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

[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.

 

[maline]

The gravitational potential energy got converted to gravitational waves, that is exactly the point.

I was asking about the negative energy due to the holes being near each other as opposed to at infinity. I would expect this to decrease the gravitational wave energy output, as compared with a simple comparison of the masses.

That is negligible.

Why? Both holes attain near-light speeds, so shouldn't the kinetic energy be comparable to, or even several times, the mass energy?

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

I thought the quoted masses referred to Lorentz-invariant rest mass. Rotational energy is frame-dependent, so shouldn't it be accounted for separately?

 

[mfb]

I was asking about the negative energy due to the holes being near each other as opposed to at infinity. I would expect this to decrease the gravitational wave energy output, as compared with a simple comparison of the masses.

It is the source of the gravitational wave output, in terms of energy balance.

Why? Both holes attain near-light speeds, so shouldn't the kinetic energy be comparable to, or even several times, the mass energy?

The initial kinetic energy is negligible. Later it increases, but only by (approximately) half the value the reducing gravitational potential energy sets free.

I thought the quoted masses referred to Lorentz-invariant rest mass. Rotational energy is frame-dependent, so shouldn't it be accounted for separately?

All numbers are as seen by an observer far away. The black hole mass is determined by the total energy.

 

[maline]

All numbers are as seen by an observer far away. The black hole mass is determined by the total energy.

So the numbers given include the kinetic & gravitational "potential" contributions as well?
And these "masses" decrease steadily as the waves are emitted, with the change mainly in the increasingly negative gravitational component which is only partially compensated by the increasing kinetic energy?
Meanwhile, the two invariant masses remain more or less constant?
And in the actual merger, the final invariant mass is actually perhaps 4 SM's less than the sum of original invariant masses, but there is also perhaps 1 SM of rotational energy, leaving the net loss at 3 SM's?
Let me know if I got it! Thanks!

 

[websterling]

It looks like you can sign-up to view the announcement online through Nature-
http://www.nature.com/news/ligo-live-inside-the-hunt-for-gravitational-waves-1.19344

And also here-
https://www.webcaster4.com/Webcast/ListenPage?companyId=219&webcastId=13131

 

[DiracPool]

There's this

I can't wait for this announcement. I keep staring at the video in post #45 waiting for the press conference to begin. It's not so bad, actually, at least I can monitor the Cosmic Microwave Background while I'm waiting..

 

[Math Amateur]

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?

I heard there was going to be a news conference announcing the discovery/detection of gravitational ways today (Thursday 11th February) ... ... has anyone got any news on this ...?

 

[e.bar.goum]

I heard there was going to be a news conference announcing the discovery/detection of gravitational ways today (Thursday 11th February) ... ... has anyone got any news on this ...?

10:30 US EST. Nature has a liveblog here: http://www.nature.com/news/ligo-live-inside-the-hunt-for-gravitational-waves-1.19344

 

[Math Amateur]

Thanks for that ... Peter

 

[ujjwal3097]

10:30 US EST. Nature has a liveblog here: http://www.nature.com/news/ligo-live-inside-the-hunt-for-gravitational-waves-1.19344

can we watch the whole conference on the nature site

 

[e.bar.goum]

can we watch the whole conference on the nature site

It's not clear, but I think so.

 

[ujjwal3097]

It's not clear, but I think so.

yes! you are right because there is no info about the video. Site just says if you want to set the reminder.

 

[Daz]

Not long to go now... Here's a link to the youtube live feed:

 

[ujjwal3097]

Not long to go now... Here's a link to the youtube live feed:

thanks so much

I hope for something good

 

[Orodruin]

So to summarise, LIGO has detected a gravitational wave signal from a black hole merger which occurred over a billion years ago. The signal was seen independently by the two detectors with perfect coincidence. The event radiated a total of 3 solar masses in gravitational waves.

 

[bcrowell]

Here's the signal:

The PRL paper is supposed to be available online at this time. Right now the PRL website appears to be overloaded and not responding :-)

 

[Orodruin]

Here's the signal:

Note the unit of strain on the y-axis. That is an incredibly small number. To detect that is truly amazing.

 

[bcrowell]

A few quick notes from the press conference:

2 colliding back holes
1.3 10^9 ly
2015 sep 14
freq increasing with time, as expected for inspiraling black holes
8:00 animation of inspiraling black holes
each 150 km diam
~30 Msun, v significant fraction of c
9:30 animation with grav waves
stretch is 1/1000 diameter of proton
12:00 big risk for NSF to fund it
15:30 signal obviously visible
16:20 seen obviously by eye
curve fitting gives initial masses, mass loss, and distance
20:00 chirp played as audio (with frequency shift)

 

[bcrowell]

This seems to be the URL of the paper:

abstract: http://link.aps.org/doi/10.1103/PhysRevLett.116.061102

pdf: http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102

The site is overloaded, so I can't tell yet whether the paper is paywalled.

Op ed piece on the Physical Review site: http://physics.aps.org/articles/v9/17

 

[JorisL]

I really enjoyed Rainer Weiss' explanation, let's hope the press has been paying attention.

 

[bcrowell]

Abstract of the paper:

On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410+160−180Mpc corresponding to a redshift z=0.09+0.03−0.04. In the source frame, the initial black hole masses are 36+5−4M⊙ and 29+4−4M⊙, and the final black hole mass is 62+4−4M⊙, with 3.0+0.5−0.5M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

The paper appears to be under a CC license and not paywalled. Currently attempting to download it.