RealityCheck - Nov 10, 2017

Does anyone have any data involving a ringdown signal arising in one LIGO but not the other(s)? If we had such data we could calculate the probability of these 'orphan' ringdowns arising in more than one at a randomly coinciding separation time which may be interpreted by analysis procedures as being one actual rindown being detected by more than one LIGO, while it may be just coincidence (which must eventually happen if there are many 'orphan' ringdown signals arising from systemic rather than 'merging event' sources). It would help minimize spurious 'detections' claims, and help the confidence levels of those 'events' that cannot be explained by this random/coincidence 'orphan' signals. If anyone has relevant data/info I would be very interested Thanks.

Uncle Ira - Nov 10, 2017

@ Really-Skippy. How you are Cher? I am fine and dandy and would feel guilty if I felt any better, thanks for asking.

Does anyone have any data involving a ringdown signal arising in one LIGO but not the other(s)?
Yeah Cher. I got him but not on this computer so you will have to wait until I get back home next week. I suppose if it is an emergency I could ask Mrs-Ira-Skippy if she could send him to me so I can send him to you. (Assuming she would be able to understand what that is and how to find him on my at home computer.)

The real scientist-Skippys have already been keeping track of that sort of thing which is why even the ignorant/troll/bot like me knows about such a thing. Since you are not the scientist you probably didn't know that is something they been talking about for a couple of years now, the single spur of the moment rings on only one detector.

Da Schneib - Nov 10, 2017

@RC, what makes you think there has ever been a ringdown signal detected at a single gravitational observatory and not detected at the others? Do you have some sort of evidence or mechanism in mind, or are you just speculating? This is a highly distinctive signature, not duplicated by any known or observed seismic phenomenon, and even if it were seismic disturbances are filtered out in the mirror suspension using the same technique, in broad strokes, as is used in noise cancelling headphones. See here: search the page for "seismic."

You can see details of the suspension design here: https://www.ligo....solation This design uses two innovative concepts: the active noise cancelling referred to above, and a four-element pendulum design which reduces sway in the fourth element to almost nothing in the first place.

Da Schneib - Nov 10, 2017

In addition to all of this, seismic events are easily detected and filtered out with simple seismometers, and several other types of interference are also detected and filtered out including magnetic, sonic, and gamma-ray noise. See the FAQ linked above and search on magnetometer.

In short, extreme precautions have been taken to isolate the LIGO mirrors from vibration, and further precautions have been taken to detect and filter out noise from local sources. Nothing is ever 100% certain, but they have 99.9999+% certainty, which is a one in 100,000 chance of it being anything but a GW, and that's only for one detection. For five detections, it's one in 10,000,000,000,000,000,000,000,000. And that's not even including the chances of observing one and then doing a follow-up in visible light and finding something, like the latest one.

This argument is pretty much over.

jonesdave - Nov 10, 2017

It would be some seismic event if they picked it up in Italy at the same precise instant as in the U.S.! Instantaneous P & S waves!

Da Schneib - Nov 10, 2017

@jones not to mention that P and S waves not only arrive at different times but also aren't ringdown waves; they're at a mostly constant frequency. The ringdown waves detected at LIGO are specifically waves that increase in frequency over time.

And that's not even discussing the facts of vibration isolation and seismic wave filtering shown by the links I provided above.

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