be a range of masses including primordial black holes that would evaporate by Hawking radiation with detectable signatures. The constraints on primordial black hole mass seem to rule out them out as dark matter: Black Holes As Dark Matter? Here's Why The Idea Falls Apart

It would be an attractive solution that somehow solves the problem that I have with 80% of mass having no effect on local gravitational conditions, that allow split second timing of 10 year journeys to Pluto and so on. I vaguely realise that if dark matter is diffuse this can have no impact around these parts, but I still deplore something like dark matter.

 

[Reality Check]

I vaguely realise that if dark matter is diffuse this can have no impact around these parts, but I still deplore something like dark matter.

Then be vague no more - the local density of dark matter is small enough that it has no detectable local effects. N.B This is from a memory of an astronomer blogging about a calculation he did about the effects of dark matter on planetary orbits.
If you learn more about dark matter then you will see just how elegant it is as a solution for how the universe acts.

 

[Pixel42]

I'm currently doing a Future Learn course on gravity, the presenters of which are organising a Hangout session this evening:

Discovery hangout

We are celebrating the recent discovery of gravitational waves by having a very special hangout from Stanford University. This will be the occasion to ask all your questions about black holes and gravitational waves, as well as the future exploration of the gravitational Universe. Recent announcements such as the first results of the LISAPathfinder mission and the latest news from LIGO (announced on June 15) will also be the focus of this hangout.

Ask your questions!

You will have the opportunity to ask your questions about the discovery of gravitational waves and the questions that it raises on 16 June at 19h00 GMT (20h00 London, 21h00 Paris, 12h00 California time) through a live event called Google+ Hangouts on Air.

This Google Hangout will be streamed live on YouTube and Google+ Hangouts for approximately 60 minutes, where you can follow the question and answers live.

We encourage you to ask your questions and I’ll select the most popular ones to ask our guests during the Hangout.

There are three ways you can do this:

•You will be able to send questions and comments before and during the event by submitting them in the Google Hangout Q&A chat window (if you have a Google account).


•You can send us questions to our Twitter account @Gravity_Paris or using the hashtag #FLGravity


•You can leave your question or comments on this step in advance. Please ‘like’ the comments you find interesting to help us choose the most useful ones.

Here's the Hangout url:

https://plus.google.com/events/c95i9qovounrbhgiovb5q8laglc

Here's the Youtube url:

https://www.youtube.com/watch?v=taDKa2gz1Ok

As far as dark matter is concerned, I think of it as being a bit like nitrogen. Nitrogen makes up 80% of the atmosphere, but as nothing breathes it and it doesn't affect the weather we're largely unaware of it. It does have an important role to play, however, as it provides the soil with essential nutrients.

 

[MaartenVergu]

Seems that it was all an illusion

LIGO's gravitational wave illusion

“We believe that LIGO has failed to make a convincing case for the detection of any gravitational wave event,” says Andrew Jackson, the physicists group’s spokesperson. According to them, the breakthrough was nothing of the sort: it was all an illusion."

 

[JeanTate]

Seems that it was all an illusion

LIGO's gravitational wave illusion

“We believe that LIGO has failed to make a convincing case for the detection of any gravitational wave event,” says Andrew Jackson, the physicists group’s spokesperson. According to them, the breakthrough was nothing of the sort: it was all an illusion."

A rather sensationalist report by New Scientist.

For a better understanding, this blogpost by Bee is good (be sure to read the comments by some of the principals!): New paper claims that LIGO’s gravitational wave detection from a neutron star merger can’t be right

tl;dr version: the LIGO results are robust.

 

[jonesdave116]

A rather sensationalist report by New Scientist.

For a better understanding, this blogpost by Bee is good (be sure to read the comments by some of the principals!): New paper claims that LIGO’s gravitational wave detection from a neutron star merger can’t be right

tl;dr version: the LIGO results are robust.

A long-lived neutron star merger remnant in GW170817: constraints and clues from X-ray observations
Piro, L. et al.
https://arxiv.org/pdf/1810.04664.pdf

 

[Reality Check]

Seems that it was all an illusion

LIGO's gravitational wave illusion

Seems this is an illusion of a post!
That is New Scientist hyping old news. A Danish group has been trying to analyze the LIGO data for the last couple of years. The main issue is that they are not experts in the analysis of the data. So they have resorted to simplified methodology that neglects the decades of expertise gained and published by the LIGO collaboration. One author with a personal opinion of an illusion does not make the multiple detections of gravitational waves an illusion.

Understanding the LIGO GW150914 event (21 Apr 2016) looks iike the first preprint with fewer authors (Naselsky, Jackson and Liu) that was published in the Journal of Cosmology and Astroparticle Physics.
A Response to “On the time lags of the LIGO signals”

On 13 Jun 2017 a paper appeared on the arXiv titled “On the time lags of the LIGO signals” by Creswell et al. This paper calls into question the 5-sigma detection claim of GW150914 and following detections. In this short response I will refute these claims.

Was it all just noise? Independent analysis casts doubt on LIGO’s detections
What the Danish group actually found was that the GW150914 signal existed but there was also a puzzling correlation in the noise between the 2 detectors. Sabine Hossenfelder explained that the LIGO collaboration had no plans for a response to the presentation or preprint.

Jackson is no unknown to the LIGO collaboration. Upon my inquiry with a member of the LIGO collaboration what to make of the paper, I got the annoyed reply that the collaboration’s management recommends to “respectfully respond that we have talked at some length with the group in the past and do not agree on the methods being used and thus with the conclusions.” Another let me know that a response is not planned.

A major shortcoming of the Danish group’s analysis that they pointed out to me is that the Danes use methods based on tutorials from the LIGO Website, but these methods do not reach the quality standard of the — more intricate — data analysis that was used to obtain the published results

Later we have On the time lags of the LIGO signals preprint posted on arXiv 13 Jun 2017.

 

[Pixel42]

No more doubts: Two independent studies confirm LIGO’s Nobel discovery

Both new papers reanalyzed the LIGO data using different algorithms than those used by the LIGO collaboration and were able to identify the same gravitational signals that the collaboration found. Green and Moffat also noted several errors in how Jackson et al. handled their data, leading to the appearance of a noise correlation that isn't really there. "Our concern is that the calculation done by the Copenhagen group was contrived to get the result they wanted to get," Green told Quanta.

 

[jonesdave116]

"Our concern is that the calculation done by the Copenhagen group was contrived to get the result they wanted to get," Green told Quanta.

Ouch! That, in scientific parlance, is pretty damning. The equivalent of accusing them of faking things.
I once read a response to a plasma cosmologist's (Verschuur, iirc) paper, that essentially accused him of the same thing, when trying to explain away the CMB. If my memory isn't failing me, the authors thanked the referee for suggestions regarding the phrasing of the piece. The implication being that they had gone a lot further in the original, compared to what got published.

 

[Cheetah]

Ouch! That, in scientific parlance, is pretty damning. The equivalent of accusing them of faking things.
I once read a response to a plasma cosmologist's (Verschuur, iirc) paper, that essentially accused him of the same thing, when trying to explain away the CMB. If my memory isn't failing me, the authors thanked the referee for suggestions regarding the phrasing of the piece. The implication being that they had gone a lot further in the original, compared to what got published.

It's not as bad as it sounds.
If I remember correctly, they did a whole bunch of simulations for BHs of different sizes merging and created signal templates for the expected waves produced.
The data was then searched for correlations with the templates to identify potential signals. The concern was that since they were searching huge amounts of data for bits that correspond to a template the 'signal' found might not be real, but an artifact.

 

[hecd2]

It's not as bad as it sounds.
If I remember correctly, they did a whole bunch of simulations for BHs of different sizes merging and created signal templates for the expected waves produced.
The data was then searched for correlations with the templates to identify potential signals. The concern was that since they were searching huge amounts of data for bits that correspond to a template the 'signal' found might not be real, but an artifact.

IIRC the rationale for the Copenhagen team's critique was not that, but was that there was correlation between the interferometers at the same temporal separation as the claimed event in what everyone agreed was background noise. Correlation between the interferometers is a necesssary condition of claiming an event. The argument then went that if there is correlation in the background then what was interpreted as an event could be merely some common mode noise of a higher than usual amplitude.


In my opinion, the recent analysis is every bit as damning of the methods of the Copenhagen team as it sounds.

 

[Cheetah]

Was thinking of a different article/issue, oops.


You guys are right, of course.