Can LIGO actually detect gravitational waves?

[tar]

swansont,

 

You are misrepresenting my case. I am assuming the GWs are real and passed through the detectors when they are proported to pass through the detectors. But if they did, they also had to pass through every other detector on the planet built to register the passing of a GW. There should be corraberating evidence galore. But if the tininess of the signal is to slight as to only be detectable by a finely tuned LIGO experiment, then only another LIGO experiment of the same fineness can corroborate. One should not have to rely on statistical methods to milk the signal you want to see out of the data, it should be in the data to be seen, as soon as you know what to look for.

 

So once the same signal is visible in two LIGO experiments, you know what to look for in a third. Once you have three you can process the data to build a simulated waveform with characteristics and a directional source. This simulation would be a model of the wave as it actually passed through Earth, with NO consideration of whether or not it complies with GR. There would have been evidence that a GW passed through, and since we already know what it does to the signals of the three, we can predict what it is going to do to the fourth. Without any supercomputers involved.

 

I take offense at being turned away from enjoying this discovery of GWs as if it has no practical use but to verify Einstein's equations. I feel like the scarecrow in front of the Wizard of OZ.

 

Regards, TAR

 

Pay no attention to the man behind the curtains.

Edited June 16, 2017 by tar

[swansont]

swansont,

 

You are misrepresenting my case. I am assuming the GWs are real and passed through the detectors when they are proported to pass through the detectors. But if they did, they also had to pass through every other detector on the planet built to register the passing of a GW. There should be corraberating evidence galore. But if the tininess of the signal is to slight as to only be detectable by a finely tuned LIGO experiment, then only another LIGO experiment of the same fineness can corroborate. One should not have to rely on statistical methods to milk the signal you want to see out of the data, it should be in the data to be seen, as soon as you know what to look for.

 

 

(emphasis added)

 

As as an experimental physicist I can tell you that you are spectacularly wrong here. The difficulty, since you are not, is in explaining just how wrong you are. (If that were to be the topic of a thread I might be able to begin to do so)

[tar]

SwansonT,

 

OK I will bow out.

 

Regards, TAR

[swansont]

So once the same signal is visible in two LIGO experiments, you know what to look for in a third. Once you have three you can process the data to build a simulated waveform with characteristics and a directional source. This simulation would be a model of the wave as it actually passed through Earth, with NO consideration of whether or not it complies with GR. There would have been evidence that a GW passed through, and since we already know what it does to the signals of the three, we can predict what it is going to do to the fourth. Without any supercomputers involved.

No, I don't think you remove the need for supercomputer models by adding a third detector. You haven't changed the waveform you're looking for, and AFAIK the models are to construct that from theory.

 

 

I take offense at being turned away from enjoying this discovery of GWs as if it has no practical use but to verify Einstein's equations. I feel like the scarecrow in front of the Wizard of OZ.

 

Regards, TAR

 

Pay no attention to the man behind the curtains.

 

I don't understand why you think you are being turned away. You're being told that your claims are not based on any experience or understanding of the process of doing experiments, but you are free to correct that.

[StringJunky]

swansont,

 

You are misrepresenting my case. I am assuming the GWs are real and passed through the detectors when they are proported to pass through the detectors. But if they did, they also had to pass through every other detector on the planet built to register the passing of a GW. There should be corraberating evidence galore. But if the tininess of the signal is to slight as to only be detectable by a finely tuned LIGO experiment, then only another LIGO experiment of the same fineness can corroborate. One should not have to rely on statistical methods to milk the signal you want to see out of the data, it should be in the data to be seen, as soon as you know what to look for.

 

So once the same signal is visible in two LIGO experiments, you know what to look for in a third. Once you have three you can process the data to build a simulated waveform with characteristics and a directional source. This simulation would be a model of the wave as it actually passed through Earth, with NO consideration of whether or not it complies with GR. There would have been evidence that a GW passed through, and since we already know what it does to the signals of the three, we can predict what it is going to do to the fourth. Without any supercomputers involved.

 

I take offense at being turned away from enjoying this discovery of GWs as if it has no practical use but to verify Einstein's equations. I feel like the scarecrow in front of the Wizard of OZ.

 

Regards, TAR

 

Pay no attention to the man behind the curtains.

There's TWO detectors 3000 miles apart and they've detected them SIX times (3 lots of two independent observations; as I mentioned before) and all those observations agree with GR.

SwansonT,

 

OK I will bow out.

 

Regards, TAR

Tar. Unless one understands the maths of the theory and the techniques used for their observations one is not in a realistic position to critique this work in any meaningful way. The best you, and I, can do is try to understand what is given.

[tar]

No, I don't think you remove the need for supercomputer models by adding a third detector. You haven't changed the waveform you're looking for, and AFAIK the models are to construct that from theory.

 

 

 

I don't understand why you think you are being turned away. You're being told that your claims are not based on any experience or understanding of the process of doing experiments, but you are free to correct that.

 

Swansont,

 

Well you have changed the waveform you are looking for from the GR based template, to the actual waveform you received during that two second period on Sept. 14. Once the two LIGO data streams, during that particular 2 second period, including the close rotations and ringdowns, has shown the same characteristics in both datastreams, those characteristics can be directly expected to show up on a third LIGO online at the time. It would not matter if that third LIGO was matched to GR simulations, all it needs to match is the pattern actually registered during the two seconds in question. The match will be automatic. You know what to look for and you know where in time, in terms of the datastream from the third , to look for it. Why would you need to match the third to a GR simulation, when you have the actual signals to match to, and you know exactly when they should show up in the data of the third?

 

And I am talking about the next GW. You have 4 LIGOs. You collaborate with the everybody with the data from three, and ignore the data from the fourth. You use the GR templates that know how BHs and NSs should behave and what kind of waves they should put out and match the noise against these simulations until you find a period of time in which all three have received the same event. You concentrate on that 2 second period in the data from the three and figure from which direction the wave came and what its strain was and what that means in terms of the mass and spin of the two objects that merged so many eons ago. This process has taken two months to put together, but everybody agrees what kind of wave passed through, and what it did in terms of deforming the space on Earth. Knowing exactly how the now known wave should have affected the space in which detector 4 was located, you now can look directly at 4's data during the time period when the GW passed and compare it, not with your simulated model, but with the pattern documented in the signals from 1,2 and 3.

 

At this point, the goal would be not to find a GW amongst a bunch of noise, but to compare the known signal from three with a fourth detector, to learn something about how gravity waves look and act when seen from various vantage points.

 

As in, learn what gravity is, not just what it does.

 

 

 

Regards, TAR

Edited June 16, 2017 by tar

[swansont]

Swansont,

 

Well you have changed the waveform you are looking for from the GR based template, to the actual waveform you received during that two second period on Sept. 14. Once the two LIGO data streams, during that particular 2 second period, including the close rotations and ringdowns, has shown the same characteristics in both datastreams, those characteristics can be directly expected to show up on a third LIGO online at the time. It would not matter if that third LIGO was matched to GR simulations, all it needs to match is the pattern actually registered during the two seconds in question. The match will be automatic. You know what to look for and you know where in time, in terms of the datastream from the third , to look for it. Why would you need to match the third to a GR simulation, when you have the actual signals to match to, and you know exactly when they should show up in the data of the third?

 

You won't see the waveform in the first two if you don't have the template of what to look for. That fact that the third detector won't need it doesn't mean there are no supercomputers involved. You still need the templates for the first two.

 

Here is what the raw data look like (this is for the second event, but not much difference) — the red and blue in the graph. The black lines are what you get after doing some analysis. Even with that, you think you can pick out a signal?

 

https://www.quantamagazine.org/ligo-reports-second-black-hole-merger-20160615/

 

And I am talking about the next GW. You have 4 LIGOs. You collaborate with the everybody with the data from three, and ignore the data from the fourth. You use the GR templates that know how BHs and NSs should behave and what kind of waves they should put out and match the noise against these simulations until you find a period of time in which all three have received the same event. You concentrate on that 2 second period in the data from the three and figure from which direction the wave came and what its strain was and what that means in terms of the mass and spin of the two objects that merged so many eons ago. This process has taken two months to put together, but everybody agrees what kind of wave passed through, and what it did in terms of deforming the space on Earth. Knowing exactly how the now known wave should have affected the space in which detector 4 was located, you now can look directly at 4's data during the time period when the GW passed and compare it, not with your simulated model, but with the pattern documented in the signals from 1,2 and 3.

 

At this point, the goal would be not to find a GW amongst a bunch of noise, but to compare the known signal from three with a fourth detector, to learn something about how gravity waves look and act when seen from various vantage points.

 

As in, learn what gravity is, not just what it does.

 

 

 

Regards, TAR

 

Now write up a proposal for several hundred million dollars to add a new detector and justify why other science shouldn't get done (because this is very much a zero-sum game), and why this is more important than detectors that would sample a different frequency range.

 

The third gets you triangulation at some level of accuracy. I don't see what a fourth buys you.

[tar]

SwansonT,

 

So the analysis required to get the black waveform is to remove local noise and experimental dust and such, right? Not to match the black line with a gw template. The match has already been made, by the time you then look at a third detector, right? I understand the need to analyze the original signal, and pull out the black line, but is this analysis done blind, or is it done expecting to pull out a known pattern?

 

That is, can you pull the black line from the third detector, during the target period, by lining it up with the black lines of detector 1 and 2, without reference to any GR template?

 

Regards, TAR

I do not need a fourth, as long as the black line on the third can be found by looking at the time period 1 and 2 had a match, without reference to any GR model.

that is, again the gravity wave was actually in detector 3. Whatever it did to detector 3 during that particular second is evident. Without reference to anything else.

Edited June 16, 2017 by tar

[swansont]

SwansonT,

 

So the analysis required to get the black waveform is to remove local noise and experimental dust and such, right? Not to match the black line with a gw template. The match has already been made, by the time you then look at a third detector, right? I understand the need to analyze the original signal, and pull out the black line, but is this analysis done blind, or is it done expecting to pull out a known pattern?

 

That is, can you pull the black line from the third detector, during the target period, by lining it up with the black lines of detector 1 and 2, without reference to any GR template?

I can't say for sure how much filtering, of what sort, and in what order, goes on in their data analysis. What I do know is that you aren't going to look at the raw data and be able to say that there is a GW signal there or not. And that's just one second of data; you have to sort through all of it, and look for correlations that are offset in time because the detectors are not the same distance from the event.

 

 

I do not need a fourth, as long as the black line on the third can be found by looking at the time period 1 and 2 had a match, without reference to any GR model.

 

that is, again the gravity wave was actually in detector 3. Whatever it did to detector 3 during that particular second is evident. Without reference to anything else.

Again, what's the point? You've already used a GR model to find the original waves. What's new to be found, other than better triangulation) in comparing to the third detector? You won't see non-GR effects, since you're only looking for GR effects in the first two detectors.

[tar]

SwansonT,

 

Once you DO get the third, to triangulate you then KNOW the second of time in which you will find the wave pattern and you know the wave pattern frequency and timing and amplitude you are looking for. You don't have to find it, it exists, there in the fringe signal of the fourth LIGO during that second. If you don't see it there, then it was not what you thought it was. If it is there you can gleen more information about the wave, as you can see how space was actually warped at that spot at that time and line it up with how space was warped at the other locations. You get a higher resolution image of the wave, and you verify your method and can make required adjustments to your model.

 

Regards, TAR

 

What is true is usually true in more than one way.

reality does not have to match the model, but the model has to match reality

Edited June 16, 2017 by tar

[swansont]

SwansonT,

 

Once you DO get the third, to triangulate you then KNOW the second of time in which you will find the wave pattern and you know the wave pattern frequency and timing and amplitude you are looking for. You don't have to find it, it exists, there in the fringe signal of the fourth LIGO during that second. If you don't see it there, then it was not what you thought it was. If it is there you can gleen more information about the wave, as you can see how space was actually warped at that spot at that time and line it up with how space was warped at the other locations. You get a higher resolution image of the wave, and you verify your method and can make required adjustments to your model.

 

Regards, TAR

 

What is true is usually true in more than one way.

 

reality does not have to match the model, but the model has to match reality

But I don't see why that's not true of the second one. The second signal is used as confirmation that it's not noise. You're adding redundancy on top of an existing redundancy. What does it add?

[Strange]

beecee,

 

"this means that the signal cannot be too different from the GR prediction or we wouldn't have seen it at all!"

 

Not sure I see Prof. Isi's logic here. If I had a theory about the magnetic effects created when a jet liner circles an airport, and theorized that this would effect the electromagnetic waves in LIGO in a certain pattern and I made such a template showing the pattern I expected, and searched the noise from LIGO with super computers and found the pattern that aligned with the template in the data from both experiments around the same time...I am not sure why that means, my theory is not falsified.

 

 

Why would such a pattern falsify your theory? If anything it would be consistent with your theory; which is the best you can hope for.

 

Note that, as well as gravitational wave sources, the LIGO team uses templates corresponding to thunderstorms, traffic, earthquakes (maybe), animals, etc. to eliminate those sources. These things would also be very unlikely to produce the same signal at both detectors. They also inject "fake" black hole signals into the detector (without telling the rest of the team, I think) to check that they are correctly rejected.

 

The idea of detecting signals by matching against a known signal is well established in many other areas such as cellphones and GPS. For example, if the only radio signal around were from a GPS satellite, it would still look like random noise. It is only the fact that we can compare (correlate) the signal with a predefined pseudo-random pattern that allows us to find and extract the data.

 

You really should read some of the background to understand how and why they are confident they can detect gravitational waves, how they identify and eliminate sources of error, etc.

SwansonT,

 

Once you DO get the third, to triangulate you then KNOW the second of time in which you will find the wave pattern and you know the wave pattern frequency and timing and amplitude you are looking for. You don't have to find it, it exists, there in the fringe signal of the fourth LIGO during that second. If you don't see it there, then it was not what you thought it was. If it is there you can gleen more information about the wave, as you can see how space was actually warped at that spot at that time and line it up with how space was warped at the other locations. You get a higher resolution image of the wave, and you verify your method and can make required adjustments to your model.

 

 

They already do that with two and will soon be doing it with three, when VIRGO comes on line. In future there will be more, including space-based ones.

[tar]

"But I don't see why that's not true of the second one. The second signal is used as confirmation that it's not noise. You're adding redundancy on top of an existing redundancy. What does it add?"

 

Considering we know very little about gravity waves, except for what we have seen in the last few years, I would think any data that would increase our knowledge of a single one, would increase our knowledge of what to expect in the future, how to recognize one amongst the noise, and how to see new things we did not expect to see in the data from the experiments.

 

Given the fact that we know now better what the signal will look like, we should be able to recognize one faster.

 

It would be good to get so good as to be able to ring a bell when the first part of a known kind of event is crossing and run other experiments, during the crossing to learn more about the characteristics of warped space.

 

If we are already happy that we have a working model, in Einstein's equations, we can just say "there" we have all we will ever need.

 

Regards, TAR

[beecee]

 

Tar. Unless one understands the maths of the theory and the techniques used for their observations one is not in a realistic position to critique this work in any meaningful way. The best you, and I, can do is try to understand what is given.

 

 

I totally agree, and as I was reiterating here....

 

 

 

I'm reasonably sure that the expert and professionals involved in the detection of gravitational radiation, have allowed for all reasonable contingencies.

If you have any reasonable assertion, supported by at least some evidence to show they have not allowed for all reasonable contingencies, then I would write up a scientific paper stating your case and showing by your "evidence" why their GR gravitational wave result maybe false, and submit it for appropriate professional peer review.

Let us know how you go.

 

I gave an example of invalid premature announcements with the BICEP2 experiment: It was other scientists involved with another experiment, that showed them to be in error. Science is always self correcting.

The gravitational wave discoveries were announced 6 months or so after their actual sightings....In the meantime checks were being put into place, to eliminate any similar error to BICEP2.

I would bet my house we now have professional experimentors, still trying to find any fault with these three findings so far, and that will continue....the same way that other theories are continued to be tested.

It's what happens at the coal face that counts.

Edited June 16, 2017 by beecee

[Strange]

Given the fact that we know now better what the signal will look like, we should be able to recognize one faster.

 

 

I'm not sure that the current detections have told us anything we didn't know; the signals look just as expected.

 

 

 

If we are already happy that we have a working model, in Einstein's equations, we can just say "there" we have all we will ever need.

 

No one ever says that in science.

[StringJunky]

 

 

I totally agree, and as I was reiterating here....

 

 

I gave an example of invalid premature announcements with the BICEP2 experiment: It was other scientists involved with another experiment, that showed them to be in error. Science is always self correcting.

The gravitational wave discoveries were announced 6 months or so after their actual sightings....In the meantime checks were being put into place, to eliminate any similar error to BICEP2.

I would bet my house we now have professional experimentors, still trying to find any fault with these three findings so far, and that will continue....the same way that other theories are continued to be tested.

It's what happens at the coal face that counts.

Well, people have been picking at GR for 102 years, so it's highly probable.

[tar]

 

 

 

I'm not sure that the current detections have told us anything we didn't know; the signals look just as expected.

 

 

No one ever says that in science.

 

 

Strange,

 

That is the part that worries me a little. That they look too much like what was expected, and we did not learn anything new from the experiment

 

 

Regards, TAR

[Mordred]

Sure we learned lots. Every wave we get we can hone in on previously unmeasured properties that were only theoretical in so far as no measured confirmation.

 

The more signals we get the more fine tuned those properties become. Often referred to as confining the possible range.

 

Various properties such as velocity is it truly c, mass (assuming graviton), quantifying gravity, etc.

 

Every recording is critical the more recordings the greater the accuracy.

 

There is a slew of applications a comprehensive and fine tuned GW model can be used for.

 

1) measuring mass of transmitting bodies, 2) measuring Baryon acoustic oscillations in the CMB. As mentioned above, we thought we did. However the dynamics we learn from measurements on Earth will allow us to hone into the CMB oscillations due to GW.

 

3) potentially garnishing further details on mass distribution of spacetime regions (similar to Sache Wolf effect with electro magnetic redshift usage)

 

There is a huge usage eventually in simply GW astronomy. Mass of an orbitting body isn't the easiest thing to pin down.

 

The more data the better.

Edited June 16, 2017 by Mordred

[StringJunky]

Strange,

 

That is the part that worries me a little. That they look too much like what was expected, and we did not learn anything new from the experiment

 

 

Regards, TAR

They weren't looking for something new they were looking to confirm a prediction. We have learnt that, yet again, the old bugger was right. Because he was right this may open opportunities to explore further back in to the evolution of the universe, at least. You are, perhaps naively, trivialising this very difficult effort and its results.

Edited June 16, 2017 by StringJunky

[beecee]

Strange,

 

That is the part that worries me a little. That they look too much like what was expected, and we did not learn anything new from the experiment

 

 

Regards, TAR

Damned if they do, damned if they don't

[StringJunky]

Damned if they do, damned if they don't

They've discovered a new form of signal, how can that not be worth looking for?

[swansont]

"But I don't see why that's not true of the second one. The second signal is used as confirmation that it's not noise. You're adding redundancy on top of an existing redundancy. What does it add?"

 

Considering we know very little about gravity waves, except for what we have seen in the last few years, I would think any data that would increase our knowledge of a single one, would increase our knowledge of what to expect in the future, how to recognize one amongst the noise, and how to see new things we did not expect to see in the data from the experiments.

 

Given the fact that we know now better what the signal will look like, we should be able to recognize one faster.

 

It would be good to get so good as to be able to ring a bell when the first part of a known kind of event is crossing and run other experiments, during the crossing to learn more about the characteristics of warped space.

 

If we are already happy that we have a working model, in Einstein's equations, we can just say "there" we have all we will ever need.

 

Regards, TAR

 

How does this give us more data? It's giving you the same data as the other detectors.

[tar]

That is exactly where I think you are underestimating the promise of gravity wave study. There is a complete difference in the strain of space at point A and point B 5,000 miiles away as a wave is coming through, and every 20th of a second this situation is flipped. In the actual data link above, with the black lines given as the signal from the GW I counted at least 20 transitions from H+ to Hx. If this many transitions can be sensed within a sec that means that the experiment can tell which way space is stressed and what the gradient is between one point and another during the wave's duration to an amazing precision.

that is, if you know what the H+ is and the Hx is at a particular instant at point A and point B you could interpolate and figure what it has to be inbetween

then if you actually have an experiment in between you could verify your interpolation, and or see where there is another aspect to the wave that you did not predict

after all the GW151226 is a very complex thing with at least 20 ripples and that is just taking a reading on a 3 dimensional event in one direction, at one spot on the shell

it matters how the wave is oriented to the experiment in several different ways, that have to do with timing and distance

squaring everything up and seeing what the wave looks like can not be done with only one station

[Strange]

VIRGO is running: http://ligo.org/news/index.php#triplelock

[imatfaal]

VIRGO is running: http://ligo.org/news/index.php#triplelock

 

News from today! Great Spot.