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Old 1st March 2016, 08:02 PM   #321
RecoveringYuppy
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Originally Posted by macdoc View Post
RY...I don't think you understand what the process is.
I'm not sure you do.
Originally Posted by macdoc View Post
Very close to two back holes you are going to be plasma but for a different reason....near vicinity is very violent space.
Not necessarily. Tell me why you think this.
Originally Posted by macdoc View Post
Further out you could in theory orbit the two but a long ways out

In neither case are there gravitational waves produced that we could detect.
Huh? We did detect them.

Originally Posted by macdoc View Post
When the two black holes merged however...3 solar masses were turned from mass to energy in an instant.
Can you cite this? In everything I've seen the 3 SM were radiated before the merger.
Originally Posted by macdoc View Post
That event produced the gravitational wave we detected .....
Are you sure? I would think the merger would be the transition point from an efficient way to emit gravitational waves (two high mass orbiting bodies) to a non-efficient way to emit them (pulsation of an object moving rapidly toward symmetry).

Originally Posted by macdoc View Post
That event would ALSO turn your distant orbiting space ship to plasma
Why?
Originally Posted by macdoc View Post
.....but it's not the GW turning you stardust ....it's the energy release....equivalent to 50 x the output of all the stars in the universe for a very brief moment. That's the point at which you join the stardust contingent ......but it's not the gravity wave dismembering you .....it's the energy release.
But the energy release you are citing IS Gravitational waves.

Originally Posted by macdoc View Post
The GW is a result of the change in gravity caused by converting mass to energy on an enormous scale.....3 solar masses worth..
Your dismemberment is a result of the energy release not of effects of the gravity wave on you.
Can you cite this???? Every time I've ready the phrase "3 solar masses" it's been in regard to the energy carried away as gravitational waves.
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Old 1st March 2016, 08:38 PM   #322
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Quote:
But the energy release you are citing IS Gravitational waves.
Not entirely

Quote:
In order to power both the gravitational wave event and the gamma-ray burst, the twin black holes must have been born close together, with an initial separation of order the size of the Earth, and merged within minutes. The newly formed single black hole then fed on the in-falling matter, consuming up to a sun’s worth of material every second and powering jets of matter that blasted outward to create the burst,” the Harvard-Smithsonian Center for Astrophysics said in a statement.

NASA’s Fermi Gamma-ray Space Telescope discovered the gamma burst just 0.4 seconds after the LIGO gravitational waves’ detection, the center said. Both events came from the same general area of the sky.
http://news.discovery.com/space/grav...tar-160223.htm
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Old 2nd March 2016, 12:46 AM   #323
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Originally Posted by Dribble Error View Post
According to these guys at 1AU it would feel more like standing next to a loudspeaker, which if true is pretty awesome (if you're at a concert that is, pretty underwhelming if you're 1AU from a collapsing black hole)
https://www.reddit.com/r/askscience/..._merger_would/
(I've broken the link as I'm not allowed to post them yet)
Good find and welcome to the forum. I did my duty by fixing your link.
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Old 2nd March 2016, 02:47 AM   #324
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Originally Posted by rjh01 View Post
Good find and welcome to the forum. I did my duty by fixing your link.
Thanks!
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Old 2nd March 2016, 05:55 AM   #325
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Originally Posted by macdoc View Post
But that isn't what you were talking about. You keep citing the 3 SM figure which is the energy contained in the gravitational waves.

And you keep attributing them to a one time abrupt loss of matter without explaining why the wave was observed to be sinusoidal. The mechanism you are describing would lead to a single step pulse.
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Old 2nd March 2016, 06:28 PM   #326
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https://www.reddit.com/r/askscience/..._merger_would/
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Old 2nd May 2016, 08:29 AM   #327
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I knew it:
Socalled gravitational waves from LIGO could have had another cause...
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Old 2nd May 2016, 08:57 AM   #328
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Originally Posted by Maartenn100 View Post
Seriously, did you actually bother to read the article, or was it just the headline?

Quote:
A team of researchers with the University of Lisbon has created simulations that indicate that the gravitational waves detected by researchers with the LIGO project, and which are believed to have come about due to two black holes colliding, could just have easily come from another object such as a gravaster (objects which are believed to have their insides made of dark energy) or even a wormhole.
The paper never disputed that Gravitational Waves had been detected, but rather noted that other things could cause them, however, since both Gravastars and Wormholes are totally theoretical currently, if one of them actually caused the waves like the paper suggests, this would be an even bigger scientific discover as it would be proof that one of these currently hypothesized objects really did occur naturally in the universe. That would be a truly momentous find. Of course the greater likelihood is that it was two black holes rather then some very exotic theoretical objects that we still have yet to even prove exist.
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Old 2nd May 2016, 12:02 PM   #329
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Originally Posted by Maartenn100 View Post

Please tell us why you used the term "so-called" when you renamed the link.
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Old 2nd May 2016, 12:36 PM   #330
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Originally Posted by Maartenn100 View Post
You seem to think this article implies that LIGO did not detect gravitational waves, when in fact, it simply speculated that there might be other causes of the the waves they detected; and detect them they most certainly did.

Furthermore, what the article is speculating; that the discovery might be proof of the existence of gravastars, would be an even more amazing discovery if true.

"Gravastars also could provide a mechanism for describing how dark energy accelerates the expansion of the universe. One possible hypothesis uses Hawking radiation as a means to exchange energy between the "parent" universe and the "child" universe, and so cause the rate of expansion to accelerate, but this area is under much speculation.

Gravastar formation may provide an alternate
explanation for sudden and intense gamma-ray bursts throughout space."

From: https://en.wikipedia.org/wiki/Gravastar

For mine, it appears to me that your trying to use this article to clutch at the most tenuous bunch of straws!
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Old 2nd May 2016, 09:06 PM   #331
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Originally Posted by Maartenn100 View Post
A bit of a lie with the text that appears nowhere in that article, Maartenn100.
A proper citation is Simulations suggest other phenomenon besides black holes merging could produce gravity waves.
Quote:
A team of researchers with the University of Lisbon has created simulations that indicate that the gravitational waves detected by researchers with the LIGO project, and which are believed to have come about due to two black holes colliding, could just have easily come from another object such as a gravaster (objects which are believed to have their insides made of dark energy) or even a wormhole. In their paper published in Physical Review Letters, the team describes the simulations they created, what was seen and what they are hoping to find in the future.
The paper shows that the detected gravitational waves may have came from some speculative objects (gravaster or wormhole).
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Old 3rd May 2016, 12:22 AM   #332
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Originally Posted by PhantomWolf View Post
Seriously, did you actually bother to read the article, or was it just the headline?
Do you really have to ask????
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Old 15th June 2016, 10:48 AM   #333
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LIGO detects another black hole crash

Quote:
The biggest discovery in science this year—the observation of ripples in space-time called gravitational waves—was no fluke. For a second time, physicists working with the two massive detectors in the Laser Interferometer Gravitational-Wave Observatory (LIGO) have detected a pulse of such waves, the LIGO team reported on 15 June at a meeting of the American Astronomical Society in San Diego, California. Once again the waves emanated from the merger of two black holes, the ultraintense gravitational fields left behind when massive stars collapse into infinitesimal points. The new observation suggests that after fine-tuning, LIGO will spot dozens or even hundreds of the otherwise undetectable events each year.

...

The new observation came at 3:38.53 Coordinated Universal Time on 26 December 2015—late on Christmas day at LIGO’s detectors in Livingston, Louisiana, and Hanford, Washington. As in the first event, the detectors sensed an oscillating stretching of space-time, the signal, according to Einstein’s 
general theory of relativity, of massive objects in violent motion. Computer modeling indicated that its source was two black holes spiraling together about 1.4 billion light-years away. (LIGO researchers had seen a weaker signal on 12 October 2015 that may be a third black hole merger.)...
http://www.sciencemag.org/news/2016/...ack-hole-crash
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Old 15th June 2016, 12:23 PM   #334
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Originally Posted by Skeptic Ginger View Post
If nothing impedes the progress, how is it detected? How does it affect mass? Are they detecting the ether moving?

I'm trying to imagine something that affects mass but is not affected by mass.
A gravity wave stretches space. Just look it up for a detailed explanation.
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Old 15th June 2016, 03:34 PM   #335
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Originally Posted by carlosy View Post
LIGO detects another black hole crash



http://www.sciencemag.org/news/2016/...ack-hole-crash
What is the inferred frequency of these astonishing events, assuming it can be estimated from this new observation?
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Old 15th June 2016, 04:04 PM   #336
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Originally Posted by Craig B View Post
What is the inferred frequency of these astonishing events, assuming it can be estimated from this new observation?
Given we have had two detected already then we can assume we will detect several every year. We should be able to detect even more if they improve the sensitivity of the devices.
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Old 15th June 2016, 04:37 PM   #337
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Originally Posted by rjh01 View Post
Given we have had two detected already then we can assume we will detect several every year. We should be able to detect even more if they improve the sensitivity of the devices.
it is suggested in this article that the objects responsible for the events are "primordial black holes" which may constitute part of the mysterious "dark matter". Does that seem at all plausible?
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Old 15th June 2016, 04:38 PM   #338
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Quote:
Mosh pits' in star clusters a likely source of LIGO's first black holes

Quote:
Northwestern University astrophysicists have predicted history. In a new study, the scientists show their theoretical predictions last year were correct: The historic merger of two massive black holes detected Sept. 14, 2015, could easily have been formed through dynamic interactions in the star-dense core of an old globular cluster.

These binary black holes are born in the chaotic "mosh pit" of a globular cluster, kicked out of the cluster and then eventually merge into one black hole. This theory, known as dynamical formation, is one of two recognized main channels for forming the binary black holes detected by the Advanced LIGO (Laser Interferometer Gravitational-Wave Observatory).
Quote:


Read more at: http://phys.org/news/2016-06-mosh-pi...ource.html#jCp
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Old 15th June 2016, 07:06 PM   #339
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Originally Posted by Craig B View Post
it is suggested in this article that the objects responsible for the events are "primordial black holes" which may constitute part of the mysterious "dark matter". Does that seem at all plausible?
It sounds great, but are there enough of the suckers? It is infinitely more attractive than something 5 times as heavy as stuff you drop on your foot, but completely non detectable.
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Old 15th June 2016, 07:51 PM   #340
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Originally Posted by Craig B View Post
it is suggested in this article that the objects responsible for the events are "primordial black holes" which may constitute part of the mysterious "dark matter". Does that seem at all plausible?
The first detection was above the mass usually expected for stellar black holes - see On the Maximum Mass of Stellar Black Holes which has a limit of 30 solar masses in favorable conditions. So suggesting primordial black holes with a higher mass was plausible.

The second detection which the letter did not know about is closer to what we expect for stellar black holes. This is not hopeful for a "lot of 30-mass events".

The evidence against this is that we have looked for Massive Compact Halo Objects including black holes in the halo of the Milky Way and not found enough to explain all dark matter.

ETA: One thing I have not seen is an explanation about why the primordial black holes would have masses like ~30 solar masses. My expectation would be a range of masses including primordial black holes that would evaporate by Hawking radiation with detectable signatures. The constraints on primordial black hole mass seem to rule out them out as dark matter: Black Holes As Dark Matter? Here's Why The Idea Falls Apart

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Old 15th June 2016, 10:22 PM   #341
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Originally Posted by Reality Check View Post
The first detection was above the mass usually expected for stellar black holes - see On the Maximum Mass of Stellar Black Holes which has a limit of 30 solar masses in favorable conditions. So suggesting primordial black holes with a higher mass was plausible.

The second detection which the letter did not know about is closer to what we expect for stellar black holes. This is not hopeful for a "lot of 30-mass events".

The evidence against this is that we have looked for Massive Compact Halo Objects including black holes in the halo of the Milky Way and not found enough to explain all dark matter.

ETA: One thing I have not seen is an explanation about why the primordial black holes would have masses like ~30 solar masses. My expectation would be a range of masses including primordial black holes that would evaporate by Hawking radiation with detectable signatures. The constraints on primordial black hole mass seem to rule out them out as dark matter: Black Holes As Dark Matter? Here's Why The Idea Falls Apart
It would be an attractive solution that somehow solves the problem that I have with 80% of mass having no effect on local gravitational conditions, that allow split second timing of 10 year journeys to Pluto and so on. I vaguely realise that if dark matter is diffuse this can have no impact around these parts, but I still deplore something like dark matter.
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Old 16th June 2016, 12:14 AM   #342
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Originally Posted by Samson View Post
I vaguely realise that if dark matter is diffuse this can have no impact around these parts, but I still deplore something like dark matter.
Then be vague no more - the local density of dark matter is small enough that it has no detectable local effects. N.B This is from a memory of an astronomer blogging about a calculation he did about the effects of dark matter on planetary orbits.
If you learn more about dark matter then you will see just how elegant it is as a solution for how the universe acts.
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Old 16th June 2016, 01:19 AM   #343
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I'm currently doing a Future Learn course on gravity, the presenters of which are organising a Hangout session this evening:

Quote:
Discovery hangout

We are celebrating the recent discovery of gravitational waves by having a very special hangout from Stanford University. This will be the occasion to ask all your questions about black holes and gravitational waves, as well as the future exploration of the gravitational Universe. Recent announcements such as the first results of the LISAPathfinder mission and the latest news from LIGO (announced on June 15) will also be the focus of this hangout.

Ask your questions!

You will have the opportunity to ask your questions about the discovery of gravitational waves and the questions that it raises on 16 June at 19h00 GMT (20h00 London, 21h00 Paris, 12h00 California time) through a live event called Google+ Hangouts on Air.

This Google Hangout will be streamed live on YouTube and Google+ Hangouts for approximately 60 minutes, where you can follow the question and answers live.

We encourage you to ask your questions and I’ll select the most popular ones to ask our guests during the Hangout.

There are three ways you can do this:

•You will be able to send questions and comments before and during the event by submitting them in the Google Hangout Q&A chat window (if you have a Google account).


•You can send us questions to our Twitter account @Gravity_Paris or using the hashtag #FLGravity


•You can leave your question or comments on this step in advance. Please ‘like’ the comments you find interesting to help us choose the most useful ones.
Here's the Hangout url:

https://plus.google.com/events/c95i9...hgiovb5q8laglc

Here's the Youtube url:

https://www.youtube.com/watch?v=taDKa2gz1Ok

As far as dark matter is concerned, I think of it as being a bit like nitrogen. Nitrogen makes up 80% of the atmosphere, but as nothing breathes it and it doesn't affect the weather we're largely unaware of it. It does have an important role to play, however, as it provides the soil with essential nutrients.
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Old 25th November 2018, 06:13 AM   #344
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Seems that it was all an illusion

LIGO's gravitational wave illusion

“We believe that LIGO has failed to make a convincing case for the detection of any gravitational wave event,” says Andrew Jackson, the physicists group’s spokesperson. According to them, the breakthrough was nothing of the sort: it was all an illusion."
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Old 25th November 2018, 08:49 AM   #345
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Originally Posted by Maartenn100 View Post
Seems that it was all an illusion

LIGO's gravitational wave illusion

“We believe that LIGO has failed to make a convincing case for the detection of any gravitational wave event,” says Andrew Jackson, the physicists group’s spokesperson. According to them, the breakthrough was nothing of the sort: it was all an illusion."
A rather sensationalist report by New Scientist.

For a better understanding, this blogpost by Bee is good (be sure to read the comments by some of the principals!): New paper claims that LIGO’s gravitational wave detection from a neutron star merger can’t be right

tl;dr version: the LIGO results are robust.
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Old 25th November 2018, 01:20 PM   #346
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Originally Posted by JeanTate View Post
A rather sensationalist report by New Scientist.

For a better understanding, this blogpost by Bee is good (be sure to read the comments by some of the principals!): New paper claims that LIGO’s gravitational wave detection from a neutron star merger can’t be right

tl;dr version: the LIGO results are robust.
A long-lived neutron star merger remnant in GW170817: constraints and clues from X-ray observations
Piro, L. et al.
https://arxiv.org/pdf/1810.04664.pdf
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Old 25th November 2018, 02:01 PM   #347
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Originally Posted by Maartenn100 View Post
Seems that it was all an illusion

LIGO's gravitational wave illusion
Seems this is an illusion of a post!
That is New Scientist hyping old news. A Danish group has been trying to analyze the LIGO data for the last couple of years. The main issue is that they are not experts in the analysis of the data. So they have resorted to simplified methodology that neglects the decades of expertise gained and published by the LIGO collaboration. One author with a personal opinion of an illusion does not make the multiple detections of gravitational waves an illusion.

Understanding the LIGO GW150914 event (21 Apr 2016) looks iike the first preprint with fewer authors (Naselsky, Jackson and Liu) that was published in the Journal of Cosmology and Astroparticle Physics.
A Response to “On the time lags of the LIGO signals”
Quote:
On 13 Jun 2017 a paper appeared on the arXiv titled “On the time lags of the LIGO signals” by Creswell et al. This paper calls into question the 5-sigma detection claim of GW150914 and following detections. In this short response I will refute these claims.

Was it all just noise? Independent analysis casts doubt on LIGO’s detections
What the Danish group actually found was that the GW150914 signal existed but there was also a puzzling correlation in the noise between the 2 detectors. Sabine Hossenfelder explained that the LIGO collaboration had no plans for a response to the presentation or preprint.
Quote:
Jackson is no unknown to the LIGO collaboration. Upon my inquiry with a member of the LIGO collaboration what to make of the paper, I got the annoyed reply that the collaboration’s management recommends to “respectfully respond that we have talked at some length with the group in the past and do not agree on the methods being used and thus with the conclusions.” Another let me know that a response is not planned.

A major shortcoming of the Danish group’s analysis that they pointed out to me is that the Danes use methods based on tutorials from the LIGO Website, but these methods do not reach the quality standard of the — more intricate — data analysis that was used to obtain the published results
Later we have On the time lags of the LIGO signals preprint posted on arXiv 13 Jun 2017.

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Old Yesterday, 02:19 PM   #348
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No more doubts: Two independent studies confirm LIGO’s Nobel discovery

Quote:
Both new papers reanalyzed the LIGO data using different algorithms than those used by the LIGO collaboration and were able to identify the same gravitational signals that the collaboration found. Green and Moffat also noted several errors in how Jackson et al. handled their data, leading to the appearance of a noise correlation that isn't really there. "Our concern is that the calculation done by the Copenhagen group was contrived to get the result they wanted to get," Green told Quanta.
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