Right, amplitude goes with 1/r. About old detectors, yes they were simply not sensitivity enough. Once they updated LIGO to Advanced LIGO (but not even full power but just 1/3 of its full potential that over time would be reached) they got a nice detection event. It was just an engineering run. But this source is actually much brighter than what most people expected particularly because of the masses of black holes involved. We had some ideas of how likely these events were and they were supposed to be too rare to be observed within Hubble time (age of the universe). Evidently we discovered that this estimate was not correct. So it was 2 important discoveries in one.
On Fri, Feb 12, 2016 at 1:01 PM, David Roberson <dlrober...@aol.com> wrote: > Sounds impressive! Perhaps I was a bit too skeptic and am warming up to > the idea. > > If a collision 1 billion plus light years away produces a 24 dB SNR, then > it is going to be amazing how clean a collision only 1 million LY's away > will produce. I would guess the amplitude would be a million times as > large if the inverse squared law applies. > > That ratio of amplitudes would lead me to assume that the generation of > detectors before this one were far, far less sensitive or that there just > happened to be no collisions during the sample time at these distances. > Has anyone address this issue? > > Dave > > > -----Original Message----- > From: Giovanni Santostasi <gsantost...@gmail.com> > To: vortex-l <vortex-l@eskimo.com> > Sent: Fri, Feb 12, 2016 11:42 am > Subject: Re: [Vo]:LIGO Gravity Waves... So what? > > There was not much filtering going on because the signal was so evident, > 24 SNR. > > Other searches like looking for GW from rotating neutron stars try to > detect very weak signals in noise because you can integrate the supposed > signal (that it is continuous and if existent could last billion of years) > over time. > This particular signal was very loud so the main cleaning was by looking > at other non gravitational channels. They have dozen of sensors that > measure seismic activity, temperature and other type of noise and the > signal is cleaned up using this information. There was some wavelet > analysis done to extract the possible original waveform but the main test > was to compare the detected signal with the GR model. > > There is a further cool thing to consider that the sensitivity of the 2 > detectors was slightly different because of the different orientation of > the huge L of the interferometers. The signal is strongest when the L is > perpendicular to the direction of motion of the wave. Because of their > different locations on earth the 2 detectors have slightly different > sensitivity (or antenna) patterns and this was perfectly evident in the > data, exactly as GR predicted. > Yes, the data looks so good that at first many of the LIGO scientists > thought it was an artificial injection to test their detection algorithms. > They had false alarms like these before. But it is not the case this time. > It is not a sudden announcement. The detection happened in September, the > conference press happened almost 6 months later (LIGO people are super nit > picking I can assure you). > > > > > > > > On Fri, Feb 12, 2016 at 11:21 AM, David Roberson <dlrober...@aol.com> > wrote: > >> That paper is damaged according to my computer but I found the one that >> Harry posted. >> >> Do you have information concerning the filtering that the signal plus >> noise is subjected to before it is interpreted? Also, do these events >> only take place at at low rate throughout the universe? I suppose that is >> true for super nova explosions and this is likely to be just as rare of an >> event. >> >> These teams need to be congratulated if the detections continue to be >> confirmed. I remain weary of announcements that are produced so quickly. >> >> Dave >> >> >> -----Original Message----- >> From: Giovanni Santostasi <gsantost...@gmail.com> >> To: vortex-l <vortex-l@eskimo.com> >> Sent: Fri, Feb 12, 2016 11:08 am >> Subject: Re: [Vo]:LIGO Gravity Waves... So what? >> >> Here is the paper: >> https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.116.061102 >> >> The detection statistics is 5.1 sigma, that corresponds to a p value of >> 3x10-7 or 1 in 3.5 million that the signal is due to chance. In the paper >> they discuss the background noise and what to expect from it. >> But what is more astounding is the waveform itself as detected by both >> detectors (with a small time shift expected by the fact the waves travel at >> the velocity of light). >> You have a beautiful time evolution of the signal. In fact you can >> separate the detected signal in 3 parts: inspiraling, merger and ring down. >> They use relativistic approximate equations (basically an expansion with >> correction at many decimal places) to find a model that fits the observed >> data and only a merger of black holes with certain masses, orientation >> towards the detector, spin and distance fits with high accuracy the data. >> It is almost incredible how well the model actually fits the data. Besides >> some non Gaussian noise that is always present in the detector the observed >> waveforms look like the solution of a GR graduate textbook end of chapter >> exercise problem. >> >> >> >> On Fri, Feb 12, 2016 at 10:57 AM, David Roberson <dlrober...@aol.com> >> wrote: >> >>> How can we be confident that this is not just a false alarm? It seems a >>> bit premature to make this announcement since the claimed event is a >>> billion light years away from Earth. Are we to assume that this particular >>> event at that great distance is the only one that is showing up on the >>> instrument? What proof is there that millions more are not present at >>> closer distances which would be noise to filter out? >>> >>> Has anyone released information concerning the signal to noise for this >>> discovery? Also, it is a bit difficult to believe that the device can tell >>> the actual distance and direction of the black hole collision. >>> >>> Has this been replicated? There is much more evidence for cold fusion >>> than for this discovery and I have a strong suspicion that it will be >>> overturned one day. Big science making big claims again...I hope it is >>> true but it is unlikely. >>> >>> Dave >>> >>> >>> -----Original Message----- >>> From: Giovanni Santostasi <gsantost...@gmail.com> >>> To: vortex-l <vortex-l@eskimo.com> >>> Sent: Thu, Feb 11, 2016 9:28 pm >>> Subject: Re: [Vo]:LIGO Gravity Waves... So what? >>> >>> By the way, gravitational waves were the topic of my dissertation so >>> feel free to ask any question about the topic. It is very fascinating. >>> >>> On Thu, Feb 11, 2016 at 9:26 PM, Giovanni Santostasi < >>> gsantost...@gmail.com> wrote: >>> >>>> It opens a complete different window on the Universe. >>>> The analogy that is often given is imagine the cosmic show is like a TV >>>> show. Until now we had video but not audio. Finally we turned the audio on. >>>> Gravitational waves are a different but complementary way to observe >>>> the universe. >>>> We already learning things we could not learn before just using EM >>>> radiation. For example that there are black holes systems with such large >>>> masses. >>>> This has consequences in terms of galaxy evolution and how stars were >>>> formed. >>>> And this is just the beginning. >>>> The ultimate price is when we will see the gravitational waves from Big >>>> Bang. >>>> While the Microwave Cosmic Background tell us abut the universe at a >>>> very early stage (500 K years) we cannot receive any earlier information >>>> about the universe using EM radiation. >>>> The equivalent gravitational wave background when detected will tells >>>> information from a fraction of a second after the Big Bang. Only >>>> gravitational radiation can give us a picture of the universe that early. >>>> >>>> Also information from events like the one just observed eventually >>>> would give us clues on how gravity and quantum mechanics work together. >>>> The consequences of this discovery are enormous. >>>> >>>> >>>> >>>> >>>> >>>> On Thu, Feb 11, 2016 at 8:22 PM, Russ George <russ.geo...@gmail.com> >>>> wrote: >>>> >>>>> It seems the announcement of showing gravity waves are real is only of >>>>> value to obscure academic discussions. Unless someone here might >>>>> illuminate >>>>> us about some practical derivatives that might be revealed due to the >>>>> findings. >>>>> >>>> >>>> >>> >> >
