Gravity waves detected for the first time ever

He doesn't know what the '5 sigma agreement' means.

 

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Gravity waves occur when a gravity field gains or loses mass, they perpetuate from the movement of objects in a gravity field, say the earth's gravity field. I don't know why they try to measure them at such great distances, they should be detectable vibrating out of heavy spinning masses hear on earth like a powerful generator or the tokomak.

 

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From the 90% confidence localization of the signal to \(590 \, \textrm{deg}^2\) that is about 1.43% of the sky. They likely would have done much better with one or two more devices of similar sensitivity working.


\(1 \, \textrm{deg}^2 \; = \; \left( \frac{\pi}{180} \right)^2 \frac{1}{4 \pi} \, \textrm{sky} \; = \; \frac{\pi}{129600} \, \textrm{sky} \; \approx \; \frac{1}{41253} \, \textrm{sky} \)

 

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Please provide calculations to support such a claim.

\( \frac{3.0 \, M_{\odot} c^2 / \textrm{s}}{\left( 10^9 \, \textrm{light years} \right)^2} = \frac{ 3.6 \times 10^{49} \, \textrm{W} }{9 \times 10^{49} \, \textrm{m}^2} = \frac{0.4 \, \textrm{W} }{ ( 1000 \, \textrm{km})^2 }\)

Do you know of a terrestrial source which loses \(0.4 \, \textrm{W}\) to gravitational radiation in the 30-150 Hz band? I think not.

I think if you take all the carbon in Earth's biomass, turn in into a diamond, and whip it around in a tight circle at orbital speeds you could just about achieve GW luminosity of \(0.4 \, \textrm{W}\).

 

What a great way to begin the New Year in!!!
Not that there was really any doubt as to the existence of such a beast imho anyway. I mean if spacetime can be warped, curved, twisted, as evidenced, why not ripples in spacetime?

Here's another angle on the news......
http://www.nature.com/news/einstein-s-gravitational-waves-found-at-last-1.19361

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http://www.nature.com/news/gravitational-waves-6-cosmic-questions-they-can-tackle-1.19337

One of the important scientific consequences of LIGO’s detection of a black-hole merger is, quite simply, that it confirms that black holes really do exist — at least as the perfectly round objects made of pure, empty, warped space-time that are predicted by general relativity.

Astronomers had plenty of circumstantial evidence for black holes, but until now, that had come from observations of the stars and super-heated gas that orbit black holes, not of black holes themselves.

LIGO’s signal has provided that evidence — and also confirms that mergers between two black holes proceed as predicted. A merger occurs when two black holes start to spiral towards each other, radiating energy as gravitational waves. LIGO detected the characteristic sound of these waves, called a chirp, which allowed scientists to measure the masses of the two objects involved in the event the observatory spotted: one about 36 times the mass of the Sun, and the other 29 solar masses.

Next, the black holes fuse. “It’s as if you get two soap bubbles so close that they form one bubble. Initially, the bigger bubble is deformed,” says Thibault Damour, a gravity theorist at the Institute of Advanced Scientific Studies near Paris. The resulting single black hole will settle into a perfectly spherical shape, but first, as LIGO saw, it radiates gravitational waves in a pattern called a ringdown.

Do gravitational waves travel at the speed of light?
When scientists start to compare observations from LIGO with those from other types of telescope, one of the first things that they will check is whether the signals arrive at the same time. Physicists hypothesize that gravity is transmitted by particles called gravitons, the gravitational analogue of photons. If, like photons, these particles have no mass, then gravitational waves would travel at the speed of light, matching the prediction of the speed of gravitational waves in classical general relativity. (Their speed can be affected by the accelerating expansion of the Universe, but that should manifest only over distances much greater than LIGO can probe4).

But it is possible that gravitons have a slight mass, which would mean that gravitational waves would travel at less than the speed of light. So if, say, LIGO and Virgo were to detect gravitational waves from a cosmic event, and find that the waves took slightly longer to arrive at Earth than the associated burst of γ-rays detected by a more conventional telescope, that could have momentous consequences for fundamental physics.
:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Other questions that gravitational waves may answer are as follows and discussed at the link.

Is space-time made of cosmic strings?
Are neutron stars rugged?
What makes stars explode?
How fast is the Universe expanding?

 

See. I badly botched that calcuation by using wrong terms throughout.

\( \frac{200 \, M_{\odot} c^2 / \textrm{s}}{\left( 10^9 \, \textrm{light years} \right)^2} = \frac{ 3.6 \times 10^{49} \, \textrm{W} }{9 \times 10^{49} \, \textrm{m}^2} = \frac{4 \times 10^{11}\, \textrm{W} }{ ( 1000 \, \textrm{km})^2 }\)

Do you know of a terrestrial source which loses \(400 \, \textrm{MW}\) to gravitational radiation in the 30-150 Hz band? I think not.

I think if you take a mass of 5.5 billion tonnes, and whip it around in a tight circle (R = 115 km) at 36% speed of light you could just about achieve GW luminosity of \(4 \times 10^{11} \, \textrm{W}\).

\( R_s = \frac{2 G M}{c^2} = 8.1685 \, \textrm{fm} \\ V = 2 \pi R f = 0.3615 \, c \\ L = \frac{c^5}{G} \left( \frac{R_s}{R} \right)^2 \left( \frac{V}{c} \right)^6 = \frac{256 \pi^6 G f^6 R^4 M^2}{c^5} \approx 4 \times 10^{11} W\)

 

What if there were nothing in the universe other than a pair of massive binary black holes; where would conservation of energy come into play? There wouldn't' be any other atoms in the universe for the GWs to affect or move, so what, if anything, moves?

 

The gravity waves themselves carry energy, so even if they are never absorbed by other matter, energy is still conserved. It's the same as how a lightbulb in an empty universe wouldn't violate conservation of energy, even though its output radiation would fly off into space.

I really hope RJBeery is reading this thread. If I recall, one of the papers cited back in the thread on frozen stars said that frozen stars can be distinguished from true black holes by their behavior during collisions: frozen stars emit a significant fraction of their collision energy as EM radiation, while black holes emit only gravitational radiation. Insofar as astronomers didn't see any bright flash in the sky to match the LIGO detection, this might count as observational evidence against the frozen star model. That's really cool, and I'm sure RJBeery would agree.

 

A really, really excellent reply. Thank you.

 

I doubt it. My guess is he's not going to comment on it. It's irrelevant other than finally showing some intellectual honesty on the subject. What's spectacular is the hard work that made this measurement possible. In the merger the energy of gravitational radiation was equivalent to 3 solar mass. Wow.

 

You botch a calculation. ?. Thanks for fixing it.

 

From all reports we can expect some more validations that have occurred since the update of LIGO.

 

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

Based on the observed signals, LIGO scientists estimate that the black holes for this event were about 29 and 36 times the mass of the sun, and the event took place 1.3 billion years ago. About 3 times the mass of the sun was converted into gravitational waves in a fraction of a second—with a peak power output about 50 times that of the whole visible universe. By looking at the time of arrival of the signals—the detector in Livingston recorded the event 7 milliseconds before the detector in Hanford—scientists can say that the source was located in the Southern Hemisphere.

 

First, black holes have also normal matter circulating it, and it is likely that this matter will very likely also show a big explosion if the BHs merge. The question is how much this gives, which is something which can be computed by computer simulations on a GR basis for various scenarios about the nearby matter. Naively I would guess that it may be possible to exclude this, because there will be some time before the merger where the small BHs simply rotate around each other, a configuration which may look quite stable, as a gravitating object, for other matter around it, so that all what happens with external matter around will happen at a larger time scale.

The other question is that the details of the merger of gravastars will depend on the particular theory of gravity which predicts the gravastar. I doubt that some generic prediction is possible here. One can, of course, reasonably hope that a large part of such theories will predict a sufficiently large visible explosion which could be seen - or not seen - by observations.

For my theory I doubt that this will be decisive, for the reasons already explained: For $ \Upsilon<0 $ the prediction will be indistinguishable from GR, for $ \Upsilon > 0 $ this will give an upper limit $ \Upsilon < \Upsilon_{max} $ and it is not even clear if upper limits for this from the early universe or the observation of the very large BHs at the centers of galaxies will be reduced: The smaller the black hole, the greater the surface time dilation, thus, the smaller the difference to GR. And these BHs are big in comparison with the Sun but very small in comparison with the BHs at the centers of the galaxies.

 

yeah right...

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Not necessarily.
I'm sure though you agree that the observations and data, along with future data on other observations yet to be properly researched, will confirm both the long sort after gravitational waves and also BH's of the GR variety, for the reasons already stated in many links.

Yes, Intermediate size BH's which have also been searched for of late.
Perhaps speculatively speaking, originally two large stars, that have gone S/N or even not gone S/N according to some late data, and formed two BH's, that have swallowed their respective accretion disks and grown to their observed sizes.
The resultant BH is also seen as a Kerr BH according to data, which also fits nicely into the scenario.

 

I'm quite sure that it supports gravitational waves, and it seems also clear that such observations can give a lot of additional information about black holes. That it will exclude some gravastar theories is also very plausible (like, for example, variants of my theory with a too large $ \Upsilon $ value).

I would not name them intermediate size, the name star-sized is much more accurate, even if the corresponding stars are quite big.

The scenario of two different stars seem implausible to me, I think that much more plausible is the collapse of a single big star, which happened asymmetrically, so that the infalling matter splitted into two parts which are very close to each other from the start.

This does not mean any disagreement with what is claimed - in particular, the collapse which has lead to this constellation can have happened very long ago, the two resulting BHs rotating around each other would define a configuration which can be stable over a long time, in the Newtonian approximation it would be simply stable forever, in GR it looses energy via gravitational waves, but this may need a long time. It is only an idea about how such a configuration - two BHs very very close to each other to collapse - may come into existence at all, if not by an extremely rare accident.

Of course, there will be no BH which does not rotate at all, the electric charge will be irrelevant, thus, it will be a Kerr BH.

 

that wasn't directed at anyone on the forum.

 

That is a hard claim to corroborate. It's not something one can simply measure since most galaxies in the observable universe are highly redshifted.

http://arxiv.org/abs/1504.05808 gives the average luminosity per stellar mass of about \(1.4 \, \frac{L_{\odot}}{M_{\odot}}\) in the V-band (optical) and \(3.2 \, \frac{L_{\odot}}{M_{\odot}}\) in the K-band (near-infrared).
http://www.skyandtelescope.com/astronomy-resources/how-many-stars-are-there/ estimates there are about \(7 \times 10^{22}\) stars in the observable universe.
https://en.wikipedia.org/wiki/Observable_universe#Extrapolation_from_number_of_stars estimates the mass of all stars at \(10^{52} kg\).
http://www.astro.princeton.edu/~gk/A403/constants.pdf gives the luminosity of the sun as \(3.826 \times 10^{26} \, \textrm{W}\) and \(\frac{L_{\odot}}{M_{\odot}} = 1.923 \times 10^{-4} \, \textrm{W}/\textrm{kg} \).

So an order of magnitude estimate, \((0.4-2.7) \times 10^{49} W\) seems like reasonable guess for the luminosity of all the stars in the observable universe.