Observation of Gravitational Waves from a Binary Black Hole Merger

[multiweb (Marc)]

Originally Posted by Shiraz

yes, that was a pity eh!

Started out quite coherently as an expression of genuine excitement at a momentous scientific discovery and then got dragged down Alice's rabbit hole...Some really good information penetrated the haze though.

Steven knows his stuff and has always had something valid to contribute. Just referring to the other background noise.

[Shiraz (Ray)]

Originally Posted by multiweb

Steven knows his stuff and has always had something valid to contribute. Just referring to the other background noise.

as was I

[gary]

IIS member Robert9 has just made a post in General Chat which includes a link
to a YouTube video recording of a seminar at Monash University
by Associate Professor Yuri Levin and Dr Eric Thrane of Monash University
who were part of the LIGO team -

Post here -
http://www.iceinspace.com.au/forum/s...9&postcount=32

Thanks again to Robert9.

[Eratosthenes (Peter)]

Originally Posted by xelasnave

Peter is playing the fool, there is no bruce.
He is trolling Steven and in an effort to insult Steven he seems to think calling him bruce is funny. It is insulting and poor behaviour from Peter. Probably breaches the tos
Peter has some sort of chip on his shoulder relating to science and scientists and he no doubt views Steven as fair game.

Given his rants I suggest he wants to divert attention away from the op.

The positive is although this site is relatively free of crank behaviour peter is here to remind us how tiresome crank behaviour is and how clever he is engaging in a battle of witts completely unarmed.

His rants need to be ignored as it is clear he is not interested in being decent.

Presumably peter has his reasons which hopefully he wont share with us.

I would encourage members to ignore peters rants for in time he may regret acting the fool...

excellent summary xelas (even though you neglected to mention one very important point)

[Shiraz (Ray)]

it looks like they could possibly have seen more than one event in the data period, even though the next most likely candidate is only at 2sigma. This could be an exciting year!!

http://physicsworld.com/cws/article/...onal-wave-data

[Somnium (Aidan)]

Originally Posted by Shiraz

it looks like they could possibly have seen more than one event in the data period, even though the next most likely candidate is only at 2sigma. This could be an exciting year

http://physicsworld.com/cws/article/...onal-wave-data

2 sigma ... meh

[Shiraz (Ray)]

Originally Posted by Somnium

2 sigma ... meh

I am about 95% confident that, had they not found a 5sigma event, the 2sigma one would have been splashed all over the media - provided of course that it is not an injected test signal.

[Somnium (Aidan)]

Originally Posted by Shiraz

I am about 95% confident that, had they not found a 5sigma event, the 2sigma one would have been splashed all over the media - provided of course that it is not an injected test signal.

i would hope they wouldn't splash a 2 sigma detection around, that just means that out of 20 candidate signals they would give a false positive reading on 1. mind you i have no idea how many candidate signals they look at but 2 sigma is way too low

[Shiraz (Ray)]

sure its is too low to qualify as a detection under the 5 sigma rule that the particle physicists have embraced. However, if you are 95% confident that you have found something, you cannot ignore it either. The particle physicists would just plough on with more runs until they had more confidence, but that is not an option with a strictly one-off gravitational wave detection. I would think that co-incident 2 sigma events at each of the two detectors would have to be quite significant - although who knows how they assess confidence when they are looking for something from a group of "sort of predictable" structured signals, at 2 sites and against noise that presumably has both random and structured components.

Let's see what they do, but it is interesting that that have already begun to publicise the extra candidate events, even those below 2sigma. My guess is that, now they have one hard detection and a lot of real noise to study, they will be able to increase the confidence estimates on any other candidate events.

[Shiraz (Ray)]

The paper itself - I don't think this has been linked to elsewhere in the thread?
http://journals.aps.org/prl/pdf/10.1...ett.116.061102

[sjastro]

Originally Posted by Shiraz

sure its is too low to qualify as a detection under the 5 sigma rule that the particle physicists have embraced. However, if you are 95% confident that you have found something, you cannot ignore it either. The particle physicists would just plough on with more runs until they had more confidence, but that is not an option with a strictly one-off gravitational wave detection. I would think that co-incident 2 sigma events at each of the two detectors would have to be quite significant - although who knows how they assess confidence when they are looking for something from a group of "sort of predictable" structured signals, at 2 sites and against noise that presumably has both random and structured components.

Let's see what they do, but it is interesting that that have already begun to publicise the extra candidate events, even those below 2sigma. My guess is that, now they have one hard detection and a lot of real noise to study, they will be able to increase the confidence estimates on any other candidate events.

Interestingly enough the neutrinos travelling faster than light fiasco was a six sigma event but with no confirmation test on different apparatus.
History has shown it was a nice strong signal of a systematic error.

Dark matter has been "detected" at three sigma using the SuperCDMS but the calculated mass/collision cross section are inconsistent with the exclusion limits of the Xenon10 and 100 detectors.
http://www.science20.com/science_20/..._matter-109299

Steven

[Dave2042 (Dave)]

Originally Posted by Shiraz

sure its is too low to qualify as a detection under the 5 sigma rule that the particle physicists have embraced. However, if you are 95% confident that you have found something, you cannot ignore it either. The particle physicists would just plough on with more runs until they had more confidence, but that is not an option with a strictly one-off gravitational wave detection. I would think that co-incident 2 sigma events at each of the two detectors would have to be quite significant - although who knows how they assess confidence when they are looking for something from a group of "sort of predictable" structured signals, at 2 sites and against noise that presumably has both random and structured components.

Let's see what they do, but it is interesting that that have already begun to publicise the extra candidate events, even those below 2sigma. My guess is that, now they have one hard detection and a lot of real noise to study, they will be able to increase the confidence estimates on any other candidate events.

Good points. I have always felt that there is a danger of missing the wood for the trees in discussions of statistical significance and sigmas.

The reasons, as I see it, that sigma is so critical in particle physics are:

1. It is generally not known what is 'expected', or predicted by an accepted theory. Indeed, whether the 'blip' is real, is a driver of whether we like one theory over another, given the endless variants of possible theory.
2. You can simply do more runs and drive sigma up as high as you like, or to zero, and settle the matter.

This is not like that.

1. We strongly expect gravitational radiation to exist, for widely accepted theoretical reasons, as well as having the second 'simultaneous' signal telling us this is not just a glitch.
2. We can't just do more runs. This is what we have and we need to work with it.

This is more than just an appeal to Bayesian stats. My point is a more fundamental one about what sigma is. All it tells you is something about the likelihood the signal could have been generated randomly. This number operates in total blindness to any theoretical background or extraneous but relevant information. That's kind of fair in much of modern particle physics, but certainly not here.

The worst (but I feel clearest) example of this misunderstanding is the one where we look at climate stats and say that the probability of the rising temperature data being random is 5%, and conclude there is only a 95% chance we are causing global warming. In fact we know (in the usual sense of the word) that it's warming and we are doing it, from basic science. The uncertainty exists only in relation to our ability to measure the current effect above a lot of background noise.

[bojan]

For those who want to understand more about GW... but in a more simple terms:
http://www.tapir.caltech.edu/~teviet/Waves/index.html

[Eratosthenes (Peter)]

Originally Posted by Dave2042

Good points. I have always felt that there is a danger of missing the wood for the trees in discussions of statistical significance and sigmas.

The reasons, as I see it, that sigma is so critical in particle physics are:

1. It is generally not known what is 'expected', or predicted by an accepted theory. Indeed, whether the 'blip' is real, is a driver of whether we like one theory over another, given the endless variants of possible theory.
2. You can simply do more runs and drive sigma up as high as you like, or to zero, and settle the matter.

This is not like that.

1. We strongly expect gravitational radiation to exist, for widely accepted theoretical reasons, as well as having the second 'simultaneous' signal telling us this is not just a glitch.
2. We can't just do more runs. This is what we have and we need to work with it.

This is more than just an appeal to Bayesian stats. My point is a more fundamental one about what sigma is. All it tells you is something about the likelihood the signal could have been generated randomly. This number operates in total blindness to any theoretical background or extraneous but relevant information. That's kind of fair in much of modern particle physics, but certainly not here.

The worst (but I feel clearest) example of this misunderstanding is the one where we look at climate stats and say that the probability of the rising temperature data being random is 5%, and conclude there is only a 95% chance we are causing global warming. In fact we know (in the usual sense of the word) that it's warming and we are doing it, from basic science. The uncertainty exists only in relation to our ability to measure the current effect above a lot of background noise.

good post. It's rare to find scientific articles (especially those based upon experimental investigation) that include the three main sources of errors - Systematic, statistical and theoretical i.e Graphs with data points that show 3 error bars.
And there is the common confusion between what is meant by precision and what is meant by accuracy.

I recall attending a session at a seminar/conference some years back where the author presented a graph with only 3 data points and no error bars included. He then fitted some sort of parabolic curve to these 3 points, and extracted a value for a maximum. I asked him how he chose the type of curve and what the regression coefficient was with just 3 data points. He answered by saying that each data point involves about 2 months work, and that he knew from other research that the relationship was non-linear.

One can fit just about any curve to 3 points. It would be like claiming a linear relationship with just two data points.

If you look at the original Hubble data you can see a general upward trend, but the scatter in the data was large and the galaxies that were observed at the time, with the equipment and techniques available, were nearby or very large galaxies. A linear relationship was nevertheless fitted by Hubble and a value for the Hubble constant extracted. It took many decades to obtain data from distant galaxies that showed the Universe was not only expanding but that this expansion was accelerating.

Error bars from all sources, and their justification is very important in the scientific profession and normally taken for granted

[Eden (Brett)]

Originally Posted by bojan

For those who want to understand more about GW... but in a more simple terms:
http://www.tapir.caltech.edu/~teviet/Waves/index.html

Definitely worth a read. I wonder how long it will be before ALIGO is up and running and making regular detections?

[gary]

In a February 23rd press release by the Harvard-Smithsonian Center
for Astrophysics (CfA), they report that the Fermi Space Telescope
detected a gamma-ray burst just a fraction of a second after LIGO's.

Originally Posted by CfA

Cambridge, MA - On September 14, 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) detected gravitational waves from the merger of two black holes 29 and 36 times the mass of the Sun. Such an event is expected to be dark, but the Fermi Space Telescope detected a gamma-ray burst just a fraction of a second after LIGO's signal. New research suggests that the two black holes might have resided inside a single, massive star whose death generated the gamma-ray burst.

Originally Posted by CfA

Normally, when a massive star reaches the end of its life, its core collapses into a single black hole. But if the star was spinning very rapidly, its core might stretch into a dumbbell shape and fragment into two clumps, each forming its own black hole.

Press release here -
https://www.cfa.harvard.edu/news/2016-05

"Electromagnetic Counterparts to Black Hole Mergers Detected by LIGO" by Loeb, full paper in PDF at arXiv -
http://arxiv.org/pdf/1602.04735v2.pdf

[Shiraz (Ray)]

but the equivalent European GR satellite did not see anything at all and it was in a position to view the whole region of the LIGO detection.
http://phys.org/news/2016-02-gamma-r...o-gravity.html
http://arxiv.org/pdf/1602.04180v1.pdf

the following is from the author of the paper dealing with the possible structure of a star with a pair of black holes at it's core: "Even if the Fermi detection is a false alarm, future LIGO events should be monitored for accompanying light irrespective of whether they originate from black hole mergers. Nature can always surprise us," says Loeb.

it's all happening

[Atmos (Colin)]

There is always a possibility that there will not be any detectable GRB or neutrino fallout with a black hole merger. Certain Type II sn are neutron star-neutron star or neutron star-black hole mergers but in cases there is at least one object that has material outside of the event horizon radius

[sjastro]

An interesting story.

The reviewer of Einstein's paper was Percy Robertson a "co father" of the Big Bang Theory.

http://www.astronomy.com/news/2016/0...tational-waves

[Eratosthenes (Peter)]

Originally Posted by Atmos

There is always a possibility that there will not be any detectable GRB or neutrino fallout with a black hole merger. Certain Type II sn are neutron star-neutron star or neutron star-black hole mergers but in cases there is at least one object that has material outside of the event horizon radius

Q.3 What is "happening" at the point of contact and subsequent merging of the event horizons in the case of two black holes colliding and forming a single black hole? How do we geometrically and mathematically describe the event horizons of the two black holes as they touch and combine? Do special contact and intersection points form? If so, what happens at these points

[25 marks]