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 LIGO Event Coincidences

Comments in Cosmology FB group to my post about LIGO Coincidences:

First comment:
'
 Earth tides go through one cycle roughly every 12 hours, LIGO can only detect signals with frequencies in the range from about 30Hz to 3kHz. If you want to claim the observations were not gravitational waves, you need to explain an alternative source
(A) in that detector bandwidth
(B) that rises in frequency in accordance with the correct power law,
(C) that increases in amplitude at the right rate and
(D) shows the same waveform at multiple sites thousands of km apart within a fraction of a millisecond such that the time difference exactly pinpoints the optical confirmation of GW170817.
'

You missed the point.

I don't have to prove anything.

LIGO hypothesis: on a binary inspiral event our equipment will detect that event and even determine the mass of the two bodies involved and the general direction to the event.

There was no confirmation of such an event happening and then the LIGO system correctly identifying it.



With each LIGO detection announcement no one asks whether there was an actual merger at those locations.

That question was never asked and LIGO is up to 29 detections.

Even worse I found all 29 events were on a date near a Moon or Sun event causing an earth tide, suggesting LIGO could be detecting something other than what is claimed.

Whether the earth tides are relevant does not matter. Maybe I could have found a correlation with the number of seconds in the day.
Noting this correlation simply demonstrates the necessity for identifying the event claimed to be detected.




his response:

'
David, it is you who missed the point, when LIGO detected the signal called GW170817 and told the world the location and range, the SWOPE telescope studied the area, found the event and it was then studied in detail by over 70 different telescopes. You need to familiarise yourself with the evidence before making such a claim, you have a very tough challenge to produce an alternative explanation.
'

my response to a comment:

I am impressed! Was this done for the other 28? Repeatability is important.

his response:

'
 That one involved the merger of two neutron stars and the angular momentum meant that a fraction of the material was ejected. That could be seen and studied. The others have involved mergers of black holes which have no matter outside the event horizon so produce no light at all. However, their gravitational signals were seen with identical waveform in more than one site within a fraction of a second which provides the confirmation.
'

my response:

Interesting coincidence on the GW  event you noted:

'
In October 2018, astronomers reported that GRB 150101B, 1.7 billion light years away from Earth, may be analogous to the historic GW170817, a gravitational wave detected in 2017
'

The two gamma ray bursts were similar. No LIGO events in 2018.

his response:

'
GRB are detected when the polar jets are points at us and can be detected at a much greater range than LIGO. Gravitational waves vary little with the angle of incidence so the orientation of the orbital plane doesn't matter but they have to be closer.

The range depends on the background noise, you can see it online here for today:
'

my response:

I must point out something critical is between the gravitational waves and their detection: the crust and software.

LIGO developed waveform templates for how Earth's crust will react to this low frequency (like sound) with small amplitude. Certainly the rigid crust must lag in its response.
Certainly these earth tides are much, much slower but if the crust can move a meter these earth tides actually disturb the crust much, much more than the gravitational waves. The LIGO software must be able to find one of 2 templates in this data that magnifies every possible disturbance. I expect with several confirmed events the model and templates could be improved but the binary was unknown for only one  event so the templates determined the possible pair.
The  earth tides do not have to mimic the template .The bottom line is LIGO is searching for a very faint signal, dampened by the rigidity of the crust, in substantial noise. How well can it do that extraction with so little signal in the noise?

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