The distance is not a free parameter. When you have 2 detectors waveforms you can fix the masses of the black holes, spins, orbital plane, final mass of the system, distance (of course within a certain level of precision that is mentioned in paper). The least constrained parameter is location in the sky as I explained before. 3 detectors would have determined the position even better. The detectors are oriented in a certain way to do some level of triangulation but there is a detector in Italy (VIRGO, that was not operating a the time of detection) that would help with the triangulation (and a 3rd LIGO planned to be constructed in India).
On Fri, Feb 12, 2016 at 1:43 PM, Giovanni Santostasi <gsantost...@gmail.com> wrote: > What I meant is that LIGO theorists came up with many different types of > possible candidate sources based on astrophysical principles, event rate > estimates and so on. > While black hole mergers were one of these possible sources the masses > that were involved in this event were on the high end limits of the range > of what was considered possible. > > So in a way LIGO was lucky that these events are more common than imagined. > I should rephrase and say black hole mergers in general seem more loud > than anticipated because large mass systems are more common than previously > thought. > This is what I meant. > > It is a little bit like what happened with planet detection. The first > detections were of strange, strange objects that were very close to the > star and very large, hot Jupiters. The first attempts to look for > signatures of planets around stars were not supposed to see anything > because they were not sensitive enough to see solar system type of planets. > They tried anyway and hold and behold they saw planets but of a strange > kind. > Nature always surprises us and it is worth to take a look anyway. > > > > > > > > On Fri, Feb 12, 2016 at 1:32 PM, David Roberson <dlrober...@aol.com> > wrote: > >> Interesting. What exactly do you mean by brighter than expected? Is >> that not how they determined the distance to the object? I assume that the >> magnitude of the response would be used to calculate the distance to the >> event according to their model using general relativity. >> >> If the model is not yielding an accurate calculation of the magnitude >> then one might question the theory used for that model. My guess is that >> the distance to the collision might not be as far as they think. Do you >> see reason to believe that they have the correct distance assumed? It >> would seem that a two dimensional measuring platform would not be able to >> accurately determine the distance once large distances are anticipated. >> >> Dave >> >> >> -----Original Message----- >> From: Giovanni Santostasi <gsantost...@gmail.com> >> To: vortex-l <vortex-l@eskimo.com> >> Sent: Fri, Feb 12, 2016 1:16 pm >> Subject: Re: [Vo]:LIGO Gravity Waves... So what? >> >> 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. >>>>>>> >>>>>> >>>>>> >>>>> >>>> >>> >> >
