Gravitational waves confirmed...

Wendy

Joined Mar 24, 2008
23,798
Black holes that are too small are unstable, and dissipate. So says modern theory at least. Read some interesting SciFi by James Hogan where this was not the case, with interesting results (Thrice Upon a Time).
 

hp1729

Joined Nov 23, 2015
2,304
It's finally happened, Einstein's prediction of gravitational waves has been confirmed:

https://www.newscientist.com/articl...s-as-gravitational-waves-seen-for-first-time/

The power released by the merging black holes was equivalent to 50 times the power of all the stars in the visible universe. In those 20 milliseconds, the energy of the waves was equivalent to annihilating the mass of three Suns.
Why is this so profound? There is gravity between objects. Of course there should be gravity waves? Is the artist's rendering just the artist's view of these waves? Do gamma rays travel at the same speed as light and gravity? They are electromagnetic just really short wavelength? (a question)
We spent over a billion dollars on this? No wonder the nation is going broke. It seems like a waste of money and brain power. Aren't there more important questions to answer that have a real effect on our lives?
 
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atferrari

Joined Jan 6, 2004
5,012
We have remote detectors separated by space/time to detect that wave signature as it moves across space but the detectors space/time separation is small in relationship to the wavelength of the signal so our directional capability is is poor even if our signal wave signature is exactly what we expected.
Hola nsaspook,

When you say time, above, is it the TOA difference between stations because they have a different location in space? Or do you mean something else?
 

hp1729

Joined Nov 23, 2015
2,304
Hola nsaspook,

When you say time, above, is it the TOA difference between stations because they have a different location in space? Or do you mean something else?
Space? Wavelength? LIGO is designed to detect gravity wavelengths in the neighborhood of 10^6 meters???
Certainly gravity waves exist. Sitting on Earth watching Mercury rotate around the Sun we would detect ripples in the gravity waves as Mercury passes along? At its closest point we would be pulled ever so slightly toward the sun as Mercury's gravity is added to the Sun's. Is this a valid statement??
 

atferrari

Joined Jan 6, 2004
5,012
Space? Wavelength? LIGO is designed to detect gravity wavelengths in the neighborhood of 10^6 meters???
Certainly gravity waves exist. Sitting on Earth watching Mercury rotate around the Sun we would detect ripples in the gravity waves as Mercury passes along? At its closest point we would be pulled ever so slightly toward the sun as Mercury's gravity is added to the Sun's. Is this a valid statement??
To whom is the above, addressed to?
 

Wendy

Joined Mar 24, 2008
23,798
The collapse of really big masses. It takes really specific conditions for small black holes. The odds of us finding one, ever, is pretty small. And hope we are not in the neighborhood when one dissipates. They do so with a large bang.

Our sun is way too small to create a black hole.
 

nsaspook

Joined Aug 27, 2009
16,326
Hola nsaspook,

When you say time, above, is it the TOA difference between stations because they have a different location in space? Or do you mean something else?
It means a different location (spatially separated ) for mass. The analogy for electromagnetic radiation detection would be separated charge (electrons) in each antenna moving slightly in response to an incoming wave EM field creating a current in the wire for a TOA calculation. I would think they need a few more active stations to use Multilateration to help pinpoint the direction of GW signals in the sky from sources with little or no EM signatures.

For gravitational waves the space (IRT the measurement instrument) between masses is moving (stretches and squeezes space) slightly in response to an incoming wave front. If the speed of light is invariant then we can detect the gravitational radiation as changes in the time EM waves travel between the L shaped legs of each laser interferometer station as space contracts and expands (and time in a different frame of GR spacetime).

https://dcc.ligo.org/public/0116/P1400230/002/lazzarini-ShanghaiForum-v2.pdf
A Michelson interferometer antenna pattern:


This burst is localized to about 1.5% of the sky. That sounds pretty good but it's still a huge amount of space (~200 trillion cubic light-years)

http://forum.allaboutcircuits.com/threads/can-ligo-actually-work.109305/
It looks like the answer is, YES!
 
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nsaspook

Joined Aug 27, 2009
16,326
Do they have visual/microwave/gamma wave confirmation of the event?
It looks like they might have a gamma wave confirmation 0.4 seconds of the GW.
http://gammaray.nsstc.nasa.gov/gbm/publications/preprints/gbm_ligo_preprint.pdf
GBM observed over 75% of the probability in the GW event sky location at the time of GW150914. A weak hard X-ray source lasting around 1 s was detected above 50 keV 0.4 s after the GW event using a technique developed to find short transients in the GBM data in coincidence with sub-threshold GW events. The GBM signal is localized to a region consistent with the LIGO sky map, with a large uncertainty on the location. If the transient event uncovered in the GBM data is associated with GW150914, then it is possible its origin under the Fermi spacecraft, combined with the weakness of the source, can account for the lack of confidence associated with the standard localization procedure applied to this event. If we assume the LIGO and GBM events have a common origin, then combining the LIGO and GBM localization maps reduces the LIGO localization area by 2/3.
...
Further observations by LIGO and Virgo in coincidence with a detector sensitive to hard X-ray or gamma-ray transient events will determine whether short bursts of high-energy electromagnetic radiation accompany stellar mass black hole binary mergers. Because of the weakness of GW150914-GBM and its large localization uncertainty, chance coincidence may play a role in both the identification of GW150914-GBM as an astrophysical phenomenon and its association with the GW event, even with the false alarm probability of 0.0022 that we calculate in section 2.2. If the association is real, then the alignment of the merger axis with our line of sight is serendipitous.
 

joeyd999

Joined Jun 6, 2011
6,300
400ms seems like a stretch to me...and they seem to have doubts regarding correlation. I think, ultimately, a second event will be required to confirm detection.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
8,765
400ms seems like a stretch to me...and they seem to have doubts regarding correlation. I think, ultimately, a second event will be required to confirm detection.
Far more sensitive instruments are going online in the next months, if I'm not mistaken. A more considerable amount of events should be detected as a result.
But you're right, repeated observations by independent parties are required for a perfect confirmation.
 

nsaspook

Joined Aug 27, 2009
16,326
400ms seems like a stretch to me...and they seem to have doubts regarding correlation. I think, ultimately, a second event will be required to confirm detection.
I agree it's not very solid but the possible origin of gamma is the accretion disk event horizon of the pair so who knows what type of time-warp weirdness is happening there with EM vs GW radiation with the two french kissing.

https://en.wikipedia.org/wiki/PSR_B1913+16#Star_system
We do have indirect evidence of GW radiation but this would be the first direct detection if confirmed.

 
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atferrari

Joined Jan 6, 2004
5,012
Another possibility is that the electromagnetic emission is not narrowly collimated
and we can expect further joint detections of stellar mass black hole binary mergers and GRBs.
Just struggling with my first oversampling, how far I am of all that and always be... :(
 

joeyd999

Joined Jun 6, 2011
6,300
Please remember, everyone, that these scientists want the data to be a confirmation of gravity waves. There will be a strong tendency for them to try to tie every blip within a second or so to the event, coincidence or not. Confirmation bias will rule the day, for at least a short time. Keep a level head, accept the data as it arrives, but always, always maintain a bit of skepticism.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
8,765
hese scientists want the data to be a confirmation of gravity waves
Agreed... but that's why it took them months to publish their results. They'll better be damn sure... now their reputation, and careers, are at stake.

Still, we have to wait for independent confirmation. That's the only real way to be sure.
 

nsaspook

Joined Aug 27, 2009
16,326
Please remember, everyone, that these scientists want the data to be a confirmation of gravity waves. There will be a strong tendency for them to try to tie every blip within a second or so to the event, coincidence or not. Confirmation bias will rule the day, for at least a short time. Keep a level head, accept the data as it arrives, but always, always maintain a bit of skepticism.
I'm full of skepticism when some reported result upsets well tested theories like the speed of c with the FTL neutrino fiasco. In this case there is actually very little doubt that gravitation waves exist because if they didn't the entire theory of a finite speed limit for information/energy about changes in the universe (gravity is not a force in GR, its a result of curved spacetime) would be not be just incomplete but in error. What would be really surprising is if LIGO conclusively failed to detect gravitational waves as the energy transport for those changes once our technology advanced to the point of building a proper detector.

The detection of gravitational waves will test that general relativity works at the extreme high end of the strong gravity scale. This brings it into the realm of study with real data instead of just theory.

That's very exciting to me but what will we hear when we listen in?
 
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