Author Topic: Gravitational Waves Have Been Detected At LIGO  (Read 55885 times)

Offline eeergo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #160 on: 02/28/2017 03:09 PM »
aVIRGO has been inaugurated today:

http://home.infn.it/it/comunicazione/comunicati-stampa/2193-taglio-del-nastro-per-advanced-virgo (still in Italian)

Construction and commissioning are complete with this ceremony, but calibration is still up for the next few months. The project has cost 23.8 M€ spread over the last 4 years. Upgrades include modifications in the optics, with heavier and higher-performing mirrors; new and more powerful electronics, new aberration-compensating system, better seismic isolation, stray light reduction system and better vacuum.

4-page interview with Giovanni Losurdo, coordinator of aVIRGO:

http://home.infn.it/newsletter-eu/pdf/NEWSLETTER_INFN_32_inglese_pag6.pdf


Extremely interesting to note that the "monolithic suspensions" (fused silica fibers where the mirrors are suspended) were in use by VIRGO before, but were damaged because of dust particles impacting them when the mirror assembly was vented to atmospheric pressure (!!!). Steel wires will be used for the commissioning and first science runs, to then re-install the silica fibers to much increase sensitivity in the low-frequency range from run 03[/size][size=78%].[/size]
« Last Edit: 02/28/2017 03:19 PM by eeergo »
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Offline 1

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #161 on: 03/08/2017 05:55 PM »
Now this is quite unfortunate.

Gravitational wave pioneer Ronald Drever dies

I'm attempting to see if an award may be made posthumously if the person was nominated before death, but it's not clear. If the person had already been awarded the prize, but died before reception, then they will still receive it, but prize announcements for 2017 won't be until October-ish. I do hope the committee rules on the lighter side of this gray area.  Looking for precedents at the moment

Regardless, the man saw his life's work validated in a spectacular fashion. I hope he died with a smile on his face.

 

Offline as58

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #162 on: 03/09/2017 05:23 PM »
Now this is quite unfortunate.

Gravitational wave pioneer Ronald Drever dies

I'm attempting to see if an award may be made posthumously if the person was nominated before death, but it's not clear. If the person had already been awarded the prize, but died before reception, then they will still receive it, but prize announcements for 2017 won't be until October-ish. I do hope the committee rules on the lighter side of this gray area.  Looking for precedents at the moment

Regardless, the man saw his life's work validated in a spectacular fashion. I hope he died with a smile on his face.

Unfortunately, the rules are clear. From http://www.nobelprize.org/nobel_organizations/nobelfoundation/statutes.html#par4:

Quote
Work produced by a person since deceased shall not be considered for an award. If, however, a prizewinner dies before he has received the prize, then the prize may be presented.

In 2011 they did award Ralph Steinman the Prize for Physiology or Medicine posthumously, but in that case the committee wasn't aware that he had died only four days earlier.

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #163 on: 05/17/2017 07:59 PM »
Physicists use Einstein’s ‘spooky’ entanglement to invent super-sensitive gravitational wave detector

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The first direct detection of gravitational waves, a phenomenon predicted by Einstein’s 1915 general theory of relativity, was reported by scientists in 2016.

Armed with this “discovery of the century”, physicists around the world have been planning new and better detectors of gravitational waves.

Physicist Professor Chunnong Zhao and his recent PhD students Haixing Miao and Yiqiu Ma are members of an international team that has created a particularly exciting new design for gravitational wave detectors.

The new design is a real breakthrough because it can measure signals below a limit that was previously believed to be an insurmountable barrier. Physicists call this limit the standard quantum limit. It is set by the quantum uncertainty principle.

The new design, published in Nature magazine this week, shows that this may not be a barrier any longer.

Using this and other new approaches may allow scientists to monitor black hole collisions and “spacequakes” across the whole of the visible universe.

https://theconversation.com/physicists-use-einsteins-spooky-entanglement-to-invent-super-sensitive-gravitational-wave-detector-77822

Offline Star One

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Gravitational Waves Have Been Detected At LIGO
« Reply #164 on: 06/01/2017 06:19 PM »
Third detection made.

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First, the merger demonstrates how the binary system was spinning before the two parts merged. In these systems, in addition to orbiting one another, each black hole spins around its own axis. For astrophysicists, the question is: Are the individual black holes spinning in the same direction as they're orbiting? The gravitational wave fingerprint from this latest observation suggests that they are.
"Our new LIGO measurements favor the scenario where both black holes spin in the same sense as the orbit," said Georgia Tech's Laura Cadonati, Deputy Spokesperson of the LIGO Scientific Collaboration, at the same teleconference. "This means they take longer to merge than if the spins are non-aligned."
The black holes' spin patterns add another puzzle piece to our picture of how black holes form. "This finding lightly favors the theory that these two black holes formed separately in a dense stellar cluster, sank to the core of the cluster, and then paired up," Cadonati said, "rather than being formed together from the collapse of two already paired stars." However, Cadonati cautioned that the finding does not definitively prove which theory of black hole formation is correct. It's only a clue that will require more support.
Luckily, it looks like LIGO may be getting a lot more clues. With this signal, LIGO has found another object in the category of heavy black holes, objects with masses 25 times or more that of our sun. Given the rate at which black holes merge, LIGO may eventually be able to pick up one new black hole merger every week—or even every day. The more signals it picks up, the more we'll learn about black hole formation, as well as more details about how gravitational waves spread through space. These events could even uncover the secrets of gravitons, the theoretical particles that could be the source of gravity.

http://www.popsci.com/ligo-spots-its-third-black-hole-merger
« Last Edit: 06/01/2017 06:39 PM by Star One »

Offline MP99

Re: Gravitational Waves Have Been Detected At LIGO
« Reply #165 on: 06/02/2017 07:33 AM »
There's an inconsistency in that report.

BBC news reporting the spins may not have been aligned, which would make the rest of that article make sense.

Cheers, Martin

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #166 on: 06/02/2017 09:28 AM »
There's an inconsistency in that report.

BBC news reporting the spins may not have been aligned, which would make the rest of that article make sense.

Cheers, Martin

Yes I was reading another article which contradicted the above in that aspect. So it seems an error.

Here it is from the horse's mouth so to speak.

https://www.ligo.caltech.edu/news/ligo20170601

Offline eeergo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #167 on: 06/19/2017 05:44 AM »
And just as I'm passing AdVIRGO's area in the high-speed train, I read this nice news item:


http://ligo.org/news/index.php#triplelock


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FIRST TRIPLE LOCK FOR LIGO AND VIRGO INTERFEROMETERS


17 June 2017 -- For the first time, all three second generation interferometers---LIGO Hanford, LIGO Livingston, and Virgo---are simultaneously in a locked state. (When an interferometer is "locked" it means that an optical resonance is set up in the arm cavities and is producing a stable interference pattern at the photodetector.) Virgo is joining in an engineering mode, in preparation for the full triple-observing mode planned for later this summer. Congratulations, Virgo!




PS: By the way, shouldn't this thread be moved to "Space Science" or, at least, to "Advanced Concepts"? It's really not speculative and diverges quite a lot from most of the other... creative topics in this subforum.
-DaviD-

Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #168 on: 06/19/2017 08:45 AM »
I'd second that: it should be moved to, my guess would be to Space Science

Offline gongora

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #169 on: 06/20/2017 05:35 PM »
By the way, shouldn't this thread be moved to "Space Science" or, at least, to "Advanced Concepts"? It's really not speculative and diverges quite a lot from most of the other... creative topics in this subforum.

The top post in this thread would put it into the New Physics for Space Technology section, but if the thread has settled into a discussion of gravitational wave detection instead of proposed uses for spaceflight it probably belongs in Space Science.

Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #170 on: 06/20/2017 08:25 PM »
ESA has selected the full LISA mission for launch in 2026.

http://www.bbc.co.uk/news/science-environment-40346410

--- Tony

Offline bolun

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #171 on: 06/20/2017 08:43 PM »

Online jebbo

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #172 on: 06/20/2017 08:46 PM »
Oops ... somehow I got it confused with the Plato date

--- Tony 

Offline Star One

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Gravitational Waves Have Been Detected At LIGO
« Reply #173 on: 06/21/2017 07:41 PM »
Yet another poor science paper comes to the attention of the internet press. This time supposedly calling into doubt the LIGO detections.

Anyway here's the whole gruesome tale as presented by one of the LIGO team. Relevant links in the article.

http://fictionalaether.blogspot.co.uk/2017/06/the-irresistible-allure-of-controversy.html?m=1

More here from another LIGO team member.

https://www.preposterousuniverse.com/blog/2017/06/18/a-response-to-on-the-time-lags-of-the-ligo-signals-guest-post/
« Last Edit: 06/21/2017 07:46 PM by Star One »

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #174 on: 07/02/2017 07:48 PM »

Offline Star One

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Gravitational Waves Have Been Detected At LIGO
« Reply #175 on: 08/23/2017 08:17 PM »
LIGO, Leaks and NGC 4993

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The rumours going round identify the optical counterpart as being in the galaxy NGC 4993 , a red band image of which, from the Second Digitized Sky Survey (DSS2) is shown below:

Quote
If there is an optical counterpart to a gravitational wave event coming from this galaxy then that suggests it may be a coalescence of neutron stars. The black hole mergers that appear to be responsible to the three existing gravitational wave signals that are claimed to have been detected are not expected to release optical light. Confirmation of this interpretation can be found by where the Hubble Space Telescope was pointed yesterday:

https://telescoper.wordpress.com/2017/08/23/ligo-leaks-and-ngc-4993/amp/
« Last Edit: 08/23/2017 08:18 PM by Star One »

Offline jgoldader

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #176 on: 08/25/2017 12:20 PM »
There's a bit of a kerfuffle about the tweet not having been appropriate (scooping the team), but I sure hope it's true.  It was a surprise to me that the LIGO team was not awarded the Nobel last year, and if they really caught a source with an optical transient, perhaps that'll be enough evidence for the Academy.
Recovering astronomer

Offline gospacex

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #177 on: 08/25/2017 02:02 PM »
There are four natural forces in the Universe. Electromagnetic, Strong Nuclear, Weak Nuclear, and Gravitational.

According to Standard Model + gravity, the above is in fact incorrect (however, it was in textbooks for some 80 years, so it will take time to be corrected).

Let's count them. #1: there is the force of gravity. Even though Standard Model does not include it, it treams gravity "semiclassically", not as quantum field. But it clearly exists.

SM proper says that gauge fields ("gauge forces") arise from internal symmetries of the unitary product group SU(3)xSU(2)xU(1). Of these:

Force #2: SU(3) is color force which binds quarks into hadrons, strong nuclear force is a residual attraction force between hadrons, a-la Wan-der-Waals forces between neutral atoms is a residual force of electromagnetism. With a bit of redefinition, you can call SU(3) force "strong force".

But it stops here. The rest of forces are not "Electromagnetic" or "Weak".

According to SM, forces #3 and #4 are SU(2) "weak isospin" and U(1) "weak hypercharge". They are peculiar in the fact that SM vacuum state is very strongly not invariant under either.

There is a linear combination of them, Q=T3+1/2Y, under which vacuum _is_ invariant. That's "electromagnetic force". According to SM, it is not a fundamental force at all, it's a fallout, an unbroken remainder of broken SU(2)xU(1) symmetry.

So these are the actual three gauge forces that SM has.

But SM has more forces than that. In general, any term in Lagrangian where more than one field is present is interaction, a "force" (one field acts on another). SM gauge forces are represented by Lagrangian terms where gauge fields (also called "vector fields" or fields of spin 1) are multiplied with fermion fields of spin 1/2.

SM also has one scalar field (spin 0): Higgs field. And it has interactions.

Forces #5 and #6: SM Lagrangian has terms where Higgs field interacts with SU(2) and U(1) weak gauge fields. These can't be considered the same as #3 and #4 because they have *different mathematical form*.

Force #7: SM Lagrangian has terms where Higgs field interacts with each fermion field (that's how fermions get their masses in SM).

SM Lagrangian also has terms where fields act on themselves - "kinetic" terms. Basically, these describe how particles move when they do not interact ("interact only with themselves"). I don't count these as forces.
« Last Edit: 08/25/2017 02:04 PM by gospacex »

Offline Star One

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #178 on: 08/25/2017 03:52 PM »
There's a bit of a kerfuffle about the tweet not having been appropriate (scooping the team), but I sure hope it's true.  It was a surprise to me that the LIGO team was not awarded the Nobel last year, and if they really caught a source with an optical transient, perhaps that'll be enough evidence for the Academy.

I assume it's not just significant for this, but also because it indicates the first evidence of a Neutron star merger.

Offline jgoldader

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Re: Gravitational Waves Have Been Detected At LIGO
« Reply #179 on: 08/25/2017 09:09 PM »
I assume it's not just significant for this, but also because it indicates the first evidence of a Neutron star merger.

Interestingly, we already knew those had to happen, though yes, this would be the first direct detection. Taylor and Hulse were awarded the Nobel for their discovery of a binary neutron star system where the NS are inspiraling and are doomed to collide one day, due to loss of kinetic energy caused by the emission of... gravitational waves!  The energy loss was as predicted by general relativity.  So we knew gravitational waves did indeed exist, decades before we directly detected them.  LIGO and VIRGO are too weak to detect the GWs from the inspiraling; only the ones emitted right near the moment of catastrophe would be strong enough to detect.  (To be clear, this event is not due to the binary NS Taylor and Hulse found.)

If this all holds together, it's got a nice sort of "closing the circle" aspect to it.
Recovering astronomer

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