LIGO: Gravity Waves detected

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JoeP
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LIGO: Gravity Waves detected

Post by JoeP »

https://www.ligo.caltech.edu/news/ligo20160211

This is interesting to me. But I am am not a physicist and haven't read much of the literature on this subject. How reliable is the above? If they can detect black hole collision from so far away, can other disturbances in the gravity field be detected? Such as moving a massive object around near the detector? I assume no, but do not understand why not.

Also, does this discovery mean that a particle like the graviton must exist to mediate gravitational force?

DeltaV
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Re: LIGO: Gravity Waves detected

Post by DeltaV »

The sound of God playing singularity croquet using black holes:
https://losc.ligo.org/s/events/GW150914 ... veform.wav

ladajo
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Re: LIGO: Gravity Waves detected

Post by ladajo »

I would have to agree with the Pundits, if these guys don't get a Nobel for this it will surprise me.

This will fundamentally change our understanding of the Universe.
I predict they will build 10Km Laser tunnel sites soon.

Although, I wonder if the data set came on the same day/time as the last DPRK nuke test... ;)
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

hanelyp
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Re: LIGO: Gravity Waves detected

Post by hanelyp »

DeltaV wrote:The sound of God playing singularity croquet using black holes:
https://losc.ligo.org/s/events/GW150914 ... veform.wav
I don't think the speakers on my laptop can do tones that low. Plugging in my good headphones I had to turn up the volume to hear the blip about 2 1/2 seconds in.
The daylight is uncomfortably bright for eyes so long in the dark.

Tom Ligon
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Re: LIGO: Gravity Waves detected

Post by Tom Ligon »

I've always been fond of the name of the instrument.

This is being billed as the discovery of the decade, but I think the Higgs has to beat it. A positive result for gravity waves is not a revolutionary result. No results would be a mystery. Seeing two black holes merge and getting nothing would have been a reset to square one.

Even the Higgs was expected. Setting the energy where it is constitutes a head-scratcher. Rumors of another peak at a higher energy where none should be found could be a revolution. And we still don't really understand what it all means. Is the fabric of space-time really quantum entanglement? What the heck is gravity, anyway.

And then there are dark matter and dark energy.

Is not verifying what we "know" that is the great discovery. It is learning something that tells us we have a lot more to learn that matters.

Let's let LIGO run for a while and see if it surprises us.

JoeP
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Re: LIGO: Gravity Waves detected

Post by JoeP »

Another thought occurred to me: how does the LIGO team know that the gravity wave detection is due to the merger of two black holes, aside from the energy calculation? It seems to me that they are just picking the most likely explanation as to what most fits the expected space-time distortion and the rough distance of the source. It isn't close enough to get any other supporting data, was it? e.g. gamma burst.

D Tibbets
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Re: LIGO: Gravity Waves detected

Post by D Tibbets »

Detecting the gravitational waves was certainly impressive, and expensive. How it changes anything is another challenging question. How it effects theories of what space time is- warps, entanglement, etc. is for the thinkers to think upon. Einstein's theory has been so well accepted with various proofs, I doubt the ideas have been ignored or challenged in any mainstream theory on how the universe works. So, the proof of this part of general relativity will, I presume, change little in the outlook.

A gravitational wave is so small in magnitude the distortion is much less than the diameter of a proton. Almost anything will cause greater deflections in the detecting apparatus. This includes a truck moving outside, small earthquakes in China, walking nearby, etc. The key is not to identify gravitational waves by dampening these other spatial disturbances completely, it is to identify the difference. The dampening of all other sources of movement did have to be enough that the anticipated gravitational wave distortions would not be completely swamped by the background noise.The two arms at right angles, and the two sites both combine to statistically exclude the vast majority of movements from consideration. The detector also obviously had to be sensitive enough to detect these extremely tiny fluctuations.

The masses and distances were calculated with assumptions based on Kepler's laws, and other astronomical considerations that have been well studied. The several waves (ringing or frequency?) detected gave information about the duration of the event, the relative masses, and roughly the possible directions in the sky (based on the time differential in detection at the two sites). I think the distance was derived from the expected speed of the two calculated mass black holes spiraling together and the anticipated magnitude of the gravitational wave distortions. Inverse square law considerations would then give the distance.

That this event happened during warm up for a several month observing session, somewhat rendering the remaining observing session superfluous is ironic. Some questions is if indeed this was the only event detected and what that implies for the frequency of such detectable events, the range of distances possible with various generating events, etc. With only one reported event over the observing time frame the frequency of candidate magnitude events can start to be defined. Would this event have been detected if it occurred two billion light years away? Would a neutron star forming supernova be detected at 1 percent of the distance? Was detecting this event a serendipitous result because they only occur every 10 or so years? Once a bunch of events have been detected and tied in with other observations and theories, much improved precision and accuracy of various theories may be possible.

Dan Tibbets
To error is human... and I'm very human.

Tom Ligon
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Re: LIGO: Gravity Waves detected

Post by Tom Ligon »

Supposedly they have detected a much weaker second event. I don't know the confidence level. The unique thing about the black hole merger is that they "chirp", producing a rising signal in the last couple of seconds before the merger. It is difficult to explain that signal with other types of events. This is not just some plop making a couple of ripples, as one might get from other highly energetic events. The article below mentions false signals ... most of the chirps are signals deliberately injected into the system to see if anyone is awake. This event was not one of those carefully controlled spoofs.

One member of the SIGMA Think Tank, Catherine Asaro, has written up an article on the discovery. Dr. Asaro is a physicist and mathematician in addition to being a SF author. In order to get this interview, she had to sleep with the astrophysicist interviewed, John Cannizzo. In fact, she slept with him for years ... he is her husband.

https://catherineasaro.wordpress.com/

A couple of years back I was on a rant about scientists who don't do a good job of peer review and let crap papers get published. Catherine jumped down my throat over it, citing the extreme care with which her husband conducts peer review. Since he works on LIGO, I'll take that as an indication that careful peer review and confirmation are a LIGO trait.

JoeP
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Re: LIGO: Gravity Waves detected

Post by JoeP »

Dan and Tom, great posts, I am enjoyed reading your thoughts on this and especially the link.

I also found this summary which additionally answered my question regarding how did they know it was a black hole merger instead of something different.
https://www.ligo.caltech.edu/system/med ... ummary.pdf
If we compare the masses of the pre- and post-merger black holes, we see that the coalescence converted about three times the mass of the Sun (or nearly six million trillion trillion kilograms) into gravitational-wave energy, most of it emitted in a fraction of a second. By contrast the Sun converts a mere two billionths of one trillionth of its mass into electromagnetic radiation every second. In fact, the gravitational wave power radiated by GW150914 was more than ten times greater than the combined luminosity (i.e. the light power) of every star and galaxy in the observable Universe.
Now that is some power!

OK, so this encouraged my non-physicist brain to ask: while I get that such vast energies are needed to make such a powerful wave, how does the mass of the two black holes, which I *think is mostly locked up in the singularities, get converted to gravitational energy and successfully emitted in the form of a wave, outside the event horizon(s)? So, if nothing, not even light, or the hypothetical graviton...or any particle for that matter, escape the hole, how do three solar masses worth of black hole stuff (mass, energy) get subtracted from them inside the respective event horizons, and get emitted? If you look at figure 3 in the PDF, energy is emitted even in the "ringdown" stage, where the new hole is still oscillating before it settles down to be an even bigger cosmic bad-ass. So energy in the form of gravity waves is getting emitted still from the new black hole, and the black hole is still apparently losing mass.

*I must have some fundamental misunderstanding of how this works :)

Tom Ligon
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Re: LIGO: Gravity Waves detected

Post by Tom Ligon »

JoeP,

This is why I have a problem with gravitons. There's something different about gravity. If gravity were mediated by a particle, even one moving at the speed of light, how would gravity escape a black hole at all? If light can't, why should a graviton?

Einstein didn't postulate gravitons, he postulated a distortion of space-time. Gravity isn't emitted from the black hole, the black hole distorts space-time. And as the merger of the two black holes approaches, their furious orbiting shakes the blanket of space-time enough to cause waves.

Which leaves us still wondering what space-time really is. Quantum entanglement? An ether? The whole idea begs for there to be some edifice out there which still allows Special Relativity to operate as if there were no ether.

I believe gravity is different in kind from the other forces, and until that is accepted I expect it will make monkeys out of the people trying to unify it with the other forces. We're obviously still missing about 96% of physics since we are pretty sure dark matter and dark energy exist, but have no clue what they are, and we base their existence on the fact that gravity does not seem to work like it should. Dark matter is known only as gravity with no visible matter associated with it. Dark energy only because it seems to be an anti-gravity push affecting the expansion of the Universe.

My hope for LIGO is that it turns up something we've been too blind to see, something we are not even looking for. Maybe we'll think it is a malfunction at first, maybe a diurnal zero drift, or noise, and finally realize we've got some signal.

ladajo
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Re: LIGO: Gravity Waves detected

Post by ladajo »

The construct is Space-Time-Force

Force can be interpreted as energy/matter as they are interchangeable.

It is also important to remember, as pointed out above, that gravity (as an energy or matter event) propagates at the speed of light. This tells us that conventional matter/energy as we know it has a propagation exchange rate maximum. This is analogous to the speed of sound, another energy/mass interactive propagation phenomena. This does not mean that there is an absolute speed limit, only that as we have seen it, speed is positively proportional to energy positively proportional to mass. Ie. the faster you try to go the more energy you have(need) and mass you have.

For me, I don't think you can't exceed SOL, but to do so, I think you need to effectively "rip" the fabric of matter/energy, which probably takes a metric shit ton of energy to do.

One thing black holes have taught us is that there seems to be not much of a compressibility limit for matter/energy. However, what we don't know its what happens at the core of a black hole. Does all the matter get reduced to the smallest constituent and then packed tightly together? Any resultant energy from the transformation is ejected/emitted? The nature of the matter is not retained as it becomes amalgamous soup (or not)? The matter is all converted to pure energy and contained by collapsing matter, but has some energy leakage (or not)? Black holes eventually exceed some limit and explode? (Variant on recurring Big Bangs or Bang)?
The development of atomic power, though it could confer unimaginable blessings on mankind, is something that is dreaded by the owners of coal mines and oil wells. (Hazlitt)
What I want to do is to look up C. . . . I call him the Forgotten Man. (Sumner)

DeltaV
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Re: LIGO: Gravity Waves detected

Post by DeltaV »

JoeP wrote:OK, so this encouraged my non-physicist brain to ask: while I get that such vast energies are needed to make such a powerful wave, how does the mass of the two black holes, which I *think is mostly locked up in the singularities, get converted to gravitational energy and successfully emitted in the form of a wave, outside the event horizon(s)? So, if nothing, not even light, or the hypothetical graviton...or any particle for that matter, escape the hole, how do three solar masses worth of black hole stuff (mass, energy) get subtracted from them inside the respective event horizons, and get emitted?
My intuitional, but not necessarily correct, view is that the emitted wave energy* mostly originates in the extremely dynamic stretching and compression of spacetime itself, as the combining event horizons advance and recede oscillatorially, leaving behind some energy, somewhat like that needed to make ripples in beach sand (sand = spacetime, water = event horizon). To carry this analogy much further requires sand that allows tensile forces and can transmit elastic deformation waves. So some of the black hole mass-energy gets deposited as a spacetime "ripple", inside the changing event horizon, then the horizon recedes and part of the ripple remains outside, the spacetime strain energy radiating away before the horizon advances again. If the ripples always remained inside the horizon, that would imply that the fabric of spacetime has infinite stretchability, which cannot be true since a given black hole does not pull in the entire universe. Back-tension eventually stops the inflow of spacetime, allowing a part of the mass-energy-produced ripple to escape as the event horizon retracts during its damped oscillation.

* For post-merge "ringing".

Pre-merge, before any significant event horizon oscillations, some of the kinetic energy of the moving masses is what goes into the emitted gravitational waves. Is that kinetic energy crossing the event horizons? I don't think it is, since mass and velocity can be inferred/observed from outside the horizon. So the ringing portion is where the black holes lose small parts of their masses, not the pre-merge inspiral. I welcome any (peer-reviewed) links that shatter this speculation.

The event horizon oscillation may resemble that of a water drop in zero g (ignoring relativistic distortions):
https://youtu.be/EzahpSqGbVg
Which qualitatively agrees with the view of the tensor slingers:
https://www.youtube.com/watch?v=1agm33iEAuo

D Tibbets
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Re: LIGO: Gravity Waves detected

Post by D Tibbets »

Space time distortion, energy radiated away in the form of gravitons? The gravitational waves detected and the calculated energy does not necessarily challenge either interpretation. Once the black holes merge- ie have a single event horizon, perhaps round or oval or dumbell shaped (?) anything happening inside them cannot radiate away photons. I do not know if gravitons are thus limited. Certainly a black hole exerts gravitational influence beyond it's event horizon despite the singularity being well within the event horizon (perhaps- general relativity is weird) . I do think that the consensus is that gravity propagates at the speed of light. There has been some work with eclipses, Jupiter dynamics that have experimentally shown this.

Light, and graviton mediated gravity (?) do not actually slow down, it's speed in a vacuum is a constant. What happens is that the light loses energy- the wavelength lengthens, At the event horizon the wavelength becomes infinite. An extension of this is that if you were seeing light generated immediately outside the event horizon, you would only be seeing extremely long radio waves, and not a lot of them because of limb darkening effects from gravitational effects, not stellar atmospheric absorption effects). That x-rays and powerful sub light particle beams are seen coming from feeding "black holes" implies that these observed energetic events are actually occurring well outside the event horizon (in the accreation disk). I'm thinking this is why gravitational waves can have very long wavelengths. the action that generates the waves with detectable intensities is occurring deeper in massive gravitational wells and the gravtion radiation is red shifted a lot... :?:

Also, recall that from our perspective the holes never merge into a single , um... singularity. Relativistic effects slows things down from our outside perspective.

And, just like the tremendous energies expelled from just outside the event horizon in feeding black holes like what we see with galactic jets, some x- ray sources, etc. the emission is occurring as matter falls towards the event horizon. The matter speeds up, and if there is other matter in the vicinity, friction and magnetic interactions generates the huge light output. All of this occurs outside the event horizon. As the black hole increases in size, I think think this external energy production increases exponentially.

Fusion up to Nickel62 converts a paltry ~0.1 percent of matter to energy. Antimatter annihilation may be ~ 100%. Gravitational conversion of potential energy to kinetic energy can approach 100% with very massive black holes. In stellar mass black holes I'm uncertain what percentage is converted, though I'm pretty sure it is way above fusion. How much of this gravitational potential energy is converted to KE and possibly radiated energy before the event horizon is reached is again uncertain, but I suspect again that it far exceeds the fusion output of a similar amount of hydrogen. There is a stupendous amount of kinetic energy produced very quickly as the masses fall towards each other, even before they touch- event horizons begin to merge.

Dan Tibbets
To error is human... and I'm very human.

JoeP
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Re: LIGO: Gravity Waves detected

Post by JoeP »

So, there may have been a gamma ray burst from the same region in space, delayed by 0.4 seconds. However, the GRB is not expected in a merger of black holes, unless they were formed in a star's core.

http://www.universetoday.com/127463/did ... detection/

D Tibbets
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Re: LIGO: Gravity Waves detected

Post by D Tibbets »

JoeP wrote:So, there may have been a gamma ray burst from the same region in space, delayed by 0.4 seconds. However, the GRB is not expected in a merger of black holes, unless they were formed in a star's core.

http://www.universetoday.com/127463/did ... detection/
I don't know if any photon / light energy would be emitted if two starving (no stray matter in the immediate vicinity of the black holes- ie a significant accreation disk) black holes spiraled together. The gravitational potential of a massive object acts on matter near it, accelerating it with associated light radiation from friction or things like acceleration energy release- like Bremsstruhlung radiation or cyclotron radiation, but if there is no matter outside the black hole then no light radiation. Gravitational radiation is a totally different form of energy. It comes from the accelerating black holes themselfs (from the event horizons, the singularity, space time distortions? In such a situation, I do not think there would be any gamma ray burst, only the conversion of gravitational potential energy to gravitational kinetic energy- in the form of gravitational waves/ space time distortions.

So, if there is gas clouds nearby in close proximity, the merger may produce large intensity gravitational waves and large amounts of light emmisions.
With smaller mass black holes or neutron stars, the gravitational energy my fall below detectable limits, but neighboring matter in gas clouds or perhaps the surfaces of the neutron stars may be accelerated so much (with magnetic effects also playing a role) that hugh amounts ogf light/ gamma rays may be emmited. Both are powered by the gravitational potential energy, but the results depends on local conditions.

Light emmiting violent events are common. A subset of these events have a large or dominate gravitational component that is driving the system in the short term*. But, because of the great difficulty in detecting the extreamly weak gravitation forces effects directly, only the light emmiting events are witnessed. With LIGO improvements, etc. this threshold between the two different types of radiation is changing.

* A type IIa supernova is a run away nuclear detonation. Gravity has a role in setting up the conditions, but the burst of energy production is almost all nuclear fusion. A type I - star collapse type supernova where a neutron star or black forms is more directly driven by gravity. Here more gravitational wave intensities may be generated, though such events are still undetectable through gravitational waves unless they are uncomfortably close . Increased sensitivity of the detectors shifts this balance. Interestingly a type I supernova that results in a neutron star generates a lot of light in large part due to the rebound of matter from the almost uncompressable surface of the neutronium. If a little more massive, the gravitational collapse overwhelms this degeneracy pressure and the matter (most of it) continues to collapse towards a singularity. In this case the light emission may be feeble and the star dies with a wimper. At least it seems that way from a light perspective. If the gravitational radiation/ space time convulsions are detected, the missing energy is found.

Dan Tibbets
To error is human... and I'm very human.

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