A Rumors of Gravitational Wave Inspiral at Advanced LIGO | Sept 2015 Launch

[phyzguy]

There is a rumor going around that a gravitational wave inspiral has been seen at advanced LIGO. The web sites say it went on line in Sept, 2015, so I guess this is possible. Has anyone here heard anything?

 

[e.bar.goum]

I've certainly heard the rumours. It seems to originate from a tweet from Lawrence Krauss. There's something in Nature: http://www.nature.com/news/has-giant-ligo-experiment-seen-gravitational-waves-1.18449 , and this: https://www.reddit.com/user/ligo_throwaway

very much rumour and innuendo, but I wouldn't be reading too much into it. The nature post about it is good.

 

[A/4]

Kicking this thread. Rumours are flying, and apparently there may be a press conference looming on the horizon (pun intended). The story is there have been at least two signal detections, one being a binary merger of two ~10x solar mass black holes.

Please share what you've heard!

 

[phyzguy]

I've heard the same thing. My source says 2-3 detections, one very weak, one strong, one medium, with the strong one being a 10's of solar mass BH merger. I've heard press conference scheduled for Feb 11.

 

[Spinnor]

Some more details here,

http://motls.blogspot.com/2016/02/ligo-wows-bh-masses-3629-to-62-suns-51.html#more

and here,

http://www.sciencemag.org/news/2016...s-rumor-gravitational-waves-have-been-spotted

from above,

 

[Vanadium 50]

This thread was started in October. Rumors seem to be a constant fact of life. Sooner or later one of them will be true, but until then I am content to wait to see what is real, rather than to speculate.

 

[mfb]

We'll know more in a week.
A loss of three solar masses in the merger would correspond to a power above 10⁴⁶ W (probably much higher), the most powerful event we ever saw.

The combined luminosity of all stars in the observable universe is about 10⁴⁹ W.

 

[FieldTheorist]

It's amusing to see one of Cliff's emails getting passed around. Cliff is a smart guy, I don't expect him to run around peddling BS, so I have some faith that this is probably true or at least that people have good reason to believe that it's true.

Even so, I'm waiting for February 11th.

 

[tzimie]

Some more details here,

http://motls.blogspot.com/2016/02/ligo-wows-bh-masses-3629-to-62-suns-51.html#more

based on the chart they provided the max frequency is about 100Hz.
but 2 stellar-size BH (20km) orbiting close to each other (R=100km? -> orbit length = 300km?) move near light speed.
So I would expect 300.000/300 = 1000Hz or even more.
strange.

EDIT
BH are much heavier than I expected.

The waves are already very strong when the distance between the two initial black holes drops to the radius of the final black hole, some 100 miles. The circumference is some 600 miles or 1,000 km. The speed of light that they nearly achieve is 300,000 km per second so the black holes may orbit each other 300 times a second at this moment.

So it makes sense

 

[ujjwal3097]

Everyone will get complete details about the topic within this week.

 

[A/4]

The presser has been advertised: 10:30am in Washington, DC:

http://www.ligo.org/news/media-advisory.php

 

[mfb]

For press not based in the Washington, D.C. area, this event will be simulcast live online, and we will try to answer some questions submitted remotely. For details about how to participate remotely, please contact anyone listed below.

I really hope the "contact those persons" are just for the remote questions, not for the livestream...

 

[reyya_42]

if that's true, i m interesting on method they used.

 

[Jando]

European Virgo collaboration inviting journalists to their site for the same date and time as in the Ligo announcement:

http://public.virgo-gw.eu/february-...update-on-the-search-for-gravitational-waves/

 

[ebos]

Wonder if the Nobel prize money gets paid back to the public purse... not!

 

[ohwilleke]

It is hard to imagine an event that would give rise to a stronger signal.

I'd love to see a short explanation of the methodology used by LIGO to detect the gravitational waves. What observables are they looking at and how does that tie into the theory?

Rumors seem to imply that the data are a dead on fit to the GR prediction as spelled out in previous published work simulating this kind of event. If so, this is going to dramatically constrain the experimentally permitted parameter space of any hypothetical tweaks to GR in the strong field regime that are currently permitted consistent with the experimental data.

 

[A/4]

It is hard to imagine an event that would give rise to a stronger signal.

Two 100 or 1000 solar mass black holes merging?

I'd love to see a short explanation of the methodology used by LIGO to detect the gravitational waves. What observables are they looking at and how does that tie into the theory?

LIGO methodologies are certainly covert, and you probably won't find them by a simple google search on their documentation (jocular sarcasm...). LIGO does matched-filtering of incoming signals, by comparing them to a giant database of templates. They have routinely placed false-positives in the stream as tests of the system.

http://arxiv.org/pdf/gr-qc/9808076.pdf

Rumors seem to imply that the data are a dead on fit to the GR prediction as spelled out in previous published work simulating this kind of event. If so, this is going to dramatically constrain the experimentally permitted parameter space of any hypothetical tweaks to GR in the strong field regime that are currently permitted consistent with the experimental data.

It may confirm GR to the accuracy of the available data and rule out some classical competitors, but it would be surprising if it placed too much constraint on quantum gravity models.

 

[ohwilleke]

Two 100 or 1000 solar mass black holes merging?

But, at that point, you are starting to talk about supermassive black holes at the center of galaxies merging which seem to be exceedingly rare phenomena that may not be likely to happen in our lifetimes. The distribution of black holes by mass seems to be pretty strongly biased towards those just large enough to form a black hole at all (a bit more than 3 stellar masses) and supermassive black holes at the centers of galaxies, with a comparatively thin frequency of mid-sized black holes in the size range observed by LIGO.

There are something on the order of 100-500 billion galaxies in the universe, albeit with a very inhomogeneous distribution crowded into galactic clusters and massive filaments of matter, but the number of that merging at anyone time is pretty small and the time that it takes for two galaxies to merge is pretty long. Even if two Milky Way sized galaxies were 99.8% into the process of merging we still wouldn't observe their supermassive central black holes merging in the lifetime of anyone alive today or their children and I'm not away of any known pairs of galaxies known to be that far along into the merger process.

 

[A/4]

But, at that point, you are starting to talk about supermassive black holes at the center of galaxies merging which seem to be exceedingly rare phenomena that may not be likely to happen in our lifetimes.

No, supermassive black holes are of the order $10^6-10^{10}$ solar masses, not 100-1000. There's a range of difference between the two mass scales, and thus associated detection probabilities. But anyway, my remark was somewhat in jest.

 

[DiracPool]

I think it's obvious that with all this hype, there's going to be a positive announcement: the "cry wolf" factor would be hard to come back from. If it were anything otherwise, they would have had the rumor police squelching the, ummm... rumor. Plus, Lawrence Krauss spilled the beans two weeks ago, and who's a better insider than the guy that walks around with a T-shirt of him sparring off with Dick Feynman:

Plus, look at the undergrad hottie in the background who is looking at, who? Feynman? No! She's looking dreamily at the Krauss-man, of course. Staged? You tell me

 

[DiracPool]

Plus, I don't know if we have an expert commentary on this but, I think on the eve of this announcement, someone should give maybe an "Insight" presentation or something as to what it is that was found here and, more importantly, how they found it and what the tolerances they had to overcome were. There's many seemingly non-sequitur statements such as... the tolerances they are working at here are the same that if the milky way galaxy stretched this or that way more than the width of a pencil eraser, LIGO would detect it... "

http://www.techinsider.io/gravitational-wave-nature-ligo-february-11-2016-2

"Put another way, detecting a gravitational wave is like noticing the Milky Way — which is about 100,000 light-years wide — has stretched or shrunk by the width of a pencil eraser."

However, at the same time a truck driving "nearby" can disrupt the experiment despite "vibration-dampening equipment?"

"It would be no wonder why it has taken researchers so long to find gravitational waves; it's terribly difficult work. (Even a truck driving on a nearby road can disturb LIGO, despite the instruments having state-of-the-art vibration-dampening equipment.)"I really don't get this order of magnitute comparison between a clumsy truck driving down a dirt road a few miles from the LIGO and the size of the milky way stretching the size of a pencil eraser. I know they have the choo-choo train sounds going off in the lab when a train rolls by, so there must be some integrity to this comment somewhere.

My guess is that they measure these tolerances so closely because they are using an interferometer running an extremely high frequency/small wavelength and that they have a technique to measure extremely small phase discrepancies. Plus, I've also read that they match these with similar findings from another detector half way across the world to rule out the local truck and rail car. But this is my abstraction from the popular media reports. I would like to know more precisely how they claim they can measure these very small tolerances.

 

[Vanadium 50]

I think it's obvious that with all this hype, there's going to be a positive announcement

This is an argument that all rumors are true. Do you really want to make that particular argument?

 

[DiracPool]

This is an argument that all rumors are true. Do you really want to make that particular argument?

No I don't, but these teasers are putting us off until the eleventh, in whatever time zone that means for you. And I will say that I HATE teasers. Just up and say it, don't set a press conference for 5 or 15 days hence. WTF is that all about?

 

[EinsteinKreuz]

It turns out that Ultracold Neutrons are far better at observing gravity than LIGO, but if these rumors are true that's way cool.

 

[PAllen]

Though I'm on pins and needles, I don't think a scheduled press conference is teasing. The rumors are teasing and were presumably not supposed to happen. On the hypothesis that there is an element of truth to the rumors, the press conference is still the only responsible way to handle it, and I can envision that what is going on now are multiple internal reviews of the strength of signal and error analysis, with a decision on whether to announce as a discovery open until the last moment. No one wants to be the next BICEP or FTL neutrinos. In this case, a 'hint' prior to final re-checks would be a mistaken thing to do.

 

[ohwilleke]

Then again, maybe the origami club had more clout booking the press conference hall than the scientists and this was just the earliest time that they could manage. ;)

 

[George Jones]

It turns out that Ultracold Neutrons are far better at observing gravity than LIGO

Reference?

Ultra cold neutrons are better at observing gravitational radiation form merging compact objects?

 

[phyzguy]

Though I'm on pins and needles, I don't think a scheduled press conference is teasing. The rumors are teasing and were presumably not supposed to happen. On the hypothesis that there is an element of truth to the rumors, the press conference is still the only responsible way to handle it, and I can envision that what is going on now are multiple internal reviews of the strength of signal and error analysis, with a decision on whether to announce as a discovery open until the last moment. No one wants to be the next BICEP or FTL neutrinos. In this case, a 'hint' prior to final re-checks would be a mistaken thing to do.

I agree. These things take time. A paper has to be written, internally reviewed, then peer reviewed. The press conference has to be scheduled, and you don't do that on 24 hours notice. It is not the LIGO collaboration's fault that things are leaking and people get wind of it. I can't wait for Thursday!

 

[mfb]

It turns out that Ultracold Neutrons are far better at observing gravity than LIGO, but if these rumors are true that's way cool.

That's like comparing neutrino detectors measuring the solar neutrino flux to "just look outside, the sun is there!". Sure, neutrino detectors do also provide evidence that the sun exists at all, but that is not their point.
If you just want to see that gravity exists, neutrons are great (but so is jumping up, just less precise). I doubt you can measure gravitational waves with them.If the rumors about ~5 sigma are true, I wouldn't expect too much in terms of a clearly visible oscillation signal. A 5 sigma oscillations spread over hundred to hundreds of datapoints is probably not visible by eye at all. Data analysis reveals it, but there won't be nice plots where you can see the individual ups and downs.

There are something on the order of 100-500 billion galaxies in the universe, albeit with a very inhomogeneous distribution crowded into galactic clusters and massive filaments of matter, but the number of that merging at anyone time is pretty small and the time that it takes for two galaxies to merge is pretty long. Even if two Milky Way sized galaxies were 99.8% into the process of merging we still wouldn't observe their supermassive central black holes merging in the lifetime of anyone alive today or their children and I'm not away of any known pairs of galaxies known to be that far along into the merger process.

If just 1% of all galactic black holes have a merger over the lifetime of the universe, we get a merger every few years. With 10%, one to several per year. If every black hole has several mergers on average, we get them all the time. Those don't have to be "millions of solar masses combine with millions of solar masses". Some observed supermassive black holes in the early universe grew very rapidly, hard to explain with just accretion.

 

[bcrowell]

In the announcement of the Washington press conference, I don't see any info on any source of live information for the general public. There's a section in the press release headed "LIVE WEBCAST," but all it says is to email one of three contact people. Presumably they don't want individuals like me who are not reporters emailing them... Is there for instance any blogger who is going to do a live blog?

 

[mfb]

I hope that the contact thing is only relevant for reporters who want to ask questions.

I know that CERN will have a live transmission (and experts available for questions afterwards), but it's CERN, of course they find some way to get a livestream.

 

[DiracPool]

Would a positive result from the LIGO project re-ignite the stunted LISA project?

http://news.discovery.com/space/a-farewell-to-lisa-110408.htm

I mean, LISA was not designed to test Einstein's prediction per se, was it? It was designed to be more of a gravitational wave "telescope," correct? So a positive result from LIGO would give legitimacy to the project. Or is it the reverse? Since gravitational waves have been detected, there's now even less justification for the LISA project?

 

[PAllen]

Would a positive result from the LIGO project re-ignite the stunted LISA project?

http://news.discovery.com/space/a-farewell-to-lisa-110408.htm

I mean, LISA was not designed to test Einstein's prediction per se, was it? It was designed to be more of a gravitational wave "telescope," correct? So a positive result from LIGO would give legitimacy to the project. Or is it the reverse? Since gravitational waves have been detected, there's now even less justification for the LISA project?

I would guess (hope) that it would add momentum to LISA (which is not dead, just smaller scale and longer time frame from NASA pulling out and only Europe invovlved). LISA would have a detection sensitivity orders beyond LIGO, able to really do GW astronomy. Though binary pulsars indirectly confirm GW at very high confidence, direct detection would (IMO) seem to make it easier to fund raise for LISA.

 

[bcrowell]

I know that CERN will have a live transmission (and experts available for questions afterwards), but it's CERN, of course they find some way to get a livestream.

You mean CERN will receive a live transmission, or CERN will provide a live transmission?

 

[A/4]

I agree. These things take time. A paper has to be written, internally reviewed, then peer reviewed. The press conference has to be scheduled, and you don't do that on 24 hours notice.

The press conference is scheduled for Feb 11th to coincide with the Feb 11th issue of Nature, which happens to have their paper in it (it was written and peer reviewed last year). Sure, another "rumor", but at some point the rumors become so intricately detailed that you can pretty much figure they're not rumors.

 

[bcrowell]

The press conference is scheduled for Feb 11th to coincide with the Feb 11th issue of Nature, which happens to have their paper in it (it was written and peer reviewed last year). Sure, another "rumor", but at some point the rumors become so intricately detailed that you can pretty much figure they're not rumors.

So I wonder if the paper (paywalled? abstract only?) will be on http://www.nature.com/nature/current_issue.html at the same time as the press conference. Wonder when it will appear on arxiv. Nature's home page has a teaser: "The first direct detection of gravitational waves is now widely expected to be announced on 11 February by the Advanced Laser Interferometer..." and a sort of preview article
http://www.nature.com/news/gravitational-waves-5-cosmic-questions-they-can-tackle-1.19337

 

[PietKuip]

If the experiment is so advanced and difficult, why cannot LIGO arrange a webcast for the public? Our physics department wants to watch, we would like to invite students too.

 

[Khashishi]

The researchers probably don't want to be overwhelmed. Disappointing, I know...

 

[mfb]

You mean CERN will receive a live transmission, or CERN will provide a live transmission?

Receive.

If the experiment is so advanced and difficult, why cannot LIGO arrange a webcast for the public? Our physics department wants to watch, we would like to invite students too.

Maybe they do. The website description is a bit unclear.

Would a positive result from the LIGO project re-ignite the stunted LISA project?

I would expect positive effects on LISA and DECIGO. They can measure so many things that LIGO/VIRGO won't see.

 

[ohwilleke]

The projects are complementary. LIGO is sensitive to higher frequencies. LISA and DECIGO are sensitive to lower frequencies.

 

[Spinnor]

LIGO Open Science Center , https://losc.ligo.org/links/

From above,

quick overview, http://www.ligo.org/science.php

publications, https://www.lsc-group.phys.uwm.edu/ppcomm/Papers.html

one of the first publications (from 2003), Detector Description and Performance for the First Coincidence Observations between LIGO and GEO,

http://arxiv.org/abs/gr-qc/0308043

POPULAR ARTICLES
Detecting Ripples in Space-Time, with a Little Help from Einstein (Space.com, August 2015)
Gravitational Waves: Sources, Detection, and Searches by K. Riles, 2012, 79pp: http://arxiv.org/abs/1209.0667
http://www.ligo.caltech.edu/docs/P/P990039-00.pdf (Physics Today, October 1999)
LIGO: An Antenna Tuned to the Songs of Gravity (Sky & Telescope, October 2000)
Catch a Gravity Wave (Astronomy, August 2001)
Waiting for Gravity (IEEE Spectrum, July 2006)
Gravitational Waves: New Observatories for New Astronomy (The Physics Teacher, October 2006)
Sounding Out the Big Bang (Physics World, June 2007)
It Takes a Huge Detector (and Plenty of Patience) to Chase Gravitational Waves (Popular Mechanics, May 2014)

- See more at: http://www.ligo.org/read.php#sthash.WKJ1EtXS.dpuf

Where looking for a needle in a haystack is child's play.

 

[JorisL]

You mean CERN will receive a live transmission, or CERN will provide a live transmission?

Receive.

Perhaps the collaboration is afraid they can't handle the load so they keep it small-scale.
This makes me wonder if CERN could rebroadcast it (they have the capacity I take it, since they broadcast regularly).

 

[DiracPool]

http://www.nature.com/news/has-giant-ligo-experiment-seen-gravitational-waves-1.18449

"And even if LIGO has seen some promising data, it could be the result of an elaborate drill — a false signal deliberately injected into the detectors to train LIGO’s data-analysis team. At this stage, only three people would know the truth, and they would not reveal that until much later, when the collaboration is ready to publish a paper and to hold a press conference."

They wouldn't dare pull this on us, would they? I've heard of this possibility from a few different sources. If this is the case, I'm going to be a bit miffed

 

[Vanadium 50]

CERN could rebroadcast it (they have the capacity I take it, since they broadcast regularly)

I believe CERN rents additional capacity when they do this. (That's what they have done in the past) Live streaming to a million people is not something you just "do". It takes real expertise and costs real money.

 

[martinbn]

There's this

 

[mfb]

Perhaps the collaboration is afraid they can't handle the load so they keep it small-scale.
This makes me wonder if CERN could rebroadcast it (they have the capacity I take it, since they broadcast regularly).

There are companies that can handle big broadcasts, Youtube/Google will not even care about the additional traffic. Most CERN webcasts don't have so many viewers, but there are some massive peaks (e.g. Higgs discovery).

"And even if LIGO has seen some promising data, it could be the result of an elaborate drill — a false signal deliberately injected into the detectors to train LIGO’s data-analysis team. At this stage, only three people would know the truth, and they would not reveal that until much later, when the collaboration is ready to publish a paper and to hold a press conference."

They are beyond the "ready to hold a press conference" step: they organized a press conference.

Edit: Wow, I made the mistake to click on one of the "related videos" and read the comments. Don't do that.

 

[Ibix]

Edit: Wow, I made the mistake to click on one of the "related videos" and read the comments. Don't do that.

"Never read the comments" seems to be a constant of nature...

 

[pervect]

There's lots of possibilities. We'll know more tomorrow.

 

[maline]

If the final rest mass in 3 SM's less than the sum of the rest masses, does that mean all that energy was emitted as gravitational waves? Isn't it natural that the final mass should be lower because the pre-collision system included plenty of gravitational potential energy, or whatever the corresponding concept is in GR?

On the other hand, what about the immense kinetic energies of the initial holes, in (whatever is similar to) the rest frame of the center of momentum? Does that all go to rotational energy of the final hole, or does it have to be added?

How do these different energies compare, in orders of magnitude?

 

[mfb]

If the final rest mass in 3 SM's less than the sum of the rest masses, does that mean all that energy was emitted as gravitational waves? Isn't it natural that the final mass should be lower because the pre-collision system included plenty of gravitational potential energy, or whatever the corresponding concept is in GR?

The gravitational potential energy got converted to gravitational waves, that is exactly the point.
Black holes are just gravitational energy, basically.

On the other hand, what about the immense kinetic energies of the initial holes, in (whatever is similar to) the rest frame of the center of momentum?

That is negligible.
Rotational energy of the final black hole is part of its total energy, so it is part of its mass.