NASASpaceFlight.com Forum
Robotic Spacecraft (Astronomy, Planetary, Earth, Solar/Heliophysics) => Space Science Coverage => Topic started by: Johnnyhinbos on 01/12/2016 01:43 pm
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So what does / can this mean for spaceflight?
Not for the first time, the world of physics is abuzz with rumours that gravitational waves have been detected by scientists in the US.
Lawrence Krauss, a cosmologist at Arizona State university, tweeted that he had received independent confirmation of a rumour that has been in circulation for months, adding: “Gravitational waves may have been discovered!!”
http://www.theguardian.com/science/2016/jan/12/gravitation-waves-signal-rumoured-science?CMP=twt_gu (http://www.theguardian.com/science/2016/jan/12/gravitation-waves-signal-rumoured-science?CMP=twt_gu)
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ESA may have a much harder time justifying LISA
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So what does / can this mean for spaceflight?
Nothing, really.
It will be a great moment for science and another conformation of General Relativity. It will advance our knowledge of the universe as gravity wave observations can begin. All of this is at the very high end of energies that has nothing to do with new propulsion or anything else that would directly apply to spaceflight. The big news would be if someone found something that didn't match predictions and would lead to new physics. New physics, especially if it enables the combination of GR and quantum theory, might lead to new technologies that apply to spaceflight.
What to look for in the next few years are the results of observations by LIGO as they start gravity wave astronomy. Also the Event Horizon Telescope project where they are trying to see via radio telescopes the environment around our galaxy's central black hole. These will be the most strenuous tests of GR yet and if there are any deviations from GR in these observations, that might lead to new physics.
http://www.eventhorizontelescope.org/ (http://www.eventhorizontelescope.org/)
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So what does / can this mean for spaceflight?
Not for the first time, the world of physics is abuzz with rumours that gravitational waves have been detected by scientists in the US.
Lawrence Krauss, a cosmologist at Arizona State university, tweeted that he had received independent confirmation of a rumour that has been in circulation for months, adding: “Gravitational waves may have been discovered!!”
http://www.theguardian.com/science/2016/jan/12/gravitation-waves-signal-rumoured-science?CMP=twt_gu
It means nothing practical concerning space propulsion during our lifetimes, but here you have:
a patent application http://www.google.com/patents/US20070001541
a recent paper (2012) http://www.gravwave.com/docs/DirectionsForGWPropGraWaV.pdf
authors that think that "Applications of the present analysis will lead to a unique propulsion system capable of enabling the fast exploration of the solar system, the local star system, and possibly the whole galaxy."
;) ::)
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ESA may have a much harder time justifying LISA
I was kind of wondering that when I posted this news in the LISA thread earlier on today?
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ESA may have a much harder time justifying LISA
If the rumors are true (and that's still very much an IF, we shouldn't get to excited yet) I'd hope for the opposite. If we know that there's something out there to observe, it might be a good time to push for the restoration of the original scope of the program. Be really nice if NASA got back on board, but I wouldn't hold my breath.
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ESA may have a much harder time justifying LISA
I would think it would be the justification of LISA. First of all a confirmed detection of grav-waves means that LISA should also succeed. Second they are looking at very different wave lengths and amplitudes of grav-waves so they will see very different things.
The point is not to just detect grav-waves. The point is to see stuff by them.
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ESA may have a much harder time justifying LISA
If the rumors are true (and that's still very much an IF, we shouldn't get to excited yet) I'd hope for the opposite. If we know that there's something out there to observe, it might be a good time to push for the restoration of the original scope of the program. Be really nice if NASA got back on board, but I wouldn't hold my breath.
By analogy, astronomers didn't stop with the first detection of radio waves. "Yup, there are radio waves out there - we can stop now."
Cheers, Martin
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ESA may have a much harder time justifying LISA
If the rumors are true (and that's still very much an IF, we shouldn't get to excited yet) I'd hope for the opposite. If we know that there's something out there to observe, it might be a good time to push for the restoration of the original scope of the program. Be really nice if NASA got back on board, but I wouldn't hold my breath.
By analogy, astronomers didn't stop with the first detection of radio waves. "Yup, there are radio waves out there - we can stop now."
Cheers, Martin
I suppose the question becomes now you can detect them can you do anything with this?
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I suppose the question becomes now you can detect them can you do anything with this?
Probe physics (general relativity predictions vs. reality) at levels we were never been able to do so far, using neutron star and/or black hole collisions. It's not an understatement to say that each time we opened a new window into the cosmos, we learned something new. "Seeing" with gravitational waves likely won't be any different.
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The original topic, as specified in the title of the thread, is not new physics, so it belongs in a different section.
Well the detection of grav-waves is new and it is physics...
But it's the same old physics.
The term "new physics" means physics different from what is commonly accepted by professional physicists. Gravitational waves are not that.
New experimental results come in all the time in physics. That doesn't make them "new physics".
What's the point of having a section with "New Physics" in the title if we're not going to follow it?
With that kind of horribly narrow definition you place yourself even further left field than cold fusion & EM drives.
At CERN they use the same definition as ChrisWilson68.
Any difference between the measured observable and prediction could indicate new physics.
http://home.cern/about/updates/2013/08/tracking-new-physics-horse-or-zebra (http://home.cern/about/updates/2013/08/tracking-new-physics-horse-or-zebra)
That's how physicists define new physics. New observations are advances in science, but it is only a hint toward new physics if the confirmed results do not match theory. If the new observations match theory, then it is a confirmation of the theory, not new physics.
When the Michelson-Morely experiment indicated that the aether did not exist, that was an indication of new physics. Quantum Theory, Special and General Relativity were the new theories that tried to explain the new physics of their day. They have been very successful, but the search for more continues.
When gravity waves are detected by LIGO or other experiments, then we will see if they match the prediction from GR. If not, then there might be some new physics behind the results.
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That's how physicists define new physics. New observations are advances in science, but it is only a hint toward new physics if the confirmed results do not match theory. If the new observations match theory, then it is a confirmation of the theory, not new physics.
When the Michelson-Morely experiment indicated that the aether did not exist, that was an indication of new physics. Quantum Theory, Special and General Relativity were the new theories that tried to explain the new physics of their day. They have been very successful, but the search for more continues.
Respectfully, as a physicist, I feel some clarification is needed here. Subsequent measurements are often advances in existing physics, but brand spankin new measurements are often considered new physics simply because they act as a forcing function on any and all other competing theories. Even GR and QM, as successful as they've proven to be, are understood to be at best incomplete; and are in need of a more generalized, unified theory. At worst, we must still accept the (very remote) possibility that they're both completely wrong. Comfirmation of gravity waves would now require the formulation of any future unified theory to support them. Else, this would not be a strict requirement. In my opinion, the first direct detection of gravity waves, much like the first direct detection of the Higgs boson, would be enough to say we've moved our knowledge into new territory.
To your example, if an aether had been detected, the Michelson-Morely experiment would still have indicated new physics as well. It would have required a new, non-local generalization of Maxwell's equations rather than a new understanding of space and time, but everyone knew something was wrong with those equations; and any result, even an 'expected' one, would lead them in a new direction.
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Perhaps the discovery of Gravity Waves will further stimulate research and development towards better means of detection. I'd read that atom lasers and atom interferometry could also conceivably be used towards detection and characterization of Gravity Waves:
http://www.scientificamerican.com/article/gravity-space-based-atom-interferometers-could-find-gravitational-waves-video/
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.110.171102
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That's how physicists define new physics. New observations are advances in science, but it is only a hint toward new physics if the confirmed results do not match theory. If the new observations match theory, then it is a confirmation of the theory, not new physics.
When the Michelson-Morely experiment indicated that the aether did not exist, that was an indication of new physics. Quantum Theory, Special and General Relativity were the new theories that tried to explain the new physics of their day. They have been very successful, but the search for more continues.
Respectfully, as a physicist, I feel some clarification is needed here. Subsequent measurements are often advances in existing physics, but brand spankin new measurements are often considered new physics simply because they act as a forcing function on any and all other competing theories. Even GR and QM, as successful as they've proven to be, are understood to be at best incomplete; and are in need of a more generalized, unified theory. At worst, we must still accept the (very remote) possibility that they're both completely wrong. Comfirmation of gravity waves would now require the formulation of any future unified theory to support them. Else, this would not be a strict requirement. In my opinion, the first direct detection of gravity waves, much like the first direct detection of the Higgs boson, would be enough to say we've moved our knowledge into new territory.
To your example, if an aether had been detected, the Michelson-Morely experiment would still have indicated new physics as well. It would have required a new, non-local generalization of Maxwell's equations rather than a new understanding of space and time, but everyone knew something was wrong with those equations; and any result, even an 'expected' one, would lead them in a new direction.
Then it looks like there isn't an agreement as to what "new physics" means. Kind of makes it a useless phrase.
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So what does / can this mean for spaceflight?
Not for the first time, the world of physics is abuzz with rumours that gravitational waves have been detected by scientists in the US.
Lawrence Krauss, a cosmologist at Arizona State university, tweeted that he had received independent confirmation of a rumour that has been in circulation for months, adding: “Gravitational waves may have been discovered!!”
http://www.theguardian.com/science/2016/jan/12/gravitation-waves-signal-rumoured-science?CMP=twt_gu
It means nothing practical concerning space propulsion during our lifetimes, but here you have:
a patent application http://www.google.com/patents/US20070001541
a recent paper (2012) http://www.gravwave.com/docs/DirectionsForGWPropGraWaV.pdf
authors that think that "Applications of the present analysis will lead to a unique propulsion system capable of enabling the fast exploration of the solar system, the local star system, and possibly the whole galaxy."
;) ::)
So presumably the OP was asking if the discovery of the existence of Gravity Waves could somehow lead us toward generating Gravity Waves ourselves, or otherwise manipulating gravity.
Isn't the Mach Effect Thruster technically supposed to be based on manipulation of inertia and in some sense, gravity?
If atomic interferometry could be used to detect and measure Gravity Waves, then couldn't it also be used to measure effects from a Mach Effect Thruster? I wonder if Paul March / Star-Drive might be able to comment on that.
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Btw, here is a presentation from NASA's Jason Hogan on the use of atom interferometry in detecting Gravity Waves:
https://www.youtube.com/watch?v=ezzvYiXSf6s
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completely unrelated but totally fascinating gravity stuff: http://www.sciencedaily.com/releases/2016/01/160108083918.htm
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"If followed, this proposal could transform physics and shake up Einstein's theory of general relativity."
Well, from this line my skepticism level just smashed through the roof and kept on going. Actually, this is the new physics forum, so that's as mundane a claim as "nice weather we're having".
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I wonder how far this has progressed.
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completely unrelated but totally fascinating gravity stuff: http://www.sciencedaily.com/releases/2016/01/160108083918.htm
Colour me sceptical when we still haven't discovered what fundamentally makes up gravity.
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I don't think the announcement will be long now.
http://www.sciencemag.org/news/2016/02/woohoo-email-stokes-rumor-gravitational-waves-have-been-spotted
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I wonder how far this has progressed.
Same here. If it becomes accepted that gravity waves are a physical thing. The next question becomes how do we generate them today within either existing technology or technology we already have on the drawing board but havent funded the engineering for yet.
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I wonder how far this has progressed.
Same here. If it becomes accepted that gravity waves are a physical thing. The next question becomes how do we generate them today within either existing technology or technology we already have on the drawing board but havent funded the engineering for yet.
I can't see how it would be possible to generate these in our foreseeable future at a level that would be useful, considering what it takes in nature to produce them.
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New Scientist has been having a dig around into the background of this latest rumour and seems to feel we may have some reason to hope for a positive announcement soon.
https://www.newscientist.com/article/2076754-latest-rumour-of-gravitational-waves-is-probably-true-this-time/
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Well, we all know that New Scientist leans towards pop-sci and tends to hype news stories.
But if Gravity Waves are really a thing, then it should be possible to constructively or destructively combine many tiny such waves together in superposition, shouldn't it?
The Mach Effect apparatus of oscillating masses should be able to produce many tiny waves, and perhaps these waves or their constructive combination could be detected by atom interferometry.
It seems to me that atom interferometry is the key to better detection and analysis of gravity waves. If this budding field of science could be developed, then it would allow gravity waves and their nature to be studied in greater detail.
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Well, we all know that New Scientist leans towards pop-sci and tends to hype news stories.
But if Gravity Waves are really a thing, then it should be possible to constructively or destructively combine many tiny such waves together in superposition, shouldn't it?
That's not a "superposition" in the sense of a quantum superposition, so it's better to use a different word to avoid confusion.
Yes, it's possible, but that doesn't really help anything. You need just as much energy to produce two waves that you combine to a particular magnitude as it would take to just create a wave of that magnitude in the first place. There's no such thing as a free lunch.
The Mach Effect apparatus of oscillating masses should be able to produce many tiny waves, and perhaps these waves or their constructive combination could be detected by atom interferometry.
Don't bring up the Mach Effect, it has nothing to do with gravitational waves.
Oscillating masses produce tiny waves. But they're so tiny that you can't produce a measurable gravity wave by combining them without have an impractically large number of them -- as much oscillating mass as if you just had one enormous mass you were oscillating. Either way, the energy involved is impractical.
That's why nobody has been able to detect gravity waves until now.
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I wonder how far this has progressed.
Same here. If it becomes accepted that gravity waves are a physical thing. The next question becomes how do we generate them today within either existing technology or technology we already have on the drawing board but havent funded the engineering for yet.
With enormous black holes. I'm not entirely sure this is that "new physics"-y (in the sense of upending existing physics), but if confirmed, has a good chance of a Nobel Prize anyway.
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Well, we all know that New Scientist leans towards pop-sci and tends to hype news stories.
But if Gravity Waves are really a thing, then it should be possible to constructively or destructively combine many tiny such waves together in superposition, shouldn't it?
The Mach Effect apparatus of oscillating masses should be able to produce many tiny waves, and perhaps these waves or their constructive combination could be detected by atom interferometry.
It seems to me that atom interferometry is the key to better detection and analysis of gravity waves. If this budding field of science could be developed, then it would allow gravity waves and their nature to be studied in greater detail.
I am not sure commentary on what New Scientist does or doesn't do is warranted in this case, especially in light of the wider background on this story. I'd rather be positive that they've actually done a bit of extra legwork in this case.
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I wonder how far this has progressed.
Same here. If it becomes accepted that gravity waves are a physical thing. The next question becomes how do we generate them today within either existing technology or technology we already have on the drawing board but havent funded the engineering for yet.
I can't see how it would be possible to generate these in our foreseeable future at a level that would be useful, considering what it takes in nature to produce them.
Dont think I am as pessimestic. "OBSERVED" Nature has not needed to do the things we want to do. Therefore I feel its safe to argue that the way nature generates G-Waves is more a side effect of other things it needed to do. Now, My next question is, How hard have we honestly looked at the possibility for generating Gravity waves. How much curiosity has been road blocked in the quest to generate them, because we didnt know if they were simply a mathematical artifact or a physical object?
In addition if g-waves are simply vibrations of space time and all mass deforms space time. Then Energy deforms space time since all mass is energy. Now that c2 part of the calculation leads to you needing alot of energy to equal the changes that asteroids, comets, planets, stars and black holes make to space time. However, energy at least in the form of EM can do something those other forms cant or at the very least havent been observed to do. Resonate. The first question I would love to see an answer to is if there is a frequency at which EM can resonate that would amplify the small changes to space time that it naturally makes.
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If this is confirmed and current testing of the technology in space goes well is there any room for the development and launch of LISA to be moved up?
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That's not a "superposition" in the sense of a quantum superposition, so it's better to use a different word to avoid confusion.
"superposition" can be used to describe behavior of either waves or particles ("quantum")
https://en.wikipedia.org/wiki/Superposition_principle#Wave_superposition
Anyway, we can say "wave interference" if that sounds better.
Yes, it's possible, but that doesn't really help anything. You need just as much energy to produce two waves that you combine to a particular magnitude as it would take to just create a wave of that magnitude in the first place. There's no such thing as a free lunch.
Well, we manipulate EM waves for various purposes, so likewise we could theorize at how to analogously manipulate gravity waves to study how gravity waves behave.
Don't bring up the Mach Effect, it has nothing to do with gravitational waves.
Alright, "Mach Effect" is an unverified conjecture, while Gravitational Waves are classical physics predicted by General Relativity. I was simply referring to the apparatus that uses oscillating masses, and not the conjecture itself. However, as a side-note, once Gravitational Waves are fully verified as real, then it would impact the theoretical conjecture around the possible Mach Effect.
Oscillating masses produce tiny waves. But they're so tiny that you can't produce a measurable gravity wave by combining them without have an impractically large number of them -- as much oscillating mass as if you just had one enormous mass you were oscillating. Either way, the energy involved is impractical.
That's why nobody has been able to detect gravity waves until now.
Whether a wave is tiny depends on what means you're using to detect it - as Einstein said, everything is relative.
That's why I mentioned atom interferometry - that method is capable of much greater sensitivity than LIGO.
It's a newer method, but one which now deserves to be developed further to help shed more light on things that light doesn't do as well on through classical interferometry.
While the Gravitational Waves LIGO is purported to have detected were generated by very large astrophysical phenomena (ie. colliding black holes), LIGO is detecting the waves from those phenomena across a very large distance of many lightyears. So while a man-made experimental apparatus that oscillates some masses is far smaller than massive black holes, at least the apparatus could be operated much closer to the detector, so that the falloff from R^2 isn't happening across many lightyears of distance. Yes, size matters - but distance matters too.
But if atom interferometers could be developed further, not only could they be used to detect the Gravitional Waves generated by large astrophysical phenomena that LIGO is detecting, but their high sensitivity could be used to one day measure man-made gravitational waves (ie. like from a tabletop apparatus with oscillating masses).
Learning how to manipulate gravity by exploiting its wave nature might not necessarily be for pulling objects. Perhaps we might learn how to create and modulate gravity waves for communications purposes, for example, just as we do with EM waves.
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Detecting gravity waves may be new physics but it isn't unexpected physics. What would be surprising is if they didn't detect gravity waves. And if you are hoping for a gravity based propulsion system then it may be better to hope that gravity waves are not detected. That at least gives you a mystery that may resolve into an unexpected finding that gives you your gravity drive.
Anyway they are expected to announce on the 11th.
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Detecting gravity waves may be new physics but it isn't unexpected physics. What would be surprising is if they didn't detect gravity waves. And if you are hoping for a gravity based propulsion system then it may be better to hope that gravity waves are not detected. That at least gives you a mystery that may resolve into an unexpected finding that gives you your gravity drive.
Anyway they are expected to announce on the 11th.
Yes this is a big discovery, but one of the main things it does is reconfirm what a genius Einstein was, but then we already knew that.:)
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I wonder how far this has progressed.
Same here. If it becomes accepted that gravity waves are a physical thing. The next question becomes how do we generate them today within either existing technology or technology we already have on the drawing board but havent funded the engineering for yet.
I can't see how it would be possible to generate these in our foreseeable future at a level that would be useful, considering what it takes in nature to produce them.
Dont think I am as pessimestic. "OBSERVED" Nature has not needed to do the things we want to do. Therefore I feel its safe to argue that the way nature generates G-Waves is more a side effect of other things it needed to do. Now, My next question is, How hard have we honestly looked at the possibility for generating Gravity waves. How much curiosity has been road blocked in the quest to generate them, because we didnt know if they were simply a mathematical artifact or a physical object?
In addition if g-waves are simply vibrations of space time and all mass deforms space time. Then Energy deforms space time since all mass is energy. Now that c2 part of the calculation leads to you needing alot of energy to equal the changes that asteroids, comets, planets, stars and black holes make to space time. However, energy at least in the form of EM can do something those other forms cant or at the very least havent been observed to do. Resonate. The first question I would love to see an answer to is if there is a frequency at which EM can resonate that would amplify the small changes to space time that it naturally makes.
If we consider the rumored 36+29=62 solar mass merger to be near our detectable threshold, then 3 solar masses were emitted as gravitational waves. Even if this is conservative and surely the merger emitted something else, it's probably safe to say the order of magnitude is right. This equates an energy release on the order of 10^30 kg = 10^30 eV/c^2 = 1,000,000 YeV/c^2 = one-hundred (short-scale) septillion TeV. Nowadays, we are able to produce ~10 TeV of center-of-mass energy with protons, around a factor of 10000 more in the lab frame: 10^17 eV. So just rounding things up to the largest measured energies, let's say we can in the foreseeable future control beams of ~10^20 eV=0.1 ZeV (not really, but just for the sake of argument). Of course, you need overtones to create resonance, so this is an unrealistically optimistic number.
We are a factor of 10 quintillion (10^19) away.
The largest Q factors achieved (for systems that in principle have nothing to do with the hypothetical high energy beams above) are ~10^11, so even in the most wildly optimistic case, we'd still be incapable of resonating anything hard enough to create gravitational waves, by a factor of almost a billion. And in any scenario approachin reality, by much, much more.
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We are a factor of 10 quintillion (10^19) away.
It's probably less extreme than that once you factor in the (as yet unknown) distance losses.
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We are a factor of 10 quintillion (10^19) away.
It's probably less extreme than that once you factor in the (as yet unknown) distance losses.
Current theories give a spacetime damping characteristic time greater than the age of the universe.
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Some details on the expected announcement tomorrow.
This year marks the 100th anniversary of the first publication of Albert Einstein’s prediction of the existence of gravitational waves. With interest in this topic piqued by the centennial, researchers from UK universities in Glasgow, Birmingham, and Cardiff will discuss their ongoing efforts to observe and measure cosmic gravitational waves for scientific research at the Science Media Centre in London starting 3pm GMT on Thursday, 11 February.
Simultaneously in the US, the National Science Foundation is gathering scientists from Caltech, MIT, and the LIGO Scientific Collaboration (LSC) at the National Press Club in Washington, DC for a status report on the effort to detect gravitational waves — or ripples in the fabric of spacetime — using the Laser Interferometer Gravitational-wave Observatory (LIGO).
http://astronomynow.com/2016/02/10/scientists-to-provide-update-on-the-search-for-gravitational-waves/
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Announcement 10:30am ET
https://www.youtube.com/watch?v=c7293kAiPZw
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We're live! :)
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We did it!! 8)
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Signal detected 14 September, 2015.
The two black holes are indeed about 30 solar masses. They are about 1.3 billion light years away.
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The two black holes are indeed about 30 solar masses. They are about 1.3 billion light years away.
Well, *were*. It's now just one black hole. :)
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This time the rumours were exactly right, except that the papers are published in PRL and ApJ instead of Nature.
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Kip Thorne cannot wait to ride those waves orbiting one of those mergers :)
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20 ms merger. During that time, the energy output was 50 times the energy released by ALL the stars in the Universe.
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The signal came from the Southern sky, in the rough direction of the Magellanic clouds, the satellite galaxies of the Milky Way. At 1.3 billion light years away, however, it is very far beyond the Magellanic clouds, deep in intergalactic space somewhere.
We have only seen spacetime like the surface on a calm ocean until now, says Thorne. Now, we are seeing a storm!
The ‘storm’, meaning the collision of the black holes, lasted for just 20 milliseconds. In that brief moment, it generated 50 times the power of all the stars in the Universe put together.
It was the equivalent of taking three stars, each the size of the Sun, and annihilating them into pure energy. Wow!
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"Einstein would be beaming today"
France Cordova
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(Cleaned up) signals in the LIGO teams in Louisiana (blue) and Washington (orange):
http://apod.nasa.gov/apod/ap160211.html
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Dr Ed Daw has been researching gravitational waves with LIGO since 1998. He works in the Physics at the University of Sheffield, and sends the following reaction.
Discoveries of this importance in Physics come along about every 30 years. A measure of its significance is that even the source of the wave - two black holes in close orbit, each tens of times heavier than the sun, which then collide violently, has never been observed before, and could not have been observed by any other method. This is just the beginning.
Imagine that your T.V. had only ever received one channel on which the shows were all rather similar to each other. One day a second one appeared which showed completely different programs, like nothing that had ever been broadcast on the old channel. Wouldn’t you want to switch over? By detecting this signal, LIGO has effectively tuned in to a new channel - a completely new way of observing the Universe.
Gravitational waves are so completely different from light, we’re probably only just beginning to understand how they reflect and shape our Universe. For example, a gravitational wave will propagate almost completely unaltered through entire planets, star systems, galaxies....how different is that from the radio waves that your mobile phone picks up - even getting too close to a building can disrupt those signals. Light, or more generally electromagnetic waves are so much more vulnerable to interference than gravitational waves.
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Advanced LIGO is still expected to increase its sensitivity by a factor of 3.
It is expected this year more signals are going to be detected.
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Thorne says that we expect to see more signals from similar sources within the next year. Tweeks and improvements will advance LIGO’s sensitivity by about three times. He promises, “A huge richness of gravitational wave signals in LIGO.”
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Signal-to-noise ratio of 24, according to the paper's abstract (which is the only thing I can access right now since APL is down :O )
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VIRGO (another detector in Italy with similar sensitivity) will join the network this year, improving the collaboration's ability to locate the sources.
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Graviton mass limit has been lowered to 10^-55 kg (!!!!), basically confirming it's massless.
Whether or not it exists, or in general how Quantum Gravity may be formulated, is still up for debate. It has just been confirmed gravitational waves propagate at the speed of light.
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Criticism for NASA.
Rainer Weiss laments NASA’s decision to pull of the space-based gravitational wave observatory LISA, and praises Europe’s determination to ‘go it alone’ with the eLISA mission and LISA Pathfinder. But he hopes for a new collaboration.
@DrStuClark Gravitational Waves sound like Radiohead's Planet Telex intro, from album The Bends. #spooky
https://mobile.twitter.com/ClickConsultLtd/status/697819704732291072?ref_src=twsrc%5Etfw
final question of the webcast press conference is whether LIGO has seen other signals. Gonzalez answers very carefully placing the emphasis back on the signal announced today. As she finishes one of her fellow panellists quips ‘that didn’t even sound rehearsed’.
Hmmm. What should we make of that?
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Imagine that your T.V. had only ever received one channel on which the shows were all rather similar to each other. One day a second one appeared which showed completely different programs, like nothing that had ever been broadcast on the old channel. Wouldn’t you want to switch over? By detecting this signal, LIGO has effectively tuned in to a new channel - a completely new way of observing the Universe.
Gravitational waves are so completely different from light, we’re probably only just beginning to understand how they reflect and shape our Universe. For example, a gravitational wave will propagate almost completely unaltered through entire planets, star systems, galaxies....how different is that from the radio waves that your mobile phone picks up - even getting too close to a building can disrupt those signals. Light, or more generally electromagnetic waves are so much more vulnerable to interference than gravitational waves.
I'm just going to point out that if I wanted to create the perfect SETI signal. This would be the way to do it...
Our technology may have just reached the point where we can begin to hear constant beacons from civilizations though out the universe since the dawn of time that can both detect and generate gravitational waves.
We can take any discussion of SETI over to a SETI thread: http://forum.nasaspaceflight.com/index.php?topic=39571.msg1490597#msg1490597
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final question of the webcast press conference is whether LIGO has seen other signals. Gonzalez answers very carefully placing the emphasis back on the signal announced today. As she finishes one of her fellow panellists quips ‘that didn’t even sound rehearsed’.
Hmmm. What should we make of that?
Rumours have been about (at least) two signals and given that they were almost exactly right about the details of the first detection, I'm pretty sure they're also right about there already being another.
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Some more details from the paper:
- Signal GW150914 was recorded on September 14, 2015 at 09:50:45 UTC, and was automatically selected as interesting 3 minutes later.
- The signal took ~7ms to arrive from Louisiana to Handford, providing the clues about its origin in the Southern sky.
- No other detector was observing at the time (VIRGO was being upgraded, GEO600 wouldn't be sensitive and anyway was not in observational mode).
- Raw signal is actually audible by human ears :) in the 35-150 Hz range, and is 8 cycles long.
- AdvLIGO's sensitivity is only in this band because of "photon shot" noise above (I suppose that means the frequency of the laser on the mirrors) and several other noises below. There are still "peaks" of noise in the window because of calibration channels and power grid noise.
- Pressure in the volumes where the beam passes is <1µPa = 10^-11 atm: practically the "atmospheric pressure" at the ISS altitude (10^-12 atm).
- Injections of fake signals for verification is done through pumping sample signals with the laser.
[more on this post http://forum.nasaspaceflight.com/index.php?topic=39297.msg1490665#msg1490665]
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What will Gravity Astronomy mainly be aimed at uncovering? Presumably, it's going to be biased towards more massive events - big stuff like black holes and galaxies colliding, or neutron stars.
Besides investigating astrophysical phenomena, how could Gravity Astronomy answer questions in fundamental physics?
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What will Gravity Astronomy mainly be aimed at uncovering? Presumably, it's going to be biased towards more massive events - big stuff like black holes and galaxies colliding, or neutron stars.
Besides investigating astrophysical phenomena, how could Gravity Astronomy answer questions in fundamental physics?
It can look through the barrier around the Big Bang.
Imagine that your T.V. had only ever received one channel on which the shows were all rather similar to each other. One day a second one appeared which showed completely different programs, like nothing that had ever been broadcast on the old channel. Wouldn’t you want to switch over? By detecting this signal, LIGO has effectively tuned in to a new channel - a completely new way of observing the Universe.
Gravitational waves are so completely different from light, we’re probably only just beginning to understand how they reflect and shape our Universe. For example, a gravitational wave will propagate almost completely unaltered through entire planets, star systems, galaxies....how different is that from the radio waves that your mobile phone picks up - even getting too close to a building can disrupt those signals. Light, or more generally electromagnetic waves are so much more vulnerable to interference than gravitational waves.
I'm just going to point out that if I wanted to create the perfect SETI signal. This would be the way to do it...
Our technology may have just reached the point where we can begin to hear constant beacons from civilizations though out the universe since the dawn of time that can both detect and generate gravitational waves.
We can take any discussion of SETI over to a SETI thread: http://forum.nasaspaceflight.com/index.php?topic=39571.msg1490597#msg1490597
Time to observe Tabby's star.
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There's a very good article in Quanta:
https://www.quantamagazine.org/20160211-gravitational-waves-discovered-at-long-last/
That article actually confirms that another weaker signal was seen a few weeks later (and now I'm hearing that there's been "several" weaker signals).
Edit:
In this New York Times article Weiss confirms that there were at least four detections in the first run:
http://www.nytimes.com/2016/02/12/science/ligo-gravitational-waves-black-holes-einstein.html?_r=0
Edit 2: fixed link
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LIGO Document P150914-v14
https://dcc.ligo.org/public/0122/P150914/014/LIGO-P150914_Detection_of_GW150914.pdf
https://dcc.ligo.org/LIGO-P150914/public
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Just a note: this discovery is a resounding confirmation of EXISTING physics theories, not new physics. It's new experimental evidence of the existing theory developed by Einstein 100 years ago.
LIGO may go on to discover new physics, but so far this is a resounding (heh) confirmation of our existing theories.
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There's a very good article in Quanta:
https://www.quantamagazine.org/20160211-gravitational-waves-discovered-at-long-last/
That article actually confirms that another weaker signal was seen a few weeks later (and now I'm hearing that there's been "several" weaker signals).
Edit:
In this New York Times article Weiss confirms that there were at least four detections in the first run:
http://www.nytimes.com/2016/02/12/science/ligo-gravitational-waves-black-holes-einstein.html?_r=0
Edit 2: fixed link
Binary Neutron stars? Which was the other phenomena they were looking to detect.
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Binary Neutron stars? Which was the other phenomena they were looking to detect.
Probably supernovae?
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[continues the paper highlights from this post http://forum.nasaspaceflight.com/index.php?topic=39297.msg1490602#msg1490602]
- Spin of the primary black hole is reasonably well understood, while the second's is weakly constrained.
- 3.0±0.5 solar masses (x c^2) were released exclusively in the form of gravitational waves (which ties into the previous discussion about artificial production).
- A Kerr (rotating) black hole is the result from the merger, and the signal is consistent with expectations.
- Graviton mass constraint: m_g < 1.2·10^-22 eV/c^2 (lower than that of the photon, FWIW). Better limits were already achieved with other model dependent bounds, but not with independently-observed ones.
- This is a direct proof of the existence of dozen-solar-mass class black holes, the existence of binaries and capability of merging. This wasn't proven before.
- It is expected there is a constant gravitational wave background of orbiting binaries which permeates the Universe. A large single wave has been detected, but there is a stormy sea underneath.
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- 3.0±0.5 solar masses (x c^2) were released exclusively in the form of gravitational waves (which ties into the previous discussion about artificial production).
What would that even look like up close? What would that intensity of gravitational wave energy do to things?
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Another in-depth, behind-the-scenes article:
http://www.newyorker.com/tech/elements/gravitational-waves-exist-heres-how-scientists-finally-found-them
Seems that many reporters have received the word in advance under embargo.
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Argentinians not only deploy huge flags on Arianespace launches, but also huge foulards in science press conferences ;D
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How do they know the distance between us and the event?
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Will Gravitational Astronomy help us to verify Dark Matter? That's supposed to have mass, but is otherwise undetectable on the EM spectrum.
Would it be possible for Gravitational Astronomy to differentiate between Dark Matter and regular matter - perhaps by cross-referencing with classical forms of astronomical observation?
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- 3.0±0.5 solar masses (x c^2) were released exclusively in the form of gravitational waves (which ties into the previous discussion about artificial production).
What would that even look like up close? What would that intensity of gravitational wave energy do to things?
I have no idea of the subtleties (and I hope to never discover firsthand ;) ) but for sure you'd see a "stretching" of depth/height/width with the observed frequency (35-100 Hz). So stretching also my imagination, I suppose you'd see a kind of flickering of "reality" by which it would be difficult to judge distances. Time distortions would possibly average out in "human" timescales.
I don't think the amplitude of the distortions, even relatively close, would be enough to see something "by eye" though. You'd probably need to be really up close to the binary, in which case there would be plenty of other effects. Since deformed space leaves matter particles relatively unaffected, if the amplitude of the waves was big enough it would possibly rip things apart, maybe even atoms themselves.
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Argentinians not only deploy huge flags on Arianespace launches, but also huge foulards in science press conferences ;D
And they also did better than Spain and Italy at the last World Soccer Cup ;)
Argentina #2
Italy and Spain did not make into the round of 16
Best player: Lionel Messi
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February 11, 2016
Dear MIT graduate,
At about 10:30 this morning in Washington, D.C., MIT, Caltech and the National Science Foundation (NSF) will make a historic announcement in physics: the first direct detection of gravitational waves, a disturbance of space-time that Albert Einstein predicted a century ago.
You can read an overview of the discovery here as well as an interview with MIT Professor Emeritus Rainer Weiss PhD '62, instigator and a leader of the Laser Interferometer Gravitational-Wave Observatory (LIGO) effort.
The beauty and power of basic science
I do not typically write to you to celebrate individual research achievements, no matter how impressive; our community produces important work all the time. But I urge you to reflect on today’s announcement because it demonstrates, on a grand scale, why and how human beings pursue deep scientific questions – and why it matters.
Today's news encompasses at least two compelling stories.
First is the one the science tells: that with his theory of general relativity, Einstein correctly predicted the behavior of gravitational waves, space-time ripples that travel to us from places in the universe where gravity is immensely strong. Those rippling messages are imperceptibly faint; until now, they had defied direct observation. Because LIGO succeeded in detecting these faint messages – from two black holes that crashed together to form a still larger one – we have remarkable evidence that the system behaves exactly as Einstein foretold.
With even the most advanced telescopes that rely on light, we could not have seen this spectacular collision, because we expect black holes to emit no light at all. With LIGO's instrumentation, however, we now have the "ears" to hear it. Equipped with this new sense, the LIGO team encountered and recorded a fundamental truth about nature that no one ever has before. And their explorations with this new tool have only just begun. This is why human beings do science!
The second story is of human achievement. It begins with Einstein: an expansive human consciousness that could form a concept so far beyond the experimental capabilities of his day that inventing the tools to prove its validity took a hundred years.
That story extends to the scientific creativity and perseverance of Rai Weiss and his collaborators. Working for decades at the edge of what was technologically possible, against the odds Rai led a global collaboration to turn a brilliant thought experiment into a triumph of scientific discovery.
Important characters in that narrative include the dozens of outside scientists and NSF administrators who, also over decades, systematically assessed the merits of this ambitious project and determined the grand investment was worth it. The most recent chapter recounts the scrupulous care the LIGO team took in presenting these findings to the physics community. Through the sacred step-by-step process of careful analysis and peer-reviewed publication, they brought us the confidence to share this news – and they opened a frontier of exploration.
At a place like MIT, where so many are engaged in solving real-world problems, we sometimes justify our nation's investment in basic science by its practical byproducts. In this case, that appears nearly irrelevant. Yet immediately useful "results" are here, too: LIGO has been a strenuous training ground for thousands of undergraduates and hundreds of PhDs – two of them now members of our faculty.
What's more, the LIGO team's technological inventiveness and creative appropriation of tools from other fields produced instrumentation of unprecedented precision. As we know so well at MIT, human beings cannot resist the lure of a new tool. LIGO technology will surely be adapted and developed, "paying off" in ways no one can yet predict. It will be fun to see where this goes.
* * *
The discovery we celebrate today embodies the paradox of fundamental science: that it is painstaking, rigorous and slow – and electrifying, revolutionary and catalytic. Without basic science, our best guess never gets any better, and "innovation" is tinkering around the edges. With the advance of basic science, society advances, too.
I am proud and grateful to belong to a community so well equipped to appreciate the beauty and meaning of this achievement – and primed to unlock its opportunities.
In wonder and admiration,
L. Rafael Reif
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How do they know the distance between us and the event?
It is a model-dependent determination (meaning it's based on assumptions), considering the standard cosmological models (ostensibly ΛCDM refined with Planck data).
They measured the redshift (I'm not sure how, since this event was not accompanied by electromagnetic (i.e. light/X-ray/UV...) detection, so it's not obvious to me what reference they used for "redshifted gravitational waves" - maybe Jonathan can help? :) ) and, assuming this standard Universe expansion model, got a distance value that would cause that redshift. This turned out to be between 250 and 570 megaparsecs.
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How do they know the distance between us and the event?
If I understood it correctly, using the observed shape of the waveform one can infer the masses involved and then the theory also gives you the energy (or power?) radiated. Then you go back to the observed amplitude of the oscillations (a.k.a. the local "strain") and, via the inverse square law, can work out the distance. With a certain error bar, of course.
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What would that even look like up close? What would that intensity of gravitational wave energy do to things?
Unless I messed up my back-of-the-envelope calculations, even only 1 AU from the black hole pair the strain would be at parts per billion level.
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How do they know the distance between us and the event?
Isn't that what they need the third detector to come online for to help with this?
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They measured the redshift (I'm not sure how, since this event was not accompanied by electromagnetic (i.e. light/X-ray/UV...) detection, so it's not obvious to me what reference they used for "redshifted gravitational waves" - maybe Jonathan can help? :) ) and, assuming this standard Universe expansion model, got a distance value that would cause that redshift. This turned out to be between 250 and 570 megaparsecs.
Aren't these ultra-violent astrophysical events like Supernova explosions and Black Hole collisions supposed to give off gamma-ray bursts at the same time? Shouldn't they have detected an accompanying gamma-ray burst signal simultaneously in connection with the gravity waves?
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How do they know the distance between us and the event?
If I understood it correctly, using the observed shape of the waveform one can infer the masses involved and then the theory also gives you the energy (or power?) radiated. Then you go back to the observed amplitude of the oscillations (a.k.a. the local "strain") and, via the inverse square law, can work out the distance. With a certain error bar, of course.
Yes, that gives the luminosity distance (for very far away objects there are several "distances"). They just convert the luminosity distance to redshift, because that's what everyone is used to in cosmology/extragalactic astronomy.
Edit: The conversion from luminosity distance to redshift does depend on the cosmological model as eeergo mentioned, but in this case the merger was close enough so that it doesn't have a large effect.
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Isn't that what they need the third detector to come online for to help with this?
They need it to better be able to triangulate the source direction in the sky. The more the better.
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How do they know the distance between us and the event?
Isn't that what they need the third detector to come online for to help with this?
That's for directionality.
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They measured the redshift (I'm not sure how, since this event was not accompanied by electromagnetic (i.e. light/X-ray/UV...) detection, so it's not obvious to me what reference they used for "redshifted gravitational waves" - maybe Jonathan can help? :) ) and, assuming this standard Universe expansion model, got a distance value that would cause that redshift. This turned out to be between 250 and 570 megaparsecs.
Aren't these ultra-violent astrophysical events like Supernova explosions and Black Hole collisions supposed to give off gamma-ray bursts at the same time? Shouldn't they have detected an accompanying gamma-ray burst signal simultaneously in connection with the gravity waves?
Not if they're non-accreting.
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Isn't that what they need the third detector to come online for to help with this?
They need it to better be able to triangulate the source direction in the sky. The more the better.
Judging by the article they should have five soon.
Sir Alex Ferguson
Sir Alex Ferguson – @Furious_Fergie
Just had Wayne Rooney on the phone asking if gravitational waves are like Mexican waves.
I just said aye.
https://mobile.twitter.com/Furious_Fergie/status/697866904019582979
http://xkcd.com/1642/
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What would that even look like up close? What would that intensity of gravitational wave energy do to things?
Unless I messed up my back-of-the-envelope calculations, even only 1 AU from the black hole pair the strain would be at parts per billion level.
I did some back of the envelope calculations myself that could be wrong. The energy this event unleashed was within a couple of orders of magnitude to what a supernova releases. Of course a supernova releases that energy not as gravitational waves but as thermal, electromagnetic, and neutrino radiation. This event released that much energy purely as gravitational waves. A supernova will ruin anyone's day within several dozens of light years. It is odd to think of that much energy being released and not harming anything a light year or further away let alone being inseparable.
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Einstein was right...again! ;D
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Jaunty MIT video.
https://youtu.be/B4XzLDM3Py8
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Actually it's more like 4 orders of magnitude... https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(energy) but I agree with the idea :0
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If my understanding is correct; the energy contained in the waves can be be measured either by the frequency or amplitude of these waves. I am however quite curious as to how LIGO would fare if the waves hit the detectors at an angle of (pi/4) or (5*pi/4). Assuming of course the two detectors are at an angle of (pi/2).
My guess is that they can calculate time dilations since they know the length of the detectors and the speed of light, but wouldn't a third detector increase the ability to filter out noise with better accuracy, even better than having multiple detectors scattered around the world?
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Actually it's more like 4 orders of magnitude... https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(energy) but I agree with the idea :0
There is a neutrino pulse in core collapse supernovas that has about 1046 Joules though some of his gets reabsorbed in the process of the collapse driving the explosion. It is crazy to think about an explosion driven by a particle that rarely interacts with anything.
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Very good New Yorker article not just on the project's history, but also confirms other weaker signals are coming down the line.
http://www.newyorker.com/tech/elements/gravitational-waves-exist-heres-how-scientists-finally-found-them (http://www.newyorker.com/tech/elements/gravitational-waves-exist-heres-how-scientists-finally-found-them)
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
Good point. Maybe more observations will find some deviation from GR, but isn't two colliding black holes as strong of a test as possible?
Congratulations LIGO teams. Another great day for science.
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Nice little video... :)
http://www.scientificamerican.com/video/watch-how-gravitational-waves-dance-across-the-universe/
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
But you're rather forgetting that quantum physics also appears, through increasing experimental evidence, to do lots of things that Einstein really didn't like. I am more confident that this realm will be the one where things will get interesting.
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Gbgs
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Because yesterday's excitement wasn't enough... turns out the Fermi observatory **might** have detected a coincident GRB, which is unexpected for this kind of merger ! Here's the technical paper preprint:
http://gammaray.nsstc.nasa.gov/gbm/publications/preprints/gbm_ligo_preprint.pdf (http://gammaray.nsstc.nasa.gov/gbm/publications/preprints/gbm_ligo_preprint.pdf)
PS: Swift didn't see anything (http://arxiv.org/pdf/1602.03868v1.pdf) but the source's favored regions from LIGO and GLAST were either obscured by the Sun or not in the instrument's FOV.
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And no coincident neutrinos were detected by either Antares (the neutrino detector, not the rocket :) ) or ICECube:
https://dcc.ligo.org/public/0123/P1500271/013/GW150914_neutrino.pdf (https://dcc.ligo.org/public/0123/P1500271/013/GW150914_neutrino.pdf) (paper)
http://icecube.wisc.edu/news/view/398 (http://icecube.wisc.edu/news/view/398)
PS: I just saw the same links posted in the "Space Science" subforum thread. I will keep these here, but if they are merged my posts are redundant since I wrote them several hours after the other guys'. Moderators please delete this and the previous post if you're merging the treads.
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How do they know the distance between us and the event?
If I understood it correctly, using the observed shape of the waveform one can infer the masses involved and then the theory also gives you the energy (or power?) radiated. Then you go back to the observed amplitude of the oscillations (a.k.a. the local "strain") and, via the inverse square law, can work out the distance. With a certain error bar, of course.
Yes, that gives the luminosity distance (for very far away objects there are several "distances"). They just convert the luminosity distance to redshift, because that's what everyone is used to in cosmology/extragalactic astronomy.
Edit: The conversion from luminosity distance to redshift does depend on the cosmological model as eeergo mentioned, but in this case the merger was close enough so that it doesn't have a large effect.
I found some more details on this in the source characterization paper: https://dcc.ligo.org/LIGO-P1500218/public/main
The observed frequency of the signal is redshifted by a factor of (1 + z), where z is the cosmological redshift. There is no intrinsic mass or length scale in vacuum general relativity, and the dimensionless quantity that incorporates frequency is fGm/c^3. Consequently, a redshifting of frequency is indistinguishable from a rescaling of the masses by the same factor. We therefore measure redshifted masses m, which are related to source frame masses by m= (1 + z)·m_source. However, the GW amplitude A_GW, Eq. (2), also scales linearly with the mass and is inversely proportional to the comoving distance in an expanding universe. This implies that A_GW ~ 1/D_L and from the GW signal alone we can directly measure the luminosity distance, but not the redshift.
The observed time delay, and the need for the registered signal at the two sites to be consistent in amplitude and phase, allow us to localize the source to a ring on the sky [34, 35]. Where there is no precession, changing the
viewing angle of the system simply changes the observed waveform by an overall amplitude and phase. Furthermore,
the two polarizations are the same up to overall amplitude and phase. Thus, for systems with minimal precession, the
distance, binary orientation, phase at coalescence and sky location of the source change the overall amplitude and
phase of the source in each detector, but they do not change the signal morphology. Phase and amplitude consistency
allow us to untangle some of the geometry of the source. If the binary is precessing, the GW amplitude and phase have
a complicated dependency on the orientation of the binary, which provides additional information.
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And no coincident neutrinos were detected by either Antares (the neutrino detector, not the rocket :) ) or ICECube:
https://dcc.ligo.org/public/0123/P1500271/013/GW150914_neutrino.pdf (https://dcc.ligo.org/public/0123/P1500271/013/GW150914_neutrino.pdf) (paper)
http://icecube.wisc.edu/news/view/398 (http://icecube.wisc.edu/news/view/398)
PS: I just saw the same links posted in the "Space Science" subforum thread. I will keep these here, but if they are merged my posts are redundant since I wrote them several hours after the other guys'. Moderators please delete this and the previous post if you're merging the treads.
Just shows that GW really can detect things nothing else can.
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Guess the communication satellite days are numbered.
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Guess the communication satellite days are numbered.
Not until someone invents a cheap and reliable way to create detectable gravity waves here on Earth. ;)
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excuse my ignorance but isn't this a confirmation for space time warp in macro scale(instead of micro) for which dr. white was looking for in egale works for warp drive potential
(https://upload.wikimedia.org/wikipedia/commons/8/81/White-Juday_Warp_Field_interferometer.png)
or is it different kind of warp of space time?
is it a little step forward or no relevance at all?
The metric derived by Alcubierre was mathematically motivated by cosmological inflation
so this would by much more solid proof of concept if i understand it correctly
of course it doesn't give an answer if we could induce such a warp artificially
still dark matter /dark energy is just a hypothesis
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LIGO-India has received initial approval!
http://pib.nic.in/newsite/erelease.aspx?relid=136479
(I post this here since the new facility falls more under the "Advanced Physics" rather than Space Science thread)
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
But you're rather forgetting that quantum physics also appears, through increasing experimental evidence, to do lots of things that Einstein really didn't like. I am more confident that this realm will be the one where things will get interesting.
Robotbeat isn't forgetting anything. Everyone knows that quantum physics and relativity/gravity are separate theories that describe different domains and we don't have a compelling theory to combine them. It's irrelevant to his point.
His point is that the LIGO data simply confirms the most widely held theories, so it in of itself simply rules out some of the more esoteric theories and doesn't do much to lead us to new ground.
New experimental results that are a surprise are much more useful to get us to understand things we didn't understand before. The LIGO results aren't a surprise. They're the opposite. We turned over another rock and found exactly what we expected. We'll keep turning over rocks, looking for surprises, and the LIGO hardware might yet help us find surprises under different rocks, but so far, no surprises, and no help toward new physics.
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
But you're rather forgetting that quantum physics also appears, through increasing experimental evidence, to do lots of things that Einstein really didn't like. I am more confident that this realm will be the one where things will get interesting.
Robotbeat isn't forgetting anything. Everyone knows that quantum physics and relativity/gravity are separate theories that describe different domains and we don't have a compelling theory to combine them. It's irrelevant to his point.
His point is that the LIGO data simply confirms the most widely held theories, so it in of itself simply rules out some of the more esoteric theories and doesn't do much to lead us to new ground.
New experimental results that are a surprise are much more useful to get us to understand things we didn't understand before. The LIGO results aren't a surprise. They're the opposite. We turned over another rock and found exactly what we expected. We'll keep turning over rocks, looking for surprises, and the LIGO hardware might yet help us find surprises under different rocks, but so far, no surprises, and no help toward new physics.
There are four natural forces in the Universe. Electromagnetic, Strong Nuclear, Weak Nuclear, and Gravitational.
Humans currently have a fairly decent mastery of the Electromagnetic force, some mastery of the strong and weak nuclear forces, though incomplete (commonplace power generating fusion reactors are still in development), and absolutely no control and limited knowledge of Gravitational.
Throughout our history we were not able to harness any of these without first gaining a more or less complete understanding of what they actually were, and how they worked in nature. To any extent, even limited use such as a nuclear weapon.
My point here was that the only shred of hope mankind will ever have of trying to master Gravity is to gain a total and full understanding of how it works in nature, and working backwards from there. That historically, is how we have gotten this far, up until now. This doesn't mean it is ultimately, or will ultimately be possible to actually gain any control over gravity under the processes by which this Universe operates, all it means is that you 100% can't without first understanding the natural force in its normal domain. THAT to me is why experiments and programs like this one, and this discovery, are so important. The more we know about the natural state the better equipped we become, if there is ever a chance of manipulating it.
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
But you're rather forgetting that quantum physics also appears, through increasing experimental evidence, to do lots of things that Einstein really didn't like. I am more confident that this realm will be the one where things will get interesting.
Robotbeat isn't forgetting anything. Everyone knows that quantum physics and relativity/gravity are separate theories that describe different domains and we don't have a compelling theory to combine them. It's irrelevant to his point.
His point is that the LIGO data simply confirms the most widely held theories, so it in of itself simply rules out some of the more esoteric theories and doesn't do much to lead us to new ground.
New experimental results that are a surprise are much more useful to get us to understand things we didn't understand before. The LIGO results aren't a surprise. They're the opposite. We turned over another rock and found exactly what we expected. We'll keep turning over rocks, looking for surprises, and the LIGO hardware might yet help us find surprises under different rocks, but so far, no surprises, and no help toward new physics.
I have seen a few articles since that have said this discovery opens the door to the possibility of artificial gravity down the line which is the exact opposite to his original claim.
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More information on the very interesting and unexpected Gamma Ray Burst that the Fermi observatory detected "with a false alarm probability of 0.0022" ( http://forum.nasaspaceflight.com/index.php?topic=39297.msg1490954#msg1490954 ), and that *may* be associated with the gravitational wave event GW150914
You could get a gamma-ray burst if the two black holes were enveloped inside a very massive star. “It’s sort of like a pregnant woman with twins in her belly,” Once the black holes merged, the star would collapse and trigger intense beams of gamma rays. For that to happen, the two black holes would have to have formed inside an extremely massive star a few hundred times heftier than the sun. As the star exhausted its nuclear fuel, its core began to collapse. Normally that would form a single black hole. But if the star were rotating very fast, centrifugal force would stretch the collapsing core, shaping it into a dumbbell. Eventually, the dumbbell would snap into two cores, each of which would continue to collapse into its own black hole. "The only way to explain the Fermi signal is to surround the black holes with a lot of dense material"
https://www.newscientist.com/article/2077783-ligos-black-holes-may-have-lived-and-died-inside-a-huge-star/
(https://d1o50x50snmhul.cloudfront.net/wp-content/uploads/2016/02/black-hole-jet-star-1200x800.jpg)
On the other hand, observations made by the European "International Gamma-Ray Astrophysics Laboratory" (INTEGRAL) cannot corroborate the Fermi observatory Gamma Ray Burst http://arxiv.org/abs/1602.04180
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excuse my ignorance but isn't this a confirmation for space time warp in macro scale(instead of micro) for which dr. white was looking for in egale works for warp drive potential
(https://upload.wikimedia.org/wikipedia/commons/8/81/White-Juday_Warp_Field_interferometer.png)
or is it different kind of warp of space time?
is it a little step forward or no relevance at all?
The metric derived by Alcubierre was mathematically motivated by cosmological inflation
so this would by much more solid proof of concept if i understand it correctly
of course it doesn't give an answer if we could induce such a warp artificially
still dark matter /dark energy is just a hypothesis
At most this shows that the idea of manipulating space/time is possible. What it doesnt prove is that it is possible to do so with the energy humanity currently has the ability to apply. It took the merger of two black holes much larger than our sun respectively to generate the detected waves.
edit:
I would also add that the interferance signal pattern could probably be used to rule out false positives in white's experiment
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This is why atom interferometry has to be further developed, because it's the ideal tool to study Gravitational Waves. After all, gravity affects matter much more obviously than it affects light, and so interferometry based on particles of matter is the ideal way to study gravity in detail, and to characterize its behavior in as much detail as possible.
Don't get me wrong - I'm not belittling the engineering marvel that is LIGO, but the Physics community can only move towards newer and better discoveries by developing newer and better instruments.
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Didn't i read an article a while back that suggested an advanced gravity wave detector could be made to fit on a desktop?
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Didn't i read an article a while back that suggested an advanced gravity wave detector could be made to fit on a desktop?
That would probably have to be an atom inferometer, or even a molecular interferometer. C60 fullerenes were among the first to be used to generate interference patterns - but all sorts of other heavy molecules have been used, including even DNA. Here's an interference pattern generated from molecules of phthalocyanine:
https://www.youtube.com/watch?v=NUS6_S1KzC8
So those molecules are even heavier than individual atoms, and so their DeBroglie wavelength is even smaller, thus affording even finer, more precise interferometry. And you don't need a giant sized LIGO apparatus to do it.
It's ironic that while we can't get General Relativity and Quantum theory to connect with each other, we can experimentally apply the knowledge given by quantum theory to detect miniscule changes in spacetime through DeBroglie wavelength.
Meanwhile, the US and India are collaborating to build INDIGO, a Gravitational Wave detector that will extend the LIGO network.
http://arstechnica.com/science/2016/02/india-to-get-a-ligo-detector-that-could-be-online-before-2025/
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i just remembered or think i remembered a detail about what i was talking about. i think it involved Bose Einstein condensate or something like that. this may have been it:
https://www.newscientist.com/article/mg22129603-500-desktop-quantum-cloud-to-hunt-elusive-space-time-waves/
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Given that even planets orbiting stars produce Gravitational Waves, I'm wondering whether Gravitational Astronomy might one day be able to detect them.
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Given that even planets orbiting stars produce Gravitational Waves, I'm wondering whether Gravitational Astronomy might one day be able to detect them.
Many, many powers of ten orders of magnitude fainter than the waves barely detected by LIGO.
For example we are several orders of magnitude closer to detecting the visual electromagnetic images of such planets than their gravitational waves and are making far more rapid progress in that realm.
Conversely, just a few orders of magnitude improvements in gravitational wave detection or even less will bring us deep into uncharted territory.
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
But you're rather forgetting that quantum physics also appears, through increasing experimental evidence, to do lots of things that Einstein really didn't like. I am more confident that this realm will be the one where things will get interesting.
Robotbeat isn't forgetting anything. Everyone knows that quantum physics and relativity/gravity are separate theories that describe different domains and we don't have a compelling theory to combine them. It's irrelevant to his point.
His point is that the LIGO data simply confirms the most widely held theories, so it in of itself simply rules out some of the more esoteric theories and doesn't do much to lead us to new ground.
New experimental results that are a surprise are much more useful to get us to understand things we didn't understand before. The LIGO results aren't a surprise. They're the opposite. We turned over another rock and found exactly what we expected. We'll keep turning over rocks, looking for surprises, and the LIGO hardware might yet help us find surprises under different rocks, but so far, no surprises, and no help toward new physics.
I have seen a few articles since that have said this discovery opens the door to the possibility of artificial gravity down the line which is the exact opposite to his original claim.
You're not trying very hard to convince me.
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Another article
http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time (http://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-time)
This is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
But you're rather forgetting that quantum physics also appears, through increasing experimental evidence, to do lots of things that Einstein really didn't like. I am more confident that this realm will be the one where things will get interesting.
Robotbeat isn't forgetting anything. Everyone knows that quantum physics and relativity/gravity are separate theories that describe different domains and we don't have a compelling theory to combine them. It's irrelevant to his point.
His point is that the LIGO data simply confirms the most widely held theories, so it in of itself simply rules out some of the more esoteric theories and doesn't do much to lead us to new ground.
New experimental results that are a surprise are much more useful to get us to understand things we didn't understand before. The LIGO results aren't a surprise. They're the opposite. We turned over another rock and found exactly what we expected. We'll keep turning over rocks, looking for surprises, and the LIGO hardware might yet help us find surprises under different rocks, but so far, no surprises, and no help toward new physics.
I have seen a few articles since that have said this discovery opens the door to the possibility of artificial gravity down the line which is the exact opposite to his original claim.
You're not trying very hard to convince me.
Tell that to the article writers.
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How gravitational wave detectors survived the Contract With America
Could a basic research project get funded now? Probably not, science advisor says.
Those were bitter political times, Lane said. After all, the Republican Congress would move to impeach Bill Clinton in a few years. But there were still Republicans and Democrats working across party lines on the appropriations process. Work was going on, staff to staff, principal to principal. Today, Lane doesn’t see that kind of cooperation, and it spells major trouble for any new programs a president might seek to fund, like construction of LIGO instruments.
“Never say never,” he said. “We should always hope, always try. I would just say the conditions are very different. Polarization is one thing. The other thing is the private sector some time ago—but even government now—is moving steadily toward short-term deliverables for everything. Expectations are not patient. If the President’s Office of Management and Budget sent this over today, I think you’d have a very hard time getting it through Congress.”
Lane is probably correct. On the very same day that physicists announced their spectacular findings in early February, the US House of Representatives passed legislation sponsored by Texas Republican Lamar Smith, HR3293, that allows the NSF to award grants only for research it can certify as being in the national interest, such as benefiting the economy or improving national defense.
“It really is an irony,” Lane said of the timing. A bitter one.
http://arstechnica.co.uk/science/2016/02/how-gravitational-wave-detectors-survived-the-contract-with-america/
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Lane is probably correct. On the very same day that physicists announced their spectacular findings in early February, the US House of Representatives passed legislation sponsored by Texas Republican Lamar Smith, HR3293, that allows the NSF to award grants only for research it can certify as being in the national interest, such as benefiting the economy or improving national defense.
That's depressing. :(
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...
New experimental results that are a surprise are much more useful to get us to understand things we didn't understand before. The LIGO results aren't a surprise. They're the opposite. We turned over another rock and found exactly what we expected. We'll keep turning over rocks, looking for surprises, and the LIGO hardware might yet help us find surprises under different rocks, but so far, no surprises, and no help toward new physics.
There are four natural forces in the Universe. Electromagnetic, Strong Nuclear, Weak Nuclear, and Gravitational.
Humans currently have a fairly decent mastery of the Electromagnetic force, some mastery of the strong and weak nuclear forces, though incomplete (commonplace power generating fusion reactors are still in development), and absolutely no control and limited knowledge of Gravitational.
Throughout our history we were not able to harness any of these without first gaining a more or less complete understanding of what they actually were, and how they worked in nature. To any extent, even limited use such as a nuclear weapon.
My point here was that the only shred of hope mankind will ever have of trying to master Gravity is to gain a total and full understanding of how it works in nature, and working backwards from there. That historically, is how we have gotten this far, up until now. This doesn't mean it is ultimately, or will ultimately be possible to actually gain any control over gravity under the processes by which this Universe operates, all it means is that you 100% can't without first understanding the natural force in its normal domain. THAT to me is why experiments and programs like this one, and this discovery, are so important. The more we know about the natural state the better equipped we become, if there is ever a chance of manipulating it.
This is an entirely inaccurate depiction of the state of science and history of scientific progress.
First, we understand gravity better than the strong or weak nuclear force. With the recent detection of gravitational waves, the last major prediction of general relativity is confirmed. Dark energy and dark matter could potentially be related to gravity, but the evidence is against that for dark matter, and we really don't know for dark energy. On the other hand, the weak and strong nuclear forces rely on our understanding of particle physics, which generally is incomplete (the standard model has 19 free parameters, not counting the fact that neutrinos shouldn't have mass but do, which adds at least 7 more.)
Using nuclear reactors is a horrible example of claiming that we have somehow understood nuclear forces, since the main challenge in fusion is slamming nuclei together hard enough to overcome the electromagnetic forces. The energy comes from binding with the strong nuclear force, but we don't need to understand the nuclear force to notice the energy released. Also, when we first invented fission bombs, we hadn't even begun to suspect the existence of quarks (first theorized in 1964), let alone the strong and weak nuclear forces.
Again for electromagnetism, the first telegraph was in 1844, but Maxwell published the first version of Maxwell's equations in 1861-1862.
While understanding gravity is useful, we don't necessarily need a full understanding of it to make use of it. (We already use gravitational assists for interplanetary missions, and GPS clocks need corrections for general relativity) Contrary to your claim, I don't know of a case where we didn't start using something before we fully understood it in any branch of science. The biggest openings we have left for truly new physics lie in particle physics, the union of General Relativity and quantum, and the few unexplained phenomena such as dark energy and dark matter.
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Well, if we bring up the weak force, I'd argue we understand the electroweak force better than we understand gravity (indeed, this is the corner of the standard model where we can make 18 digit predictions). But the strong force, while we understand it's basic laws, is definitely very poorly understood even for very simple systems in the sense of solving it to make predictions.
In fact, we understand gravity incredibly well even at our current particle physics energy scales. Gravity is not incompatible with quantum mechanics in that sense, in fact gravity can be treated as a quantum force very effectively. The actual issue is that a direct interpretation of GR as a quantum force leads to ultraviolet divergences, i.e. there exists an energy scale (the Planck scale) far beyond our current accelerators at which the equations explicitly stop being applicable.
I will also note that this is also the case, although in a different way, for quantum electrodynamics which has a Landau pole. This is a sign that it needs to be included into electroweak theory, and in this sense gravity can be said to be understood just as well as electromagnetism was before it was integrated into electroweak theory (at the level of fundamental laws, obviously GR is harder to find solutions for). Electroweak theory also has a landau pole, which means it has to be integrated into a GUT eventually, and so on.
There isn't a lack of theories that could fully describe quantum gravity either, string theory is a very natural and beautiful self-consistent candidate.
The actual issue is not really that we lack theoretical understanding, but rather that our current approximative description of the universe is so ridiculously accurate that we're struggling to build experiments that can actually falsify it and give us pointers on which possible candidate theory is the most accurate extension.
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in the work of Zvi, Dixon and friends for which they won the Sakurai prize N=8 supergravity does not lead to ultraviolet divergences so far as has been calculated which may be as many as five loops so far.
http://www.preposterousuniverse.com/blog/2013/10/03/guest-post-lance-dixon-on-calculating-amplitudes/
Finally, let me mention N=8 supergravity. This theory was invented by Eugene Cremmer and Bernard Julia in the late 1970s, with other important contributions from Bernard deWit and Hermann Nicolai, Joel Scherk and others. When superstring theory had its 1984 revolution, N=8 supergravity was quickly pronounced dead — because string theory was manifestly free of all ultraviolet divergences, and how could any point-particle theory dare to make that claim? However, it never received a proper burial. At that time, it was generally thought that N=8 supergravity would diverge at three loops, but no-one could do a full calculation past one loop. With the unitarity method, we could get to two loops in 1998 (with Zvi, Dave Dunbar, Maxim Perelstein and Joel Rozowsky), to three loops in 2007 (with Zvi, David, John Joseph Carrasco, Henrik Johansson and Radu Roiban), and to four loops in 2009. We still have found no direct sign of a divergence in N=8 supergravity, although the conventional wisdom has retreated from a first divergence at three loops to a first one at seven or eight loops. Zvi, John Joseph, Henrik and Radu are pushing ahead to five loops, which will also give important indications about seven loops. A first divergence at even the seven loop order would be the smallest infinity known to man…
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in the work of Zvi, Dixon and friends for which they won the Sakurai prize N=8 supergravity does not lead to ultraviolet divergences so far as has been calculated which may be as many as five loops so far.
http://www.preposterousuniverse.com/blog/2013/10/03/guest-post-lance-dixon-on-calculating-amplitudes/
Finally, let me mention N=8 supergravity. This theory was invented by Eugene Cremmer and Bernard Julia in the late 1970s, with other important contributions from Bernard deWit and Hermann Nicolai, Joel Scherk and others. When superstring theory had its 1984 revolution, N=8 supergravity was quickly pronounced dead — because string theory was manifestly free of all ultraviolet divergences, and how could any point-particle theory dare to make that claim? However, it never received a proper burial. At that time, it was generally thought that N=8 supergravity would diverge at three loops, but no-one could do a full calculation past one loop. With the unitarity method, we could get to two loops in 1998 (with Zvi, Dave Dunbar, Maxim Perelstein and Joel Rozowsky), to three loops in 2007 (with Zvi, David, John Joseph Carrasco, Henrik Johansson and Radu Roiban), and to four loops in 2009. We still have found no direct sign of a divergence in N=8 supergravity, although the conventional wisdom has retreated from a first divergence at three loops to a first one at seven or eight loops. Zvi, John Joseph, Henrik and Radu are pushing ahead to five loops, which will also give important indications about seven loops. A first divergence at even the seven loop order would be the smallest infinity known to man…
Right, I was considering a mention of SUSY and how it makes everything so much simpler, but left it at a brief mention of string theory, which provably has no UV divergences and requires SUSY for fermions. SUSY is a very natural geometric idea which can in a way be viewed as just a stronger form of conservation of momentum (since the simplest form essentially boils down to introducing a pair of spinor charges whose anticommutator is the momentum, and positing that both charges are conserved, not just their anticommutator).
Sadly we don't yet have experimental evidence for SUSY, and it is not at all obvious that we will obtain it within our lifetimes. However its simplicity and the fact that it makes so many things simpler means that it is imho overwhelmingly likely that we will find it at some point.
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There isn't a lack of theories that could fully describe quantum gravity either, string theory is a very natural and beautiful self-consistent candidate.
The actual issue is not really that we lack theoretical understanding, but rather that our current approximative description of the universe is so ridiculously accurate that we're struggling to build experiments that can actually falsify it and give us pointers on which possible candidate theory is the most accurate extension.
Right, I was considering a mention of SUSY and how it makes everything so much simpler, but left it at a brief mention of string theory, which provably has no UV divergences and requires SUSY for fermions. SUSY is a very natural geometric idea which can in a way be viewed as just a stronger form of conservation of momentum (since the simplest form essentially boils down to introducing a pair of spinor charges whose anticommutator is the momentum, and positing that both charges are conserved, not just their anticommutator).
Sadly we don't yet have experimental evidence for SUSY, and it is not at all obvious that we will obtain it within our lifetimes. However its simplicity and the fact that it makes so many things simpler means that it is imho overwhelmingly likely that we will find it at some point.
A good summation of the state of modern physics.
Unfortunately, no matter how natural and beautifully self-consistent the math, a theory that doesn't make predictions that can be tested is more philosophy than theory. Of course, as you mentioned the problem is our current theories are too accurate. We need to find some flaws in current theory to point the way.
Perhaps continued observations by LIGO will spot a small deviation from theory. If not, we'll have to keep trying.
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PRIZE IN FUNDAMENTAL PHYSICS AWARDED FOR DETECTION OF GRAVITATIONAL WAVES 100 YEARS AFTER ALBERT EINSTEIN PREDICTED THEIR EXISTENCE
Selection Committee of previous Breakthrough Prize winners recognizes contributors to experiment recording waves from two black holes colliding over a billion light years away
$3 million prize shared between LIGO founders Ronald W. P. Drever, Kip S. Thorne and Rainer Weiss and 1012 contributors to the discovery
https://breakthroughprize.org/News/32
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PRIZE IN FUNDAMENTAL PHYSICS AWARDED FOR DETECTION OF GRAVITATIONAL WAVES 100 YEARS AFTER ALBERT EINSTEIN PREDICTED THEIR EXISTENCE
Selection Committee of previous Breakthrough Prize winners recognizes contributors to experiment recording waves from two black holes colliding over a billion light years away
$3 million prize shared between LIGO founders Ronald W. P. Drever, Kip S. Thorne and Rainer Weiss and 1012 contributors to the discovery
https://breakthroughprize.org/News/32
Mazel Tov!!!
I couldn't agree more with the award for this discovery!
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I don't think it works out to much each.
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I don't think it works out to much each.
I meant the award, not the cash. Though I guess they can all take their families to Disney with $3k.
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From the quoted article: (https://breakthroughprize.org/News/32)
The Special Breakthrough Prize can be conferred at any time in recognition of an extraordinary scientific achievement. The $3 million award will be shared between two groups of laureates: the three founders of the Laser Interferometer Gravitational-Wave Observatory (LIGO), who will each equally share $1 million; and 1012 contributors to the experiment, who will each equally share $2 million.
So the main three don't quite get the lions share, so to speak, but they do get the largest individual slices by far. I think this is a good split. It recognizing both the importance and sheer magnitude of the vision of the three founders, but also the huge amount of work and contributions done by the other 1012. Congrats to all involved.
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Just a shame the Nobel prize cannot be subdivided so.
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Colliding Black Holes May Sing Different Gravitational Songs
This simple cosmic song may not be the only music these gravitational-wave emitters are capable of producing. At the American Physical Society April Meeting, held April 16 to 19 in Salt Lake City, Niels Warburton, a postdoctoral fellow at the MIT Kavli Institute, discussed simulations showing what kind of gravitational-wave "song" should be produced by collisions involving black holes that spin faster and are significantly larger than those that have been detected by LIGO.
The two black holes that LIGO observed merged together and produced a "chirp" — that is, the frequency of the signal rose steadily, then was cut off abruptly when the two objects combined. But Warburton and his colleagues showed that fast-spinning black holes create a signal that reaches a peak frequency, and then starts to lower in frequency, before fading out.
"Instead of chirping, you get this kind of singing sound from the black hole," Warburton said. "It'll rise, it won't get cut off, it'll sing, and then it's quiet at the end."
"[It's] a completely different gravitational-wave signature … than what was detected [by LIGO]," he said. If a gravitational-wave detector picked up a signal that looked like the one the researchers' model describes, "you would know you were looking at a gargantuan system, something that is rotating extremely close to the maximum," he said.
This runs contrary to what scientists expected from a merger involving a very fast-spinning black hole, according to Jolyon Bloomfield, a lecturer at MIT, who presented research at the same press conference.
"It was certainly very unexpected to see something that didn't chirp," Bloomfield said, when asked during the press conference what he thought of the results. "Every template that we've seen so far … has had this beautiful, chirping feature, and we just assumed that [if we] make [the spin of the black hole] bigger … it chirps bigger. But this is quite interesting work that says no, the chirp actually goes away. Something else is happening here."
http://www.space.com/32723-colliding-black-holes-sing-different-songs.html
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Was gravitational wave signal from a gravastar, not black holes?
“Our signal is consistent with both the formation of a black hole and a horizonless object – we just can’t tell,” says B. S. Sathyaprakash of Cardiff University, UK, who is part of the LIGO team. But if we can detect larger black holes merging, or a pair that is closer to us, it should settle the matter, he says. “That’s when we can conclusively say if the late-time signal is consistent with the merged object being a black hole or some other exotic object.”
Ultimately, the black hole explanation is likely to win out, but it is worth double-checking, says Pani. “As scientists, we try to play the devil’s advocate and not believe in paradigms without observational evidence.”
https://www.newscientist.com/article/mg23030724-100-was-gravitational-wave-signal-from-a-gravastar-not-black-holes/
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LIGO and VIRGO announced a second observation of a gravitational-wave signal produced by the coalescence of two stellar-mass black holes.
This event was much smaller than the first detection: The first event involved black holes that were 29 and 36 times as massive as the sun, while this new collision, which took place 1.4 billion years ago, brought together black holes of 8 and 14 solar masses. While the first detection “jumped out” from the data, the researchers say, the second one was only noticed thanks to the analysis of specially developed software.
The detection of smaller black holes makes some LIGO researchers hope that they’ll soon detect the interactions of ultra-dense neutron stars, which are even less massive and very poorly understood.
The signal, GW151226, was observed by the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) on December 26, 2015 at 03:38:53 UTC. The signal was initially identified within 70 s by an online matched-filter search targeting binary coalescences. All uncertainties define a 90% credible interval. This second gravitational-wave observation provides improved constraints on stellar populations and on deviations from general relativity.
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.241103
https://www.washingtonpost.com/news/speaking-of-science/wp/2016/06/15/ligo-scientists-announce-their-second-detection-of-gravitational-waves/
https://www.facebook.com/apsphysics/videos/10154335027472952/
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These lower mass BHs & collision/mergers should be more common. Hopefully lots of detections to come when they start up again this fall with increased sensitivity.
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Is the vibration after the merging meaningful?
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sensitivity for these sorts of instrument may be about to take another quantum leap:
http://nextbigfuture.com/2016/06/russian-physicists-create-high.html
June 23, 2016
Russian physicists create a high-precision 'quantum ruler'
Physicists from the Russian Quantum Center (RQC), MIPT, the Lebedev Physical Institute, and L'Institut d'Optique (Palaiseau, France) have devised a method for creating a special quantum entangled state. This state enables producing a high-precision ruler capable of measuring large distances to an accuracy of billionths of a metre. The results of the study have been published in Nature Communications.
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Event Horizon ringing damped by unstable space-time
Probing the event horizon of a black hole is not so easy.
Now that gravitational waves have been detected, theoreticians have been furiously speculating about what we might learn from our gravitational wave observatories. Now that we have a couple of observed black hole collisions under our belt, it is time to consider what we might study. There's some speculation that, depending on the sort of physics at play, the event horizon of a black hole might be studied through gravitational waves.
For this to work, the gravitational wave signal has to change depending on what type of black holes are merging. A recent paper in Physical Review Letters indicates that, unfortunately, reality will probably not cooperate.
http://arstechnica.com/science/2016/06/event-horizon-ringing-damped-by-unstable-space-time/
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People ask if this could revolutionise space flight. What if it discovered something like this in our vicinity? Something we hadn't been able to see before precisely because it wasn't shooting vast amounts of dangerous radiation our way?
http://www.centauri-dreams.org/?p=25605
The "Dyson Slingshot"
Two neutron stars, each with a diameter of 20 kilometers and a mass of one solar mass — and a combined orbital period of 0.005 seconds — would provide a departure velocity of 0.27 c
This was taken from my "dark matter planet/oberth effect" thread, but this example requires neither dark matter or oberth effect, is just more powerful and less hypothetical, and someone has apparently already done the math. It might be more interesting to discuss in terms of detection. Could we have missed an object like this and could gravity waves give us a way to detect it?
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Criticism for NASA.
Rainer Weiss laments NASA’s decision to pull of the space-based gravitational wave observatory LISA, and praises Europe’s determination to ‘go it alone’ with the eLISA mission and LISA Pathfinder. But he hopes for a new collaboration.
@DrStuClark Gravitational Waves sound like Radiohead's Planet Telex intro, from album The Bends. #spooky
https://mobile.twitter.com/ClickConsultLtd/status/697819704732291072?ref_src=twsrc%5Etfw
final question of the webcast press conference is whether LIGO has seen other signals. Gonzalez answers very carefully placing the emphasis back on the signal announced today. As she finishes one of her fellow panellists quips ‘that didn’t even sound rehearsed’.
Hmmm. What should we make of that?
http://english.nssc.cas.cn/ns/headline/201605/t20160518_163197.html
The 12th China-ESA Space Science Bilateral Meeting Opens in Shanghai
In addition, both parties introduced the respective gravitational wave detection plans and agreed that there is a cooperation possibility in this area.
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Scientists from Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory are using powerful X-rays to study high-performance mirror coatings that could help make the LIGO gravitational wave observatory 10 times more sensitive to cosmic events that ripple space-time.
http://media.slac.stanford.edu/news/2016/07-19-stanford-slac-xray-studies-help-make-ligo-gravitational-wave-detector-10-times-more-sensitive/
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chrislintott – Verified account @chrislintott
The region of the sky within which an observed gravitational wave signal might lie is called an ‘error banana’
https://mobile.twitter.com/chrislintott/status/760143862132273153
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Nobel not just snubbing LIGO today but still snubbing Vera Rubin.
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Nobel not just snubbing LIGO today but still snubbing Vera Rubin.
Nomination deadline is Feb 1, announcement was Feb 11th. Let's wait and see what 2017 brings. Rubin probably won't be likely to win until dark matter is better characterized.
In the meantime, congratulations are due to David Thouless, Duncan Haldane and Michael Kosterlitz for their well-deserved awards.
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LIGO Black Hole Echoes Hint at General Relativity Breakdown
Gravitational wave data show tentative signs of firewalls or other exotic physics
It was hailed as an elegant confirmation of Einstein’s general theory of relativity — but ironically the discovery of gravitational waves earlier this year could herald the first evidence that the theory breaks down at the edge of black holes. Physicists have analysed the publicly released data from the Laser Interferometer Gravitational-Wave Observatory (LIGO), and claim to have found “echoes” of the waves that seem to contradict general relativity’s predictions1.
The echoes could yet disappear with more data. If they persist, the finding would be extraordinary. Physicists have predicted that Einstein’s hugely successful theory could break down in extreme scenarios, such as at the centre of black holes. The echoes would indicate the even more dramatic possibility that relativity fails at the black hole’s edge, far from its core.
If the echoes go away, then general relativity will have withstood a test of its power — previously, it wasn’t clear that physicists would be able to test their non-standard predictions.
“The LIGO detections, and the prospect of many more, offer an exciting opportunity to investigate a new physical regime,” says Steve Giddings, a black-hole researcher at the University of California, Santa Barbara. The LIGO team says that it is aware of the prediction and searching its data for echoes.
https://www.scientificamerican.com/article/ligo-black-hole-echoes-hint-at-general-relativity-breakdown1/
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LIGO Black Hole Echoes Hint at General Relativity Breakdown
Gravitational wave data show tentative signs of firewalls or other exotic physics
It was hailed as an elegant confirmation of Einstein’s general theory of relativity — but ironically the discovery of gravitational waves earlier this year could herald the first evidence that the theory breaks down at the edge of black holes. Physicists have analysed the publicly released data from the Laser Interferometer Gravitational-Wave Observatory (LIGO), and claim to have found “echoes” of the waves that seem to contradict general relativity’s predictions1.
The echoes could yet disappear with more data. If they persist, the finding would be extraordinary. Physicists have predicted that Einstein’s hugely successful theory could break down in extreme scenarios, such as at the centre of black holes. The echoes would indicate the even more dramatic possibility that relativity fails at the black hole’s edge, far from its core.
If the echoes go away, then general relativity will have withstood a test of its power — previously, it wasn’t clear that physicists would be able to test their non-standard predictions.
“The LIGO detections, and the prospect of many more, offer an exciting opportunity to investigate a new physical regime,” says Steve Giddings, a black-hole researcher at the University of California, Santa Barbara. The LIGO team says that it is aware of the prediction and searching its data for echoes.
https://www.scientificamerican.com/article/ligo-black-hole-echoes-hint-at-general-relativity-breakdown1/
Just a general note: this preprint has been criticised quite heavily (see for example https://telescoper.wordpress.com/2016/12/12/ligo-echoes-p-values-and-the-false-discovery-rate/). In particular, whether there's anything that could be called even a hint. The general idea is interesting, but a lot more data is needed (and luckily, should be available in not too distant future).
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Layman here. I know that early 2000s LIGO was greatly upgraded and I thought I'd read that the new enhanced LIGO was supposed to detect grav wave events at 10s to a hundred or more per year. If so...
1) Is LIGO still not operating at its touted SNR?
2) Has the sigma criteria for reporting events been raised?
3) Is it just a long time from detection, to analysis, and then publication?
4) Is there something unexpected, not understood, going on?
If not so, then point is moot.
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Layman here. I know that early 2000s LIGO was greatly upgraded and I thought I'd read that the new enhanced LIGO was supposed to detect grav wave events at 10s to a hundred or more per year. If so...
1) Is LIGO still not operating at its touted SNR?
2) Has the sigma criteria for reporting events been raised?
3) Is it just a long time from detection, to analysis, and then publication?
4) Is there something unexpected, not understood, going on?
If not so, then point is moot.
LIGO is under constant upgrade. For example its most recent run saw it running in an upgraded configuration from the one that made the first detections last year.
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Layman here. I know that early 2000s LIGO was greatly upgraded and I thought I'd read that the new enhanced LIGO was supposed to detect grav wave events at 10s to a hundred or more per year. If so...
1) Is LIGO still not operating at its touted SNR?
2) Has the sigma criteria for reporting events been raised?
3) Is it just a long time from detection, to analysis, and then publication?
4) Is there something unexpected, not understood, going on?
If not so, then point is moot.
The year-end issue of SN says, on p. 18, that the sensitivity upgrade which is expected to allow almost-daily detections, will be complete "perhaps by 2019".
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Layman here. I know that early 2000s LIGO was greatly upgraded and I thought I'd read that the new enhanced LIGO was supposed to detect grav wave events at 10s to a hundred or more per year. If so...
1) Is LIGO still not operating at its touted SNR?
2) Has the sigma criteria for reporting events been raised?
3) Is it just a long time from detection, to analysis, and then publication?
4) Is there something unexpected, not understood, going on?
If not so, then point is moot.
The year-end issue of SN says, on p. 18, that the sensitivity upgrade which is expected to allow almost-daily detections, will be complete "perhaps by 2019".
SN?
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Layman here. I know that early 2000s LIGO was greatly upgraded and I thought I'd read that the new enhanced LIGO was supposed to detect grav wave events at 10s to a hundred or more per year. If so...
1) Is LIGO still not operating at its touted SNR?
2) Has the sigma criteria for reporting events been raised?
3) Is it just a long time from detection, to analysis, and then publication?
4) Is there something unexpected, not understood, going on?
If not so, then point is moot.
The year-end issue of SN says, on p. 18, that the sensitivity upgrade which is expected to allow almost-daily detections, will be complete "perhaps by 2019".
SN?
Science News magazine.
https://www.sciencenews.org/
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Layman here. I know that early 2000s LIGO was greatly upgraded and I thought I'd read that the new enhanced LIGO was supposed to detect grav wave events at 10s to a hundred or more per year. If so...
1) Is LIGO still not operating at its touted SNR?
2) Has the sigma criteria for reporting events been raised?
3) Is it just a long time from detection, to analysis, and then publication?
4) Is there something unexpected, not understood, going on?
If not so, then point is moot.
The year-end issue of SN says, on p. 18, that the sensitivity upgrade which is expected to allow almost-daily detections, will be complete "perhaps by 2019".
This is explained in the official LIGO website: http://www.ligo.org/science/Publication-ObservingScenario/index.php (http://www.ligo.org/science/Publication-ObservingScenario/index.php)
The Advanced LIGO detectors officially began their first observing run, which is called O1, on 18 September 2015. The detectors are not yet at final sensitivity, but are roughly four times more sensitive than the pre-Advanced LIGO best. It is a long and complicated process to improve our gravitational-wave detectors. Rather than wait until they are at their final sensitivity before beginning observations, we plan to carry out several observing runs along the way. This is done because we are excited to start the search for gravitational waves as soon as possible; because we want to gain experience operating our detectors in stable, undisturbed observing state, and because we want to test out our data-analysis methods. Figuring out how to extract all the information we can from our data (while checking carefully for any gravitational waves that might be present) is just as tricky as getting the instruments working in the first place. O1 is planned to last for four months, closing mid-January 2016. Then work will start on upgrading the instruments for our second observing run, which is called O2; those upgrades will be informed by what we have learned about the instruments during O1. O2 will start in 2016 and last around six months . Hopefully, around this time Advanced LIGO will be joined by Advanced Virgo. Following O2 we will upgrade again, before observing for nine months in our third observing run, which is called (you can probably guess) O3. Each upgrade should improve the sensitivities of our detectors and increase our chances of detecting gravitational waves. Eventually, if all goes according to plan, both Advanced LIGO and Advanced Virgo will be running at full sensitivity by 2021.
More details about what the short-term upgrades involve: https://www.advancedligo.mit.edu/aug_2016_news.html (https://www.advancedligo.mit.edu/aug_2016_news.html)
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Layman here. I know that early 2000s LIGO was greatly upgraded and I thought I'd read that the new enhanced LIGO was supposed to detect grav wave events at 10s to a hundred or more per year. If so...
1) Is LIGO still not operating at its touted SNR?
2) Has the sigma criteria for reporting events been raised?
3) Is it just a long time from detection, to analysis, and then publication?
4) Is there something unexpected, not understood, going on?
If not so, then point is moot.
The year-end issue of SN says, on p. 18, that the sensitivity upgrade which is expected to allow almost-daily detections, will be complete "perhaps by 2019".
SN?
Science News magazine.
https://www.sciencenews.org/
Thank you. SN could have just as easily referred to Spaceflight Now for example.
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Layman here. I know that early 2000s LIGO was greatly upgraded and I thought I'd read that the new enhanced LIGO was supposed to detect grav wave events at 10s to a hundred or more per year. If so...
1) Is LIGO still not operating at its touted SNR?
2) Has the sigma criteria for reporting events been raised?
3) Is it just a long time from detection, to analysis, and then publication?
4) Is there something unexpected, not understood, going on?
If not so, then point is moot.
The year-end issue of SN says, on p. 18, that the sensitivity upgrade which is expected to allow almost-daily detections, will be complete "perhaps by 2019".
SN?
Science News magazine.
https://www.sciencenews.org/
Thank you. SN could have just as easily referred to Spaceflight Now for example.
The magazine's name is SN, in characters about 1-1/2" tall on the cover. Below that, in characters perhaps 3/16" tall, is "SCIENCE NEWS MAGAZINE", a description of the magazine's nature, and its former title (or close to it; it may have just been Science News). Before that, IIRC, it was Science Newsletter. SN is its actual, correct, name, not an abbreviation by me.
But this is off topic. Let's move on.
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The detection of gravitational waves is being named the breakthrough of the year for 2016:
https://thespacereporter.com/2016/12/detection-gravitational-waves-named-breakthrough-year/
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Looking at one of the speakers here I wonder if we might get another detection announcement.
http://europeanastrofest.com/conference/
Astronomy Now – @AstronomyNow
@skyinspector More details will be posted tomorrow. Just confirming times with speakers. Show is 2nd weekend Feb, week later than usual.
As looking at the above it will be the first anniversary of the initial announcement.
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Jeff Foust – @jeff_foust
Lisa Barsotti, MIT: detected 2 candidate events since second Advanced LIGO run started late November; analysis in progress. #apsapril
https://mobile.twitter.com/jeff_foust/status/825789056554373121
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Gravitational wave detector prepares to peer into bizarre stars
LIGO’s second run began on 30 November 2016. On 28 January, the team announced that it had seen two event candidates so far, which matches the expected rate of about one per month.
If they turn out to be real events, they will probably be more gravitational waves from merging black holes. Building up our bank of data on black holes is useful for comparisons and will help test questions like how stars evolve and whether Einstein’s theory of general relativity holds true.
“The only way we’re ever going to answer them is with more detections of the same type,” says Larson.
https://www.newscientist.com/article/2120507-gravitational-wave-detector-prepares-to-peer-into-bizarre-stars/
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A new article on Virgo in Nature News: http://www.nature.com/news/ligo-s-underdog-cousin-ready-to-enhance-gravitational-wave-hunt-1.21437
Inauguration will be on 20th of February, but it will take 'several more weeks' before science data is taken. Still, that should mean that Virgo and aLIGO's second science run should overlap for a couple of months. With some luck there could be a detection by all three detectors, which should allow much better constraints on location of the event.
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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.
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aVIRGO has been inaugurated today:
http://home.infn.it/it/comunicazione/comunicati-stampa/2193-taglio-del-nastro-per-advanced-virgo (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 (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]
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Now this is quite unfortunate.
Gravitational wave pioneer Ronald Drever dies (http://www.bbc.co.uk/news/science-environment-39212305)
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.
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Now this is quite unfortunate.
Gravitational wave pioneer Ronald Drever dies (http://www.bbc.co.uk/news/science-environment-39212305)
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:
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.
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Physicists use Einstein’s ‘spooky’ entanglement to invent super-sensitive gravitational wave detector
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
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Third detection made.
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
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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
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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
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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
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.
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I'd second that: it should be moved to, my guess would be to Space Science
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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.
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ESA has selected the full LISA mission for launch in 2026.
http://www.bbc.co.uk/news/science-environment-40346410 (http://www.bbc.co.uk/news/science-environment-40346410)
--- Tony
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ESA has selected the full LISA mission for launch in 2026.
http://www.bbc.co.uk/news/science-environment-40346410 (http://www.bbc.co.uk/news/science-environment-40346410)
--- Tony
According to the ESA's press release the launch is expected in 2034.
http://www.esa.int/Our_Activities/Space_Science/Gravitational_wave_mission_selected_planet-hunting_mission_moves_forward
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Oops ... somehow I got it confused with the Plato date
--- Tony
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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/
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Strange Noise in Gravitational-Wave Data Sparks Debate
https://www.quantamagazine.org/strange-noise-in-gravitational-wave-data-sparks-debate-20170630/
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LIGO, Leaks and NGC 4993
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:
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/
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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.
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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.
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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.
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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.
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LIGO themselves have now posted an update.
A VERY EXCITING LIGO-VIRGO OBSERVING RUN IS DRAWING TO A CLOSE AUGUST 25
25 August 2017 -- The Virgo and LIGO Scientific Collaborations have been observing since November 30, 2016 in the second Advanced Detector Observing Run ‘O2’ , searching for gravitational-wave signals, first with the two LIGO detectors, then with both LIGO and Virgo instruments operating together since August 1, 2017. Some promising gravitational-wave candidates have been identified in data from both LIGO and Virgo during our preliminary analysis, and we have shared what we currently know with astronomical observing partners. We are working hard to assure that the candidates are valid gravitational-wave events, and it will require time to establish the level of confidence needed to bring any results to the scientific community and the greater public. We will let you know as soon we have information ready to share.
http://www.ligo.org/news.php
This article from Nature is worth a look as well for the evidence trail so to speak.
The short GRB that telescopes might have observed would be significant, too — not least because if it is associated with gravitational waves, it would validate decades of astrophysical theorizing that GRBs are associated with neutron-star collisions. “Only gravitational waves could give us the smoking gun,” says Eleonora Troja, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Still, a short GRB would be an important discovery on its own. Most such events are seen in the distant Universe, billions of parsecs away. NGC 4993, at 40 million parsecs away, would probably be the closest short GRB ever detected, says astrophysicist Derek Fox of Pennsylvania State University in University Park.
Details of the gravitational waves at the time of the collision and in the following instances could also reveal information about the structure of neutron stars — which is largely unknown — and whether their merger resulted again in a neutron star or in the formation of a new black hole.
http://www.nature.com/news/rumours-swell-over-new-kind-of-gravitational-wave-sighting-1.22482
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Direct link to the streaming feed for the combined LIGO/VIRGO "announcement on the science of gravitational waves" coming up in 20 mins.
http://85.94.219.252/MIUR/streaming_out.php (http://85.94.219.252/MIUR/streaming_out.php)
or Youtube:
watch?v=xR6d8V5oh0o
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Fourth BH binary merger, first significant detection for VIRGO: GW170814 .
Now to see how close they got with position reconstruction.
https://www.ligo.caltech.edu/news/ligo20170927 (https://www.ligo.caltech.edu/news/ligo20170927)
Webcast is up.
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Live from Turin, Italy (framed in the G7 meeting being held there today and tomorrow)
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Highly significant uncertainty reduction in the position reconstruction of the event (see figure)!
Polarization of these gravitational waves has been probed for the first time thanks to this.
Paper: https://tds.virgo-gw.eu/GW170814
Supplemental info: http://www.virgo-gw.eu/docs/GW170814/
Interactive skymap for all detected events so far: http://www.virgo-gw.eu/skymap.html
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What about the merging neutron stars?
Anyone asked them about that and also any update on when Japan’s detector comes online?
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Some numbers:
* 30.5(+5.7/-3.0) and 25.3(+2.8/-4.2) solar masses for the merged black holes, radiated energy in form of gravitational waves around ~2.7 solar masses. This makes GW170814 the second-largest merger, after the very first one GW150914.
* S/N ratio of 18.
* Demonstrated AdVIRGO improves the false alarm probability by an order of magnitude.
* Polarization (6 possible ones) is consistent with GR so far, favoring pure tensor (spin-2) polarization of the waves.
* ~60 deg^2 area of 90% confidence-level localization (12 times better than with just LIGO), with a luminosity distance of 540(+130/-210) Mpc.
* No optical, IR, X-ray, gamma or neutrino counterparts discovered.
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So this one was a lot like GW150914, the first LIGO detection. Just a bit less massive (though still large for stellar-mass black holes) and a bit farther away.
Of course, this is not what people were hoping to hear about ;). Instead of garden-variety black holes, we wanted to know about the rumoured neutron star merger with EM counterpart.
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Lots of shiny talk on "multimessenger astronomy", the new buzzword in Astrophysics right now :)
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What about the merging neutron stars?
Anyone asked them about that and also any update on when Japan’s detector comes online?
No questions asked during coverage :o No NS merger news.
Latest update I have about KAGRA is their presentation by Yuta Michimura in TAUP2017 a couple of months ago (relevant slides below)
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So this one was a lot like GW150914, the first LIGO detection. Just a bit less massive (though still large for stellar-mass black holes) and a bit farther away.
Of course, this is not what people were hoping to hear about ;). Instead of garden-variety black holes, we wanted to know about the rumoured neutron star merger with EM counterpart.
Makes me wonder about the formation mechanisms for such systems ... masses rather large for normal stellar black holes, especially in binaries.
--- Tony
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And for a concise read here’s the Nature news article on this detection.
https://youtu.be/PsahiVGiiR4
http://www.nature.com/news/european-detector-spots-its-first-gravitational-wave-1.22690
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Well, this isn't the "optical transient neutron star merger" that had been rumored, but that localization was pretty darned impressive nonetheless. Note: Nobel Prize in Physics will be awarded next Tuesday. I'm really hoping the LIGO team gets at least a share. This independent confirmation, though the Virgo data were of lower S/N, ought to put a damper on the notion of spurious coincidences.
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I can't image any situation where the LIGO leads don't win the Nobel. My random guess would be Kip Thorne for 1/2, and two other very deserving people for the two 1/4 splits. Maybe Barish and Weiss. Lots of good people it could go to.
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Nobel prize might wait another few years. The prize committee isn't very quick and kind of has a line-up. Physics is so much these days. Edwin Hubble, the discoverer of both intergalactic space and the expansion of the universe, perhaps the most important astronomer of the 20th century, never got the Nobel prize. It was motivated by there not being any Nobel prize awarded for astronomy, and that astronomy is not physics (but just a branch of mathematics about the geometry of the dots in the sky). Well, that has changed. I'll hear Kip Thorne live in Stockholm!
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I can't image any situation where the LIGO leads don't win the Nobel. My random guess would be Kip Thorne for 1/2, and two other very deserving people for the two 1/4 splits. Maybe Barish and Weiss. Lots of good people it could go to.
Drever unfortunately made the committee's job easier by dying during the year. Now the committee can pick their maximum of 3 folks without lots of second guessing which of the big four should be left out.
The persistence needed to make this real is amazing. Like Voyager, the basic idea was around in the early 1970s. But while Voyager was built, launched, toured 4 planets, and is now in its senior citizen stage, LIGO was just being optimized, constructed, and commissioned. It's just starting to return data as Voyager, a long lived project by itself, has gone through its entire life cycle.
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Nobel prize might wait another few years. The prize committee isn't very quick and kind of has a line-up.
Normally I'd agree completely, but I see this as more analogous to the Higgs boson detection and awards. Like Higgs, detection of gravitational waves has been long sought and eagerly anticipated for decades. Couple that with this:
Drever unfortunately made the committee's job easier by dying during the year.
and I'd bet that the noble committee won't risk making these guys wait any longer than necessary. I'd have even given pretty good odds of those guys winning last year had the detection been announced before the nomination deadline. Lou's right about how herculean this task has been. IMO, LIGO will jump to the front of the award line.
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In a completely unsurprising award the LIGO team have won the Nobel prize for physics. Well done to all concerned.
https://www.theguardian.com/science/2017/oct/03/nobel-prize-physics-discovery-gravitational-waves-ligo (https://www.theguardian.com/science/2017/oct/03/nobel-prize-physics-discovery-gravitational-waves-ligo)
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In a completely unsurprising award they have won the Nobel prize for physics.
https://www.theguardian.com/science/2017/oct/03/nobel-prize-physics-discovery-gravitational-waves-ligo
Woooo! Agreed, I'd have been more surprised if they did NOT get it, but the award was richly deserved nonetheless, and I couldn't be more pleased. Thorne literally wrote the book on gravity (Misner, Thorne & Wheeler), and the successful concept behind LIGO, for which the team received the prize, was a stroke of genius. The direct detection of gravitational waves has enabled an entirely new branch of observational astrophysics, as did the detection of neutrinos from the Sun and SN 1987A (which were awarded Nobels as well).
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Thorne literally wrote the book on gravity (Misner, Thorne & Wheeler)
Yes he did; and now my copy is even more valuable to me!
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In a completely unsurprising award they have won the Nobel prize for physics.
https://www.theguardian.com/science/2017/oct/03/nobel-prize-physics-discovery-gravitational-waves-ligo
Woooo! Agreed, I'd have been more surprised if they did NOT get it, but the award was richly deserved nonetheless, and I couldn't be more pleased. Thorne literally wrote the book on gravity (Misner, Thorne & Wheeler), and the successful concept behind LIGO, for which the team received the prize, was a stroke of genius. The direct detection of gravitational waves has enabled an entirely new branch of observational astrophysics, as did the detection of neutrinos from the Sun and SN 1987A (which were awarded Nobels as well).
All too late unfortunately for Ronald Drever.
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The only maybe slightly surprising thing about this Nobel was sharing it 1/2 to Weiss, 1/4 to both Thorne and Barish.
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Comprehensive article from Nature on the award.
http://www.nature.com/news/gravitational-wave-detection-wins-physics-nobel-1.22737
https://youtu.be/aKPO4nE3E1s
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Weiss very strongly hinted in his press conference talk after the Nobel that a neutron star merger has been observed and will be announced on October the 16th (around 8:40 and 16:40, though the rest of it is good, too).
https://www.youtube.com/watch?v=eJMOzmwYT8A
edit: They're not really trying to hide it anymore: https://tigers.phys.lsu.edu/wordpress/program-schedule
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They must have detected/seen something to be that blatant.
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Suspect this means there is an optical counterpart:
Media #Advisory: 16.10, 16:00 CEST, #press conference @ESO HQ announcing unprecedented discovery
https://twitter.com/ESO/status/918114198613381120
Unless the timing is coincidental.
--- Tony
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Suspect this means there is an optical counterpart:
Media #Advisory: 16.10, 16:00 CEST, #press conference @ESO HQ announcing unprecedented discovery
https://twitter.com/ESO/status/918114198613381120
Unless the timing is coincidental.
--- Tony
I was assuming that this announcement will be about the rumored neutron star merger with optical counterpart from a while ago.
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Do two neutron stars just make another neutron star or do they collapse further into a black hole is the question I would hope to see answered by this.
Here’s the actual press release.
https://www.eso.org/public/announcements/ann17071/
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Do two neutron stars just make another neutron star or do they collapse further into a black hole is the question I would hope to see answered by this.
Depends on combined mass.
I'm more interested in what it will tell us about dense matter and heavy-element nucleosynthesis.
--- Tony
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Do two neutron stars just make another neutron star or do they collapse further into a black hole is the question I would hope to see answered by this.
Depends on combined mass.
I'm more interested in what it will tell us about dense matter and heavy-element nucleosynthesis.
--- Tony
What is the mass threshold to collapse into a black hole?
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2 - 3 Msol ... there are a lot of uncertainties in the properties of neutron degenerate matter, but it is limited at the lower end by the mass of known pulsars.
So knowing if the collapse forms a black hole or not is actually the same as my desire to know more about the properties of dense matter :-)
--- Tony
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The collapse threshold is a function not just of mass, but of known unknowns, like the neutron star equation of state (think ideal gas law) as Tony said, and I think even the angular momentum (fights against collapse). I seem to remember that if the neutrons break apart into quarks, there might be an intermediate state between neutron star and black hole (neutron crust, quark interior); but I don't know there've been many constraints on the physics. That's all far beyond this simple observer, for sure.
I'm hoping the rumor of a neutron star merger with optical counterpart is real. I wonder what the visible light curve of a NS merger would look like, especially if it could look like something else (have we seen and maybe misclassified others?); and the spectra, as there should be nucelosynthesis. To think that we're measuring neutrinos from supernovae and gravitational waves from merging black holes and maybe merging neutron stars...what a time to be alive.
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http://public.virgo-gw.eu/ligo-virgo-scientists-to-discuss-new-developments-in-gravitational-wave-astronomy/
It looks very likely an electromagnetic counterpart will be announced: "Scientists representing LIGO, Virgo, and some 70 observatories will reveal [...]"
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Very strong hints it is a binary neutron star merger with associated short GRB and counterparts at other wavelengths (the afterglow of the r-process kilonova).
For example:
Hard info on next Monday's GW news emerging here & there: it was merging neutron stars, a GRB was seen & after effects at other wavelengths
https://twitter.com/cosmos4u/status/918601057453985797 (https://twitter.com/cosmos4u/status/918601057453985797)
The timing of a couple of theoretical papers looks slightly suspicious as well:
https://arxiv.org/abs/1709.08512 (https://arxiv.org/abs/1709.08512)
https://arxiv.org/abs/1709.09630 (https://arxiv.org/abs/1709.09630)
--- Tony
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Very strong hints it is a binary neutron star merger with associated short GRB and counterparts at other wavelengths (the afterglow of the r-process kilonova).
For example:
Hard info on next Monday's GW news emerging here & there: it was merging neutron stars, a GRB was seen & after effects at other wavelengths
https://twitter.com/cosmos4u/status/918601057453985797 (https://twitter.com/cosmos4u/status/918601057453985797)
The timing of a couple of theoretical papers looks slightly suspicious as well:
https://arxiv.org/abs/1709.08512 (https://arxiv.org/abs/1709.08512)
https://arxiv.org/abs/1709.09630 (https://arxiv.org/abs/1709.09630)
--- Tony
Please note this Tweet has now been removed and instead brings up a 404 error.
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Still works for me.
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Still works for me.
Tried it again & just get the message sorry this page doesn’t exist.
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And it still works for me. Weird.
But regardless, this still seems to be the predominant rumour. Hoping the spectrum/light-curve of the kilonova pins down the EOS of neutron stars ... and perhaps tells us more about r-process nucleosynthesis
--- Tony
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Still works for me as well.
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Found it by going onto his feed. Seems embedded Twitter links will not work with Tapatalk.
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LIGO are doing a Reddit /r/IamA on the 17th Oct at 1500 GMT:
https://twitter.com/LIGO/status/918842671963213825 (https://twitter.com/LIGO/status/918842671963213825)
Suspect I might attend :-)
--- Tony
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Going to modify my prediction slightly: the GRB is detected indirectly as they are highly directional and we're off-beam.
--- Tony
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Live feed for the latest announcement:
https://www.youtube.com/watch?v=mtLPKYl4AHs
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Neutron star merger confirmed.
Lied within one of VIRGO's blind spots, so they were able to point telescopes rapidly to a narrow area. EM counterparts detected.
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Name of the event: GW170817
Paper: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.161101 (https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.161101) (pdf: http://www.ligo.org/detections/GW170817/paper/GW170817-PRLpublished.pdf (http://www.ligo.org/detections/GW170817/paper/GW170817-PRLpublished.pdf))
Flyer on the basic info about the detection: http://www.ligo.org/science/Publication-GW170817BNS/flyer.pdf (http://www.ligo.org/science/Publication-GW170817BNS/flyer.pdf)
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Much longer signal (~1 minute of inspiral gravitational waves, 200 complete cycles of the merging stars)
7 space-based observatories involved, along with telescopes in *every* continent on the planet, including Antarctica.
Coming from Hydra, 130 Mly away. Position constrained to ~30 deg^2.
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Antenna pattern of detector sensitivity explains why LIGO got most of the signal and VIRGO couldn't get most of it.
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Took ~10h to sift through the ~50 galaxies in the region of the sky where the gamma-ray telescopes were seeing gamma signals, in order to correlate them with the GW signal.
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Fermi-LAT detected GRB lasting ~2s. MSFC personnel working in both Fermi and LIGO noticed first the correlation between GRB and GW. INTEGRAL from ESA also saw it.
Confirmed prediction that some GRBs are caused by neutron star mergers.
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Why didn't it appear as bright as expected for a GRB so close to Earth? Possibly not looking close to the vertical of the jets.
Both gamma emissions and GW arrived at practically the same time, telling us both travel at the same speed. Difference is caused by different processes.
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Chilean ESO VLT telescopes detected a new bright EM source NGC4993. Telescopes around the world followed it for a week, seeing how it changed from gamma-ray, blue/UV, infrared to then pass on to be an X-ray and radio emitter.
No neutrinos detected for this event, maybe in the future.
From ~10ms before the merger to a few seconds after, matter is tidally violently ejected from the system, and this is the area where the EM counterpart is produced (jets, in the image), as well as nucleosynthesis (first direct detection of heavy-element nucleosynthesis in this event (!!!) as seen in the second image, previous speaker was explaining how the material for his gold watch was probably created in such a merger billions of years ago).
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Explaining the history of neutron star binaries, and how they sometimes appear as pulsars. One such system provided the first indirect evidence of GW before the current interferometers.
One older NS was joined by a newly-formed NS long ago, and the pair was kicked out of its stable position within NGC4993, making both travel around the galaxy until they merged.
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---- Q: What didn't fit the predictions?
A: Faintness of gammas, in spite of the closeness. Delay in X-rays also connected mystery. More info coming in second panel.
---- Q: Something to gain from an automated integrated system, before people realize about it and have time to react?
A: Yes, this case was special because of the small localization region, but more complicated ones could benefit a lot from an automated system.
---- Q: What's the benefits of multimessenger astronomy and what are you looking forward to?
A: (Nearby) supernova explosion would be visible in GW, EM and neutrinos. One every ~50 years in average. Looking forward to that (last one was of course 1987A). Getting closer to deep cosmological questions the more sources of information you have.
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Q: Can we predict the frequency of these events based on the proportion of heavier-than-iron metals in the Universe?
A: Studies are underway on this, but high uncertainty on how much of each element is produced in these events, but it's better to infer it directly from GW frequency. In a galaxy like the Milky Way, an event like this happens 30-500 times every million years. Of course, LIGO/VIRGO are listening to tens of millions of galaxies, so we can expect one such event from somewhere much more often.
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Gosh, Sky & Telescope asked my question on EOS almost verbatim!
--- Tony
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Q: What's the end state of the neutron star merger? Another neutron star?
A: We don't have a clear picture. Some X-ray observations suggest it may be a black hole, but it's on the limit: it could be a very light black hole or a very heavy neutron star.
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Observing run has been finished at the end of August, now making improvements in order to get ~8x improvement in detection frequency (and ~2x in S/N).
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Second panel with more details in about 20 minutes. I will be in a meeting for my own (neutrino) experiment, so if someone wants to take over coverage, please feel free :)
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Q: What's the end state of the neutron star merger? Another neutron star?
A: We don't have a clear picture. Some X-ray observations suggest it may be a black hole, but it's on the limit: it could be a very light black hole or a very heavy neutron star.
Hooray someone asked my question.
Decent article from The Atlantic.
https://www.theatlantic.com/science/archive/2017/10/astronomers-have-seen-the-light/542907/
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The press conference was more circumspect than LIGO Hanford:
Sure did! The final mass of the resulting black hole was one of the lightest observed coming in at 2.74 times the mass of the sun!
https://twitter.com/LIGOWA/status/919945224457031681 (https://twitter.com/LIGOWA/status/919945224457031681)
Also, a bunch of papers here: https://dcc.ligo.org/LIGO-P170817/public (https://dcc.ligo.org/LIGO-P170817/public)
--- Tony
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The press conference was more circumspect than LIGO Hanford:
Sure did! The final mass of the resulting black hole was one of the lightest observed coming in at 2.74 times the mass of the sun!
https://twitter.com/LIGOWA/status/919945224457031681 (https://twitter.com/LIGOWA/status/919945224457031681)
Also, a bunch of papers here: https://dcc.ligo.org/LIGO-P170817/public (https://dcc.ligo.org/LIGO-P170817/public)
--- Tony
Are they really sure it’s a black hole as that’s within Neutron star range?
Couldn’t it be a Quark star?
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They can't be 100% certain yet as no ring-down was observed (not sensitive enough to see that). But I doubt they'd have replied to me as they did unless they were pretty sure.
Also, continued observations should pin it down one way or the other.
--- Tony
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Was really hoping to see a spectrum with the heavy metal features called out, but the main follow-up collaboration paper did refer to seeing spectral features of highly short-lived lanthanides, that particular paper is in preparation. Wow. I tip my hat to the theory folks who nailed this one, the production of heavy elements in NS mergers, years ago.
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They can't be 100% certain yet as no ring-down was observed (not sensitive enough to see that). But I doubt they'd have replied to me as they did unless they were pretty sure.
Also, continued observations should pin it down one way or the other.
--- Tony
Do you know if they can detect white dwarf mergers, do they become neutron stars or black holes I wonder?
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The questions from press/audience seemed to be fixated on creation of gold and platinum and unfortunately there wasn't a question (or at least I didn't hear one) about what was known about the remnant.
Do you know if they can detect white dwarf mergers, do they become neutron stars or black holes I wonder?
White dwarf mergers would emit GWs at lower frequencies, so I think they'd be difficult to detect with LIGO/VIRGO.
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The questions from press/audience seemed to be fixated on creation of gold and platinum and unfortunately there wasn't a question (or at least I didn't hear one) about what was known about the remnant.
I asked that on Twitter and the YouTube chat (which was a zoo where the sane were largely drowned out by idiots), and though It wasn't answered in the main presser or the Q&A session, the Hanford Twitter folks answered my basic question about whether the merger resulted in a black hole (see above).
As LIGO can't see the 6kHz ring-down, I'm guessing the constraints on the EOS in fig 5 of https://dcc.ligo.org/LIGO-P170817/public (https://dcc.ligo.org/LIGO-P170817/public) make it highly likely it formed a BH.
--- Tony
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Was really hoping to see a spectrum with the heavy metal features called out, but the main follow-up collaboration paper did refer to seeing spectral features of highly short-lived lanthanides, that particular paper is in preparation. Wow. I tip my hat to the theory folks who nailed this one, the production of heavy elements in NS mergers, years ago.
This paper: https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733b.pdf (https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733b.pdf)?
These are also on the ESO site:
* https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733a.pdf (https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733a.pdf)
* https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733c.pdf (https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733c.pdf)
* https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733d.pdf (https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733d.pdf)
* https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733e.pdf (https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733e.pdf)
* https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733f.pdf (https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733f.pdf)
--- Tony
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The questions from press/audience seemed to be fixated on creation of gold and platinum and unfortunately there wasn't a question (or at least I didn't hear one) about what was known about the remnant.
Do you know if they can detect white dwarf mergers, do they become neutron stars or black holes I wonder?
White dwarf mergers would emit GWs at lower frequencies, so I think they'd be difficult to detect with LIGO/VIRGO.
Thank you.
I see there are a number online still believing none of this happened even after all this. If it was possible I would send them in the direction of the next merger and ask them if the Kilonova happened or not!
By the way have they just coined the term Kilonova or was it an existing term?
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These are also on the ESO site:
* https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733a.pdf (https://www.eso.org/public/archives/releases/sciencepapers/eso1733/eso1733a.pdf)
You got the first link right, thanks; this paper here is the one that presents the optical spectroscopy, but there are no figures attached.
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You got the first link right, thanks; this paper here is the one that presents the optical spectroscopy, but there are no figures attached.
Darn, I thought it was just the PDF viewer on my tablet not rendering them :-/
--- Tony
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By the way have they just coined the term Kilonova or was it an existing term?
While Hypernova is an existing term, it seems that ESA coined the new term Kilonova to emphasis the energy difference.
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There are some spectra in the paper linked here: http://kilonova.org/p4.html (http://kilonova.org/p4.html)
--- Tony
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By the way have they just coined the term Kilonova or was it an existing term?
While Hypernova is an existing term, it seems that ESA coined the new term Kilonova to emphasis the energy difference.
No, it's been used for a few years at least.
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Thomas Robitaille
@astrofrog
New #LIGO discovery letter stats:
* 4000+ authors
* 6000+ words in acknowledgment section
* NO acknowledgment of any software used
https://mobile.twitter.com/astrofrog/status/919970139893915648
NASA Missions Catch First Light From a Gravitational-Wave Event
http://hubblesite.org/news_release/news/2017-41
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Awesome summary image showing how wideband things have gotten with time, and how much GW170817 had to offer across all wavelengths:
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They can't be 100% certain yet as no ring-down was observed (not sensitive enough to see that). But I doubt they'd have replied to me as they did unless they were pretty sure.
Also, continued observations should pin it down one way or the other.
--- Tony
Do you know if they can detect white dwarf mergers, do they become neutron stars or black holes I wonder?
Will need LISA for that
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What’s NANOGrav & GEO600?
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What’s NANOGrav & GEO600?
GEO600 was the direct precursor interferometer to the current generation of detectors (AdvLIGO & AdVIRGO), somewhat in between what the original LIGO/VIRGO could do and the current sensitivities. No luck for them, as they lie precisely at the limit where they could see something, although they're still working on improving. Their arms are too small (600m), among other things.
NANOGrav is part of the IPTA project (https://en.wikipedia.org/wiki/International_Pulsar_Timing_Array), and while I don't have much a-priori knowledge of its technique or status, it appears to be a lower-sensitivity collaboration using pulsar timing instead of the laser beams in GW interferometers. They apparently are focusing more on establishing lower limits rather than actual detections at this stage.
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LIGO/Virgo Gravitational Wave News (Panel 2)
NASA Jet Propulsion Laboratory
Original air date: Oct. 16, 2017 at 11:15 a.m. ET (8:15 a.m. PT, 1515 UTC).
The National Science Foundation brought scientists from the LIGO and Virgo collaborations, as well as representatives for some 70 observatories at the National Press Club in Washington. The gathering began with an overview of new findings from LIGO, Virgo, and partners that span the globe, followed by details from telescopes that work with the LIGO and Virgo Collaboration to study extreme events in the cosmos.
Moderator: Jim Ulvestad, NSF Assistant Director (Acting) for Mathematical and Physical Sciences
• Laura Cadonati, Deputy Spokesperson, LIGO Scientific Collaboration/Georgia Tech
• Andy Howell, Staff Scientist at Las Cumbres Observatory/UC-Santa Barbara
• Ryan Foley, Assistant Professor of Astronomy and Astrophysics, University of California-Santa Cruz
• Marcelle Soares-Santos, Assistant Professor of Physics, Brandeis University
• David Sand, Assistant Professor in Astronomy, University of Arizona
• Nial Tanvir, Professor of Astrophysics, University of Leicester, UK
• Edo Berger, Professor of Astronomy, Harvard University
• Eleonora Troja, Research Scientist at NASA Goddard Space Flight Center/University of Maryland
• Alessandra Corsi, Assistant Professor, Department of Physics and Astronomy, Texas Tech University
https://youtu.be/6zLgGT6xBeQ?t=001
https://youtu.be/6zLgGT6xBeQ
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I remember from The Atlantic article that this event is also helping with the cosmic scale distance. Apparently gravitational waves also measure distance (or is it some other observation?) and this gives an independent measure of the distance of that galaxy, helping constrain the cosmic ladder. More information would be welcome
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A bunch of papers are now all on arxiv.org:
The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817:
* https://arxiv.org/abs/1710.05459 (https://arxiv.org/abs/1710.05459) I. Dark Energy Camera Discovery of the Optical Counterpart
* https://arxiv.org/abs/1710.05440 (https://arxiv.org/abs/1710.05440) II. UV, Optical, and Near-IR Light Curves and Comparison to Kilonova Models
* https://arxiv.org/abs/1710.05456 (https://arxiv.org/abs/1710.05456) III. Optical and UV Spectra of a Blue Kilonova From Fast Polar Ejecta
* https://arxiv.org/abs/1710.05454 (https://arxiv.org/abs/1710.05454) IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South
* https://arxiv.org/abs/1710.05431 (https://arxiv.org/abs/1710.05431) V. Rising X-ray Emission from an Off-Axis Jet
* https://arxiv.org/abs/1710.05457 (https://arxiv.org/abs/1710.05457) VI. Radio Constraints on a Relativistic Jet and Predictions for Late-Time Emission from the Kilonova Ejecta
* https://arxiv.org/abs/1710.05458 (https://arxiv.org/abs/1710.05458) VII. Properties of the Host Galaxy and Constraints on the Merger Timescale
* https://arxiv.org/abs/1710.05438 (https://arxiv.org/abs/1710.05438) VIII. A Comparison to Cosmological Short-duration Gamma-ray Bursts
I've only included the 8 summary papers on the electromagnetic counterpart. There are *load* of papers from individual observatories and exploring various topics (a total of 64!) ... but there's a lot of reading there :-)
--- Tony
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I remember from The Atlantic article that this event is also helping with the cosmic scale distance. Apparently gravitational waves also measure distance (or is it some other observation?) and this gives an independent measure of the distance of that galaxy, helping constrain the cosmic ladder. More information would be welcome
Yes indeed. The paper you are looking for is here: https://arxiv.org/abs/1710.05835 (https://arxiv.org/abs/1710.05835)
--- Tony
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INTEGRAL SEES BLAST TRAVELLING WITH GRAVITATIONAL WAVES
16 October 2017
ESA's INTEGRAL satellite recently played a crucial role in discovering the flash of gamma rays linked to the gravitational waves released by the collision of two neutron stars.
On 17 August, a burst of gamma rays lit up in space for almost two seconds. It was promptly recorded by INTEGRAL and NASA's Fermi satellite.
Such short gamma-ray bursts are not uncommon: INTEGRAL catches about 20 every year. But this one was special: just seconds before the two satellites saw the blast, an entirely different instrument was triggered on Earth.
One of the two detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) experiment, in the USA, recorded the passage of gravitational waves – fluctuations in the fabric of spacetime caused by powerful cosmic events.
http://sci.esa.int/integral/59664-integral-sees-blast-travelling-with-gravitational-waves/
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The LIGO folks are doing a Reddit Ask Me Anything at 15:00 GMT.
Here: https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/ (https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/)
--- Tony
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The LIGO folks are doing a Reddit Ask Me Anything at 15:00 GMT.
Here: https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/ (https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/)
--- Tony
I noticed on there someone asked what secondary applications LIGO has. I am sure I read in the New Scientist it’s considered a highly sensitive seismic detector, that actual scientific research is done from this side as well?
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So this is going to be a question straight out of the depths of my uninformed, naïve mind, and I apologise in advance for that. One of the take-aways I get from this discovery is that g-waves are confirmed to move at the speed of light. My understanding is that g-waves are distortions in space-time. If changes in space-time can move only at velocities limited to the speed of light, does this automatically rule out Alcubierre-type "warp drive" systems? (aside from all the obvious stuff about a lack of plausible mechanism to generate negative energy density, etc).
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So this is going to be a question straight out of the depths of my uninformed, naïve mind, and I apologise in advance for that. One of the take-aways I get from this discovery is that g-waves are confirmed to move at the speed of light. My understanding is that g-waves are distortions in space-time. If changes in space-time can move only at velocities limited to the speed of light, does this automatically rule out Alcubierre-type "warp drive" systems? (aside from all the obvious stuff about a lack of plausible mechanism to generate negative energy density, etc).
Alcubierre warp drive (with caveats you mentioned) is predicted by the same theory of GR that predicts that gravitational waves travel at the speed of light, so this should be support not contradiction. Now that you point it out it does seem strange, but there are many stranger things in physics, especially some of the other things you could do with negative energy density.
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So this is going to be a question straight out of the depths of my uninformed, naïve mind, and I apologise in advance for that. One of the take-aways I get from this discovery is that g-waves are confirmed to move at the speed of light. My understanding is that g-waves are distortions in space-time. If changes in space-time can move only at velocities limited to the speed of light, does this automatically rule out Alcubierre-type "warp drive" systems? (aside from all the obvious stuff about a lack of plausible mechanism to generate negative energy density, etc).
Alcubierre warp drive (with caveats you mentioned) is predicted by the same theory of GR that predicts that gravitational waves travel at the speed of light, so this should be support not contradiction. Now that you point it out it does seem strange, but there are many stranger things in physics, especially some of the other things you could do with negative energy density.
I am surprised to hear that people thought that gravity might move at anything other than the speed of light.
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I am surprised to hear that people thought that gravity might move at anything other than the speed of light.
This gets a lengthy treatment in section 4 here: http://iopscience.iop.org/article/10.3847/2041-8213/aa920c/meta (http://iopscience.iop.org/article/10.3847/2041-8213/aa920c/meta).
tl;dr the expectation is they propagate at identical speeds, and this event puts stringent constraints on any deviation from that :)
--- Tony
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Do you know if they can detect white dwarf mergers, do they become neutron stars or black holes I wonder?
A white dwarf merger would result in a supernova that would completely disrupt both stars.
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Do you know if they can detect white dwarf mergers, do they become neutron stars or black holes I wonder?
A white dwarf merger would result in a supernova that would completely disrupt both stars.
But wouldn’t some kind of body still be left behind?
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I wondered too, and a quick look turned up this paper
http://iopscience.iop.org/article/10.1088/0004-637X/746/1/62/meta
which suggests a remnant is usually left behind after white dwarf mergers. IANA stellar evolution expert, but what the remnant is, depends on the total mass left over after the explosion. For low enough remnant masses, it would be another carbon-oxygen degenerate star, like a white dwarf; but you'd get a neutron star if the remnant mass exceeds the Chandrasekhar limit of about 1.4 M_sun, the most massive an object held up by electron degeneracy can be. I don't think two WDs colliding could make a black hole; those typically shouldn't show up below 3 M_sun, which is greater than twice the Chandrasekhar limit.
Reminds me of the Calvin & Hobbes cartoon where Calvin's playing with his toys, and he's got several things crashing together at the same time, and he says something like, "This is gonna be good!"
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There's also this https://arxiv.org/abs/1505.01646 (https://arxiv.org/abs/1505.01646)
--- Tony
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Giant star smash-up may have made the biggest neutron star ever
When we watched two neutron stars smash into each other in August, producing gravitational waves and a huge explosion, we weren’t quite sure what was left over afterward: a single colossal neutron star or a black hole.
Now, Yun-Wei Yu at Central China Normal University and Zi-Gao Dai at Nanjing University in China have modelled that explosion, a so-called kilonova that could last weeks to months, and they say there is a neutron star left over at the spot where the smash-up occurred.
https://www.newscientist.com/article/2152822-giant-star-smash-up-may-have-made-the-biggest-neutron-star-ever/
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Listening for Gravitational Waves Using Pulsars
https://www.jpl.nasa.gov/news/news.php?feature=6998
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Another detection
GW170608: Observation of a 19-solar-mass Binary Black Hole Coalescence
On June 8, 2017 at 02:01:16.49 UTC, a gravitational-wave signal from the merger of two stellar-mass black holes was observed by the two Advanced LIGO detectors with a network signal-to-noise ratio of 13. This system is the lightest black hole binary so far observed, with component masses 12+7−2M⊙ and 7+2−2M⊙ (90% credible intervals). These lie in the range of measured black hole masses in low-mass X-ray binaries, thus allowing us to compare black holes detected through gravitational waves with electromagnetic observations. The source's luminosity distance is 340+140−140 Mpc, corresponding to redshift 0.07+0.03−0.03. We verify that the signal waveform is consistent with the predictions of general relativity.
https://arxiv.org/abs/1711.05578 (https://arxiv.org/abs/1711.05578)
--- Tony
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Here’s the press release for the detection.
LIGO and Virgo announce the detection of a black hole binary merger from June 8, 2017
News Release • November 15, 2017
Scientists searching for gravitational waves have confirmed yet another detection from their fruitful observing run earlier this year. Dubbed GW170608, the latest discovery was produced by the merger of two relatively light black holes, 7 and 12 times the mass of the sun, at a distance of about a billion light-years from Earth. The merger left behind a final black hole 18 times the mass of the sun, meaning that energy equivalent to about 1 solar mass was emitted as gravitational waves during the collision.
This event, detected by the two NSF-supported LIGO detectors at 02:01:16 UTC on June 8, 2017 (or 10:01:16 pm on June 7 in US Eastern Daylight time), was actually the second binary black hole merger observed during LIGO’s second observation run since being upgraded in a program called Advanced LIGO. But its announcement was delayed due to the time required to understand two other discoveries: a LIGO-Virgo three-detector observation of gravitational waves from another binary black hole merger (GW170814) on August 14, and the first-ever detection of a binary neutron star merger (GW170817) in light and gravitational waves on August 17.
A paper describing the newly confirmed observation, “GW170608: Observation of a 19-solar-mass binary black hole coalescence,” authored by the LIGO Scientific Collaboration and the Virgo Collaboration has been submitted to The Astrophysical Journal Letters and is available to read on the arXiv. Additional information for the scientific and general public can be found at
https://www.ligo.caltech.edu/news/ligo20171115?source=techstories.org
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GW170817 Most Likely Made a Black Hole
The detection of the neutron-star merger kilonova and short hard gamma-ray burst event GW170817 has been widely described, but one outstanding issue remains: the nature of the remnant of the event. Within the initial uncertainties, the remnant could be either a massive, rotating, magnetic neutron star or a black hole. One of the ways to distinguish these possibilities is with sensitive X-ray observations. We report here Chandra X-ray Observatory Director's Discretionary Time observations made on 2017 Dec 03 and Dec 06 and conclude that X-ray data is consistent with synchrotron radiation in the external shock, and the most likely remnant is a black hole.
https://arxiv.org/abs/1712.03240
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A new LIGO detector will be built in India by 2025:
http://www.thehindu.com/sci-tech/technology/a-new-ligo-gravitational-wave-detector-to-be-built-in-india-by-2025/article22149855.ece
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A new LIGO detector will be built in India by 2025:
http://www.thehindu.com/sci-tech/technology/a-new-ligo-gravitational-wave-detector-to-be-built-in-india-by-2025/article22149855.ece
Curious way that article is written makes it sound like it will be the third detector online, in fact by then it will be the fifth after Italy & Japan.
Thanks though as have been waiting to hear some more information on it.
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A new LIGO detector will be built in India by 2025:
http://www.thehindu.com/sci-tech/technology/a-new-ligo-gravitational-wave-detector-to-be-built-in-india-by-2025/article22149855.ece
Curious way that article is written makes it sound like it will be the third detector online, in fact by then it will be the fifth after Italy & Japan.
Thanks though as have been waiting to hear some more information on it.
It will be the third LIGO observatory, not the third gravity wave observatory.
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A new LIGO detector will be built in India by 2025:
http://www.thehindu.com/sci-tech/technology/a-new-ligo-gravitational-wave-detector-to-be-built-in-india-by-2025/article22149855.ece
Curious way that article is written makes it sound like it will be the third detector online, in fact by then it will be the fifth after Italy & Japan.
Thanks though as have been waiting to hear some more information on it.
It will be the third LIGO observatory, not the third gravity wave observatory.
I did wonder if that might be the explanation.
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Details of an upgrade to the Virgo detector.
A team of researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover and from the Institute for Gravitational Physics at Leibniz Universität Hannover has developed an advanced squeezed-light source for the gravitational-wave detector Virgo near Pisa. Now, the Hannover scientists have delivered the setup, installed it, and handed it over to their Virgo colleagues. Beginning in autumn 2018 Virgo will use the squeezed-light source to listen to Einstein's gravitational waves together with the worldwide network of detectors with higher sensitivity than ever before.
https://phys.org/news/2018-01-squeezed-light-source-gravitational-detector-sensitive.amp
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Details of an upgrade to the Virgo detector.
A team of researchers from the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hannover and from the Institute for Gravitational Physics at Leibniz Universität Hannover has developed an advanced squeezed-light source for the gravitational-wave detector Virgo near Pisa. Now, the Hannover scientists have delivered the setup, installed it, and handed it over to their Virgo colleagues. Beginning in autumn 2018 Virgo will use the squeezed-light source to listen to Einstein's gravitational waves together with the worldwide network of detectors with higher sensitivity than ever before.
https://phys.org/news/2018-01-squeezed-light-source-gravitational-detector-sensitive.amp
It has increased the part of the Universe that GEO600 listens to by a factor of up to four,
I guess this means that it's increased volume by a factor of four, and hence range by 1.6*, and sensitivity by 2.5* or so.
It would be nice if there was a readily available graph of sensitivity over time for the whole network, including planned updates and estimated occurrance rates of things, but I've not seen anything similar.
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The most interesting consequence of this (for me anyway), is that the increased sensitivity means we can probably spot NS-NS mergers up to 15 mins *before* merger, so a better chance of getting more instruments watching earlier. It'll still be tough though, as the sky location still covers a large area.
--- Tony
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Is there some reason that the instrument is given as a loan rather than a permanent addition to Virgo?
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Is there some reason that the instrument is given as a loan rather than a permanent addition to Virgo?
Well, it's a permanent loan. I guess there are some legal/contractual/funding reasons, which make it necessary that German institutions retain the ownership.
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The most interesting consequence of this (for me anyway), is that the increased sensitivity means we can probably spot NS-NS mergers up to 15 mins *before* merger, so a better chance of getting more instruments watching earlier. It'll still be tough though, as the sky location still covers a large area.
Where are you getting that from?
GW170817 was detected 1.7s before coalescence at 30Hz or so.
Once you get to 10Hz or so, the performance of LIGO is crashing, and is (by eyeballing off the end of a sensitivity graph) 3 orders of magnitude or so worse.
In order for 15 min to be true, with a 2-fold improvement in sensitivity, it would need to be at 20hz for 15 minutes, which seems unlikely.
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The most interesting consequence of this (for me anyway), is that the increased sensitivity means we can probably spot NS-NS mergers up to 15 mins *before* merger, so a better chance of getting more instruments watching earlier. It'll still be tough though, as the sky location still covers a large area.
Where are you getting that from?
GW170817 was detected 1.7s before coalescence at 30Hz or so.
Once you get to 10Hz or so, the performance of LIGO is crashing, and is (by eyeballing off the end of a sensitivity graph) 3 orders of magnitude or so worse.
In order for 15 min to be true, with a 2-fold improvement in sensitivity, it would need to be at 20hz for 15 minutes, which seems unlikely.
For neutron star inspirals the merger timescale is much longer than for more massive objects with the same orbital period. About 15 minutes in LIGO sensitivity band for NS-NS mergers sounds about right to me. I'll see if I can find a reference...
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For neutron star inspirals the merger timescale is much longer than for more massive objects with the same orbital period. About 15 minutes in LIGO sensitivity band for NS-NS mergers sounds about right to me. I'll see if I can find a reference...
If we neglect frequency and say an equal amount of energy as gravity waves comes out in the last 1.7 seconds and the 15 minutes before that, that is 1/500th the power.
Boosting sensitivity by a factor of 2 can't get you at all close to this, unless the merger is some 16 times closer.
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For neutron star inspirals the merger timescale is much longer than for more massive objects with the same orbital period. About 15 minutes in LIGO sensitivity band for NS-NS mergers sounds about right to me. I'll see if I can find a reference...
If we neglect frequency and say an equal amount of energy as gravity waves comes out in the last 1.7 seconds and the 15 minutes before that, that is 1/500th the power.
Boosting sensitivity by a factor of 2 can't get you at all close to this, unless the merger is some 16 times closer.
GW170817 was seen for about 100 seconds, so I'm not sure what 1.7 seconds refers to. Anyway, see this (https://physics.stackexchange.com/questions/363306/why-did-the-neutron-star-merger-signal-last-for-so-much-longer-than-the-black-ho) Physics Stack Exchange question and especially the second answer about how the chirp mass changes the timescale and amplitude of GW signal.
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For neutron star inspirals the merger timescale is much longer than for more massive objects with the same orbital period. About 15 minutes in LIGO sensitivity band for NS-NS mergers sounds about right to me. I'll see if I can find a reference...
If we neglect frequency and say an equal amount of energy as gravity waves comes out in the last 1.7 seconds and the 15 minutes before that, that is 1/500th the power.
Boosting sensitivity by a factor of 2 can't get you at all close to this, unless the merger is some 16 times closer.
GW170817 was seen for about 100 seconds, so I'm not sure what 1.7 seconds refers to. Anyway, see this (https://physics.stackexchange.com/questions/363306/why-did-the-neutron-star-merger-signal-last-for-so-much-longer-than-the-black-ho) Physics Stack Exchange question and especially the second answer about how the chirp mass changes the timescale and amplitude of GW signal.
Apologies, I misread the initial paper - https://arxiv.org/abs/1710.05832 and somehow my eye hit 1.7s (the gamma ray delay) rather than 100s for the time.
100s is the time 'in the detector bandwidth' - the signal only becomes visibly apparent in the graphs presented at -30s or so.
While all of the signal in principle contributes to the detection, if you only consider up to a 'now' point - you will not detect it until it gets to a given threshold - that 100s is not detectable immediately, but maybe only 40 or 15 seconds before the event.
Signals from the three detectors in the above event, from the discovery paper.
(https://i.imgur.com/cq8AImi.jpg)
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See the reddit they did: https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/ (https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/)
More specifically, this reply:
This is an excellent question. The gravitational-wave signal from a binary neutron star such as GW170817 lasts tens of seconds in the most sensitive frequency band of ground-based instruments like LIGO and Virgo. If the signal is sufficiently strong, we can in principle recognize its presence before the merger. We have some seconds of latency due to data transfers between computing centers. Localization also takes some additional seconds. So at the moment this is in practice a bit challenging. Once the detectors reach design sensitivity, however, they will be sensitive to even lower frequencies (starting at about 10 Hz) which effectively increases the duration of the visible signal, possibly even to 15 minutes. Therefore, in the future it should definitely be possible to detect and localize a low-mass binary merger before the actual merger. This is important and exciting as it will allow us to witness the merger with many different observatories.
--- Tony
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See the reddit they did: https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/ (https://www.reddit.com/r/IAmA/comments/76yu54/we_are_the_ligo_scientific_collaboration_the/)
More specifically, this reply:
This is an excellent question. The gravitational-wave signal from a binary neutron star such as GW170817 lasts tens of seconds in the most sensitive frequency band of ground-based instruments like LIGO and Virgo. If the signal is sufficiently strong, we can in principle recognize its presence before the merger. We have some seconds of latency due to data transfers between computing centers. Localization also takes some additional seconds. So at the moment this is in practice a bit challenging. Once the detectors reach design sensitivity, however, they will be sensitive to even lower frequencies (starting at about 10 Hz) which effectively increases the duration of the visible signal, possibly even to 15 minutes. Therefore, in the future it should definitely be possible to detect and localize a low-mass binary merger before the actual merger. This is important and exciting as it will allow us to witness the merger with many different observatories.
--- Tony
How far away are they to design sensitivity, as it seems like since the first GW detection that they’ve been under constant upgrade?
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How far away are they to design sensitivity, as it seems like since the first GW detection that they’ve been under constant upgrade?
Good question. The next observing run (O3) is planned to be a long one (12+ months) running to about the end of 2019. I think they plan on reaching design sensitivity on the next run in ~2020-1, though it isn't clear to me what that next upgrade will bring as I believe the "squeezed light" upgrades are the most significant one and will be done for O3.
Localisation of the sources will be helped when the Japanese instrument, Kagra, joins the network around 2020, which makes any early warning more useful.
So I may have to wait a while longer for us to get as much as 15 minutes warning, but I'm an optimist ;)
Edit: this paper gives more details https://arxiv.org/abs/1304.0670 (https://arxiv.org/abs/1304.0670). Looks like sky localisation will still be problematic until the Indian instrument joins ~2024.
--- Tony
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How far away are they to design sensitivity, as it seems like since the first GW detection that they’ve been under constant upgrade?
Good question. The next observing run (O3) is planned to be a long one (12+ months) running to about the end of 2019. I think they plan on reaching design sensitivity on the next run in ~2020-1, though it isn't clear to me what that next upgrade will bring as I believe the "squeezed light" upgrades are the most significant one and will be done for O3.
Localisation of the sources will be helped when the Japanese instrument, Kagra, joins the network around 2020, which makes any early warning more useful.
So I may have to wait a while longer for us to get as much as 15 minutes warning, but I'm an optimist ;)
Edit: this paper gives more details https://arxiv.org/abs/1304.0670 (https://arxiv.org/abs/1304.0670). Looks like sky localisation will still be problematic until the Indian instrument joins ~2024.
--- Tony
Thank you.
Is there a more definitive date yet when the Indian LIGO detector will join the network? I’ve previously seen 2024/2025.
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In this week’s New Scientist magazine there is a special investigation casting doubt on the 2015 discovery of gravitational waves. I don’t have all the details as I only received my copy today and haven’t had a chance to read the article properly yet but it appears to be based on the work of a gentleman called Andrew Jackson who is the spokesman for a group based at the Niels Bohr Institute in Copenhagen. The basics of the article after skimming it are that the LIGO group are too secretive with their data when it comes to independent verification, that we have to rely on effectively one instrument for the detections and that some members of the LIGO group have been churlish when papers have been put out raising concerns about their work. Also that the group needs to put out materials explaining how they work with the noise produced in LIGO.
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In this week’s New Scientist magazine there is a special investigation casting doubt on the 2015 discovery of gravitational waves.
Not having read the article, I'll just note that the more recent detections, especially the corobborated neutron star mergers do imply that it was reasonable that the first detection was legit.
I do agree that more open data would be nice.
https://www.gw-openscience.org/events/ - does have some, but this is as I understand it all after their cleanup pipelines.
However, the cleanup pipeline to remove noise is going to be almost impenetrable without detailed knowledge of the instrument.
Also on that page is email notices to astronomers (https://gcn.gsfc.nasa.gov/other/G184098.gcn3) at the time of the releases, and their responses.
This is the most recent neutron star coalescance made public. (https://gcn.gsfc.nasa.gov/other/G298048.gcn3)
(to be clear, I have no insight on if there are unpublished events)
TITLE: GCN CIRCULAR
NUMBER: 21505
SUBJECT: LIGO/Virgo G298048: Fermi GBM trigger 524666471/170817529: LIGO/Virgo Identification of a possible gravitational-wave counterpart
DATE: 17/08/17 13:21:42 GMT
FROM: Reed Clasey Essick at MIT <[email protected]>
The LIGO Scientific Collaboration and the Virgo Collaboration report:
The online CBC pipeline (gstlal) has made a preliminary
identification of a GW candidate associated with the time
of Fermi GBM trigger 524666471/170817529 at gps time 1187008884.47
(Thu Aug 17 12:41:06 GMT 2017) with RA=186.62deg Dec=-48.84deg and an error radius of 17.45deg.
The candidate is consistent with a neutron star binary coalescence with
False Alarm Rate of ~1/10,000 years.
An offline analysis is ongoing. Any significant updates will be provided
by a new Circular.
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The group even question the neutron star merger pointing out it was initially flagged as a false positive.
Here’s an abstract from the online version of the article, to see the full thing you have to be a subscriber.
https://www.newscientist.com/article/mg24032022-600-exclusive-grave-doubts-over-ligos-discovery-of-gravitational-waves/
But here’s an accessible article on the same matter.
https://arstechnica.com/science/2018/10/danish-physicists-claim-to-cast-doubt-on-detection-of-gravitational-waves/
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Suggesting fraud or incompetence may be a strategy to get better or earlier access to the data.
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The group even question the neutron star merger pointing out it was initially flagged as a false positive.
As the Ars article points out, Jackson's group has actually been pushing this for several years, and don't appear to have gotten much traction in the broader community. New Scientist pushing it as an "exclusive" seems pretty clickbaity. Maybe there's some new paper or detail, but basic outline doesn't seem to be at all new.
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The group even question the neutron star merger pointing out it was initially flagged as a false positive.
As the Ars article points out, Jackson's group has actually been pushing this for several years, and don't appear to have gotten much traction in the broader community. New Scientist pushing it as an "exclusive" seems pretty clickbaity. Maybe there's some new paper or detail, but basic outline doesn't seem to be at all new.
As I said I’ve only skimmed it so far but there is this paragraph in it.
And there are legitimate questions about that trust. New Scientist has learned, for instance, that the collaboration decided to publish data plots that were not derived from actual analysis. The paper on the first detection in Physical Review Letters used a data plot that was more “illustrative” than precise, says Cornish. Some of the results presented in that paper were not found using analysis algorithms, but were done “by eye”.
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The group even question the neutron star merger pointing out it was initially flagged as a false positive.
This in particular fails the smell test.
First, the Fermi gamma ray observatory detected a GRB co-incident within 2 seconds. That's low probability for a false alarm right there.
And crucially VIRGO saw the same event, at the same time, within a few milliseconds (as expected). So now we have the same event detected within a few milliseconds in Washington, Louisiana, and Italy. That's incredibly unlikely for a false positive.
And most important, using the VIRGO and LIGO data, they estimated where to look. When they did so, the optical telescopes found an extremely rare and transient event, a kilo-nova, not known to be seen before. If the LIGO and VIRGO events were false alarms, this would imply that this was just luck. But the same telescopes are in use all the time, and have not seen many (any?) corresponding events. So seeing such a rare event, just where and when LIGO said to look, would be an incredible coincidence.
So the gravitational waves from the neutron star collision are established beyond any reasonable doubt.
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This in particular fails the smell test.
First, the Fermi gamma ray observatory detected a GRB co-incident within 2 seconds. That's low probability for a false alarm right there.
And crucially VIRGO saw the same event, at the same time, within a few milliseconds (as expected). So now we have the same event detected within a few milliseconds in Washington, Louisiana, and Italy. That's incredibly unlikely for a false positive.
And most important, using the VIRGO and LIGO data, they estimated where to look. When they did so, the optical telescopes found an extremely rare and transient event, a kilo-nova, not known to be seen before. If the LIGO and VIRGO events were false alarms, this would imply that this was just luck. But the same telescopes are in use all the time, and have not seen many (any?) corresponding events. So seeing such a rare event, just where and when LIGO said to look, would be an incredible coincidence.
So the gravitational waves from the neutron star collision are established beyond any reasonable doubt.
Well... LIGO saw it, but Virgo didn't, which helped pin down the source location. See https://www.ligo.org/detections/GW170817/paper/GW170817-PRLpublished.pdf
But the GW detection for this source was very different from the earlier BH mergers; it lasted ~30 seconds, as expected for a NS merger, instead of the fraction of a second of the BH merger candidates. So you have a detection that looked like a NS merger, with the first GRB associated with a GW detection, in the GW error ellipse, and the optical transient that looked like the expectations of a NS merger... that's a lot of coincidences for it to not be a real association.
I would expect that when LIGO/VIRGO are both back online, we'll have more detections, some from both observatories, and that will probably close the case. If we don't get simultaneous detections...
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And crucially VIRGO saw the same event, at the same time, within a few milliseconds (as expected). So now we have the same event detected within a few milliseconds in Washington, Louisiana, and Italy. That's incredibly unlikely for a false positive.
And most important, using the VIRGO and LIGO data, they estimated where to look. [...]
So the gravitational waves from the neutron star collision are established beyond any reasonable doubt.
Well... LIGO saw it, but Virgo didn't, which helped pin down the source location. See https://www.ligo.org/detections/GW170817/paper/GW170817-PRLpublished.pdf
VIRGO *did* see the event, but with a low signal-to-noise (just 2.0). This was not enough to claim an independent detection, but did help in narrowing down the search box. From the article above,
The combined SNR of GW 170817 is estimated to be 32.4, with values 18.8, 26.4, and 2.0 in the LIGO-Hanford, LIGO-Livingston, and VIRGO data respectively.
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I would expect that when LIGO/VIRGO are both back online, we'll have more detections, some from both observatories, and that will probably close the case. If we don't get simultaneous detections...
I think there is about a 2x improvement in the next observing run, which (from memory; I'll try and dig out the source) means they expect a detection about once a week.
--- Tony
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I have a feeling that the other scientists supporting them in the New Scientist article but indications that they still believe that GW will be confirmed are actually looking to prise open what is perceived as the LIGO collaboration overly secretive analysis methods. Especially important as it says in the article that LIGO are the only ones with the detector, and it cannot be independently verified.
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I have a feeling that the other scientists supporting them in the New Scientist article but indications that they still believe that GW will be confirmed are actually looking to prise open what is perceived as the LIGO collaboration overly secretive analysis methods.
This is not unusual for big science. I'm working on a project that, while not LIGO or CERN scale, is still 10s of millions of $$ over many years. I'm all for releasing data as we acquire it and tools as we develop them, but I'm in the distinct minority,. The grad students and postdocs are scared that someone will take a quick look at the data and scoop some phenomena they need for either a thesis or top-journal papers they need to get an academic position. The higher management wants a big unified data/PR release, so they get a big splash for all the money they spent, rather than an un-memorable sequence of smaller releases. And (unfortunately in my mind) acquiring the data does not get nearly the credit as analyzing it. so if a project spends $$$ on acquiring data, then in return they want to be the first to analyze it. And they naturally want to do a thorough job, not just a quick look, so the data stays private even longer.
I personally believe the risk of adverse events is low, and science would be better served by faster release. But I can remember worrying about being scooped as a grad student (I was quite relieved when I presented my work at a conference, since that established priority). It's also understandable that the folks who provide the big bucks want the credit to go to their group, who have invested not only dollars but many years of their time. So this is likely a tradeoff that is needed to get the big bucks for big projects.
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I have a feeling that the other scientists supporting them in the New Scientist article but indications that they still believe that GW will be confirmed are actually looking to prise open what is perceived as the LIGO collaboration overly secretive analysis methods.
This is not unusual for big science. I'm working on a project that, while not LIGO or CERN scale, is still 10s of millions of $$ over many years. I'm all for releasing data as we acquire it and tools as we develop them, but I'm in the distinct minority,. The grad students and postdocs are scared that someone will take a quick look at the data and scoop some phenomena they need for either a thesis or top-journal papers they need to get an academic position. The higher management wants a big unified data/PR release, so they get a big splash for all the money they spent, rather than an un-memorable sequence of smaller releases. And (unfortunately in my mind) acquiring the data does not get nearly the credit as analyzing it. so if a project spends $$$ on acquiring data, then in return they want to be the first to analyze it. And they naturally want to do a thorough job, not just a quick look, so the data stays private even longer.
I personally believe the risk of adverse events is low, and science would be better served by faster release. But I can remember worrying about being scooped as a grad student (I was quite relieved when I presented my work at a conference, since that established priority). It's also understandable that the folks who provide the big bucks want the credit to go to their group, who have invested not only dollars but many years of their time. So this is likely a tradeoff that is needed to get the big bucks for big projects.
Thank you for that info. In the case of the LIGO though it sounds like it has engendered suspicion of their methods in others.
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KAGRA is expected to join the global GW array in about a year's time, about halfway through LIGO and VIRGO's O3 campaign, in its "baseline" (bKAGRA) configuration.
https://arxiv.org/pdf/1811.08079.pdf
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Important update with four new detections!
GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO and Virgo during the First and Second Observing Runs
We present the results from three gravitational-wave searches for coalescing compact binaries with component masses above 1M⊙ during the first and second observing runs of the Advanced gravitational-wave detector network. During the first observing run (O1), from September 12th, 2015 to January 19th, 2016, gravitational waves from three binary black hole mergers were detected. The second observing run (O2), which ran from November 30th, 2016 to August 25th, 2017, saw the first detection of gravitational waves from a binary neutron star inspiral, in addition to the observation of gravitational waves from a total of seven binary black hole mergers, four of which we report here for the first time: GW170729, GW170809, GW170818 and GW170823. For all significant gravitational-wave events, we provide estimates of the source properties. The detected binary black holes have total masses between 18.6+3.1−0.7M⊙, and 85.1+15.6−10.9M⊙, and range in distance between 320+120−110 Mpc and 2750+1350−1320 Mpc. No neutron star - black hole mergers were detected. In addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false alarm rate less than 1 per 30 days. From these results over the first two observing runs, which include approximately one gravitational-wave detection per 15 days of data searched, we infer merger rates at the 90% confidence intervals of 110 - 3840 Gpc−3y−1 for binary neutron stars and 9.7 - 101 Gpc−3y−1 for binary black holes, and determine a neutron star - black hole merger rate 90% upper limit of 610 Gpc−3y−1.
Arxiv paper (https://arxiv.org/abs/1811.12907)
--- Tony
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Important update with four new detections!
. In addition to highly significant gravitational-wave events, we also provide a list of marginal event candidates with an estimated false alarm rate less than 1 per 30 days. .
They believe if they understand the instrument properly, they should have seen under five of these marginal events. While they can't say for certain that any particular one of them is meaningful - they believe the fact they saw 14 means at least some may be real adding constraints on the event rate.
For the next observing run, they plan on not requiring people who they are sharing the data with to sign agreements to keep it secret.
https://wiki.gw-astronomy.org/OpenLVEM/WebHome
This is the community forum on multi-messenger observations connected to Gravitational Wave (GW) transient event detections. This forum has no requirements for participation -- anyone interested can join. This open forum started in January 2018. The LIGO-Virgo Collaboration will use this forum to communicate and interact with the community.
The next test run begins in december for a week or so, then O3 begins in March or so and will run for one year.
(https://www.ligo.caltech.edu/system/media_files/binaries/409/large/G1801056-v4.png)
The next event of interest will be our engineering run ER13, planned for 14 Dec 2018 08:00 US Pacific time to 18 December 06:00 US Pacific time.
https://www.ligo.caltech.edu/page/observatory-status
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Also useful:
https://twitter.com/NUCIERA/status/1068882965525090304
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And another. This time a visualisation of the sky position of all the detections
https://twitter.com/LIGO/status/1069587054571458560
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LIGO to publish new paper in wake of New Scientist investigation (https://www.newscientist.com/article/2184360-ligo-to-publish-new-paper-in-wake-of-new-scientist-investigation/)
The LIGO Scientific Collaboration, which detected gravitational waves in 2015, has announced that it will publish a detailed explanation of how it analyses the noise in its detectors.
The announcement, on 1 November, comes in the wake of an exclusive New Scientist investigation that exposed questions about the analysis underpinning the breakthrough discovery.
The fact that they are going to do this certainly seems to indicate that those on here and elsewhere who thought there was no case to answer were wrong.
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The fact that they are going to do this certainly seems to indicate that those on here and elsewhere who thought there was no case to answer were wrong.
Or that the team involved wanted to get the papers with actual data out before going into a 'how we did it' paper that would presumably not be nearly as highly cited because the number of people outside LIGO with meaningful gravitational detectors is zero.
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The fact that they are going to do this certainly seems to indicate that those on here and elsewhere who thought there was no case to answer were wrong.
Or that the team involved wanted to get the papers with actual data out before going into a 'how we did it' paper that would presumably not be nearly as highly cited because the number of people outside LIGO with meaningful gravitational detectors is zero.
To me the important thing is that it is being written. Except with a small minority I don’t think people were believing they hadn’t detected gravitational waves, more the case of please show us your working out.
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http://www.aei.mpg.de/2318389/new-squeezing-record-at-geo600
Light squeezing record at GEO-600, necessary for future 3rd-generation detectors such as Einstein and key to the expected sensitivity improvements in LIGO/Virgo during O3.
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This business about if gravitational waves have been detected or not has now developed into a back and forth of letters in the New Scientist.
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This business about if gravitational waves have been detected or not has now developed into a back and forth of letters in the New Scientist.
A longer story about the situation in Quanta: https://www.quantamagazine.org/studies-rescue-ligos-gravitational-wave-signal-from-the-noise-20181213/
Apparently two studies from groups unaffiliated with LIGO confirm that the LIGO analysis is basically correct. Jackson, however, sticks with his claims of errors in LIGO analysis and has some unkind words about the new papers.
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This business about if gravitational waves have been detected or not has now developed into a back and forth of letters in the New Scientist.
A longer story about the situation in Quanta: https://www.quantamagazine.org/studies-rescue-ligos-gravitational-wave-signal-from-the-noise-20181213/
Apparently two studies from groups unaffiliated with LIGO confirm that the LIGO analysis is basically correct. Jackson, however, sticks with his claims of errors in LIGO analysis and has some unkind words about the new papers.
In the most issue I read of New Scientist there was a letter from what you would call an informed lay-person stating they had become disillusioned with the LIGO results because of the doubts raised. So that’s the effect it’s having.
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I’m not sure the opinion of an informed layperson means much.
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I’m not sure the opinion of an informed layperson means much.
Tip of the iceberg possibly. Lest we be reminded that these enterprises are publicly funded, in what is arguably an anti-science public environment especially in sections of the US.
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Layman's opinion here; an earth quakes propagate at speed of sound on the ground, and clearly can't be a reason for all the detections. Gravity waves propagate in speed of light, and there is no EM source in Earth that can affect both of the detectors. So Jackson's "glitches" and thunder storms come of bit "hand wavy"...
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Accusing other people of being "anti-science" while questioning a science result that has been peer-reviewed and their methodology reproduced is, how shall we put this, brave.
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Accusing other people of being "anti-science" while questioning a science result that has been peer-reviewed and their methodology reproduced is, how shall we put this, brave.
Missing the point as I was clearing talking about society. Have you not noticed who senior politicians are like these days?
Also how is it anti-science to debate results or do you think they should just go unchallenged, as that would be an anti-science viewpoint.
As witnessed by this new video from Seeker.
https://youtu.be/aQ1entvy7vI
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No more doubts: Two independent studies confirm LIGO’s Nobel discovery (https://arstechnica.com/science/2018/12/two-independent-analyses-confirm-ligos-discovery-of-gravitational-waves/)
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.
LIGO didn't escape criticism, either. Nielsen et al. think that some of the Jackson team's errors resulted from Figure 1 in LIGO's 2016 Physical Review Letters paper describing their discovery. Pieces of that figure were illustrative, something that was not made crystal clear at the time. LIGO's claims of detection weren't based on that plot, but on a more rigorous analysis. Jackson et al., however, based their code on Figure 1's template waveform, leading to false correlations in the noise.
For most physicists, however, LIGO has been vindicated. “Seeing those two non-Collaboration re-analyses does reaffirm my certainty that the detections [of gravitational waves] are genuine,” Shoemaker told Quanta, “and also is a reinforcement of our earlier perception of where the Jackson et al. paper has problems. That the Jackson et al. work has stimulated some additional independent investigations can be seen as a positive outcome, but I personally think it comes with a fully unnecessary cost of ‘drama.’”
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Unfortunately many 'informed laypersons' remember only the controversy and will be suspicious about the LIGO results even after the experts have almost universally accepted them.
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Unfortunately many 'informed laypersons' remember only the controversy and will be suspicious about the LIGO results even after the experts have almost universally accepted them.
Also some dunderheads continue to assert, seriously, that Earth is flat and the moon landings faked. At this point, anybody who thinks the LIGO result is in error, fake, a glitch, or a fraud is a kook.
Matthew
Edit; changed "afraid" to "a fraud"
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Jackson et al look to be out on their own now. I am assuming they have a reason for this, rather than just being stubborn.
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Meanwhile, haters gonna hate:
https://twitter.com/LIGO/status/1074505895986352129 (https://twitter.com/LIGO/status/1074505895986352129)
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Yes, there is currently an engineering run in progress - this *might* include some actual observations but it's only a couple of days I think so chances are relatively low for detections.
--- Tony
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LIGO Gravitational Wave Observatory Getting $30 Million Upgrade (https://www.popularmechanics.com/space/telescopes/a26362135/ligo-gravitational-wave-observatory-update/)
Now, thanks to a $34 million investment from the U.S., the U.K., and Australia, LIGO will be even more sensitive. The money will go toward upgrading the equipment, including adapting techniques from quantum mechanics to improve the lasers and taking advantage of new mirror coating technologies. With these upgrades LIGO will be able to detect gravitational waves that are much fainter.
This means LIGO will be able to pick up waves from less massive objects, including smaller black holes and neutron stars as well as nearby supernovas and star collisions. But most importantly, LIGO will be able to pick up gravitational waves from much farther away. The upgrade will be able to extend LIGO’s range by almost seven times, which should make picking up a gravitational wave event an almost daily occurrence.
The upgrade is scheduled to be complete by 2024. In the meantime, LIGO is expected to continue in its current configuration starting this spring.
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LIGO and Virgo Resume Search for Ripples in Space and Time (https://www.ligo.caltech.edu/news/ligo20190326)
The National Science Foundation's LIGO (Laser Interferometer Gravitational-Wave Observatory) is set to resume its hunt for gravitational waves—ripples in space and time—on April 1, after receiving a series of upgrades to its lasers, mirrors, and other components. LIGO—which consists of twin detectors located in Washington and Louisiana—now has a combined increase in sensitivity of about 40 percent over its last run, which means that it can survey an even larger volume of space than before for powerful, wave-making events, such as the collisions of black holes.
Joining the search will be Virgo, the European-based gravitational-wave detector, located at the European Gravitational Observatory (EGO) in Italy, which has almost doubled its sensitivity since its last run and is also starting up April 1.
"For this third observational run, we achieved significantly greater improvements to the detectors' sensitivity than we did for the last run," says Peter Fritschel, LIGO's chief detector scientist at MIT. "And with LIGO and Virgo observing together for the next year, we will surely detect many more gravitational waves from the types of sources we've seen so far. We're eager to see new events too, such as a merger of a black hole and a neutron star."
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First alert!
https://twitter.com/LIGO/status/1115350053491703819
https://twitter.com/DanHoak/status/1115376743181844481
--- Tony
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And another one: https://gracedb.ligo.org/superevents/S190412m
The estimated detection rate of ~1 per week seems to be holding pretty well.
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Keep 'em coming:
https://twitter.com/LIGO/status/1120437648517214210
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First-ever open public alerts now available from LIGO
Two probable black-hole mergers spotted in first weeks after gravitational-wave detector is updated
UNIVERSITY PARK, Pa. — Two new probable gravitational waves — ripples in the fabric of spacetime caused by cataclysmic cosmic events and first predicted by Albert Einstein over 100 years ago — have been detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo observatory in Italy in the first weeks after the detectors were updated. The source of both waves is believed to be the merging of a pair of black holes.
LIGO announced the discovery of the first new gravitational wave in its first-ever open public alert on April 8, and quickly followed up with a second announcement on April 12. LIGO detected the first-ever gravitational wave in September 2015, and announced the discovery in February 2016. Ten more gravitational waves were detected over the following three years, but with updates to LIGO and Virgo, scientists expect to see as many as one per week, which so far has proven true.
Updates to LIGO and Virgo have combined to increase its sensitivity by about 40 percent over its last run. Additionally, with this third observing run, LIGO and Virgo transitioned to a system whereby they alert the astronomy community almost immediately of a potential gravitational wave detection. This allows electromagnetic telescopes (X-ray, UV, optical, radio) to search for and hopefully find an electromagnetic signal from the same source, which can be key to understanding the dynamics of the event.
The Penn State team of LIGO scientists, led by Chad Hanna, associate professor of physics and of astronomy and astrophysics, Freed Early Career Professor, and Institute for CyberScience faculty co-hire at Penn State, played a critical role.
"Penn State is part of a small team of LIGO scientists that analyze the data in almost real-time,” said Cody Messick, a graduate student in physics at Penn State and member of the LIGO team. “We are constantly comparing the data to hundreds of thousands of different possible gravitational waves and upload any significant candidates to a database as soon as possible. Although there are several different teams all performing similar analyses, the analysis ran by the Penn State team uploaded the candidates that were made public for both of these detections."
Messick has spent the last nine months working to ensure that uploaded gravitational wave candidates contain information from all of the detectors running at the time of a detection, even if the signal is extremely quiet in one of them. This helps with localizing the signals and has the potential to reduce the predicted area on the sky that the signal came from by over an order of magnitude. All of the LIGO public alerts will include a sky-map showing the possible location of the source on the sky, the time of the event, and what kind of event it is believed to be.
“These are near real-time detections of gravitational waves produced from two probable black holes colliding,” said Ryan Magee, a graduate student in physics at Penn State and member of the LIGO team. “We detected the first signal within about 20 seconds of its arrival to earth. We can set up automatic alerts to get phone calls and texts when a significant candidate is identified. I thought I was getting a spam phone call at first!”
The source of both gravitational waves is suspected to be compact binary mergers — the collision of two massive and incredibly dense cosmic objects into one another. Compact binary mergers can occur between two neutron stars, two black holes, or a neutron star and a black hole. Each of these different types of mergers create gravitational waves with strikingly different signals, so the LIGO team can identify the type of event that created the gravitational waves.
“With the updates to LIGO, I expect to see more signals,” said Magee. “I would really like to see a neutron star-black hole merger, which hasn’t been observed yet.”
LIGO consists of two massive detectors approximately 3,000 kilometers apart, one in Livingston, Louisiana, and one in Hanford, Washington. The signal from both gravitational waves was detected at both observatories as well as the Virgo gravitational wave observatory in Italy, and immediately made public.
“This is the first LIGO observation that was made public right away in an automated fashion,” said Surabhi Sachdev, Eberly Postdoctoral Research Fellow in physics at Penn State and member of the LIGO team. “This is the new LIGO policy starting with this observing run. Events are instantly made public automatically. After human vetting, a confirmation or retraction is issued within hours.”
In addition to Hanna, Messick, Magee and Sachdev, the LIGO team working on these discoveries at Penn State includes Bangalore Sathyaprakash, Patrick Godwin, Alex Pace, Ssohrab Borhanian, Anuradha Gupta, Becca Ewing, Divya Singh and Rachael Huxford.
https://news.psu.edu/story/569655/2019/04/16/research/first-ever-open-public-alerts-now-available-ligo
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First candidate binary neutron star merger for O3!
https://gracedb.ligo.org/superevents/S190425z/view/
--- Tony
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Very poor localisation as Hanford was offline.
https://twitter.com/mpi_grav/status/1121345345554980864
But INTEGRAL might have caught it at T+6s
https://www.astro.unige.ch/cdci/integral/transients/lvc-s190425z
--- Tony
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Good candidate for the EM counterpart:
TITLE: GCN CIRCULAR
NUMBER: 24221
SUBJECT: LIGO/Virgo GW190425z: GTC spectroscopic classification of AT2019ebq/PS19qp
DATE: 19/04/26 12:36:32 GMT
FROM: Peter Jonker at SRON/RU <[email protected]>
Peter Jonker (SRON/RU), Daniel Mata-Sanchez (Manchester), Morgan Fraser (UCD), Pablo RodrÃguez Gil (IAC), Kate Maguire (TCD), Andrew Levan (RU), Manuel Perez Torres (IAC), Danny Steeghs (Warwick), Stephen Smartt (Belfast), Nieves Castro (GTC) and Daniel Perez Valladares (GTC) report on behalf of the EMBOSS & ENGRAVE collaborations:
We observed the candidate optical counterpart AT2019ebq (reported in GCN 24210) with the Gran Telescopio Canarias (GTC) at the Observatorio del Roque de los Muchachos on La Palma.
We acquired one 1800 s spectrum using the R1000R grism beginning at 05:08:30 UT on 20190426. A preliminary host-subtracted spectrum shows broad absorption features unlike normal supernovae, with the most prominent centered at ~8600 Angstrom, making this target a prime candidate for the EM counterpart to GW190425.
https://gcn.gsfc.nasa.gov/gcn3/24221.gcn3
Edit: ruled out; supernova
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And another!
TITLE: GCN CIRCULAR
NUMBER: 24237
SUBJECT: LIGO/Virgo S190426c: Identification of a GW compact binary merger candidate
DATE: 19/04/26 16:45:04 GMT
FROM: Deep Chatterjee at University of Wisconsin,Milwaukee <[email protected]>
The LIGO Scientific Collaboration and the Virgo Collaboration report:
We identified the compact binary merger candidate S190426c during
real-time processing of data from LIGO Hanford Observatory (H1), LIGO
Livingston Observatory (L1), and Virgo Observatory (V1) at 2019-04-26
15:21:55.337 UTC (GPS time: 1240327333.337). The candidate was found
by the GstLAL [1], MBTAOnline [2], PyCBC Live [3], and SPIIR [4]
analysis pipelines.
S190426c is an event of interest because its false alarm rate, as
estimated by the online analysis, is 1.9e-08 Hz, or about one in 1
year, 7 months. The event's properties can be found at this URL:
https://gracedb.ligo.org/superevents/S190426c
The classification of the GW signal, in order of descending
probability, is BNS (49%), MassGap (24%), Terrestrial (14%), NSBH
(13%), or BBH (<1%).
Assuming the candidate is astrophysical in origin, there is strong
evidence for the lighter compact object having a mass < 3 solar
masses (HasNS: >99%). Using the masses and spins inferred from the
signal, there is strong evidence for matter outside the final compact
object (HasRemnant: >99%).
Two skymaps are available at this time and can be retrieved from the
GraceDB event page:
* bayestar.fits.gz, the preliminary sky localization generated by
BAYESTAR [5], distributed via GCN notice about 25 minutes after
the candidate,
* bayestar1.fits.gz, an updated localization distributed via GCN
notice about an hour after the candidate. This is the preferred
skymap at this time.
For the bayestar1.fits.gz skymap, the 90% credible region is 1262
deg2. Marginalized over the whole sky, the a posteriori luminosity
distance estimate is 375 +/- 108 Mpc (a posteriori mean +/- standard
deviation).
https://gcn.gsfc.nasa.gov/gcn3/24237.gcn3
https://gracedb.ligo.org/superevents/S190426c/
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Things move fast in the world of #GravitationalWaves astronomy. Here's an updated skymap and volume plot for our new candidate #S190426c, with better sky localization and a closer estimated distance. Watch for more updates at (link: https://gracedb.ligo.org/superevents/S190426c/view/) gracedb.ligo.org/superevents/S1… #O3ishere
https://twitter.com/LIGO/status/1121816429882482688
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LIGO detects gravitational waves from another neutron star merger (http://www.astronomy.com/news/2019/04/ligo-detects-gravitational-waves-from-another-neutron-star-merger)
For just the second time, physicists working on the Laser Interferometer Gravitational-Wave Observatory (LIGO) have caught the gravitational waves of two neutron stars colliding to likely form a black hole.
The ripples in space-time traveled some 500 million light-years and reached the detectors at LIGO, as well as its Italian sister observatory, Virgo, at around 4 a.m. E.T. Thursday, April 25. Team members say there’s a more than 99 percent chance that the gravitational waves were created from a binary neutron star merger.
And instead of finding one potential binary neutron star merger, astronomers turned up at least two different candidates. Now the question is which, if any, are related to the gravitational wave that LIGO saw. Sorting that out will require more observations, which were already happening around the world as darkness fell.
“I would assume that every observatory in the world is observing this now,” says astronomer Josh Simon of the Carnegie Observatories. “These two candidates (they’ve) found are relatively close to the equator, so they can be seen from both the Northern and Southern Hemisphere.”
Simon also says that, as of Thursday afternoon in the United States, telescopes in Europe and elsewhere should be gathering spectra on these objects. His fellow astronomers at the Carnegie Observatories turned their telescopes at Chile’s Las Campanas Observatory to the event Thursday night.
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As if the #GravitationalWaves excitement this week weren't already enough, on Sunday Apr 28 you can tune in to follow
@LIGO
Exec Director Dave Reitze's public lecture on the #GravitationalWaves story so far, and the field's extremely bright future!
https://twitter.com/LIGO/status/1122204105504641026
Thanks to those who worked late into the night, here's an updated estimate of the source location for #S190426c Northern hemisphere now looking more probable. LALINference1.fits.gz available from (link: https://gracedb.ligo.org/superevents/S190426c/view/) gracedb.ligo.org/superevent]Thanks to those who worked late into the night, here's an updated estimate of the source location for #S190426c Northern hemisphere now looking more probable. LALINference1.fits.gz available from (link: https://gracedb.ligo.org/superevents/S190426c/view/) gracedb.ligo.org/superevent
https://mobile.twitter.com/cplberry/status/1122144943190028288
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Gravitational Waves Hint at a Black Hole Eating a Neutron Star (https://www.scientificamerican.com/article/gravitational-waves-hint-at-a-black-hole-eating-a-neutron-star/)
Gravitational waves may have just delivered the first sighting of a black hole devouring a neutron star. If confirmed, it would be the first evidence of the existence of such binary systems. The news comes just a day after astronomers had detected gravitational waves from a merger of two neutron stars for only the second time.
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The current state of gravitational wave searches with LIGO/Virgo:
https://www.youtube.com/watch?v=4sXC-M1wfzk
This is from Princeton University's Institute for Advanced Study Physics group, of whom Einstein was once a member. The analyzed the LIGO observation runs 1 and 2 data after they were made public, and found 7 more events that the LIGO collaboration had missed. Also an overview of what is the state of the science of gravitational waves
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A Hubble constant measurement from superluminal motion of the jet in GW170817
The Hubble constant (H0) measures the current expansion rate of the Universe, and plays a fundamental role in cosmology. Tremendous effort has been dedicated over the past decades to measure H0 (refs. 1,2,3,4,5,6,7,8,9,10). Gravitational wave (GW) sources accompanied by electromagnetic (EM) counterparts offer an independent standard siren measurement of H0(refs. 11,12,13), as demonstrated following the discovery of the neutron star merger, GW170817 (refs. 14,15,16). This measurement does not assume a cosmological model and is independent of a cosmic distance ladder. The first joint analysis of the GW signal from GW170817 and its EM localization led to a measurement of 0=74+16−8kms−1Mpc−1H0=74−8+16kms−1Mpc−1 (median and symmetric 68% credible interval)13. In this analysis, the degeneracy in the GW signal between the source distance and the observing angle dominated the H0measurement uncertainty. Recently, tight constraints on the observing angle using high angular resolution imaging of the radio counterpart of GW170817 have been obtained17. Here, we report an improved measurement 0=70.3+5.3−5.0kms−1Mpc−1H0=70.3−5.0+5.3kms−1Mpc−1 by using these new radio observations, combined with the previous GW and EM data. We estimate that 15 more GW170817-like events, having radio images and light curve data, as compared with 50–100 GW events without such data18,19, will potentially resolve the tension between the Planck and Cepheid–supernova measurements.
https://www.nature.com/articles/s41550-019-0820-1
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We estimate that 15 more GW170817-like events, having radio images and light curve data, as compared with 50–100 GW events without such data18,19, will potentially resolve the tension between the Planck and Cepheid–supernova measurements.
Well, as it's been nearly two years since the first (and only) such event, I'm not holding my breath for the next 15! :)
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We estimate that 15 more GW170817-like events, having radio images and light curve data, as compared with 50–100 GW events without such data18,19, will potentially resolve the tension between the Planck and Cepheid–supernova measurements.
Well, as it's been nearly two years since the first (and only) such event, I'm not holding my breath for the next 15! :)
To be fair they believed they had detected another just to the best of my knowledge they didn’t get the follow up observations.
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We estimate that 15 more GW170817-like events, having radio images and light curve data, as compared with 50–100 GW events without such data18,19, will potentially resolve the tension between the Planck and Cepheid–supernova measurements.
Well, as it's been nearly two years since the first (and only) such event, I'm not holding my breath for the next 15! :)
Sensitivity has just gone up quite a lot, so 15*2 may be a pessimistic guess.
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We estimate that 15 more GW170817-like events, having radio images and light curve data, as compared with 50–100 GW events without such data18,19, will potentially resolve the tension between the Planck and Cepheid–supernova measurements.
Well, as it's been nearly two years since the first (and only) such event, I'm not holding my breath for the next 15! :)
Of course, you realize that O2 ended a week after the 170817 event in 2017, and O3 started 3 months ago, right?
In this time, they've been getting a rate an event candidate per week (of course, just a small subset of them will have electromagnetic counterparts, both in principle (BH-BH) and because it's not detectable in practice).
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We estimate that 15 more GW170817-like events, having radio images and light curve data, as compared with 50–100 GW events without such data18,19, will potentially resolve the tension between the Planck and Cepheid–supernova measurements.
Well, as it's been nearly two years since the first (and only) such event, I'm not holding my breath for the next 15! :)
Of course, you realize that O2 ended a week after the 170817 event in 2017, and O3 started 3 months ago, right?
In this time, they've been getting a rate an event candidate per week (of course, just a small subset of them will have electromagnetic counterparts, both in principle (BH-BH) and because it's not detectable in practice).
One event every three months means it's 3.75 years for fifteen. And that's observing time. Total time elapsed will be significantly greater. And the frequency of suitable detection may be more than one every three months, which will increase the total time further. So, at the current time, I'm not holding my breath. Of course, they may just have been unlucky and be in a bit of a lull, and if the frequency of suitable events increases sharply I shall reconsider my breathing pattern! :)
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We estimate that 15 more GW170817-like events, having radio images and light curve data, as compared with 50–100 GW events without such data18,19, will potentially resolve the tension between the Planck and Cepheid–supernova measurements.
Well, as it's been nearly two years since the first (and only) such event, I'm not holding my breath for the next 15! :)
Of course, you realize that O2 ended a week after the 170817 event in 2017, and O3 started 3 months ago, right?
In this time, they've been getting a rate an event candidate per week (of course, just a small subset of them will have electromagnetic counterparts, both in principle (BH-BH) and because it's not detectable in practice).
One event every three months means it's 3.75 years for fifteen. And that's observing time. Total time elapsed will be significantly greater. And the frequency of suitable detection may be more than one every three months, which will increase the total time further. So, at the current time, I'm not holding my breath. Of course, they may just have been unlucky and be in a bit of a lull, and if the frequency of suitable events increases sharply I shall reconsider my breathing pattern! :)
That kind of statement just screams hostage to fortune.
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Just detected a much better candidate for a black hole & neutron star merger than the earlier one this year. Currently other telescopes are engaged in follow up observations.
https://www.nationalgeographic.com/science/2019/08/astronomers-probably-just-saw-black-hole-swallow-neutron-star/
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New signal detected...
https://twitter.com/LIGO/status/1164350786765316102
Amazing...
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The above has now been retracted.
https://twitter.com/LIGO/status/1164379917922033666
https://twitter.com/LIGO/status/1164376727616798722
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https://www.sciencenews.org/article/gravitational-waves-ringing-black-hole-support-no-hair-theorem%5B
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https://www.sciencenews.org/article/gravitational-waves-ringing-black-hole-support-no-hair-theorem%5B
The link have some kind the problem:
https://www.sciencenews.org/article/gravitational-waves-ringing-black-hole-support-no-hair-theorem
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Testing the No-Hair Theorem with GW150914 (https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.111102) (Physical Review Letters, subscription required)
(Abstract)
We analyze gravitational-wave data from the first LIGO detection of a binary black-hole merger (GW150914) in search of the ringdown of the remnant black hole. Using observations beginning at the peak of the signal, we find evidence of the fundamental quasinormal mode and at least one overtone, both associated with the dominant angular mode (ℓ=m=2), with 3.6σ confidence. A ringdown model including overtones allows us to measure the final mass and spin magnitude of the remnant exclusively from postinspiral data, obtaining an estimate in agreement with the values inferred from the full signal. The mass and spin values we measure from the ringdown agree with those obtained using solely the fundamental mode at a later time, but have smaller uncertainties. Agreement between the postinspiral measurements of mass and spin and those using the full waveform supports the hypothesis that the GW150914 merger produced a Kerr black hole, as predicted by general relativity, and provides a test of the no-hair theorem at the ∼10% level. An independent measurement of the frequency of the first overtone yields agreement with the no-hair hypothesis at the ∼20% level. As the detector sensitivity improves and the detected population of black-hole mergers grows, we can expect that using overtones will provide even stronger tests.
A Kerr black hole is one with zero electrical charge - despite what Science News says, a black hole can also be distinguished by its electric charge as well as its mass and angular momentum. AIUI, the no-hair theorem has not been proved for Kerr black holes and is of interest because it conflicts with the quantum mechanics requirement of no information loss and it's hoped will point towards a description of quantum gravity.
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https://twitter.com/LIGO/status/1179579283431403520
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https://twitter.com/ligo/status/1193668974803898368
https://twitter.com/LIGO/status/1193672224038936576
Curious.
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Scientists with the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo collaborations have announced the detection of a second pair of neutron stars that went bump in the night. The announcement was made at the meeting of the American Astronomical Society in Honolulu and the results will appear in an upcoming issue of Astrophysical Journal Letters.
And more generally.
Meanwhile, the KAGRA detector in Japan is coming online, and two other detectors in India and Germany will see first their first signals within a few years. By the end of the decade, the network of gravitational-wave detectors will be able to see events out to a billion light-years away.
Astronomers expect this network to detect up to hundreds of black hole mergers every month, and up to a dozen neutron star mergers a year. “Going from three detectors to five within the decade, we will go from some 50 events to more than 10,000,” says Aidan Brookes (LIGO).
Not only will this near-future network be extraordinarily sensitive to the gravitational-wave universe, it will also be able to pinpoint locations to a sky area 10 times smaller, which will make follow-up observations more feasible. The delay for Processing of the signals will also be sped up, so that alerts can be sent out mere seconds after an event occurs, compared to the several minutes required now.
“The take-away message,” says LIGO Executive Director David Reitze (Caltech), “is buckle your seat belts!”
https://www.skyandtelescope.com/astronomy-news/gravitational-waves-from-second-neutron-star-collision-observed/
https://youtu.be/853sZWxVto4
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(Potentially very) exciting stuff?
https://twitter.com/LIGO/status/1216914957977227272
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(Potentially very) exciting stuff?
Short duration one, that's for sure. What's it centered around in the sky?
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(Potentially very) exciting stuff?
Short duration one, that's for sure. What's it centered around in the sky?
Some discussion: https://twitter.com/d_a_howell/status/1216924894505496577
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Some discussion:
Well that's interesting. Thanks! :D
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As no light by now, then not Betelgeuse?
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As no light by now, then not Betelgeuse?
Nope, should have been seen in neutrinos soon after the GW event too, if that was the case.
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Some (unsatisfying, for now) followup:
https://twitter.com/d_a_howell/status/1217623983853432832
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Nope, should have been seen in neutrinos soon after the GW event too, if that was the case.
I think we should actually detect neutrinos *before* the GW event, during the Si-burning phase; so perhaps a day before boom 8)
--- Tony
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Nope, should have been seen in neutrinos soon after the GW event too, if that was the case.
I think we should actually detect neutrinos *before* the GW event, during the Si-burning phase; so perhaps a day before boom 8)
--- Tony
Why would neutrino luminosity be that high already then?
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Why would neutrino luminosity be that high already then?
Pretty much every nuclear reaction emits a neutrino, and the reaction rate increases dramatically as the star climbs the alpha-ladder. SNEWS should be able to detect these above the background for a few hours prior to the core-collapse.
See:
- https://aasnova.org/2018/04/20/capturing-neutrinos-from-a-stars-final-hours/
- https://arxiv.org/abs/1705.04750
--- Tony
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Nope, should have been seen in neutrinos soon after the GW event too, if that was the case.
I think we should actually detect neutrinos *before* the GW event, during the Si-burning phase; so perhaps a day before boom 8)
--- Tony
[/quote
Why would neutrino luminosity be that high already then?
Also see this https://en.m.wikipedia.org/wiki/SN_1987A#Neutrino_emissions
Visible light travels with the shockwave, neutrinos don’t care, they don’t wait.
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https://twitter.com/LIGO/status/1217322692002619392
Not sure how to read this why only refer to one component what about the other?
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Not sure how to read this why only refer to one component what about the other?
The BH component falls into the "mass gap", so 3-5 solar masses. The other component is lighter, and a neutron star (i.e. in the vertical part of the green bar of the attached)
Chris Berry covers this event here: https://twitter.com/cplberry/status/1217314034602725376
--- Tony
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Why would neutrino luminosity be that high already then?
Pretty much every nuclear reaction emits a neutrino, and the reaction rate increases dramatically as the star climbs the alpha-ladder. SNEWS should be able to detect these above the background for a few hours prior to the core-collapse.
See:
- https://aasnova.org/2018/04/20/capturing-neutrinos-from-a-stars-final-hours/
- https://arxiv.org/abs/1705.04750
--- Tony
Thanks, I hadn't realised how much the sensitivity of neutrino observatories has improved.
Even though the neutrino luminosity is high immediately pre-collapse, it's still a factor of 1e5 or so below the luminosity of the ~10 second neutrino pulse from collapse. But indeed, it seems that for relatively nearby SNe a detection could be possible even hour earlier.
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Even though the neutrino luminosity is high immediately pre-collapse, it's still a factor of 1e5 or so below the luminosity of the ~10 second neutrino pulse from collapse. But indeed, it seems that for relatively nearby SNe a detection could be possible even hour earlier.
Yup. Also relevant to this, we might be able to probe the mass ordering:
https://twitter.com/kevaba/status/1217593046600048640
--- Tony
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Nope, should have been seen in neutrinos soon after the GW event too, if that was the case.
I think we should actually detect neutrinos *before* the GW event, during the Si-burning phase; so perhaps a day before boom 8)
--- Tony
Si-burning neutrinos are sub-dominant and probably would only be disentangled *after* the event with current analysis and techniques, even if visible. In a few years, with the newer-generation neutrino detectors coming online and improved early-warning networks, it will be possible to use them to warn about an impending SN as you say.
Burst SN neutrinos necessarily arrive after the bang since they have a positive mass (even if tiny) and GWs travel at the speed of light, no ifs or buts. At typical galactic SN distances, this time delay is milliseconds - that's my "soon after", arguably coincident but not really: neutrino absolute masses could be derived from that time delay measurement if sufficiently large.
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Nope, should have been seen in neutrinos soon after the GW event too, if that was the case.
I think we should actually detect neutrinos *before* the GW event, during the Si-burning phase; so perhaps a day before boom 8)
--- Tony
Si-burning neutrinos are sub-dominant and probably would only be disentangled *after* the event with current analysis and techniques, even if visible. In a few years, with the newer-generation neutrino detectors coming online and improved early-warning networks, it will be possible to use them to warn about an impending SN as you say.
Burst SN neutrinos necessarily arrive after the bang since they have a positive mass (even if tiny) and GWs travel at the speed of light, no ifs or buts. At typical galactic SN distances, this time delay is milliseconds - that's my "soon after", arguably coincident but not really: neutrino absolute masses could be derived from that time delay measurement if sufficiently large.
I think the time scale of the neutrino emission after the "bang" is too long (more like seconds instead of milliseconds) to allow the determination of neutrino masses from the delay between GW and neutrino signals at least for Galactic SNe.
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I think the time scale of the neutrino emission after the "bang" is too long (more like seconds instead of milliseconds) to allow the determination of neutrino masses from the delay between GW and neutrino signals at least for Galactic SNe.
Of course you're basing your measurement/limit on the first SN neutrino event you measure. Accidental coincidences or backgrounds should be low enough that you can assume everything you see in those few seconds are actual SN neutrinos.
The uncertainties derived from that will impact the result and limit how well you can do, but it is estimated (here for example: https://arxiv.org/pdf/hep-ph/0109027.pdf) current detectors like SuperK, in conjunction with GW interferometers, can reach a sensitivity of around 1 eV. Ground-based experiments based on other techniques can do better than that (currently Katrin expects to reach 0.2 eV, and has already published 1.1 eV), but newer neutrino detectors with longer reach/more sensitivity could lower that limit quite further.
Measuring the time delay between the arrivals of the first galactic SN burst neutrinos and the first GWs (or increased photon flux if that particular star is being observed sufficiently precisely in that moment) is actually a golden channel for absolute neutrino mass determination, since there will be a delay in the times of flight between massive (neutrinos) and massless (photons, gravitons) - see for instance Section 8.4 here for a straightforward derivation: https://arxiv.org/pdf/hep-ph/0211462.pdf
My order-of-milliseconds figure was coming from a quantification I recently read in this paper by the JUNO collaboration (the neutrino detector under construction in China, not Juno the Jovian spacecraft): https://arxiv.org/pdf/1412.7418.pdf
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Thought this might of interest to this thread:
https://twitter.com/GravitySpyZoo/status/1217932791515619329
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Si-burning neutrinos are sub-dominant and probably would only be disentangled *after* the event with current analysis and techniques, even if visible. In a few years, with the newer-generation neutrino detectors coming online and improved early-warning networks, it will be possible to use them to warn about an impending SN as you say.
Cheers! Thinking about it, I'm pretty sure I was remembering stuff from the JUNO papers, so as you say, not commissioned yet
--- Tony
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Last week an unusual gravitational wave event was detected at Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo interferometer.
Articles:
https://www.livescience.com/mysterious-gravitational-burst.html (https://www.livescience.com/mysterious-gravitational-burst.html)
https://www.foxnews.com/science/mysterious-gravitational-waves-hit-earth (https://www.foxnews.com/science/mysterious-gravitational-waves-hit-earth)
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KAGRA has started observations! Three long-arm interferometers working in unison now :) I had the honor of working next to it, in the neutrino section of the observatory, for the last two years - but sadly didn't get the chance to visit its gallery.
https://gwcenter.icrr.u-tokyo.ac.jp/en/archives/1381
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Unknown object collided with a black hole, heavier than a Neutron Star is expected to be, yet lighter than a Black Hole is expected to be.
https://www.ligo.org/science/Publication-GW190814/
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Now researchers have detected a signal from what may be the most massive black hole merger yet observed in gravitational waves. The product of the merger is the first clear detection of an "intermediate-mass" black hole, with a mass between 100 and 1,000 times that of the sun.
They detected the signal, which they have labeled GW190521, on May 21, 2019, with the National Science Foundation's Laser Interferometer Gravitational-wave Observatory (LIGO), a pair of identical, 4-kilometer-long interferometers in the United States; and Virgo, a 3-kilometer-long detector in Italy.
https://phys.org/news/2020-09-ligo-virgo-detectors-massive-gravitational-wave.html
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A great article on GW190521
https://cplberry.com/2020/09/02/gw190521-the-big-one/amp/?__twitter_impression=true
--- Tony
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A great article on GW190521
https://cplberry.com/2020/09/02/gw190521-the-big-one/amp/?__twitter_impression=true
--- Tony
Loving it, thanks for the link (I liked it so much that thought a mere "like" was not enough - it's really well explained)
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Scott Manley on this discovery:
https://youtu.be/FtYwsw3hefc
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A tabletop gravity wave detector powered by a nanoscopic diamond could revolutionize particle physics, its creators say. And unlike existing detectors, it fits on a tabletop.
In a preprint paper, researchers describe a small device with the modified diamond in the center. The diamond is prepared by trading one carbon for one nitrogen, which opens a critical electron gap where a new and functional electron is inserted.
https://www.popularmechanics.com/science/a33812780/tabletop-device-measure-gravity-waves-quantum/
Here’s the preprint paper:
https://iopscience.iop.org/article/10.1088/1367-2630/ab9f6c/meta
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Related to 2017's Nobel Prize on physics, this year's goes to Penrose, Genzel and Ghez for their contributions to the physics of black holes.
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There’s an interview with Roger Penrose on The Times newspaper website but unfortunately it’s behind a paywall.
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The black hole always chirps twice: Scientists find clues to decipher the shape of black holes
A team of gravitational wave researchers led by the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav) report that when two black holes collide and merge, the remnant black hole "chirps" not once, but multiple times, emitting gravitational waves—intense ripples in the fabric space and time—that reveal information about its shape. Their study has been published in Communications Physics.
https://phys.org/news/2020-10-black-hole-chirps-scientists-clues.amp
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Gravitational waves are distortions in spacetime caused by super violent cosmic events. Something so cataclysmic may seem like it would be hard to miss, but in reality, these events happen so far away that detecting gravitational waves is quite a challenge. Three massive gravitational wave detection facilities were built in the mid-1990s, but for decades, scientists searched for faint signals with no avail. After the first gravitational wave events were recorded in 2015, it took four years for researchers to spot only 11 more faint signals.
Now, thanks to ever more sensitive equipment, gravitational wave observations have gone from an astronomical rarity to a near-weekly occurrence. In 2019, scientists measured 39 new wave events in just six months, Emily Conover reports for Science News.
https://www.smithsonianmag.com/smart-news/dozens-new-gravitational-wave-measurements-collected-last-year-180976174/
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Gravitational wave lensing beyond general relativity: Birefringence, echoes, and shadows
ABSTRACT
Gravitational waves (GW), as light, are gravitationally lensed by intervening matter, deflecting their trajectories, delaying their arrival and occasionally producing multiple images. In theories beyond general relativity, new gravitational degrees of freedom add an extra layer of complexity and richness to GW lensing. We develop a formalism to compute GW propagation beyond general relativity over general space-times, including kinetic interactions with new fields. Our framework relies on identifying the dynamical propagation eigenstates (linear combinations of the metric and additional fields) at leading order in a short-wave expansion. We determine these eigenstates and the conditions under which they acquire a different propagation speed around a lens. Differences in speed between eigenstates cause birefringence phenomena, including time delays between the metric polarizations (orthogonal superpositions of
h
+
,
h
×
) observable without an electromagnetic counterpart. In particular, GW echoes are produced when the accumulated delay is larger than the signal’s duration, while shorter time delays produce a scrambling of the waveform. We also describe the formation of GW shadows as nonpropagating metric components are sourced by the background of the additional fields around the lens. As an example, we apply our methodology to quartic Horndeski theories with Vainshtein screening and show that birefringence effects probe a region of the parameter space complementary to the constraints from the multimessenger event GW170817. In the future, identified strongly lensed GWs and binary black holes merging near dense environments, such as active galactic nuclei, will fulfill the potential of these novel tests of gravity.
https://journals.aps.org/prd/abstract/10.1103/PhysRevD.102.124048
Their paper lays out the conditions for how to find such effects in future data. The next LIGO run is scheduled to begin in 2022, with an upgrade to make the detectors even more sensitive than they already are.
"In our last observing run with LIGO, we were seeing a new gravitational wave reading every six days, which is amazing. But in the entire universe, we think they're actually happening once every five minutes," Ezquiaga said. "In the next upgrade, we could see so many of those—hundreds of events per year."
The increased numbers, he said, make it more likely that one or more wave will have traveled through a massive object, and that scientists will be able to analyze them for clues to the missing components.
https://phys.org/news/2020-12-ripples-space-time-clues-components-universe.html
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Honest question : am curious whether we now have more (than one) LIGO events confirmed via optical or other telescopes? I lost track of such reports.
This goes back to a blog at the backreaction from a year ago (https://backreaction.blogspot.com/2019/11/have-we-really-measured-gravitational.html) However, no telescope has so far seen a signal that fits to any of the gravitational wave events. This may simply mean that the signals have been too weak for the telescopes to see them. But whatever the reason, the consequence is that we still do not know that what LIGO and Virgo see are actually signals from outer space.
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Honest question : am curious whether we now have more (than one) LIGO events confirmed via optical or other telescopes? I lost track of such reports.
This goes back to a blog at the backreaction from a year ago (https://backreaction.blogspot.com/2019/11/have-we-really-measured-gravitational.html) However, no telescope has so far seen a signal that fits to any of the gravitational wave events. This may simply mean that the signals have been too weak for the telescopes to see them. But whatever the reason, the consequence is that we still do not know that what LIGO and Virgo see are actually signals from outer space.
No (though they did detect another binary neutron star collision, but no EM counter part), and there won't be any for a while. O3 run was suspended early in March due to COVID-19, and the next observing run will only start NET June 2022 after some upgrades.
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Honest question : am curious whether we now have more (than one) LIGO events confirmed via optical or other telescopes? I lost track of such reports.
This goes back to a blog at the backreaction from a year ago (https://backreaction.blogspot.com/2019/11/have-we-really-measured-gravitational.html) However, no telescope has so far seen a signal that fits to any of the gravitational wave events. This may simply mean that the signals have been too weak for the telescopes to see them. But whatever the reason, the consequence is that we still do not know that what LIGO and Virgo see are actually signals from outer space.
No (though they did detect another binary neutron star collision, but no EM counter part), and there won't be any for a while. O3 run was suspended early in March due to COVID-19, and the next observing run will only start NET June 2022 after some upgrades.
The article I posted above seems to indicate they are expecting a big increase in detections, are they now expecting daily detections being as they same article indicates a theorised even rate of every five minutes somewhere in the universe.
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GEO600 reaches 6 dB of squeezing
Gravitational waves cause tiny length changes in the kilometer-size detectors of the international network (GEO600, KAGRA, LIGO, Virgo). The instruments use laser light to detect these effects and are so sensitive that they are fundamentally limited by quantum mechanics. This limit manifests as an ever-present background noise which can never be fully removed and which overlaps with gravitational-wave signals. But one can change the noise properties – using a process called squeezing – such that it does not disturb the measurements as much. Now, GEO600 researchers have achieved the strongest squeezing ever seen in a gravitational-wave detector. They lowered the quantum mechanical noise by up to a factor of two. This is a big step to third-generation detectors such as the Einstein Telescope and Cosmic Explorer. The GEO600 team is confident to reach even better squeezing in the future.
https://www.aei.mpg.de/626965/geo600-reaches-6-db-of-squeezing
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GW190521 as a Merger of Proca Stars: A Potential New Vector Boson of 8.7×10−13eV
ABSTRACT
Advanced LIGO-Virgo have reported a short gravitational-wave signal (GW190521) interpreted as a quasicircular merger of black holes, one at least populating the pair-instability supernova gap, that formed a remnant black hole of Mf∼142M at a luminosity distance of dL∼5.3Gpc. With barely visible pre-merger emission, however, GW190521 merits further investigation of the pre-merger dynamics and even of the very nature of the colliding objects. We show that GW190521 is consistent with numerically simulated signals from head-on collisions of two (equal mass and spin) horizonless vector boson stars (aka Proca stars), forming a final black hole with Mf=231+13−17M, located at a distance of dL=571+348−181Mpc. This provides the first demonstration of close degeneracy between these two theoretical models, for a real gravitational-wave event. The favored mass for the ultralight vector boson constituent of the Proca stars is μV=8.72+0.73−0.82×10−13 eV. Confirmation of the Proca star interpretation, which we find statistically slightly preferred, would provide the first evidence for a long sought dark matter particle.
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.126.081101
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Is there more info on Proca Stars? I found all links pointed to this article or others where they just say it's a Bose-Einstein boson star.
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Is there more info on Proca Stars? I found all links pointed to this article or others where they just say it's a Bose-Einstein boson star.
Doing a search on the term returns numerous papers unrelated to this one.
See the link below as an example.
https://arxiv.org/abs/1508.05395
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Is there more info on Proca Stars? I found all links pointed to this article or others where they just say it's a Bose-Einstein boson star.
Well yes, that is what it is. Proca stars are a vector boson (spin 1) version of hypothesised scalar boson (spin 0) stars, usually called SBS. They are self-gravitating condensates of a new theoretical low-mass boson. They can be incredibly dense, but as long as they are stable they won't collapse into a singularity; unless of course they collide, disrupting the condensate. Part of the interest in the idea is that in some ways they would mimic black holes, which may be why we see what we think are black holes in the LIGO observations but with masses that don't seem possible with the collapse of ordinary matter. If Proca stars exist and indeed are made up of a new low-mass boson they are a dark matter candidate.
It's a relatively new and esoteric subject so there is very little accessibly written on it so far. Pretty much everything discussing them is an academic paper. This is probably the best layman explanation of the situation,
https://spaceaustralia.com/index.php/feature/black-holes-or-boson-stars-mystery-gw190521
Edit: Also,
https://briankoberlein.com/blog/proca-stars/
https://www.sciencealert.com/there-could-be-transparent-stars-made-of-bosons-masquerading-as-black-holes
(Though it refers to the scalar boson version.)
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I've got that. But you can hypothesize about a stellar object composed only of up quarks, or whatever. But how would they have formed? Why would they be formed of just that? Etc. Explaining a middle mass black hole can be explained by a massive companion that it slowly consumed. I don't understand how you can say that a a stellar object made up only of a single boson is a better explanation than a black hole that ate a companion or more.
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A ground-breaking detector that aims to use quartz to capture high frequency gravitational waves has been built by researchers at the ARC Centre of Excellence for Dark Matter Particle Physics (CDM) and The University of Western Australia.
In its first 153 days of operation, two events were detected that could, in principle, be high frequency gravitational waves, which have not been recorded by scientists before.
Such high frequency gravitational waves may have been created by a primordial black hole or a cloud of dark matter particles.
https://www.uwa.edu.au/news/Article/2021/August/World-first-detector-reports-rare-events
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90 GW event detected so far:
https://twitter.com/ego_virgo/status/1457513267941855236
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GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo During the Second Part of the Third Observing Run
The third Gravitational-wave Transient Catalog (GWTC-3) describes signals detected with Advanced LIGO and Advanced Virgo up to the end of their third observing run. Updating the previous GWTC-2.1, we present candidate gravitational waves from compact binary coalescences during the second half of the third observing run (O3b) between 1 November 2019, 15:00 UTC and 27 March 2020, 17:00 UTC. There are 35 compact binary coalescence candidates identified by at least one of our search algorithms with a probability of astrophysical origin pastro>0.5. Of these, 18 were previously reported as low-latency public alerts, and 17 are reported here for the first time. Based upon estimates for the component masses, our O3b candidates with pastro>0.5 are consistent with gravitational-wave signals from binary black holes or neutron star-black hole binaries, and we identify none from binary neutron stars. However, from the gravitational-wave data alone, we are not able to measure matter effects that distinguish whether the binary components are neutron stars or black holes. The range of inferred component masses is similar to that found with previous catalogs, but the O3b candidates include the first confident observations of neutron star-black hole binaries. Including the 35 candidates from O3b in addition to those from GWTC-2.1, GWTC-3 contains 90 candidates found by our analysis with pastro>0.5 across the first three observing runs. These observations of compact binary coalescences present an unprecedented view of the properties of black holes and neutron stars.
https://arxiv.org/abs/2111.03606
Source: https://phys.org/news/2021-11-scientists-tsunami-gravitational.html
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Scientists recently observed two black holes that united into one, and in the process got a “kick” that flung the newly formed black hole away at high speed. That black hole zoomed off at about 5 million kilometers per hour, give or take a few million, researchers report in a paper in press in Physical Review Letters. That’s blazingly quick: The speed of light is just 200 times as fast.
https://www.sciencenews.org/article/black-hole-gravitational-waves-kick-ligo-merger-spacetime
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After being offline for three years for upgrades LIGO and associated facilities begin the O4 observing run from the 25/05.
Details below.
On Wednesday, the LIGO-Virgo-KAGRA (LVK) collaboration began a new observing run with upgraded instruments, new and even more accurate signal models, and more advanced data analysis methods. The LVK collaboration consists of scientists across the globe who use a network of observatories — LIGO in the United States, Virgo in Europe, and KAGRA in Japan — to search for gravitational waves, or ripples in space-time, generated by colliding black holes and other extreme cosmic events.
This observing run, known as O4, promises to take gravitational-wave astronomy to the next level. Beginning on May 24 and lasting 20 months, including up to two months of commissioning breaks, O4 will be the most sensitive search yet for gravitational waves. LIGO will resume operations May 24, while Virgo will join later in the year. KAGRA will join for one month, beginning May 24, rejoining later in the run after some upgrades.
https://news.mit.edu/2023/gravitational-wave-detectors-start-next-observing-run-0525
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Already 9 O4 candidates
https://gracedb.ligo.org/superevents/public/
--- Tony