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1. Oct 8, 2015

### 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?

2. Oct 8, 2015

3. Feb 1, 2016

### 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.

4. Feb 1, 2016

### 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.

5. Feb 6, 2016

### Spinnor

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6. Feb 6, 2016

Staff Emeritus
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.

7. Feb 6, 2016

### Staff: Mentor

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.

8. Feb 6, 2016

### 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.

9. Feb 8, 2016

### tzimie

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.

So it makes sense

10. Feb 8, 2016

### ujjwal3097

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

11. Feb 8, 2016

### A/4

12. Feb 8, 2016

### Staff: Mentor

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

13. Feb 8, 2016

### reyya_42

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

14. Feb 8, 2016

### Jando

15. Feb 8, 2016

### ebos

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

16. Feb 8, 2016

### 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.

17. Feb 8, 2016

### A/4

Two 100 or 1000 solar mass black holes merging?

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

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.

18. Feb 8, 2016

### ohwilleke

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 any one 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.

19. Feb 8, 2016

### A/4

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.

Last edited by a moderator: Feb 9, 2016
20. Feb 9, 2016

### 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

Last edited: Feb 9, 2016
21. Feb 9, 2016

### 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.

22. Feb 9, 2016

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

23. Feb 9, 2016

### DiracPool

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?

24. Feb 9, 2016

### 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.

25. Feb 9, 2016

### 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.