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LIGO confirm existence of Gravity Waves?

slo1
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2/11/2016 5:19:01 PM
Posted: 9 months ago
How LIGO works

I imagine the misalignment of laser can be impacted by geological events. I wonder how they filter that out?
http://www.space.com...
slo1
Posts: 4,312
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2/11/2016 5:22:00 PM
Posted: 9 months ago
http://arstechnica.com...

They indeed did announce confirmation of Gravity waves.

It is pretty amazing thinking that your body changes shape ever so slightly due to ripples in space time.
RuvDraba
Posts: 6,033
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2/12/2016 12:18:09 AM
Posted: 9 months ago
At 2/11/2016 1:15:09 PM, slo1 wrote:
If you can live stream this. I hear they also say the waves they detected were from two colliding black holes.

http://heavy.com...

Yes, Slo... I responded to a later thread first, but the relevant paper is published here: [http://journals.aps.org...].
slo1
Posts: 4,312
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2/12/2016 12:04:58 PM
Posted: 9 months ago
At 2/12/2016 12:18:09 AM, RuvDraba wrote:
At 2/11/2016 1:15:09 PM, slo1 wrote:
If you can live stream this. I hear they also say the waves they detected were from two colliding black holes.

http://heavy.com...

Yes, Slo... I responded to a later thread first, but the relevant paper is published here: [http://journals.aps.org...].

Thanks. I need to see how they measure mass of black holes. I imagine the mass loss they measured relates to the size of the waves when calculated.

All those in denial of black holes better wake up and get on board or come up with some other plausible reason for these waves.
RuvDraba
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2/12/2016 6:56:45 PM
Posted: 9 months ago
At 2/12/2016 12:04:58 PM, slo1 wrote:
At 2/12/2016 12:18:09 AM, RuvDraba wrote:
At 2/11/2016 1:15:09 PM, slo1 wrote:
If you can live stream this. I hear they also say the waves they detected were from two colliding black holes.

http://heavy.com...

Yes, Slo... I responded to a later thread first, but the relevant paper is published here: [http://journals.aps.org...].

Thanks. I need to see how they measure mass of black holes.

Slo, from reading discussions between physicists [http://physics.stackexchange.com...], I understand that you can work out mass from Kepler's Third Law: the square of the orbital period is directly proportional to the cube of the semi-major axis [https://en.wikipedia.org...'s_laws_of_planetary_motion#Third_law], or algebraically:
G . m . t ^ 2 = 4 . pi ^ 2 . r ^ 3

Black holes throw out a lot of energy, so you can observe the period -- especially in binary black holes. The period gives you the radius, and together they solve for combined mass.

But, that method would seem to need direct observation of the bodies, and that seems not to have occurred in this case, because if I understand correctly, they don't have enough sufficiently sensitive LIGO instruments operating to triangulate and work out precisely where the event occurred :( [See below.] So perhaps they're working backwards from characteristics of the gravitational signals themselves.

I imagine the mass loss they measured relates to the size of the waves when calculated.
I'm still reading, backgrounding and digesting but if I understand correctly:

* Advanced LIGO is presently one-of-a-kind so there aren't any sufficiently sensitive LIGOs to correlate, and the other LIGO installations were all not observing at the time anyway. So it was able to detect the event and get an approximate idea of direction, but couldn't triangulate on where the event occurred.
* The event occurs in three predicted parts: a 'chirp' as the black holes spiral into one another; a 'burst' as they merge and then a 'ringing' recoil before final decay. Only two events predicted to do this: black hole collision and a neutron star collision, but the frequencies predicted are different -- and this one had a 'black-hole' frequency.
* While there was no other observation available to correlate, Advanced LIGO uses two methods to detect a collision event. Each method confirmed that the event occurred in three parts precisely as predicted. If I understand the paper correctly, the black holes were interpreted to have been spiraling around one another at 75 times per second before finally colliding!
* The way LIGO works is that each installation is actually comprised of two sites at distance, used to screen out ambient vibrations. The paper reports that full instrument testing had occurred before and after the event, so they seem confident about the signal to noise ratio -- and the fact that the event happened in three parts as expected also seems to make noise alone an improbable explanation.
* From all the above, if the signal quality is good enough, there should be three distinct pieces of information from which to calculate the masses involved, and it sounds like chirp frequency may relate to period anyway, so perhaps Kepler's third law might've been used to calculate mass after all, even if not through direct observation.

Since the objects involved weren't more directly observed and now (probably) can't be, I think now the quantities reported will need to be fed back into the theory and independently validated that way.

All those in denial of black holes better wake up and get on board or come up with some other plausible reason for these waves.
Given that this one was picked up unexpectedly, it sounds like there may be a lot of these events occurring, and if they can triangulate, there will likely be some (more) direct observations soon to correlate with and support the indirect observations.

Between the gravitational lensing effects, the specific properties of energy ejection and now the gravity waves, assuming all those data correlate, I suspect we're about to pass the likelihood of credible alternative theories, Slo. I think we're now about to enter the phase of a science where the theory is so mature, we just add to it and refine it until and unless we see something so completely mystifying it makes us revisit everything. :D
SNP1
Posts: 2,403
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2/12/2016 8:01:59 PM
Posted: 9 months ago
At 2/11/2016 1:15:09 PM, slo1 wrote:
If you can live stream this. I hear they also say the waves they detected were from two colliding black holes.

http://heavy.com...

The real question, that no physicists have responded to when I have asked, is if this discovery can also support Lorentz Ether Theory or not.
If not, then it is even greater of a discovery than people think.
If so, then I wonder why everyone keeps focusing on Einstein's theory of relativity. Yes, he got a prediction right, but it wouldn't "prove" his theory.
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