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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