# Gravitational waves confirmed...

#### cmartinez

Joined Jan 17, 2007
7,220

#### nsaspook

Joined Aug 27, 2009
7,869

A very small signal from a billion years ago. Amazing.

Paper abstract:
On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10−21. It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410+160−180Mpc corresponding to a redshift z=0.09+0.03−0.04. In the source frame, the initial black hole masses are 36+5−4M⊙ and 29+4−4M⊙, and the final black hole mass is 62+4−4M⊙, with 3.0+0.5−0.5M⊙c2 radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.
https://dcc.ligo.org/LIGO-P150914/public

#### cmartinez

Joined Jan 17, 2007
7,220
This is huge! it's a once-in-a-lifetime scientific event. Being here to witness this part of history is exciting for me. Imagine... the Higgs boson and gravitational waves confirmed in the lapse of less than three years!

#### joeyd999

Joined Jun 6, 2011
4,479
This is huge! it's a once-in-a-lifetime scientific event. Being here to witness this part of history is exciting for me. Imagine... the Higgs boson and gravitational waves confirmed in the lapse of less than three years!
Do they have visual/microwave/gamma wave confirmation of the event?

#### alfacliff

Joined Dec 13, 2013
2,458
the real big thing about it is how much information they got from such a small amount of data. for something that happened 1.3 billion years ago, they can now determine how massive those two black holes were before they hit, and how fast they were traveling. since nobody was looking at that area of the southern sky when the wave got here last september, the actual lcation is not very well known.

#### joeyd999

Joined Jun 6, 2011
4,479
they can now determine how massive those two black holes were before they hit
In fact, they somehow computed each (which are different) to within around 1 solar mass. I find this fishy.

#### nsaspook

Joined Aug 27, 2009
7,869
the real big thing about it is how much information they got from such a small amount of data. for something that happened 1.3 billion years ago, they can now determine how massive those two black holes were before they hit, and how fast they were traveling. since nobody was looking at that area of the southern sky when the wave got here last september, the actual lcation is not very well known.
They are using the same techniques used with radio, sonar and radar arrays for ages for target detection, range , size and analysis. Gravitational waves travel at c much like electromagnetic waves so once you have a high fidelity signal that matches the known constraints of the target signature it's possible to reconstruct that event with good statistical confidence.
This search targets gravitational-wave emission from binary systems with individual masses from 1 to 99M⊙, total mass less than 100M⊙, and dimensionless spins up to 0.99 [44]. To model systems with total mass larger than 4M⊙, we use the effective-one-body formalism [75], which combines results from the post-Newtonian approach [11,76] with results from black hole perturbation theory and numerical relativity. The waveform model [77,78] assumes that the spins of the merging objects are aligned with the orbital angular momentum, but the resulting templates can, nonetheless, effectively recover systems with misaligned spins in the parameter region of GW150914 [44]. Approximately 250 000 template waveforms are used to cover this parameter space.

#### KL7AJ

Joined Nov 4, 2008
2,229
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.
It's hard to find many science experiments in recent years with BETTER corroboration. This is science at its best.

#### Wendy

Joined Mar 24, 2008
22,205
If they could get a few more detectors they can even cut the S/N ratio way down, increasing the sensitivity significantly.

#### KL7AJ

Joined Nov 4, 2008
2,229
If they could get a few more detectors they can even cut the S/N ratio way down, increasing the sensitivity significantly.
This is certainly true...however just those two signals are amazingly clean. I would have expected a LOT more "fuzz."

#### KL7AJ

Joined Nov 4, 2008
2,229
Oh, if science were this simple again!

#### Glenn Holland

Joined Dec 26, 2014
705
Pardon me for being the Skunk at the garden party, but I'm very skeptical about this "discovery".

The science/industrial complex is a money hog and always looking for (and getting) federal funding for all sorts of obscure and fraudulent endeavors. Case in point: According to a group of scientists at the USGS in Menlo Park, claim they successfully predicted over 100 earthquakes and they want even more $$for a large scale earthquake prediction program. The Obama administration has announced a federal grant for an earthquake early warning system that will supposedly do all sorts of wonderful things like park elevators at floors, stop trains, restrict the operation of nuclear power plants and refineries. Heeeeeeellllllllllllllooooooo !!!! - This technology was successfully invented way back in 1972 and it's been fully implemented since1983. Goes to show you that if you pour enough$$$into political campaign coffers, you can get a federal grant for research or to develop anything. Next thing, someone will announce a break thorough that they've invented a round thing that makes it easier for objects to move over streets and highways and it will revolutionize the future of transportation. Caltech is a very politically connected institution and heavily reliant on government funded research projects. If there's enough government$, everything will eventually be success.

#### alfacliff

Joined Dec 13, 2013
2,458
They are using the same techniques used with radio, sonar and radar arrays for ages for target detection, range , size and analysis. Gravitational waves travel at c much like electromagnetic waves so once you have a high fidelity signal that matches the known constraints of the target signature it's possible to reconstruct that event with good statistical confidence.
so they sent the origional signal out and therefore know the pulse width and shape of it? maybe they use the doppler? for dopler you need to know the origional frequency and the frequency shift. even the military cant tell how far radar pulses have traveled from the source, that data isnt found anywhere in the origional signal without triangulation by two recieving stations. there wasnt enough info to do that, as told by the "swomewhere in the southern sky" direction mentioned in the artical.

#### nsaspook

Joined Aug 27, 2009
7,869
so they sent the origional signal out and therefore know the pulse width and shape of it? maybe they use the doppler? for dopler you need to know the origional frequency and the frequency shift. even the military cant tell how far radar pulses have traveled from the source, that data isnt found anywhere in the origional signal without triangulation by two recieving stations. there wasnt enough info to do that, as told by the "swomewhere in the southern sky" direction mentioned in the artical.
You're smarter than that and know about passive detection/identification of signal sources other than by simple triangulation. The current GW detection method seems pretty close to passive sonar (Passive_sonar_signal_detection_and_classification). We have a physical model (confirmed by experimental data) using GR of how the mass and energy of the signal creating event should interact to transmit waves and how the characteristics of those waves change in time as they travel with finite speed. 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. We've seen the modeled (using GR) signature before with electromagnetic signals so would it have been a real shocker if the gravitational wave signature (also modeled with GR) was missing.

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#### alfacliff

Joined Dec 13, 2013
2,458
passive sonar uses the time difference of incoming signals to determine info such as distance and direction. this requires more than one detector. the more detectors there are, the beter the resolution. there were only two LIGO detectors so far. barely enough to get an "over there somewhere" direction. and since triangulation over such a small baseline compared to the distance from the source is so great, not much could actually be gotten. basicly, 2.8 miliseconds delay is all they got along with the wave signature. is that enough to imply all the information on something which they only have as a theory up to now?

#### nsaspook

Joined Aug 27, 2009
7,869
passive sonar uses the time difference of incoming signals to determine info such as distance and direction. this requires more than one detector. the more detectors there are, the beter the resolution. there were only two LIGO detectors so far. barely enough to get an "over there somewhere" direction. and since triangulation over such a small baseline compared to the distance from the source is so great, not much could actually be gotten. basicly, 2.8 miliseconds delay is all they got along with the wave signature. is that enough to imply all the information on something which they only have as a theory up to now?
That 2.8 (actually about 7 ms) milliseconds delay between detectors is very important. First you have signal wave that's not electromagnetic traveling at c (confirmed by the delay) and it allows us to detect minute differences in the phase when we see that signal change in frequency and amplitude over a short time with an energy (gravitational radiation) at almost unimaginable levels. The theory that explains this is a 100 years old so yes, we've had a while to model what that unique wave signature means in physical terms if GR is correct.
http://arxiv.org/pdf/astro-ph/0302125.pdf
The final gravitational radiation-driven coalescence can be thought of as proceeding in 3 stages: an adiabatic inspiral, followed by a dynamical merger, and a final ringdown. As the binary evolves from inspiral through merger and ringdown, the gravitational wave frequency increases. As long as any accompanying accretion disks are dynamically negligible, black hole binaries coalescing through the emission of gravitational radiation are solutions to the vacuum (i.e., source-free) equations of general relativity. As such, their timescales are proportional to the total mass and, after time scaling, all other properties of the dynamics and waveforms depend only on ratios involving the masses and spins of the components. Thus, calcuations of the gravitational waveforms from all three stages of black hole binary coalescence can be easily scaled to apply to any masses and spins [3].

During the slow inspiral, the black holes are well-separated and spiral together adiabatically. The resulting gravitational waveform is a “chirp,” which is a sinusoid that increases in frequency and amplitude as the orbital period shrinks; see Eq. (4). The gravitational waveforms from this inspiral phase are computed analytically using higher order post-Newtonian techniques in which the black holes are approximated as point masses [19]. These waveforms can be used as templates for data analysis algorithms based on matched filtering [20]
Two merging black holes fit, all other things do not fit.

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#### Monika Verma

Joined Jan 23, 2016
14
Today black hole is also a mystry. Can we solve it by this detector? Its gravitational force become so high that light also can't comes out from its surface. Then where its gone. Is it no have any capacity? Or light is less thn its capacity?

#### Glenn Holland

Joined Dec 26, 2014
705
Today black hole is also a mystry. Can we solve it by this detector? Its gravitational force become so high that light also can't comes out from its surface. Then where its gone. Is it no have any capacity? Or light is less thn its capacity?
Black holes capture light that enters the so called "event horizon".

They can also capture mass by the conventional process of gravitational acceleration. The captured mass then adds to the existing mass and the object supposedly remains stabile.

My question about mass capacity is whether a black hole can reach a limit where it becomes unstable and it may disintegrate. A similar question can be asked about the original object that produced the big bang. What was there before the bang and why was it stabile up until it exploded.

#### Monika Verma

Joined Jan 23, 2016
14
Its depends on the mass of star that black hole happens or not. If its mass nearly to sun than it becomes so large red giant and also unstable, and it explosed-compression. At this time its outer layer left its surface and become a ring. And immidiately its inner corecompressed and makes white dwarf.