[ExI] Gravity wave math

[John Clark]

On Sun, May 28, 2017 Tomaz Kristan <protokol2020 at gmail.com> wrote:

​> ​
> I am sceptical. The first "strong observation" was on time for the 100th
> anniversary, but we don't have the second one yet.
>

​Yes we do. The first confirmed gravitational wave event occurred on
September 14 2015, and the second occurred on December 26 2015. Both had a
sigma of 5.3. In addition there was a third event on October 12 2015 that
was probably yet another case of inspiraling black holes but that signal
was weaker than the other two and was short of 5 sigma that physicists need
to claim a discovery, for that one there was a 9% chance it was just noise
and that just isn't good enough.  5 sigma means there is only one chance in
3.5 million it was caused by random noise. All this happened during LIGO's
first observation run, the second run is happening right now but none of
the results have been released yet.

​> ​
> Just as we have 1 (one) "strong observation" for the Higgs.
>

In the case ​of the Higgs things were quite different, nobody has ever
directly observed a Higgs and nobody ever will, it's half life is far too
short for that, but you can observe the Higgs decay products and that is a
unique signature. But the experiment is very noisy so to find a signal
lurking in the noise, if there is one, you've got to run it many billions
of times and then do a statistical analysis with some of the largest
supercomputers in the world. Eventually after many months of colliding
protons and operating supercomputers they got to 5 sigma.

In contrast the September 14 2015 LIGO signal was so strong that in just
hours nearly all the scientists involved were convinced they'd found
colliding Black Holes, although they didn't say so publicly for about 6
months. There has been some criticism. justified I think, that they kept it
secret too long. I'll bet they've already found some cool stuff in the
second observing run that they won't talk about until they've finished
writing the journal paper.

John K Clark
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