[ExI] Gravitational Waves Detected By LIGO!

[Tomaz Kristan]

Interesting ... Still, what's bothering me is also the super-massive black
hole in our Galaxy, five orders of magnitude closer and about five orders
of magnitude as massive, orbiting by many massive stars ... but no gravity
waves from there.

That was my line of reasoning all along. If we can't gravitationally see
this, how we could see something much smaller, so far away?

I am not saying that it is entirely impossible, I am just hard to be
convinced in such circumstances.



On Fri, Feb 12, 2016 at 10:38 PM, John Clark <johnkclark at gmail.com> wrote:

>
> On Fri, Feb 12, 2016 at 10:28 AM, Tomaz Kristan <protokol2020 at gmail.com>
> wrote:
>
> >
>>> ​>​
>>>  The strain produced by the waves decays with 1/r. Tidal forces are
>>> proportional to 1/r^3 so they decay very fast as you move away from the
>>> source.
>>
>>
>> ​>​
>> It's then either G-wave originated 10^9 ly away, or some tidal effect
>> 10^3 ly away. Like a neutron star inner collapse to a black hole, for
>> example.
>> ​ ​
>> Those two are indistinguishable for LIGO, I presume
>> ​.​
>>
>>
> One way LIGO can distinguish a gravitational wave from other sources of
> distortion of the mirrors is that if it's a
> ​ ​
> gravitational
> ​ ​
> wave then as one leg of the L shaped LIGO
> ​ ​
> detector
> ​ ​
> shrinks the other must expand
> ​ ​
> by the same amount; and if it were caused by tidal forces something would
> have to be circling the Earth 250 times a second. And
> ​nothing can be in orbit around the ​
> Earth like that.
>
> ​ John K Clark​
>
>
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