Laser Inferometer Gravitational Wave Observatory

Caltech Press Release Caltech Scientists Awarded 2017 Nobel Prize in Physics https://www.ligo.caltech.edu/page/press-release-2017-nobel-prize "I am humbled and honored to receive this award," says Barish. "The detection of gravitational waves is truly a triumph of modern large-scale experimental physics. Over several decades, our teams at Caltech and MIT developed LIGO into the incredibly sensitive device that made the discovery. When the signal reached LIGO from a collision of two stellar black holes that occurred 1.3 billion years ago, the 1,000-scientist-strong LIGO Scientific Collaboration was able to both identify the candidate event within minutes and perform the detailed analysis that convincingly demonstrated that gravitational waves exist."

On September 14, 2015, LIGO, run by the Massachusetts Institute of Technology (M.I.T.) and California Institute of Technology (CalTech) made its landmark discovery — the direct detection of gravitational waves..... Or did they?  Seems to be some dispute.... Albert Einstein’s 1916 theory of general relativity, which claimed their existence, asserted they would remain undetectable.... As did Ron Hatch....     Questioning the results.... https://www.researchgate.net/post/Am_I_the_only_one_that_is_doubtful_of_LIGOs_detection_of_gravitational_wave_GW150914 Peter Hahn 11.28 Northern Alberta Institute of Tech Am I the only one that is doubtful of LIGO’s detection of gravitational wave GW150914? It seems rather odd that GW150914 was detected during LIGO’s Engineering Run rather than during its Observational Run. The engineering run is a time when numerous LIGO engineers are making final adjustments to hardware and software systems.   One Answer from what appears to be legit Physicist at Max Plank Institute.... 3 years ago W.W. Engelhardt JET, Max-Planck-Institut für Plasmaphysik (retired) I am missing much more: How do they manage to keep the amplitudes of the interfering beams exactly equal within a factor 10-12? How do they manage to reduce the stray light in the dark field by a factor of 10-24 compared to the bright field? How do they keep the circulating power constant within a factor 10-12 in order to avoid motions of the mirrors induced by fluctuating radiation pressure? Where is the calibration curve showing displacement of the mirrors as a function of the radiation pressure? (10-18 m displacement are caused by 10-7 W light power during .2 s) How do they know that the velocity of light is unaffected when "spacetime" is "compressed"?  

Caltech Press Release Caltech Scientists Awarded 2017 Nobel Prize in Physics https://www.ligo.caltech.edu/page/press-release-2017-nobel-prize "I am humbled and honored to receive this award," says Barish. "The detection of gravitational waves is truly a triumph of modern large-scale experimental physics. Over several decades, our teams at Caltech and MIT developed LIGO into the incredibly sensitive device that made the discovery. When the signal reached LIGO from a collision of two stellar black holes that occurred 1.3 billion years ago, the 1,000-scientist-strong LIGO Scientific Collaboration was able to both identify the candidate event within minutes and perform the detailed analysis that convincingly demonstrated that gravitational waves exist."           Some Info on what is referred to as 'Blind Injections' of data, taken from the LIGO site....  Like WTF? https://www.ligo.org/news/blind-injection.php#sthash.xcYObjtZ.dpuf   Blind injections: The LIGO Scientific Collaboration and the Virgo Collaboration conducted their latest joint observation run (using the LIGO Hanford, LIGO Livingston, Virgo and GEO 600 detectors) from July, 2009 through October 2010, and are jointly searching through the resulting data for gravitational wave signals standing above the detector noise levels. To make sure they get it right, they train and test their search procedures with many simulated signals that are injected into the detectors, or directly into the data streams. The data analysts agreed in advance to a "blind" test: a few carefully-selected members of the collaborations would secretly inject some (zero, one, or maybe more) signals into the data without telling anyone. The secret goes into a "Blind Injection Envelope", to be opened when the searches are complete. Such a "mock data challenge" has the potential to stress-test the full procedure and uncover problems that could not be found in other ways. The outcomes from previous blind injection exercises were reported in 2010, in https://journals.aps.org/prd/abstract/10.1103/PhysRevD.81.102001 and https://journals.aps.org/prd/abstract/10.1103/PhysRevD.82.102001 The signal: A rather strong signal was observed on September 16, 2010, within a minute or so of its apparent arrival at the detectors. The scientists on duty at the detector sites immediately recognized the tell-tale chirp signal expected from the merger of two black holes and/or neutron stars, and sprang into action. They knew that it could be a blind injection, but they also knew to act like it was the real thing. The event was beautifully consistent with the expected signal from such a merger. The figures below show the strength of the signal (redder colors indicate more signal power) in time (horizontal axis) and frequency (vertical axis). The signal sweeps upwards in frequency ("chirp") as the stars spiral into one another, approaching merger. The first plot is what was seen in the LIGO Hanford detector, and the second is what was seen at the same time in the LIGO Livingston detector. Despite apparent differences, the two signals are completely consistent with one another. The dark and light blue regions are typical of fluctuating noise in the detectors. The detector network is capable of locating the source in the sky only crudely; it seemed to be coming from the constellation Canis Major (the "Big Dog") in the southern hemisphere (the event was dubbed "the Big Dog" shortly thereafter). They sent alerts to partners operating robotic optical telescopes in the southern hemisphere (ROTSE, TAROT, Skymapper, Zadko) and the Swift X-ray space telescope, all of which took images of the sky on that and/or subsequent days in the hope of capturing an optical or X-ray "afterglow". Is it real? In the subsequent days and weeks, numerous teams of scientists tried to get definitive answers to many questions. The event was seen strongly in the two LIGO detectors, less strongly in the Virgo detector, and nothing was seen in the less sensitive GEO detector. Could the event be explained as an accidental coincidence of noise fluctuations? The initial estimate was that the chance of the event being due to noise in the detectors was "much less than 1%", but much more work was required to say how much; after careful analysis, the teams agreed that such a noise coincidence might happen once in 7,000 years. Could the detectors have exhibited some never-before-seen instrumental effect just then, maybe one that could somehow be correlated between sites that are separated by thousands of kilometers? Despite many investigations and much thought, no plausible scenario for this could be found (except for a blind injection). After studying all of the evidence, the hundreds of scientists in the collaborations convinced themselves and each other that this was not an instrumental artifact. Is there an afterglow? Was there any sign of an optical or X-ray "transient" in the telescope images? A binary black hole merger would not be expected to emit any kind of light; but if one of the objects was a neutron star rather than a black hole, it would emit a burst of gamma rays that could be seen from across the universe, and an afterglow of X-rays and optical light. Teams worked with their partner astronomers to analyze the images, which only covered a small part of the sky that the signal could have come from. They looked for transients, and eliminated imposters such as variable stars, near-earth asteroids, distant supernovae, etc. Preliminary results revealed no candidate optical or X-ray transient event on the sky that could be associated with this signal. What kind of merger? Mergers of black holes and/or neutron stars are very rare, but they can come in many shapes and sizes. What were the masses of the two stars? If one was significantly less than 3 solar masses, it could be a neutron star, not a black hole, and this is an important distinction to astrophysicists. Whether black holes or neutron stars, they might be expected to be spinning; can this be determined from the signal? And where, precisely is the system located on the sky, and at what distance? All told, there are fifteen parameters that can be extracted from the signals at the LIGO and Virgo detectors, and several different teams of scientists were able to measure them. The result, however, depended on the waveform models used, and the most realistic models were also the most complex. Documenting the "Evidence": The scientists gathered all this information together in a paper entitled "Evidence for the Direct Detection of Gravitational Waves from a Black Hole Binary Coalescence". (Coalescence refers to the inspiral of the two stars, their merger into a single perturbed black hole, and the "ringdown" into a final quiet black hole, all through the emission of gravitational waves). A second paper described the parameter estimation procedures and results. A third summarized the search for binary coalescence and the overall results (only one event was observed above the background noise). Material was prepared for the open release of data relevant to this event, and a whole suite of resources for education and public outreach was assembled. The event was renamed "GW100916", for the year, month and date that it was recorded. Opening the envelope: An independent "Detection Committee" reviewed and double-checked all of this work, and reported their findings to the two collaborations. Everyone voted on whether the work, and all the documentation, was sufficient to announce the first detection; the result was a unanimous "yes". The Blind Injection Envelope was opened on March 14, 2011 at a joint meeting of the LIGO Scientific Collaboration and the Virgo Collaboration in Arcadia, CA. There were 300 people in the room and another 100 connecting through a video teleconference. The envelope was opened -- and there was the event: it was a blind injection, not the first direct detection of gravitational waves. Did they get it right? The event parameters were revealed: it was indeed a binary merger injected at the time when the "big dog" event was observed. The waveform recovered by the search was a good match to the one which was injected. However, there were some surprises: the injected signal was composed of a neutron star and a black hole, not two black holes; and it wasn't from anywhere near Canis Major. What happened? Within hours, the answer became clear: there was a problem in the blind injection software. The team that injected the simulated gravitational wave signal into the detector had used some old software containing two "bugs": an old waveform model that had more recently been replaced by an improved one (this explained why the signal looked like two black holes), and a sign error in the injection to one detector that made it look like the signal was coming from a different part of the sky. When these errors were taken into account, the analysis easily recovered the "right" parameters. But most importantly, those bugs did not prevent the scientists from finding the injected event in the first place. Lessons learned: Aside from that one problem, everything else in the process seemed to go right. Procedures are now being established to ensure that problems like these will not happen again, which is one of the primary purposes of these mock data challenges. The blind injection challenge was an extremely successful exercise for the LIGO and Virgo scientists, demonstrating their ability to detect gravitational waves from coalescing binaries and providing a concrete example of how the momentous first detection might play out. Of course, the first real detection may well look nothing like this exercise: it could be a burst signal from a core-collapse supernova; a continuous sine wave from a spinning neutron star in our Galaxy; a hiss of noise from the earliest moment of the Big Bang; or something that they have not yet anticipated. It could be in the data already collected, since the searches for all anticipated signals are not yet complete. Or we might have to wait a few more years for the data from the next generation of detectors. Overall, it was an exhilarating and extremely valuable exercise, even if it was disappointing in the end. The LIGO and Virgo teams are now much more prepared for the first real detections.   More info from above link...   "In the initial phase of LIGO, in order to isolate the detectors from the earth's motion, we used a suspension system that consisted of test-mass mirrors hung by piano wire and used a multiple-stage set of passive shock absorbers, similar to those in your car. We knew this probably would not be good enough to detect gravitational waves, so we, in the LIGO Laboratory, developed an ambitious program for Advanced LIGO that incorporated a new suspension system to stabilize the mirrors and an active seismic isolation system to sense and correct for ground motions," says Barish. The active seismic isolation system developed for Advanced LIGO works in a similar fashion to noise-canceling headphones, except it can measure and cancel out ground vibrations coming from many directions. In conjunction with this system, a new "quieter" way to suspend LIGO's mirrors was developed with the help of the Glasgow group, which involved hanging the mirrors with a four-stage pendulum. The combination of these two advances gave LIGO a huge improvement in sensitivity to lower frequencies of gravitational waves, which was ultimately what was needed to detect the crashing of two black holes. Barish also created the LIGO of today: a collaboration of approximately 1,200 scientists and engineers at about 100 institutions in 19 nations called the LIGO Scientific Collaboration (LSC).   From a paper LIGO published with some more intel on their 'blind injections' Following the completion of this analysis, the event was revealed to be a blind injection. While the analy- sis groups did not know the event was an injection prior to its unblinding, they did know that one or more blind injections may be performed during the analysis period. Such blind injections have been carried out before: see [4] for the results of a blind injection performed in a previ- ous run. This event was the only coherent CBC blind injection performed during S6 and VSR2 and 3. The in- jection was identified as a gravitational-wave candidate with high probability, and the blind injection challenge was considered to be successful. https://arxiv.org/pdf/1111.7314.pdf  Page 8         LIGO measurement claim lifted from their site, noticed some media outlets had suggested the ability to measure to 1/10,000 the diameter of a proton, LIGO only makes the claim of 1/1,000th the diameter of a proton.... LIGO's interferometers are the largest ever built. With arms 4 km (2.5 mi.) long, they are 360 times larger than the one used in the Michelson-Morley experiment (which had arms 11 m (33 feet) long). This is particularly important in the search for gravitational waves because the longer the arms of an interferometer, the farther the laser travels, and the more sensitive the instrument becomes. Attempting to measure a change in arm length 1,000 times smaller than a proton means that LIGO has to be more sensitive than any scientific instrument ever built, so the longer the better. But there are obvious limitations to how long one can build an interferometer. Even with arms 4 km long, if LIGO's interferometers were basic Michelsons they would still not be long enough to detect gravitational waves...and yet they are. How is this possible? https://www.ligo.caltech.edu/WA/page/ligos-ifo   But wait, LIGO DOES make the claim of 1/10,000th of a proton on a different page.... L-R: The LIGO Livingston Observatory, LIGO Hanford Observatory, and Virgo These are "first-generation" detectors, designed to demonstrate the technologies that can sense motions at the level of one-ten-thousandth of the diameter of a proton (or 10-19 meter), which may only be barely sensitive enough to detect the waves. https://www.ligo.org/news/blind-injection.php I see now where the confusion in the media comes from, LIGO itself....   Poorly done LIGO....  Shame a scientific outfit that has had billions of dollars thrown at it can't seem to proof their own website very well.... Have to go with the SI unit they used in the second link, 10 to the minus 19 of a meter....                                      

On September 14, 2015, LIGO, run by the Massachusetts Institute of Technology (M.I.T.) and California Institute of Technology (CalTech) made its landmark discovery — the direct detection of gravitational waves..... Or did they?  Seems to be some dispute.... Albert Einstein’s 1916 theory of general relativity, which claimed their existence, asserted they would remain undetectable.... As did Ron Hatch....

Questioning the results.... https://www.researchgate.net/post/Am_I_the_only_one_that_is_doubtful_of_LIGOs_detection_of_gravitational_wave_GW150914

Peter Hahn Northern Alberta Institute of Technology   "Am I the only one that is doubtful of LIGO’s detection of gravitational wave GW150914? It seems rather odd that GW150914 was detected during LIGO’s Engineering Run rather than during its Observational Run. The engineering run is a time when numerous LIGO engineers are making final adjustments to hardware and software systems."

One Answer from what appears to be legit Physicist at Max Plank Institute.... 3 years ago W.W. Englehart JET, Max-Planck-Institut für Plasmaphysik (retired) "I am missing much more: How do they manage to keep the amplitudes of the interfering beams exactly equal within a factor 10-12? How do they manage to reduce the stray light in the dark field by a factor of 10-24 compared to the bright field? How do they keep the circulating power constant within a factor 10-12 in order to avoid motions of the mirrors induced by fluctuating radiation pressure? Where is the calibration curve showing displacement of the mirrors as a function of the radiation pressure? (10-18 m displacement are caused by 10-7 W light power during .2 s) How do they know that the velocity of light is unaffected when "spacetime" is "compressed"?"

Some Info on what is referred to as 'Blind Injections' of data, taken from the LIGO site....  Like WTF? https://www.ligo.org/news/blind-injection.php#sthash.xcYObjtZ.dpuf

Blind injections: The LIGO Scientific Collaboration and the Virgo Collaboration conducted their latest joint observation run (using the LIGO Hanford, LIGO Livingston, Virgo and GEO 600 detectors) from July, 2009 through October 2010, and are jointly searching through the resulting data for gravitational wave signals standing above the detector noise levels. To make sure they get it right, they train and test their search procedures with many simulated signals that are injected into the detectors, or directly into the data streams. The data analysts agreed in advance to a "blind" test: a few carefully-selected members of the collaborations would secretly inject some (zero, one, or maybe more) signals into the data without telling anyone. The secret goes into a "Blind Injection Envelope", to be opened when the searches are complete. Such a "mock data challenge" has the potential to stress-test the full procedure and uncover problems that could not be found in other ways.

The outcomes from previous blind injection exercises were reported in 2010, in https://journals.aps.org/prd/abstract/10.1103/PhysRevD.81.102001 and https://journals.aps.org/prd/abstract/10.1103/PhysRevD.82.102001

The signal: A rather strong signal was observed on September 16, 2010, within a minute or so of its apparent arrival at the detectors. The scientists on duty at the detector sites immediately recognized the tell-tale chirp signal expected from the merger of two black holes and/or neutron stars, and sprang into action. They knew that it could be a blind injection, but they also knew to act like it was the real thing. The event was beautifully consistent with the expected signal from such a merger. The figures below show the strength of the signal (redder colors indicate more signal power) in time (horizontal axis) and frequency (vertical axis). The signal sweeps upwards in frequency ("chirp") as the stars spiral into one another, approaching merger. The first plot is what was seen in the LIGO Hanford detector, and the second is what was seen at the same time in the LIGO Livingston detector. Despite apparent differences, the two signals are completely consistent with one another. The dark and light blue regions are typical of fluctuating noise in the detectors. The detector network is capable of locating the source in the sky only crudely; it seemed to be coming from the constellation Canis Major (the "Big Dog") in the southern hemisphere (the event was dubbed "the Big Dog" shortly thereafter). They sent alerts to partners operating robotic optical telescopes in the southern hemisphere (ROTSE, TAROT, Skymapper, Zadko) and the Swift X-ray space telescope, all of which took images of the sky on that and/or subsequent days in the hope of capturing an optical or X-ray "afterglow". Is it real? In the subsequent days and weeks, numerous teams of scientists tried to get definitive answers to many questions. The event was seen strongly in the two LIGO detectors, less strongly in the Virgo detector, and nothing was seen in the less sensitive GEO detector. Could the event be explained as an accidental coincidence of noise fluctuations? The initial estimate was that the chance of the event being due to noise in the detectors was "much less than 1%", but much more work was required to say how much; after careful analysis, the teams agreed that such a noise coincidence might happen once in 7,000 years. Could the detectors have exhibited some never-before-seen instrumental effect just then, maybe one that could somehow be correlated between sites that are separated by thousands of kilometers? Despite many investigations and much thought, no plausible scenario for this could be found (except for a blind injection). After studying all of the evidence, the hundreds of scientists in the collaborations convinced themselves and each other that this was not an instrumental artifact. Is there an afterglow? Was there any sign of an optical or X-ray "transient" in the telescope images? A binary black hole merger would not be expected to emit any kind of light; but if one of the objects was a neutron star rather than a black hole, it would emit a burst of gamma rays that could be seen from across the universe, and an afterglow of X-rays and optical light. Teams worked with their partner astronomers to analyze the images, which only covered a small part of the sky that the signal could have come from. They looked for transients, and eliminated imposters such as variable stars, near-earth asteroids, distant supernovae, etc. Preliminary results revealed no candidate optical or X-ray transient event on the sky that could be associated with this signal. What kind of merger? Mergers of black holes and/or neutron stars are very rare, but they can come in many shapes and sizes. What were the masses of the two stars? If one was significantly less than 3 solar masses, it could be a neutron star, not a black hole, and this is an important distinction to astrophysicists. Whether black holes or neutron stars, they might be expected to be spinning; can this be determined from the signal? And where, precisely is the system located on the sky, and at what distance? All told, there are fifteen parameters that can be extracted from the signals at the LIGO and Virgo detectors, and several different teams of scientists were able to measure them. The result, however, depended on the waveform models used, and the most realistic models were also the most complex. Documenting the "Evidence": The scientists gathered all this information together in a paper entitled "Evidence for the Direct Detection of Gravitational Waves from a Black Hole Binary Coalescence". (Coalescence refers to the inspiral of the two stars, their merger into a single perturbed black hole, and the "ringdown" into a final quiet black hole, all through the emission of gravitational waves). A second paper described the parameter estimation procedures and results. A third summarized the search for binary coalescence and the overall results (only one event was observed above the background noise). Material was prepared for the open release of data relevant to this event, and a whole suite of resources for education and public outreach was assembled. The event was renamed "GW100916", for the year, month and date that it was recorded. Opening the envelope: An independent "Detection Committee" reviewed and double-checked all of this work, and reported their findings to the two collaborations. Everyone voted on whether the work, and all the documentation, was sufficient to announce the first detection; the result was a unanimous "yes". The Blind Injection Envelope was opened on March 14, 2011 at a joint meeting of the LIGO Scientific Collaboration and the Virgo Collaboration in Arcadia, CA. There were 300 people in the room and another 100 connecting through a video teleconference. The envelope was opened -- and there was the event: it was a blind injection, not the first direct detection of gravitational waves. Did they get it right? The event parameters were revealed: it was indeed a binary merger injected at the time when the "big dog" event was observed. The waveform recovered by the search was a good match to the one which was injected. However, there were some surprises: the injected signal was composed of a neutron star and a black hole, not two black holes; and it wasn't from anywhere near Canis Major. What happened? Within hours, the answer became clear: there was a problem in the blind injection software. The team that injected the simulated gravitational wave signal into the detector had used some old software containing two "bugs": an old waveform model that had more recently been replaced by an improved one (this explained why the signal looked like two black holes), and a sign error in the injection to one detector that made it look like the signal was coming from a different part of the sky. When these errors were taken into account, the analysis easily recovered the "right" parameters. But most importantly, those bugs did not prevent the scientists from finding the injected event in the first place. Lessons learned: Aside from that one problem, everything else in the process seemed to go right. Procedures are now being established to ensure that problems like these will not happen again, which is one of the primary purposes of these mock data challenges. The blind injection challenge was an extremely successful exercise for the LIGO and Virgo scientists, demonstrating their ability to detect gravitational waves from coalescing binaries and providing a concrete example of how the momentous first detection might play out. Of course, the first real detection may well look nothing like this exercise: it could be a burst signal from a core-collapse supernova; a continuous sine wave from a spinning neutron star in our Galaxy; a hiss of noise from the earliest moment of the Big Bang; or something that they have not yet anticipated. It could be in the data already collected, since the searches for all anticipated signals are not yet complete. Or we might have to wait a few more years for the data from the next generation of detectors. Overall, it was an exhilarating and extremely valuable exercise, even if it was disappointing in the end. The LIGO and Virgo teams are now much more prepared for the first real detections.

More info from above link...   "In the initial phase of LIGO, in order to isolate the detectors from the earth's motion, we used a suspension system that consisted of test-mass mirrors hung by piano wire and used a multiple-stage set of passive shock absorbers, similar to those in your car. We knew this probably would not be good enough to detect gravitational waves, so we, in the LIGO Laboratory, developed an ambitious program for Advanced LIGO that incorporated a new suspension system to stabilize the mirrors and an active seismic isolation system to sense and correct for ground motions," says Barish. The active seismic isolation system developed for Advanced LIGO works in a similar fashion to noise-canceling headphones, except it can measure and cancel out ground vibrations coming from many directions. In conjunction with this system, a new "quieter" way to suspend LIGO's mirrors was developed with the help of the Glasgow group, which involved hanging the mirrors with a four-stage pendulum. The combination of these two advances gave LIGO a huge improvement in sensitivity to lower frequencies of gravitational waves, which was ultimately what was needed to detect the crashing of two black holes. Barish also created the LIGO of today: a collaboration of approximately 1,200 scientists and engineers at about 100 institutions in 19 nations called the LIGO Scientific Collaboration (LSC).

From a paper LIGO published with some more intel on their 'blind injections' From a paper LIGO published with some more intel on their 'blind injections' https://arxiv.org/pdf/1111.7314.pdf  Page 8 From a paper LIGO published with some more intel on their 'blind injections' Following the completion of this analysis, the event was revealed to be a blind injection. While the analy- sis groups did not know the event was an injection prior to its unblinding, they did know that one or more blind injections may be performed during the analysis period. Such blind injections have been carried out before: see [4] for the results of a blind injection performed in a previ- ous run. This event was the only coherent CBC blind injection performed during S6 and VSR2 and 3. The in- jection was identified as a gravitational-wave candidate with high probability, and the blind injection challenge was considered to be successful.    

https://www.ligo.caltech.edu/WA/page/ligos-ifo LIGO measurement claim lifted from their site, noticed some media outlets had suggested the ability to measure to 1/10,000 the diameter of a proton, LIGO only makes the claim of 1/1,000th the diameter of a proton.... LIGO's interferometers are the largest ever built. With arms 4 km (2.5 mi.) long, they are 360 times larger than the one used in the Michelson-Morley experiment (which had arms 11 m (33 feet) long). This is particularly important in the search for gravitational waves because the longer the arms of an interferometer, the farther the laser travels, and the more sensitive the instrument becomes. Attempting to measure a change in arm length 1,000 times smaller than a proton means that LIGO has to be more sensitive than any scientific instrument ever built, so the longer the better. But there are obvious limitations to how long one can build an interferometer. Even with arms 4 km long, if LIGO's interferometers were basic Michelsons they would still not be long enough to detect gravitational waves...and yet they are. How is this possible?  

But wait, LIGO DOES make the claim of 1/10,000th of a proton on a different page.... L-R: The LIGO Livingston Observatory, LIGO Hanford Observatory, and Virgo These are "first-generation" detectors, designed to demonstrate the technologies that can sense motions at the level of one-ten-thousandth of the diameter of a proton (or 10-19 meter), which may only be barely sensitive enough to detect the waves. https://www.ligo.org/news/blind-injection.php

I see now where the confusion in the media comes from, LIGO itself....   Poorly done LIGO....  Shame a scientific outfit that has had billions of dollars thrown at it can't seem to proof their own website very well.... Have to go with the SI unit they used in the second link, 10 to the minus 19 of a meter....

Sensitivity had been given an order of magnitude boost when the 2010-14 upgrade was complete, leading to the analogy of a hairs width sensitivity at 4.2 light years distance....   https://www.ligo.caltech.edu/page/facts The lessons learned during Initial LIGO's operation led to a complete redesign of LIGO's instruments, which were rebuilt between 2010 and 2014. This redesign and subsequent improvements will ultimately make LIGO's interferometers 10 times more sensitive than their initial incarnation. A 10-fold increase in sensitivity means that LIGO will be able to detect gravitational waves 10 times farther away than Initial LIGO, which translates into 'sampling' 1000-times more volume of space (volume increases with the cube of the distance. So 10 times farther away means 10x10x10=1000 times the volume of space), and 1000-times more galaxies containing sources of gravitational waves.

LIGO makes a claim of the earth curving one full meter over the span of four kilometers... https://www.ligo.caltech.edu/page/facts   Seemed a little much, ran a quick google and found that calculating the drop required more than a quick google..... 8 inches per mile squared works for short distances such as this. Some links that were chased down in the course of looking at this seemingly easy calculation..... Darn flat earthers polluting google with links that must be sorted thru..... Have to chuckle at some of their logic posted in the threads I have clicked on... "Theories are just that and gravity is the biggest lie as Einstein never proved e=mc2. Just open you mind and think for yourself and ask if earth is so old why are trees so small. If the earth spins 1,000 mph then how do planes fly east and west at the same time frame. Why did a flight from Japan emergency land in Alaska."         This from my Canadian Brethern   http://mathcentral.uregina.ca/QQ/database/QQ.09.15/h/sean1.html http://mathcentral.uregina.ca/QQ/database/QQ.09.02/shirley3.html   This sidetrip of the earths curvature is interesting....   " Now, the important bit here is it is NOT linear. The drop isnt so many feet per mile away. It changes because you are drawing a straight horizontal line, but the earth drops as a circle. So it wont be a constant linear feet dropped per mile away." https://www.quora.com/How-many-feet-per-mile-does-the-earth-curve-down-from-where-you-stand   I get it now, there is an answer out there, a variable that can be used for a sphere of a known size.  It's just a matter of finding it.  Surprisingly enough, it is not easily found via google search. Most of these equations are calculating on a straight line out from the starting point, extending into space.  I am looking for distance travelled ON THE SURFACE OF THE CURVE.   Variables: * ASSUMING A SPHERICAL EARTH Diameter of Earth at equator:  12,756 km R = 6,378 km   Circumference = pi D Circumference =  40074.1558892  ()significant digits be damned, it's a copy pasta   UGHH..... moving away to a brainwave.... Use a calculator to see speed and period of a satellite orbitting at 1 meter above sea level, use big G and time periods to model average drop.....   https://www.quora.com/How-much-more-quickly-would-a-satellite-at-sea-level-orbit-the-earth-than-a-satellite-at-the-lowest-normal-altitude-Or-one-at-geosynchronous-orbit Radius of the Earth is r = 6,371 km = 6,371,000 m T = 84.35 minutes = 1 hour, 24 minutes, 21 seconds v = 7,909 m/s = 7.9 km/s   https://keisan.casio.com/exec/system/1224665242 v = 7.9053638172551 km/s T = 1:24.29.35 Orbital Radius: 6,378.141                        

First article in Mainstream I could dig up questioning LIGO signal validity. https://www.forbes.com/sites/startswithabang/2017/06/16/was-it-all-just-noise-independent-analysis-casts-doubt-on-ligos-detections/#2f78dc515516 A team of five researchers — James Creswell, Sebastian von Hausegger, Andrew D. Jackson, Hao Liu and Pavel Naselsky — from the Niels Bohr Institute in Copenhagen, presented their own analysis of the openly available LIGO data. And, unlike the LIGO collaboration itself, they come to a disturbing conclusion: that these gravitational waves might not be signals at all, but rather patterns in the noise that have hoodwinked even the best scientists working on this puzzle.   References a video presentation of Jacksons (Neils Bohr Institute). http://Understanding the LIGO gravitational wave event (GW150914) Professor Andrew D. Jackson, The Niels Bohr Institute, Copenhagen    

Thursday, November 01, 2018 Backreaction blogspot Sabine Hossenfelder, aka Bee Research Fellow at the Frankfurt Institute for advanced studies Story about LIGO noise resurfaces in New Scientist http://backreaction.blogspot.com/2018/11/story-about-ligo-noise-resurfaces-in.html     Actual New Scientist article,  31 October 2018 https://www.newscientist.com/article/mg24032022-600-exclusive-grave-doubts-over-ligos-discovery-of-gravitational-waves/ The Danish group’s independent checks, published in three peer-reviewed papers, found there was little evidence for the presence of gravitational waves in the September 2015 signal. On a scale from certain at 1 to definitely not there at 0, Jackson says the analysis puts the probability of the first detection being from an event involving black holes with the properties claimed by LIGO at 0.000004. That is roughly the same as the odds that your eventual cause of death will be a comet or asteroid strike – or, as Jackson puts it,”consistent with zero”. The probability of the signal being due to a merger of any sort of black holes is not huge either. Jackson and his colleagues calculate it as 0.008.          

Actual New Scientist article,  31 October 2018 https://www.newscientist.com/article/mg24032022-600-exclusive-grave-doubts-over-ligos-discovery-of-gravitational-waves/ The Danish group’s independent checks, published in three peer-reviewed papers, found there was little evidence for the presence of gravitational waves in the September 2015 signal. On a scale from certain at 1 to definitely not there at 0, Jackson says the analysis puts the probability of the first detection being from an event involving black holes with the properties claimed by LIGO at 0.000004. That is roughly the same as the odds that your eventual cause of death will be a comet or asteroid strike – or, as Jackson puts it,”consistent with zero”. The probability of the signal being due to a merger of any sort of black holes is not huge either. Jackson and his colleagues calculate it as 0.008.

ARS Technica article, Danish physicists claim to cast doubt on detection of gravitational waves LIGO responds: "There is absolutely no validity to their claims." Jennifer Ouellette - 10/31/2018      

LIGO Responds on their website....   https://www.ligo.org/news/index.php?fbclid=IwAR3rApGoMb1UB1qVEqU_uce3gBhM7g55Ca6be7GTRJ6Gm3NLK2I-k3G1YeI#LVCdata LIGO and Virgo Collaborations Working to Make Data and Analysis Techniques Available to All 1 Nov 2018 -- Claims in a paper by Creswell et al. of puzzling correlations in LIGO data have broadened interest in understanding the publicly available LIGO data around the times of the detected gravitational-wave events. The features presented in Creswell et al. arose from misunderstandings of public data products and the ways that the LIGO data need to be treated. The LIGO Scientific Collaboration and Virgo Collaboration (LVC) have full confidence in our published results. We are preparing a paper that will provide more details about LIGO detector noise properties and the data analysis techniques used by the LVC to detect gravitational-wave signals and infer their source properties. The entire gravitational-wave signal data stream from the first observing run is already publicly available at the Gravitational-Wave Open Science Center, along with additional information on analyzing LIGO data. This resource, along with presentations from a recent Open Data Workshop, will be of interest to all who wish to understand our results in more depth.  

First paper revised from Jackson etal https://arxiv.org/abs/1706.04191