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  • richardmitnick 1:45 pm on March 29, 2017 Permalink | Reply
    Tags: , , , Caltech/MIT Advanced aLigo, , ,   

    From aeon: “Echoes of a black hole” 



    An infrared image from NASA’s Spitzer Space Telescope shows the centre of the Milky Way galaxy where the brightest white spot marks the site of a supermassive black hole

    Sabine Hossenfelder

    A billion years ago, two dancing black holes make a final spin, merge, and – in a matter of seconds – release a cataclysmic amount of energy. Much as a falling pebble spreads waves on the surface of a still lake, the merger initiates gravitational waves in the space-time continuum. Fast-forward to planet Earth and the year 2015. After an immense journey, the gravitational waves from the black-hole merger pass through our solar system. On the morning of 14 September, they oh-so-slightly wiggle the arms of the twin Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in Louisiana and Washington state.

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Niayesh Afshordi at the University of Waterloo in Canada first heard of LIGO’s seminal detection over lunch in a bistro. It was late 2015 and still weeks to go until the results were officially released. But rumours were buzzing, and a colleague who had seen the unpublished paper spilled the beans. Afshordi, an astrophysicist who also works at the Perimeter Institute in Waterloo, instantly appreciated the importance of the news – both for the physics community at large, and for his own unconventional theory about the construction of the Universe.

    ‘I had an existential crisis at some point. I thought all the problems in cosmology had been solved,’ Afshordi recalled. ‘But then I came up with this idea that dark energy is made by black holes.’ Studies of distant stellar explosions and other lines of evidence show that our universe grows at an accelerating pace, but nobody knows the cause. Matter alone cannot have this effect, so cosmologists blame the expansion on a peculiar type of energy, called dark energy. Its origin and nature were, and are, a mystery.

    In 2009, Afshordi, together with his colleagues Chanda Prescod-Weinstein and Michael Balogh, put forward a theory according to which black holes seed a long-range field that mimics dark energy. The field spills out from black holes and spans through the Universe. It’s an intriguing explanation for the origin of dark energy and, by Afshordi’s calculations, the number of black holes estimated to exist should create just about the right amount of field energy to fit the observations.

    But Afshordi’s idea overthrows what physicists believed they knew about black holes. In Albert Einstein’s theory of general relativity, the event horizon of a black hole – the surface beyond which there is no escape – is insubstantial. Nothing special happens upon crossing it, just that there is no turning around later. If Afshordi is right, however, the inside of the black hole past the event horizon no longer exists. Instead, a Planck-length away from where the horizon would have been, quantum gravitational effects become large, and space-time fluctuations go wild. (The Planck length is a minuscule distance: about 10-35 metres, or 10-20 times the diameter of a proton.) It’s a complete break with relativity.

    When he heard of the LIGO results, Afshordi realised that his so-far entirely theoretical idea could be observationally tested. If event horizons are different than expected, the gravitational-wave bursts from merging black holes should be different, too. Events picked up by LIGO should have echoes, a subtle but clear signal that would indicate a departure from standard physics. Such a discovery would be a breakthrough in the long search for a quantum theory of gravity. ‘If they confirm it, I should probably book a ticket to Stockholm,’ Afshordi said, laughing.

    Quantum gravity is the missing unification of general relativity with the quantum field theories of the standard model of particle physics. If just thrown together, the two theories lead to internal contradictions, and fail to make sense. Black holes are one of the most studied examples for such a contradiction. Use quantum field theory near the horizon and you find that the black hole emits particles, slowly evaporating. Those particles carry away mass but, as Stephen Hawking demonstrated in the 1970s, they cannot carry information about what formed the black hole. And so, if the black hole evaporates entirely, all the information about what fell in has been destroyed. In quantum field theory, however, information is always preserved. Something in the mathematics, therefore, doesn’t fit correctly.

    The culprit, most physicists think, is that the calculation doesn’t take into account the quantum behaviour of space and time because the theory for this – quantum gravity – is still unknown. For decades, physicists thought that the quantum gravitational effects necessary to solve the black-hole conundrum were hidden behind the event horizon. They thought that it is only near the singularity, at the centre of the black hole, that the effects of quantum gravity become relevant. But recently, they have had to rethink.

    In 2012, a group of researchers from the University of California, Santa Barbara, found an unexpected consequence of the currently favoured idea that information somehow escapes with the radiation from a black hole. To make the idea work, large deviations from general relativity are required, not only near the singularity but also at the event horizon. Those deviations would create what the researchers dubbed a ‘black hole firewall’, a barrier of high energy just outside the horizon.

    Such a firewall (if it exists) would become noticeable only for an infalling observer, and would not emit observable signatures that could show up in our telescopes. However, the firewalls lent support to Afshordi’s earlier idea that black holes create a field that acts as dark energy. If that was so, then the near-horizon region of black holes should be very different from what general relativity predicts; a firewall that solves the black hole information-loss problem could be one effect of that deviation. Afshordi’s proposal for how to modify general relativity might therefore hold the key to resolving the tension between quantum theory and general relativity. It was an idea that wouldn’t let him go.

    When he learned of LIGO’s first detection, Afshordi began to explore whether the gravitational waves emitted from a black-hole merger could reveal intimate details about what happens near the black-hole horizon. At first it seemed too much to hope for. ‘I didn’t really think we could see quantum gravity effects in the gravitational-wave signal because we had already looked in so many places,’ Afshordi said. ‘But I changed my mind about this.’

    What made Afshordi reconsider was work by Vítor Cardoso and colleagues at the Instituto Superior Técnico in Portugal on gravitational-wave echoes from black holes. Cardoso had laid out on general grounds that a merger of two objects that are compact but do not have an event horizon would produce gravitational waves very similar to those of black holes – similar, but not identical. The key feature indicating the horizon’s absence, Cardoso argued, would be a periodic recurrence in the signal from the merger. Instead of a single peak followed by a ringdown (think a big splash on a pond, and then rapidly dissipating ripples), the gravitational waves should come as a series of fading pulses – fainter echoes of the original event. Afshordi found that the near-horizon modification described by his theory would cause exactly such echoes. Moreover, he could calculate their recurrence time as a function of the final black hole’s mass, allowing a precise prediction.

    Nobody had ever sought such a signal before, and finding it would not be easy. So far there are only two public, well-defined gravitational-wave detections from LIGO. Together with a collaborator, Afshordi analysed the LIGO data for traces of echoes. By comparing the openly available recordings to random noise, they found an echo at the calculated recurrence time. The statistical significance is not high, however. In scientific terms, it has an estimated significance of 2.9 sigma. Such a signal can be caused by pure noise with a chance of about a one-in-200. In physics, an event of such low confidence is interesting but does not amount to a discovery.

    The LIGO experiment is really just getting started, however. The most remarkable thing about the first two gravitational wave events is that the facilities were able to record them at all. The technological challenges were tremendous. Each site, both in Louisiana and in Washington state, has an interferometer with two perpendicular arms about 4 kilometres long in which a laser beam bounces back and forth between mirrors; when recombined, the beams interfere with each other. Interference of the laser’s light-waves is sensitive to deformations in the arms’ relative length as little as a thousandth the diameter of a proton. That is the level of sensitivity required to pick up gravitational effects of colliding black holes.

    A gravitational wave passing through the interferometer deforms both arms at different times, thereby skewing the interference pattern. Requiring an event to be recorded at both sites provides protection against false alarms. By design, LIGO detects gravitational waves best at wavelengths of hundreds to thousands of kilometres, the range expected for black-hole mergers. Other gravitational-wave detectors are planned to cover different parts of the spectrum, each tuned to different types of phenomena.

    Gravitational waves are an unavoidable prediction of general relativity. Einstein recognised that space-time is dynamic – it stretches, it curves, and it wiggles in response to gravitational disturbances. When it wiggles, the waves can travel freely into the far distance, carrying away energy and manifesting themselves by a periodic expansion and contraction of space in orthogonal directions. We have long had indirect evidence for gravitational waves. Because they carry away energy, they cause a small but measurable decay in the mutual orbit of binary pulsars. This effect was first observed in the 1970s, and was awarded a Nobel Prize in 1993. But until LIGO’s detection, we had no direct evidence for the existence of gravitational waves.

    LIGO’s first event – the September 2015 detection that so excited Afshordi – was remarkable, and not only because it happened just a few days after a long-planned instrumental upgrade. It stood out also because the merging black holes were so heavy, with masses estimated at 29 and 36 times the Sun’s mass. ‘A lot of people expected the black hole events to have lower masses,’ said Ofek Birnholtz, a member of the LIGO collaboration’s group on compact binary coalescence and a physicist at the Max Planck Institute in Germany. The strikingly clean signal, together with the collaboration’s openness in sharing the data, has been an inspiration for physicists in other communities who, like Afshordi, are now exploring how to use the new observations for their own work.

    On 26 December 2015, LIGO recorded a second event. The age of gravitational-wave astronomy had officially begun, after many years of slow progress and false starts. ‘Some of my PhD colleagues had left the field of gravitational-wave astronomy,’ Birnholtz said and added, laughing, ‘but are returning because suddenly it’s hot again.’ This is uncharted territory, basic research at its finest. What kind of black hole and compact stellar systems are there? Where are they within the galaxies? What do the gravitational waves reveal about their origins? If a neutron star merges with a black hole, what can be learned about matter in such extreme conditions? Do black holes behave the way that our calculations predict?

    Afshordi’s theory of black holes and dark energy is just one example of the kinds of enquiries that are now possible. A wealth of information is waiting to be explored, openly, around the world.

    A few days after Afshordi’s result appears on the open-access server arXiv.org, members of the LIGO collaboration scrutinise the analysis. It takes only a few weeks until they publish a reply, criticise the methodology, and call for different statistical tools. Birnholtz is one of the authors of that criticism.

    ‘The claim is surprising,’ said Birnholtz. ‘I have no prior as to whether or not there should be echoes. That’s physics nobody can guess at. But I do have a strong intuition, working with LIGO data, that the amplitude is probably not large enough to claim such a significance at this stage.’ Birnholtz has suggestions for how to improve the analysis, but avoids making statements about the chances of confirming the result. Alex Nielsen, another member of the LIGO collaboration and one of Birnholtz’s co-authors, reiterates the need for caution: ‘As members of the LIGO collaboration, we have to be very careful about what statements we make in public, before we have full collaboration approval. But the data is public and people can do with it what they want.’

    The LIGO collaboration has an open science centre, where data recorded for one hour around the time of confirmed gravitational events is publicly available. ‘People are welcome to use it and contact us for any questions,’ Birnholtz said. ‘If they find anything interesting, they can share it with us, and we can work on it together. This is part of the scientific experience.’

    The collaboration has several thousand members worldwide, distributed at more than a hundred institutions. They meet twice a year; the most recent meeting was in March in Pasadena, California. Some members of the collaboration are now trying to reproduce Afshordi’s analysis. Birnholtz expects the effort to take several months. ‘The result might be disappointing,’ he warned. ‘Not in that it says there are no echoes, but that we can’t say whether there are echoes.’ Gravitational-wave astronomy is still a field in its infancy, though, and much more data are on the way. The collaboration estimates that by the completion of the third observing run in 2018, LIGO is likely to have made 40 high-quality detections of black-hole mergers. Each will offer another opportunity to test Afshordi’s theory.

    Because they interact so weakly and deposit so little energy as they pass by, gravitational waves are exceedingly difficult to measure. The deformation they cause is tiny, and enormous care is necessary to extract a clean signal. The discovery threshold used by the LIGO collaboration is 5 sigma, corresponding to a chance of less than one in 3 million that the signal was coincidence, which is far above the significance level of Afshordi’s signal. The weak interaction of gravitational waves, however, is also the reason why they are excellent messengers. Unlike particles or light, they are barely affected on their way to us, carrying with them pristine information about where and how they were generated. They allow entirely new precision tests of general relativity in a regime that has never before been explored.

    If black hole echoes should be confirmed, that would almost certainly indicate a stark deviation from general relativity. Finding echoes would not uniquely confirm Afshordi’s theory that black holes seed dark energy. But some truly novel idea would be needed to explain it. ‘I don’t know of such echoes in any simulation that we have done to date,’ Birnholtz said. ‘If we were to confirm that there was an echo, that would be very interesting. We would have to look into what could produce such an echo.’

    Afshordi has research plans in case the statistical significance of his signal increases. He wants to improve his model of black-hole mergers, and run a numerical simulation to support the analytical estimate of what the echoes should look like. The next step would then be to better understand the underlying theory of space-time that could give rise to such a behaviour of the black-hole horizon. Cosmologists would also want to look much more closely at the implications of this new explanation for dark energy.

    Afshordi is aware just how speculative it is to alter general relativity so drastically. But he’s a rebel with a mission: ‘I want to encourage people to keep an open mind and not to dismiss ideas because they don’t match their preconceived notions.’ With LIGO exposing the workings of the Universe in ways never before studied, a lot of preconceived notions may soon be set aside.

    See the full article here .

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  • richardmitnick 6:12 pm on March 7, 2017 Permalink | Reply
    Tags: , Caltech/MIT Advanced aLigo, , , ,   

    From APS: “Gravitational Waves: Hints, Allegations, and Things Left Unsaid” 


    American Physical Society

    APS April Meeting 2017

    If the APS April Meeting 2016 was a champagne-soaked celebration for gravitational wave scientists, the 2017 meeting was more like spring training — there was lots of potential, but the real action is yet to come.

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    The Laser Interferometer Gravitational-Wave Observatory, or LIGO, launched the era of gravitational wave astronomy in February 2016 with the announcement of a collision between two black holes observed in September 2015. “I’m contractually obligated to show the slide [of the original detection] at any LIGO talk for at least another year,” joked Jocelyn Read, a physicist at California State University, Fullerton, during her presentation at this year’s meeting.

    The scientific collaboration that operates the two LIGO detectors netted a second merger between slightly smaller black holes on December 26, 2015. (A third “trigger” showed up in LIGO data on October 12, 2015, but ultimately did not meet the stringent “five-sigma” statistical significance standard that physicists generally insist on.)

    The detectors then went offline in January 2016 for repairs and upgrades. The second observing run began on November 30, but due to weather-related shutdowns and other logistical hurdles, the two detectors had operated simultaneously on only 12 days as of this year’s meeting, which limited the experiment’s statistical power. Collaboration members said they had no new detections to announce.

    Instead, scientists focused on sharpening theoretical estimates of how often various events occur. In particular, they are eager to see collisions involving neutron stars, which lack sufficient mass to collapse all the way to a black hole. Neutron star collisions are thought to be plentiful, but would emit weaker gravitational waves than do mergers of more massive black holes, so the volume of space the LIGO detectors can scan for such events is smaller.

    Even with recent upgrades, failure to detect a neutron star merger during the current observing run would not rule out existing models, said Read. But she added that with future improvements and the long-anticipated addition of Virgo, a LIGO-like detector based in Cascina, Italy, neutron stars should soon come out of hiding.

    VIRGO Gravitational Wave interferometer, near Pisa, Italy [Not yet operational]

    “We’re expecting that with a little more volume and a little more time, we’re going to be starting to make some astrophysically interesting statements.”

    LIGO scientists are also looking for signals from individual pulsars — rapidly rotating neutron stars that are observed on earth as pulses of radio waves. A bump on a pulsar’s surface should produce gravitational waves, but so far, no waves with the right shape have been picked up. This absence puts a limit on the size of any irregularities and on the emission power of gravitational waves from nearby pulsars such as the Crab and Vela pulsars, said Michael Landry, head of the Hanford LIGO observatory, and could soon start putting limits on more distant ones.

    Presenters dropped a few hints of possible excitement to come. LIGO data taken through the end of January produced two short signals that were unusual enough to exceed the experiment’s “false alarm” threshold — signals with shapes and strengths expected to show up once a month or less by chance alone. Both LIGO collaboration members and astronomers at conventional telescopes are investigating the data to determine whether they represent real events.

    For now, potential events will continue to be scrutinized by collaboration members, and released to the public via announcements coming months after initial detection. But LIGO leaders expect to shorten the lag time as detections become more frequent, perhaps eventually putting out monthly updates. “We hope to make it quicker,” said LIGO collaboration spokesperson Gabriela González, a physicist at Louisiana State University in Baton Rouge.

    LIGO is not the only means by which scientists are searching for gravitational waves. Some scientists are using powerful radio telescopes to track signals emanating from dozens of extremely fast-rotating pulsars. A specific pattern of correlations between tiny hiccups in the arrival times of these pulses would be a signature of long-wavelength gravitational waves expected from mergers of distant supermassive black holes.

    Teams in the U.S., Europe, and Australia have monitored pulsars for more than a decade, so far without positive results. But in an invited talk, Laura Sampson of Northwestern University in Evanston, Illinois, coyly announced “hints of some interesting signals.” With 11 years of timing data from 18 pulsars tracked by the Green Bank Telescope in West Virginia and the Arecibo Telescope in Puerto Rico, Sampson and other scientists affiliated with a collaboration called NANOGrav have eked out a result with a statistical significance of around 1.5 to 2 sigma.

    GBO radio telescope, Green Bank, West Virginia, USA

    NAIC/Arecibo Observatory, Puerto Rico, USA

    Data from the Green Bank Telescope in West Virginia and Arecibo Telescope in Puerto Rico help researchers use pulsars to study gravitational waves.

    “It’s the first hint we’ve ever had that there might be a signal in the data,” Sampson said. “Everything we’ve done before was straight-up limits.”

    As NANOGrav continues to gather data, their signal could grow toward the 5-sigma gold standard, or it could vanish. Sampson and her colleagues hope to have an answer in the next year or two. “This is of course very exciting news,” said Gonzalez.

    See the full article here .

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    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries.

  • richardmitnick 12:15 pm on March 5, 2017 Permalink | Reply
    Tags: , , Caltech/MIT Advanced aLigo, , ,   

    From Nautilus: “Gravity’s Kiss – The third ripple. 



    Harry Collins

    Gravity’s Kiss by Harry Collins, is published by the MIT Press.

    LIGO bloc new
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    VIRGO Collaboration bloc
    VIRGO Gravitational Wave interferometer, near Pisa, Italy
    VIRGO Gravitational Wave interferometer, near Pisa, Italy [not yet operational]

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project
    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib
    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    Gravitational waves are finding their way to the general public. There is massive television news coverage with never a doubt expressed; gravitational waves have simply “been detected”—exciting but no more dubious than, say, the moon landing. What is happening is that gravitational waves are being “domesticated” in the same way as black holes or the Higgs have been domesticated. Everyone knows what a black hole is—it is a feature of everyone’s day-to-day life embedded in a “semantic net” that includes “the cosmos,” “the big bang,” “Stephen Hawking,” “brilliant scientists,” “Einstein,” “space,” “alternative universes,” “time travel,” “worm-holes,” “astronomy,” “rockets,” and “being sucked into things”—and this is in spite of the fact that, before The Event, no black hole had been observed except by inference. As for the Higgs, everyone knows that it was found by the huge and brilliant team at CERN, but, familiar as it is, no one knows what it is. I know it is the last piece in the jigsaw puzzle of the particle “zoo” known as the standard model, but what I have is “beer-mat knowledge,” good for answering questions in Trivial Pursuit but that’s about it. On the other hand, the fact that we can imagine encountering questions about black holes and the Higgs while playing Trivial Pursuit is one of the things that makes them real: all this familiar knowledge makes stuff real. The moon landing, note, is pretty real for everyone but, just as in the case of what is building in respect of The Event, there are conspiracy theories about that too; and, just as in this case, you have to stray from the mainstream to find them.

    On Friday I gather a good selection of the United Kingdom print newspapers; they are big contributors to the domestication process. The Guardian is a broadsheet for the left-liberal middle classes and its news section is 38 pages long. It gives the story the lead and whole of page 11. It had also given it the whole of page 3 on Wednesday, building the story on the rumors. On Saturday, The Guardian’s regular political cartoon features the Syrian peace talks represented as some kind of funny-looking celestial object with the caption: “Not gravitational waving but gravitational drowning.” Thus do gravitational waves spread into the ordinary language.

    EXTRA! EXTRA!Newspaper front pages from around the world.
    Courtesy of LIGO

    The Independent has a similar readership to The Guardian but has a smaller tabloid format with 72 pages. It gives the story the entire page 1 and pages 6–8; it opines that this is “one of the greatest achievements in human history.”

    The Telegraph is another broadsheet, with 38 pages in its news section. It is a right-wing, patriotic paper for the educated. It makes gravitational waves the second story on page 1, leading with:

    A British scientist who was pivotal in the project to detect gravitational waves could not celebrate the momentous discovery with colleagues because he is suffering from dementia.

    This, of course, is Ron Drever. The paper also gives up pages 10 and 11 to the story.

    Martin Rees, the Astronomer Royal, writes columns in The Independent and the Telegraph. He opines that this is of similar importance to the discovery of the Higgs; most other commentators say it is much more important than the Higgs, but Rees has long been said by gravitational wave physicists to be less than enthusiastic about the enterprise.

    The Daily Mail is a “little Englander” tabloid with 92 pages serving those with strong right-wing opinions. It gives the story half of page 10, mistakenly claiming that Einstein predicted that colliding stars would generate gravitational waves that could be detected on Earth, whereas he actually thought they would remain completely undetectable.

    The Mirror is a left-leaning tabloid with 80 pages. It gives the story most of page 21 but says that LIGO was invented by Thorne and Weiss, missing out on Drever.

    The Sun is a tabloid with 60 pages that began its life by publishing photographs of topless models on the notorious “page 3” (now dropped). The only science I could find was on the bottom third of page 15, head-lined: “Top Prof Dies in Rubber Suit with Dog Lead Round Neck.” The “Top Prof” does not seem to have been one of the gravitational wave team.

    The Guardian website of February 12 includes a hilarious cartoon—one of a series called “First Dog on the Moon,” which anticipates one of my major sociological theses. The fourth panel of the cartoon opines:

    Obviously we can’t see these waves—the only way we know they are real is by using another extremely sensitive device which detects scientists having feelings of excitement.

    The excitement evoked in scientists by a gravitational wave is calibrated using the marginally smaller effect of a cheese salad sandwich as a standard candle.

    Later I will discover that my major thesis about social construction, which turns on pointing out that no gravitational waves were seen but merely a few numbers that were interpreted as gravitational waves, has been thoroughly anticipated (albeit on a strange, flat-earther YouTube channel that appears to treat conspiracy theories as an art form). It claims scientists have not seen gravitational waves, nor has their machine seen gravitational waves, but that the machine produces lots of glitchy noises out of which they have picked one and interpreted it as a gravitational wave.

    A member of the LIGO team has put together a collection of newspaper front pages from around the world. And, as though to put an indelible stamp on the soon to be taken for granted nature of this exotic phenomenon, in the United States the discovery is presented on Saturday Night Live and The Tonight Show, and, on Saturday, February 13, the humorous U.S. radio show A Prairie Home Companion devotes about five minutes to gravitational waves. Gravitational waves have arrived!

    The physicists continue to do my job for me by gathering more indications of the domestication of gravitational waves. On February 16, a French (presumably humorous) website normalizes the waves in contemporary fashion by calling for a ban on them and the distribution of protective helmets. This is a Google translation from the French with my minor edits:

    “For a Moratorium on Gravitational Waves

    Bringing together hundreds of independent researchers, the “Collective for a moratorium on gravitational waves” (COMOG) sent us this platform. We publish it verbatim in our columns:

    In recent days, highlighting the “gravitational waves” continues to make the press headlines. Everyone welcomes this alleged “scientific breakthrough,” which was published in the Physical Review Letters, a journal under orders of the nuclear lobby.

    Now, our collective, consisting of independent researchers who wish to remain anonymous for their own reasons, is concerned about the apparent toxicity of gravitational waves.

    To date, there is in fact no serious study establishing the actual safety of these waves. That is why we propose an action plan of four points.

    1. We recall, first, that the oscillations of the curvature of space-time can present health risks found, especially on the neurological system of employees too long exposed to the gravitational waves. It is appropriate in this case to call for the government to strictly enforce the Labour Code, to limit the time of exposure to gravitational waves, and equip the wage earners with protective helmets.

    2. To these health risks are added, as often environmental, of deleterious economic effects. The curvature of space-time is likely to cause untoward inconvenience, especially in the field of transport and travel. An example: If space-time is curved in the wrong direction when one performs a trip from Paris to Bordeaux, the journey can last more than 25 hours, according to our estimates. Gravitational waves expose the French economy to serious danger that cannot be underestimated.

    3. It appears that the production of gravitational waves calls for masses of matter and energy that are absolutely astounding: black holes, neutron stars, washing machines, etc. We ask that the environmental and climate impact of gravitational waves be measured in France by an independent body and a carbon footprint be determined as quickly as possible.

    4. As a result, we ask Ségolène Royal, Minister of Environment, Energy and the Sea, responsible for international relations on the climate, to apply the constitutional principle of precaution, and to take by decree related measures that are defined and recommended in principle 15 of the Rio Declaration. It seems to us urgent that France decide on a moratorium on gravitational waves.

    If the government does not abide by these basic precautions, peaceful COMOG teams will be forced to resort to direct action. Within six months, we will proceed to the systematic dismantling of gravitational wave antennas. Our teams of volunteer harvesters shall uproot the plants of space-time curvatures. Finally, we will not hesitate to leave Paris to set up a zone to defend Proxima Centauri, even against the advice of the prefect.

    We call upon our fellow citizens to join our fight. Gravitational waves, no thank you!”

    On February 18, the Huddersfield Daily Examiner (Huddersfield is a town in North England with a football club—“Huddersfield Town”—all about as provincially English as can be) carries a story about the “Huddersfield Town Supporters Association” (HTSA). It includes:

    Our HTSA column last week touched upon the subject of regional supporters groups and their recent cosmic rise in popularity. The Laser Interferometer Gravitational-Wave Observatory (LIGO) can probably demonstrate whether this is due to colliding Black Holes over Bexleyheath.

    And Barack Obama had tweeted on February 11:

    Einstein was right! Congrats to @NSF and @LIGO on detecting gravitational waves—a huge breakthrough in how we understand the universe.

    At the forthcoming American Physical Society (APS) meeting, Dave Reitze, the director of LIGO, will present a slide showing a woman wearing a dress patterned with the waveform, an Australian competition swimmer with the waveform on his swim-cap, and a New York advertisement for apartments.

    Fashionably wavy. More domestication of gravitational waves. No image credits.

    I attend two meetings in March: a general relativity 100th anniversary meeting at Caltech and the LIGO-Virgo collaboration meeting in Pasadena. Of course, the cat is now out of the bag so a big topic at the Caltech meeting is The Event. I follow Barry Barish onto the platform; he describes the technicalities and I talk about the way small science and big science had combined to create this possibility, with Barish bringing about the necessary transformation, and I talk about what it meant for me as a sociologist to be confronted by such a sudden and certain result. At neither meeting is there any criticism but the LVC is selling huge numbers of T-shirts and polo shirts with the waveform of The Event printed or embroidered on them: The waveform is becoming an icon! Many more such garments will be sold at the April APS meeting.

    At the March meeting of the APS—a much larger meeting than the April meeting I am going to attend—a group of physicists who have nothing to do with LIGO or gravitational waves performed a song based on the Neil Diamond/Monkees’ “I’m a Believer.” The lyrics are as follows:

    “I’m a LIGO Believer.” Lyrics: Marian McKenzie. Tune: “I’m a Believer,” by Neil Diamond (courtesy Marian McKenzie).

    I thought waves of gravity were fairy tales—fine for dilettantes, but not for me.
    What’s the use of searching?
    Noise is all you’ll find.
    I don’t want to clutter up my mind—

    [Chorus:] Then I saw the graph—Now I’m a believer!
    You can laugh, and hold me in scorn.
    I’m convinced, oooh, I’m a believer
    In Weiss, Reitze, Drever, Gonzalez, and Thorne!

    Einstein spoke of grav wave propagation.
    Weber tried to find them on the moon.
    BICEP2 announced them,
    Then said “Never mind.”
    —Do you wonder I was disinclined?

    [Sing chorus] [instrumental interlude] and repeat”

    The whole song can be seen and heard on YouTube.

    surfing the googleEnormous spike in interest in gravitational waves around February 11. No image credit.

    What about social media? Google Trends (see chart above) shows the huge spike in interest in gravitational waves around the February 11 press conferences by tracking hits on Google. Unfortunately, we have only the normalized trend, the scale having a maximum of 100, not absolute numbers.

    Breaking the internet. The enormous spike in interest in gravitational waves compared to hits for Kim Kardashian.

    Gravitational waves are not, however, about to take over the popular imagination. The chart above shows the same spike in comparison to Google hits for Kim Kardashian, the reality TV star. Gravitational waves’ enormous spike is a mere 2 percent as high as Kardashian’s peak performance and only about 5 percent as high as her average day-to-day score. Aside from the spike, gravitational waves score zero when compared to Kardashian’s average.

    See the full article here .

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    Welcome to Nautilus. We are delighted you joined us. We are here to tell you about science and its endless connections to our lives. Each month we choose a single topic. And each Thursday we publish a new chapter on that topic online. Each issue combines the sciences, culture and philosophy into a single story told by the world’s leading thinkers and writers. We follow the story wherever it leads us. Read our essays, investigative reports, and blogs. Fiction, too. Take in our games, videos, and graphic stories. Stop in for a minute, or an hour. Nautilus lets science spill over its usual borders. We are science, connected.

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  • richardmitnick 11:55 am on March 2, 2017 Permalink | Reply
    Tags: , , , Caltech/MIT Advanced aLigo, , , , Primordial black holes, Quasar microlensing   

    From IAC: “A new look at the nature of dark matter” 


    Instituto de Astrofísica de Canarias – IAC

    Mar. 2, 2017
    Evencio Mediavilla (IAC)
    +34 922 605 318

    A new study suggests that the gravitational waves detected by the LIGO experiment must have come from black holes generated during the collapse of stars, and not in the earliest phases of the Universe.

    The nature of the dark matter which apparently makes up 80% of the mass of the particles in the universe is still one of the great unsolved mysteries of present day sciences. The lack of experimental evidence, which could allow us to identify it with one or other of the new elementary particles predicted by the theorists, as well as the recent discovery of gravitational waves coming from the merging of two black holes (with masses some 30 times that of the Sun) by LIGO the Laser Interferometer Gravitational Wave Observatory) have revived interest in the possibility that dark matter might take the form of primordial black holes with masses between 10 and 1000 times that of the Sun.

    LIGO bloc new
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project
    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Primordial black holes, which would have originated in high density fluctuations of matter during the first moments of the Universe, are in principle very interesting. As opposed to those which form from stars, whose abundance and masses are limited by models of stellar formation and evolution, primordial black holes could exist with a wide range of masses and abundances. They would be found in the halos of galaxies, and the occasional meeting between two of them having masses 30 times that of the Sun, followed by a subsequent merger, might have given rise to the gravitational waves detected by LIGO.

    “Microlensing effect”


    If there were an appreciable number of black holes in the halos of galaxies, some of them intercept the light coming towards us from a distant quasar. Because of their strong gravitational fields, their gravity could concentrate the rays of light, and cause an increase in the apparent brightness of the quasar. This effect, known as “gravitational microlensing” is bigger the bigger the mass of the black hole, and the probability of detecting it would be bigger the more the presence of these black holes. So although the black holes themselves cannot be directly detected, they would be detected by increases in the brightness of observed quasars.

    On this assumption, a group of scientists has used the microlensing effect on quasars to estimate the numbers of primordial black holes of intermediate mass in galaxies. The study, led by the researcher at the Instituto de Astrofísica de Canarias (IAC) and the University of La Laguna (ULL), Evencio Mediavilla Gradolph, shows that normal stars like the Sun cause the microlensing effects, thus ruling out the existence of a large population of primordial black holes with intermediate mass.

    Computer simulations

    Using computer simulations, they have compared the rise in brightness, in visible light and in X-rays, of 24 distant quasars with the values predicted by the microlensing effect. They have found that the strength of the effect is relatively low, as would be expected from objects with a mass between 0.05 and 0.45 times that of the Sun, and well below that of intermediate mass black holes. In addition they have estimated that these microlenses form roughly 20% of the total mass of a galaxy, equivalent to the mass expected to be found in stars. So their results show that, with high probability, it is normal stars and not primordial intermediate mass black holes which are responsible for the observed microlensing.

    “This study implies “says Evencio Mediavilla, “that it is not at all probable that black holes with masses between 10 and 100 times the mass of the Sun make up a significant fraction of the dark matter”. For that reason the black holes whose merging was detected by LIGO were probably formed by the collapse of stars, and were not primordial black holes”.

    Astronomers participating in this research include Jorge Jiménez-Vicente and José Calderón-Infante (University of Granada) and José A. Muñoz Lozano, and Héctor Vives-Arias, (University of Valencia).

    Article: Limits on the Mass and Abundance of Primordial Black Holes from Quasar Gravitational Microlensing, by E. Mediavilla et al. Published in The Astrophysical Journal Letters. Reference: E. Mediavilla et al 2017 ApJL 836 L18.

    See the full article here.

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    The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

    The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
    The Centro de Astrofísica en La Palma (CALP)
    The Observatorio del Teide (OT), in Izaña (Tenerife).
    The Observatorio del Roque de los Muchachos (ORM), in Garafía (La Palma).

    These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

    The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

    The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

    The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

    The IAC’s research programme includes astrophysical research and technological development projects.

    The IAC is also involved in researcher training, university teachingand outreachactivities.

    The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.

    Gran Telescopio  Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC
    Gran Telescopio CANARIAS, GTC

  • richardmitnick 11:17 am on February 12, 2017 Permalink | Reply
    Tags: Caltech/MIT Advanced aLigo, , ,   

    From Science Alert: “Surprise! LIGO Can Also Make Gravitational Waves” 


    Science Alert



    11 FEB 2017


    We can produce gravitational waves now.

    It’s been almost a year now since the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced the greatest scientific discovery of 2016.

    LIGO bloc new
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Though the first gravitational waves were actually detected in September 2015, it was only after additional detections were made in June 2016 that LIGO scientists finally confirmed that the elusive waves exist, solidifying Albert Einstein’s major prediction in his theory of relativity.

    Now, the most sensitive detector of spacetime ripples in the world turns out to also be the best producer of gravitational waves.

    “When we optimise LIGO for detection, we also optimise it for emission [of gravitational waves],” said physicist Belinda Pang from the California Institute of Technology (Caltech) in Pasadena according to a report in Science.

    Pang was speaking at a meeting of the American Physical Society last week, representing her team of physicists.

    Gravitational waves are ripples that are produced when massive objects warp spacetime.

    They essentially stretch out space, and according to Einstein, they can be produced by certain swirling configurations of mass. Using uber-sensitive twin detectors in Hanford, Washington, and Livingston, Louisiana, LIGO is able to detect this stretching of space.

    Once they realised they could detect gravitational waves, the physicists posited that the sensitivity of their detectors would enable them to efficiently generate these ripples, too.

    “The fundamental thing about a detector is that it couples to gravitational waves,” said Fan Zhang, a physicist at Beijing Normal University.

    “When you have coupling, it’s going to go both ways.”

    The LIGO team tested their idea using a quantum mathematical model and found that they were right: their detectors did generate tiny, optimally efficient spacetime ripples.

    Quantum mechanics says that small objects, such as electrons, can be in two places at once, and some physicists think that it’s possible to coax macroscopic objects into a similar state of quantum motion.

    According to Pang, LIGO and these waves could be just the things to make it happen.

    Though that delicate state couldn’t be sustained for very long periods, any amount of time could give us added insight into quantum mechanics.

    We could measure how long it takes for decoherence to occur and see what role gravity might play in the existence of quantum states between macroscopic objects.

    “It’s an interesting idea, but experimentally it’s very challenging,” explained Caltech physicist Yiqui Ma, one of Pang’s colleagues.

    “It’s unbelievably difficult, but if you want to do it, what we’re saying is that LIGO is the best place to do it.”

    Any added insight into quantum activity could not only help us build better quantum computers, it could completely revolutionise our understanding of the physical universe.

    LIGO is already in the process of receiving upgrades that will help it detect even fainter gravitational waves, and eventually, the plan is to build the Evolved Laser Interferometer Space Antenna (eLISA), a gravitational wave observatory in space.

    ESA/LISA Pathfinder
    ESA/LISA Pathfinder


    Within the next decade, not only could LIGO be regularly detecting gravitational waves, it could also be finding ever more advanced ways to create them and furthering our understanding of the quantum world in unimaginable ways.

    See the full article here .

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  • richardmitnick 12:43 pm on December 14, 2016 Permalink | Reply
    Tags: , Caltech/MIT Advanced aLigo, ,   

    From Ethan Siegel: “Has LIGO already discovered evidence for quantum gravity?” 

    From Ethan Siegel


    Two merging black holes. Image credit: SXS, the Simulating eXtreme Spacetimes (SXS) project (http://www.black-holes.org).

    Merging black holes are some of the most extreme events in the Universe. Could a modified event horizon reveal quantum gravity?

    “The bedrock nature of space and time and the unification of cosmos and quantum are surely among science’s great ‘open frontiers.’ These are parts of the intellectual map where we’re still groping for the truth — where, in the fashion of ancient cartographers, we must still inscribe ‘here be dragons.’”
    -Martin Rees

    When Einstein first wrote down the general theory of relativity in 1915, this brand new theory of gravity not only explained phenomena that Newton’s old one couldn’t, it predicted a whole host of new ones. In strong gravitational fields, clocks would run slower, light would shift its frequency, particle trajectories would bend, and accelerating masses would emit a new type of radiation: gravitational waves. While a great many of Einstein’s predictions had been borne out and verified over the years, it took until 2015 for the first gravitational wave signals to be directly detected by humanity. There were two that had enough significance to be announced as “discoveries,” while one other remains a strong candidate. But perhaps these events — created by merging black holes — will do us one better than Einstein: perhaps they’ve already given us our first hints of quantum gravity. In a new paper by theoretical physicists Jahed Abedi, Hannah Dykaar and Niayesh Afshordi, they claim the first evidence of gravitational effects beyond general relativity in the data of these mergers.

    The reason it’s so difficult to go beyond general relativity is because the scale at which quantum effects should become important happen at extreme scales. Not extreme like at the LHC or in the center of the Sun, but at energies well beyond anything the Universe has seen since the Big Bang, or at distance scales some 10¹⁸ times smaller than a proton’s width. While quantum effects show up for the other forces at much more accessible scales and energies, part of why a theory of quantum gravity has been so elusive is that we have no experiments to guide us. The only hopes we have, realistically, are to look in two places:

    1. At the echoes of cosmic inflation, the ultra-high-energy state of spacetime prior to the Big Bang.
    2. At and around the event horizons of black holes during catastrophic events, where quantum effects will be strongest.

    Gravitational waves can only be generated from inflation if gravity is an inherently quantum theory. Image credit: BICEP2 Collaboration.

    Bicep 2 Collaboration Steffen Richter Harvard
    Bicep 2 Collaboration Steffen Richter Harvard

    For the first one, there are teams looking for particular polarization signals of the Big Bang’s leftover glow. If that signal shows up in the data with a particular pattern on a variety of angular scales, it will be an unambiguous verification of inflation, plus the first direct evidence that gravity is quantum in nature. While many things in the Universe produce gravitational waves, some of these processes are classical (like inspiraling black holes), while others are purely quantum. The quantum ones rely on the fact that gravitation, like the other forces, should exhibit quantum fluctuations in space and time, along with the inherent uncertainty that quantum physics brings with it. In cosmic inflation, those fluctuations get stretched across the Universe, and can imprint in the Big Bang’s leftover glow. While the initial report of such a detection a few years ago, by BICEP2, was shown to be false, the prospects remain enticing.

    Gravitational Wave Background from BICEP 2
    Gravitational Wave Background from BICEP 2 proven to be false

    Gravitational wave signals and their origins, including what detectors will be sensitive to them. Image credit: NASA Goddard Space Flight Center.

    But there’s another approach: to look for quantum effects that show up along with the classical ones in the strongest gravitational wave signals this Universe generates. LIGO’s announcements earlier this year gave the scientific community a celebratory jolt, as the first and second gravitational wave events from merging black holes were unambiguously detected.

    LIGO bloc new
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib
    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    A third probably detection was also released, but was just below the significance threshold for discovery. While LIGO has just recently fired back up at increased sensitivity, a new idea gives us something important to look for: quantum corrections that show up in the mergers.

    The LIGO signal (blue line) for gravitational waves emitted by the first-ever detected merger may have quantum corrections (black), which could alter the total signal (yellow) that shows up in the detector. Image credit: Abedi, Dykaar and Afshordi, 2016, via https://arxiv.org/abs/1612.00266.

    According to Einstein, a black hole’s event horizon should have specific properties, determined by its mass, charge and angular momentum. In most ideas of what quantum gravity would look like, that event horizon would be no different. Some models, however, predict notably different event horizons, and it’s those departure models that offer a glimmer of hope for quantum gravity. If we see a difference from what Einstein’s theory predicts, perhaps we can uncover not only that gravity must be a quantum theory, but what properties quantum gravity actually has.

    The inspiral and merger gravitational wave signal extracted from the event on December 26, 2015. Image credit: Figure 1 from B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. Lett. 116, 241103 — Published 15 June 2016.

    The templates for LIGO generated by teams working with numerical relativity fit the merger events extremely well. After all, that’s how they were able to tease the signal out of such spectacular noise; they knew exactly what they were looking for and how to find it. If there’s a secondary, sub-dominant signal in there, arising from quantum gravity, a similar approach should be able to uncover it. The key — if these are quantum gravitational effects — is that they should occur at the Planck scale: at energies of 10¹⁹ GeV or distance scales of around 10^-33 meters. This is exactly the type of signal that Abedi, Dykaar and Afshordi decided to look for.

    While Einstein’s theory makes explicit predictions for a black hole’s event horizon and the spacetime just outside, quantum corrections could alter that significantly. Image credit: NASA.

    In classical (Einstein’s) general relativity, there are a few problems that arise from black holes: that there ought to be a firewall at the event horizon; that information about what falls into the black hole appears to be destroyed; how you reconcile a black hole-containing Universe with one that has a non-zero, positive cosmological constant. Some of the proposed quantum gravitational resolutions modify the event horizon of a black hole. When two black holes merge under these scenarios, the differences in the event horizons from Einstein’s theory should lead to “echoes” visible in the merging gravitational wave signal. They’ll be dominated by the main, Einsteinian prediction, but with good enough data and good enough algorithms, we should be able to tease that signal out, too.

    Spacetime depiction of gravitational wave echoes from a membrane/firewall on the stretched horizon, following a black hole merger event. Image credit: Abedi, Dykaar and Afshordi, 2016, via https://arxiv.org/abs/1612.00266.

    In particular, there should be an echoing timescale, defined solely by the masses of the merging black holes and the frequencies at which they are merging or inspiraling. There should be these periodic echoes as the signals from the two event horizons interact, and it should exhibit “after-echoes” that continue for some time after the merger is complete.

    LIGO original template for GW150914, along with their best fit template for the echoes. Image credit: Abedi, Dykaar and Afshordi, 2016, via https://arxiv.org/abs/1612.00266.

    Interestingly, when they compare it to the data from all three mergers, they arrive at a prediction for what they ought to see: it ought to exhibit these extra waves on timescales related to the echo period and the merger/inspiral period. The most unambiguous and easy-to-detect signal, from GW150914, contains the greatest information and significance: it shows evidence for this signal at almost exactly the predicted frequency, with only a 0.54% offset. (And they searched over a range with a ±5% offset.) If you then add in the signals for the other two black hole mergers using those same parameters, the statistical significance increases from 95% (about a 1-in-20 chance of random fluctuations) to 99.6% (about a 1-in-270 chance).

    The signal and its significance from GW150914 (red) and from all three waves combined (black). Image credit: Abedi, Dykaar and Afshordi, 2016, via https://arxiv.org/abs/1612.00266.

    On the one hand, this is incredible. There are very few prospects for detecting a signal from quantum gravity because of the fact that we don’t have a working theory of quantum gravity; all we have are models and approximations. Yet some classes of models make some actual, testable predictions, albeit with uncertainties, and one of those predictions is that merging black holes, in some models, should emit additional echoes of particular frequencies and amplitudes.

    Under General Relativity alone, gravitational waves should make a particular patterns and signal. If some models of quantum gravity are correct, there should be an additional signal superimposed over the main, Einsteinian one. Image credit: NASA/Ames Research Center/C. Henze.

    But on the other hand, there are reasons to doubt that this effect is real.

    Only the first gravitational wave signal, GW150914, exhibits enough significance to have this additional signal stand out against the background on its own. The other two are undetectable without assuming the prior results from GW150914.
    There is an additional signal offset by -2.8% from the predicted frequency at nearly 95% confidence when all three gravitational wave signals are included, and three more at greater than 80% confidence.
    And perhaps most damningly, we have known for months that there are additional signals, likely from external sources, superimposed on the LIGO data at a 3.2-sigma (99.9%) confidence level.

    In other words, there may or may not be a real signal there, and it may have nothing to do with quantum gravity at all even if it is real.

    But this new paper is remarkable for the fact that it makes an explicit prediction for what a quantum gravitational signature in the LIGO data will look like. It takes advantage of the actual LIGO data to show that there is the hint of a signal already there, and it explicitly tells the LIGO team what signatures they should look for in future events to see if this model of quantum gravity has it right. As LIGO is now operational once again at even greater sensitivity than during its prior run, we have every reason to expect that more black hole mergers are coming. The smart money is still on this signal not being real (or if it is, that it’s due to an external source rather than quantum gravity), but science never advanced without looking for an out-of-the-mainstream possibility. This time, the technology is already in place, and the next 24 months should be critical in revealing whether quantum gravity shows itself in the physics of merging black holes!

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

  • richardmitnick 12:52 pm on December 13, 2016 Permalink | Reply
    Tags: Caltech/MIT Advanced aLigo, Einstein's general theory of relativity, ,   

    From Science Alert: “Echoes in gravitational waves hint at a breakdown of Einstein’s general relativity” 


    Science Alert

    Dana Berry/NASA

    12 DEC 2016

    The physics discovery of 2016 just got more tantalising.

    In February, astronomers made a monumental discovery. Almost 100 years after Albert Einstein first predicted them, researchers detected gravitational waves – ripples in space time that had radiated out from the merging of two black holes.

    It was a striking confirmation of Einstein’s general theory of relativity – but in an unexpected twist, the discovery has also provided the first tantalising evidence that his theory breaks down at the event horizon of black holes.

    Since February, the Laser Interferometer Gravitational-Wave Observatory (LIGO) has observed three gravitational wave events in total. And now researchers have pored over this data, and claim they’ve found evidence of ‘echoes’ in the waves that defy Einstein’s predictions of black holes.

    For now, the new claims have been published on ArXiv.org, where they can be examined by the rest of the physics community before being submitted for peer-review – so there’s a very real possibility that these echoes could go away with more scrutiny of the data.

    And the evidence so far falls short of the crucial 5-sigma error margin, which is the gold-standard in the physics world that means there’s a one in 3.5 million chance that the result could be a fluke.

    But if further research shows that these ‘echoes’ are really there, it would be a huge day for physics. It’s already thought that general relativity breaks down at the centre of black holes, but this would show that it fails at their edges, too. And that could herald the birth of new physics.

    “The LIGO detections, and the prospect of many more, offer an exciting opportunity to investigate a new physical regime,” Steve Giddings, a black-hole researcher from the University of California, Santa Barbara, who wasn’t involved in the study, told Zeeya Merali at Nature.

    If the echoes disappear, general relativity would have just withstood yet another test. For decades, physicists have been attempting to poke holes in the theory, trying to find ways it could be more compatible with quantum mechanics, but so far, Einstein’s original version has held up incredibly well.

    But before we get too carried away, what are these ‘echoes’, and what do they have to do with general relativity?

    It all comes down to something called the black hole information paradox.

    According to Einstein’s general theory of relativity, anything that crosses a black hole’s event horizon should disappear, with no trace left behind. The traditional thinking is that not even light can escape a black hole, hence the name ‘black’.

    More recently, though, researchers have questioned that idea. Because according to quantum mechanics, matter swallowed by a black hole would actually leave a trace of itself on the outside.

    So how can an event horizon satisfy both general relativity (and destroy everything that passes its boundary) and quantum mechanics (leave some trace of it)?

    This is one of the biggest problems in physics, and scientists still don’t have an answer.

    One explanation is the firewall hypothesis, which was proposed in 2012, and suggests that there’s a ring of high-energy particles surrounding a black hole’s event horizon that burns up any matter that passes through.

    Physicist Stephen Hawking has a different idea – that black holes are surrounded by soft ‘hair’. The ‘hair’ is low-energy quantum excitations that store a signature pattern of everything that’s been sucked up by a black hole.

    Regardless of which hypothesis you think is the most convincing, the overarching message is the same: instead of the clean event horizon predicted by general relativity, black holes might be ‘fluffier’ than we imagined.

    The only problem is we’ve had no way to actually test any of these ideas, until LIGO detected gravitational waves earlier this year.

    Now, with their latest data in hand, a team of international researchers has proposed a way to measure what’s going on around black holes.

    The prediction is that, if the edges of black holes really do defy general relativity and are fuzzy, then a series of echoes should be released after an initial gravitational wave burst.

    That’s because the team predicts the fuzziness surrounding a black hole will act kind of like a hall of mirrors, trapping some of the gravitational waves escaping the black hole merger and bouncing them around for a bit, so only a few escape at a time, meaning they would have hit LIGO slightly later.

    According to the team’s calculations, these echoes would have been detected by LIGO at 0.1, 0.2 and 0.3 seconds after the initial gravitational wave burst, and that’s exactly what the data show.

    Not only after the first gravitational wave burst detected in February, but all three events seen since.

    Of course, three gravitational wave bursts is still a pretty tiny sample size. And there’s a chance that these echoes are just some kind of background noise – around a 1 in 270 chance, to be precise, or 2.9 sigma – but further observations should help narrow down those odds.

    “The good thing is that new LIGO data with improved sensitivity will be coming in, so we should be able to confirm this or rule it out within the next two years,” lead research Niayesh Afshordi told Nature.

    Even if the echoes can be confirmed, they still don’t provide any insight into what kind of fuzzy boundary black holes might actually have, so we’ve got a long way to go before that information paradox is solved.

    But one thing’s for sure: the physics discovery of the year just got even more tantalising.

    See the full article here .

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  • richardmitnick 8:33 am on October 26, 2016 Permalink | Reply
    Tags: , , Caltech/MIT Advanced aLigo, , , , , Next step towards a gravitational-wave observatory in space   

    From ESA: “Next step towards a gravitational-wave observatory in space” 

    ESA Space For Europe Banner

    European Space Agency

    25 October 2016

    Merging black holes. No image credit.

    Today, ESA has invited European scientists to propose concepts for the third large mission in its science programme, to study the gravitational Universe.

    A spaceborne observatory of gravitational waves – ripples in the fabric of spacetime created by accelerating massive objects – was identified in 2013 as the goal for the third large mission (L3) in ESA’s Cosmic Vision plan.

    A Gravitational Observatory Advisory Team was appointed in 2014, composed of independent experts. The team completed its final report earlier this year, further recommending ESA to pursue the mission having verified the feasibility of a multisatellite design with free-falling test masses linked over millions of kilometres by lasers.

    Now, following the first detection of the elusive waves with ground-based experiments and the successful performance of ESA’s LISA Pathfinder mission, which demonstrated some of the key technologies needed to detect gravitational waves from space, the agency is inviting the scientific community to submit proposals for the first space mission to observe gravitational waves.

    ESA/LISA Pathfinder
    ESA/LISA Pathfinder


    Gravitational waves promise to open a new window for astronomy, revealing powerful phenomena across the Universe that are not accessible via observations of cosmic light,” says Alvaro Gimenez, ESA’s Director of Science.

    Predicted a century ago by Albert Einstein’s general theory of relativity, gravitational waves remained elusive until the first direct detection by the ground-based Laser Interferometer Gravitational-Wave Observatory and Virgo collaborations, made in September 2015 and announced earlier this year.

    LIGO bloc new
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    The signal originated from the coalescence of two black holes, each with some 30 times the mass of the Sun and about 1.3 billion light-years away. A second detection was made in December 2015 and announced in June, and revealed gravitational waves from another black hole merger, this time involving smaller objects with masses around 7 and 14 solar masses.

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project
    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    LISA Pathfinder performance. No image credit.

    Meanwhile, the LISA Pathfinder mission was launched in December 2015 and started its scientific operations in March this year, testing some of the key technologies that can be used to build a space observatory of gravitational waves.

    Data collected during its first two months showed that it is indeed possible to eliminate external disturbances on test masses placed in freefall at the level of precision required to measure passing gravitational waves disturbing their motion.

    While ground-based detectors are sensitive to gravitational waves with frequencies of around 100 Hz – or a hundred oscillation cycles per second – an observatory in space will be able to detect lower-frequency waves, from 1 Hz down to 0.1 mHz. Gravitational waves with different frequencies carry information about different events in the cosmos, much like astronomical observations in visible light are sensitive to stars in the main stages of their lives while X-ray observations can reveal the early phases of stellar life or the remnants of their demise.

    In particular, low-frequency gravitational waves are linked to even more exotic cosmic objects than their higher-frequency counterparts: supermassive black holes, with masses of millions to billions of times that of the Sun, that sit at the centre of massive galaxies. The waves are released when two such black holes are coalescing during a merger of galaxies, or when a smaller compact object, like a neutron star or a stellar-mass black hole, spirals towards a supermassive black hole.

    Observing the oscillations in the fabric of spacetime produced by these powerful events will provide an opportunity to study how galaxies have formed and evolved over the lifetime of the Universe, and to test Einstein’s general relativity in its strong regime.

    Concepts for ESA’s L3 mission will have to address the exploration of the Universe with low-frequency gravitational waves, complementing the observations performed on the ground to fully exploit the new field of gravitational astronomy. The planned launch date for the mission is 2034.

    Lessons learned from LISA Pathfinder will be crucial to developing this mission, but much new technology will also be needed to extend the single-satellite design to multiple satellites. For example, lasers much more powerful than those used on LISA Pathfinder, as well as highly stable telescopes, will be necessary to link the freely falling masses over millions of kilometres.

    Large missions in ESA’s Science Programme are ESA-led, but also allow for international collaboration. The first large-class mission is Juice, the JUpiter ICy moons Explorer, planned for launch in 2022, and the second is Athena, the Advanced Telescope for High-ENergy Astrophysics, an X-ray observatory to investigate the hot and energetic Universe, with a planned launch date in 2028.

    ESA/Juice spacecraft

    ESA/Athena spacecraft
    ESA/Athena spacecraft

    Letters of intent for ESA’s new gravitational-wave space observatory must be submitted by 15 November, and the deadline for the full proposal is 16 January 2017. The selection is expected to take place in the first half of 2017, with a preliminary internal study phase planned for later in the year.

    See the full article here .

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    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

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  • richardmitnick 1:09 pm on September 9, 2016 Permalink | Reply
    Tags: , , , Caltech/MIT Advanced aLigo, , ,   

    From Symmetry: “A tale of two black holes” 

    Symmetry Mag


    Liz Kruesi


    The historic detection of gravitational waves announced earlier this year breathed new life into a theory that’s been around for decades: that black holes created in the first second of the universe might make up dark matter. It also inspired a new idea: that those so-called primordial black holes could be contributing to a diffuse background light.

    The connection between these perhaps seemingly disparate areas of astronomy were tied together neatly in a theory from Alexander Kashlinsky, an astrophysicist at NASA’s Goddard Spaceflight Center. And while it’s an unusual idea, as he says, it could be proven true in only a few years.

    Mapping the glow

    Kashlinsky’s focus has been on a residual infrared glow in the universe, the accumulated light of the earliest stars. Unfortunately, all the stars, galaxies and other bright objects in the sky—the known sources of light—oversaturate this diffuse glow. That means that Kashlinsky and his colleagues have to subtract them out of infrared images to find the light that’s left behind.

    They’ve been doing precisely that since 2005, using data from the Spitzer space telescope to arrive at the residual infrared glow: the cosmic infrared background (CIB).

    NASA/Spitzer Telescope
    “NASA/Spitzer Telescope

    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA)
    Cosmic Infrared Background, Credit: Michael Hauser (Space Telescope Science Institute), the COBE/DIRBE Science Team, and NASA

    Other astronomers followed a similar process using Chandra X-ray Observatory data to map the cosmic X-ray background (CXB), the diffuse glow of hotter cosmic material and more energetic sources.

    NASA/Chandra Telescope
    NASA/Chandra Telescope

    Cosmic X-ray Background, imagine.gsfc.nasa.gov
    Cosmic X-ray Background, imagine.gsfc.nasa.gov

    In 2013, Kashlinsky and colleagues compared the CIB and CXB and found correlations between the patchy patterns in the two datasets, indicating that something is contributing to both types of background light. So what might be the culprit for both types of light?

    “The only sources that could be coherent across this wide range of wavelengths are black holes,” he says.

    To explain the correlation they found, roughly 1 in 5 of the sources had to be black holes that lived in the first few hundred million years of our universe. But that ratio is oddly large.

    “For comparison,” Kashlinsky says, “in the present populations, we have 1 in 1000 of the emitting sources that are black holes. At the peak of star formation, it’s 1 in 100.”

    He wasn’t sure how the universe could have ever had enough black holes to produce the patterns his team saw in the CIB and CXB. Then the Laser Interferometric Gravitational-wave Observatory (LIGO) discovered a pair of strange beasts: two roughly-30-solar-mass black holes merging and emitting gravitational waves.

    LSC LIGO Scientific Collaboration
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project
    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    A few months later, Kashlinsky saw a study led by Simeon Bird analyzing the possibility that the black holes LIGO had detected were primordial—formed in the universe’s first second. “And it just all came together,” Kashlinsky says.

    Gravitational secrets

    The crucial ripples in space-time picked up by the LIGO detector on September 14, 2015, came from the last dance of two black holes orbiting each other and colliding. One black hole was 36 times the sun’s mass, the other 29 times. Those black-hole weights aren’t easy to make.

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib
    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    The majority of the universe’s black holes are less than about 15 solar masses and form as massive stars collapse at the end of their lives. A black hole weighing 30 solar masses would have to start from a star closer to 100 times our sun’s mass—and nature seems to have a hard time making stars that enormous. To compound the strangeness of the situation, the LIGO detection is from a pair of those black holes. Scientists weren’t expecting such a system, but the universe has a tendency to surprise us.

    Bird and his colleagues from Johns Hopkins University next looked at the possibility that those black holes formed not from massive stars but instead during the universe’s first fractions of a second. Astronomers haven’t yet seen what the cosmos looked like at that time, so they have to rely on theoretical models.

    In all of these models, the early universe exists with density variations. If there were regions of very high-contrasting density, those could have collapsed into black holes in the universe’s first second. If those black holes were at least as heavy as mountains when they formed, they’d stick around until today, dark and seemingly invisible and acting through the gravitational force. And because these primordial black holes formed from density perturbations, they wouldn’t be comprised of protons and neutrons, the particles that make up you, me, stars and, thus, the material that leads to normal black holes.

    All of those characteristics make primordial black holes a tempting candidate for the universe’s mysterious dark matter, which we believe makes up some 25 percent of the universe and reveals itself only through the gravitational force. This possible connection has been around since the 1970s, and astronomers have looked for hints of primordial black holes since. Even though they’ve slowly narrowed down the possibilities, there are a few remaining hiding spots—including the region where the black holes that LIGO detected fall, between about 20 and 1000 solar masses.

    Astronomers have been looking for explanations of what dark matter is for decades. The leading theory is that it’s a new type of particle, but searches keep coming up empty. On the other hand, we know black holes exist; they stem naturally from the theory of gravity.

    “They’re an aesthetically pleasing candidate because they don’t need any new physics,” Bird says.

    A glowing contribution

    Kashlinsky’s newest analysis took the idea of primordial black holes the size that LIGO detected and looked at what that population would do to the diffuse infrared light of the universe. He evolved a model of the early universe, looking at how the first black holes would congregate and grow into clumps. These black holes matched the residual glow of the CIB and, he found, “would be just right to explain the patchiness of infrared background by sources that we measured in the first couple hundred million years of the universe.”

    This theory fits nicely together, but it’s just one analysis of one possible model that came out of an observation of one astrophysical system. Researchers need several more pieces of evidence to say whether primordial black holes are in fact the dark matter. The good news is LIGO will soon begin another observing run that will be able to see black hole collisions even farther away from Earth and thus further back in time. The European gravitational wave observatory VIRGO will also come online in January, providing more data and working in tandem with LIGO.

    VIRGO Collaboration bloc
    VIRGO interferometer EGO Campus
    VIRGO interferometer EGO Campus, in Cascina, Italy

    More cases of gravitational waves from black holes around this 30-solar-masses range could add evidence that there is a population of primordial black holes. Bird and his colleague Ilias Cholis suggest looking for a more unique signal, though, in future gravitational-wave data. For two primordial black holes to become locked in a binary system and merge, they would likely be gravitationally captured during a glancing interaction, which could result in a signal with multiple frequencies or tones at any one moment.

    “This is a rare event, but it would be very characteristic of our scenario,” Cholis says. “In the next 5 to 10 years, we might see one.”

    This smoking-gun signature, as they call it, would be a strong piece of evidence that primordial black holes exist. And if such objects are floating around our universe, it might not be such a stretch to connect them to dark matter.

    See the full article here .

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    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 10:19 am on September 8, 2016 Permalink | Reply
    Tags: Caltech/MIT Advanced aLigo, , OzGRav,   

    From Swinburne: “New ARC Centre of Excellence for Gravitational Wave Discovery announced” 

    Swinburne U bloc

    Swinburne University

    8 September 2016
    Julia Scott
    +61 3 9214 5968

    In summary

    $31.3 million ARC Centre of Excellence for Gravitational Wave Discovery
    Led by Swinburne University of Technology
    The Centre will be called OzGRav
    Professor Matthew Bailes announced as Director
    Centre opens early 2017

    The Australian Research Council (ARC) today announced a new $31.3 million ARC Centre of Excellence for Gravitational Wave Discovery to be led by Swinburne University of Technology.

    The Centre, to be called OzGRav, will capitalise on the first detections of gravitational waves to understand the extreme physics of black holes and warped space-time.

    The discovery of gravitational waves

    Gravitational waves were first predicted by Albert Einstein in 1915 in his theory of General Relativity, which described how gravity warps and distorts space-time.

    Einstein’s mathematics showed that massive accelerating objects (such as neutron stars or black holes orbiting each other) distort both space and time and emit a new type of radiation, known as gravitational waves.

    These predicted gravitational waves are incredibly feeble. They went undetected for one hundred years until recent advances in detector sensitivity at the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO) enabled their detection for the first time, opening a new window on the Universe.

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation
    Caltech/MIT Advanced aLigo Hanford, WA, USA installation

    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA
    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    In September 2015, aLIGO physically sensed distortions in space-time itself caused by passing gravitational waves generated by two colliding black holes nearly 1.3 billion light years away!

    The arms of the detector changed their length by the equivalent of just the width of a human hair at the distance of the nearest star!

    Expanding Australia’s role in gravitational wave astronomy

    Many of OZGRav’s chief investigators helped aLIGO achieve this amazing feat and are thrilled to be able to expand Australia’s role in this nascent field of science as a result of the ARC announcement.

    “Through this centre, Australian scientists and students will have the opportunity to fully participate in the birth of gravitational wave astronomy,” says Centre Director and Professor Matthew Bailes.

    “It will enable us to develop some amazing technologies like quantum squeezing to further enhance the detectors, supercomputers and advanced algorithms to find the waves, and these will lead to a revolution in our understanding of the Universe.”

    This new window on the Universe will help answer key scientific questions such as:

    Is Einstein’s General Relativity correct when applied to the most extreme gravitational forces?
    What and where are the sources of gravitational waves?
    Do supermassive black holes merge often enough for us to see their death-cries with the Square Kilometre Array telescope?
    Can General Relativity be used to determine neutron star masses to help define the equation of state of nuclear matter?

    It will also contribute to improving the sensitivity of aLIGO, thus increasing the volume of the Universe that can be probed by an order of magnitude and lay the ground work for future gravitational wave detectors that will probe the entire Universe.

    Swinburne to host OzGRav headquarters

    “The world stands at the dawn of a new field of astrophysics. A field that demands the most exquisite instrumentation, intense signal processing and rapid follow-up with modern telescopes, Swinburne Deputy Vice-Chancellor (Research and Development) Professor Subic says.

    “As an internationally-renowned university of technology, with an exceptional physics base, there is no better place to host the headquarters of this exciting world-wide collaboration than at Swinburne.

    “I am particularly pleased that the new centre will be led by our Australian Laureate Fellow, Professor Matthew Bailes.”

    As part of its support for OzGRav, Swinburne will fund a new $3.5 million supercomputer in 2017. Up to 35 per cent of its time will be dedicated for gravitational wave searches.

    “It would be fantastic to think that we might discover new sources of gravitational waves right here on campus”, says Professor Jarrod Hurley, who will design OzGRav’s supercomputer.

    Part of the Centre’s mission is to capitalise on the public’s fascination with black holes to help spark an interest in science, technology, engineering and mathematics using school activities, social media and prominent science advocates such as Dr Alan Duffy and Olympic swimmer and physics student, Cameron McEvoy.

    Australian partners in this Centre of Excellence are Monash University, Australian National University, the University of Melbourne, the University of Western Australia, The University of Adelaide, CSIRO, and the Australian Astronomical Observatory.

    International partners include the LIGO Observatory, Caltech, the University of Florida, the University of Glasgow, the Max Planck Institutes of Gravitational Physics and Radio Astronomy, MIT, NASA, the University of Warwick and the Universita degli Studi di Urbino ‘Carlo Bo’.

    The Centre will open in early 2017.

    See the full article here .

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    Swinburne U Campus

    Swinburne is a large and culturally diverse organisation. A desire to innovate and bring about positive change motivates our students and staff. The result is in an institution that grows and evolves each year.

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