[ExI] Gravitational Waves Detected By LIGO!

John Clark johnkclark at gmail.com
Sun Feb 14 22:48:57 UTC 2016

On Sun, Feb 14, 2016 at 1:56 PM, Tomaz Kristan <protokol2020 at gmail.com>

> > How did you calculate that "
> at least one every second
> ​" figure?​
> ​> ​
>> 10^11 galaxies with a supermassive black hole.
​When a supermassive black hole of millions or billions of solar masses
forms and goes through it's ring down phase it produces enormously powerful
gravitational waves but the frequency of the waves is very low, less than a
tenth a cycle a second, but LIGO is most sensitive when the frequency is
several hundred cycles a second. So if the black holes is larger than a few
hundred solar masses LIGO is not going to see it. And even when the source
produces the right frequency it can't see everything in the observable
universe, LIGO won't see it if it's too far away.

In a decade or 2 the space based eLISA observatory could detect
gravitational waves from supermassive black holes, but not LIGO.

> ​> ​
> This is about several*10^17 small black holes already collided.

If they've
already collided
​ then it's too late for any detector to see them.​

​ John K Clark​
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