Do we know the speed of gravitational waves

[colbourne]

Has the speed of gravitational waves been accurately measured ?<br /> <div class="Discussion_UserSignature"> </div>

 

[vogon13]

There is a thread here somewhere about a radioastronomy observation involving Jupiter and distant quasars that addressed this.<br /><br />IIRC, the answer is :<br /><br />c<br /><br /><br /><br /> <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[yevaud]

Correct. Gravitation propagation time appears to be exactly C. Experiment done in, IIRC, 2001. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[heyscottie]

There was some question about what was really being measured in that experiment, though, if I remember right. Some claimed that the experiment, while trying to measure the speed of gravity, was really only measuring the speed of light, which of course came out as c.<br /><br />I'm not sure if the debate ever resolved itself or not. I expect it did not, because I believe it is still a more or less open question as to the what the speed of gravity is, though the vast majority seem to agree that it does travel at the speed of light....<br /><br />Scott

 

[why06]

Yes how can you measure the speed of gravity with light.... its like measuring the speed of light with light. <div class="Discussion_UserSignature"> <div>________________________________________ <br /></div><div><ul><li><font color="#008000"><em>your move...</em></font></li></ul></div> </div>

 

[heyscottie]

The experiment involved observing the transit of Jupiter in front of some distant object. I don't recall the details, but watching this event helped the observers measure the speed of gravitational radiation to be close to the speed of light. Others disagreed, saying that the very nature of their observation really only was measuring the speed of light.

 

[heyscottie]

Here's a cut and paste from Wikipedia:<br /><br />http://en.wikipedia.org/wiki/Speed_of_gravity<br /><br />In September 2002, Sergei Kopeikin and Edward Fomalont announced in a conference in Seattle, Washington that they had made an indirect measurement of the speed of gravity, using their data from VLBI measurement of the ******** position of Jupiter on its orbit during Jupiter's transit across the line-of-sight of a bright radio source - quasar QSO J0842+1835. Kopeikin and Fomalont concluded that the speed of gravity is between 0.8 and 1.2 times the speed of light, which would be fully consistent with the theoretical prediction of general relativity that the speed of gravity is exactly the same as the speed of light.<br /><br />Several physicists, including Clifford M. Will and Steve Carlip, have criticized these claims on the grounds that they have allegedly misinterpreted the results of their measurements. However, Kopeikin and Fomalont continue to vigorously argue their case. (See the citations below for the details of the arguments pro and con.)<br /><br />It is important to understand that none of the participants in this controversy are claiming that general relativity is "wrong". Rather, the debate concerns whether or not Kopeikin and Fomalont have really provided yet another verification of one of its fundamental predictions.<br />

 

[vandivx]

"Has the speed of gravitational waves been accurately measured ?"<br />----<br />ehm, perhaps we should find them first<br /><br />vanDivX <div class="Discussion_UserSignature"> </div>

 

[bonzelite]

the thead premise assumes straight away that gravitational waves are actually in existence. like yeah, right, buddy! <img src="/images/icons/rolleyes.gif" /> <br /><br />you might as well have premised: "Jason and the Argonauts theory confirmed when Yeti spotted atop Mt Hood" and it would have been more believeable! <br /><br />gravitational waves = LOL!! = <i>Leprechaun</i>

 

[doubletruncation]

<font color="yellow">the thead premise assumes straight away that gravitational waves are actually in existence. like yeah, right, buddy!<br /><br />you might as well have premised: "Jason and the Argonauts theory confirmed when Yeti spotted atop Mt Hood" and it would have been more believeable!<br /><br />gravitational waves = LOL!! = Leprechaun</font><br /><br />Yeah, but you never know until you look. Unlike leprechauns, there are good reasons to think that gravity waves do exist. In particular, the binary pulsar PSR1913+16 discovered back in the 70's has had a change in orbital period at a rate that is exactly what is predicted by general relativity as a result of energy being radiated away by gravity waves - <br />http://jersey.uoregon.edu/~imamura/talks/gravity_waves/psr1913.html<br />(Other binary pulsars have been found since and confirmed this result). <br /><br />Sure this indirect evidence is not nearly as compelling as the direct detection of gravity waves would be, but I think it certainly is a good motivator to look for them. <div class="Discussion_UserSignature"> </div>

 

[search]

The hard way:<br />LINK<br /><br />6.4 Speed of gravitational waves<br /><br />According to GR, in the limit in which the wavelength of gravitational waves is small compared to the radius of curvature of the background spacetime, the waves propagate along null geodesics of the background spacetime,i.e. they have the same speed c as light (in this section, we do not set c =1). In other theories, the speed could differ from c because of coupling of gravitation to ``background'' gravitational fields. For example, in the Rosen bimetric theory with a flat background metric "n", gravitational waves follow null geodesics of "n", while light follows null geodesics of "g". <br /><br />The easy way:<br />Ask an Astrophysicist<br />The Question<br /><br />(Submitted September 05, 1998)<br />I am a first-year college student and I have a questions about gravity. Is it known how fast gravity waves travel?<br /><br /><br />The Answer<br /><br />Gravitational waves, just like photons, are waves that travel at the speed of light. However, even now, astronomers can not detect them directly, but can observe their effect on the bodies emitting them.<br />Gravitational waves are believed to be emitted close to compact stars, like a neutron star or a black hole. Just as ripples spread away from a stone tossed into a pond, so gravitational waves spread across space, bending it up and down. Two scientists at the University of Massachusetts, Taylor and Hulse, were able to prove their existence from observing a binary system of pulsars. They proved that gravitational waves do exist and were awarded the 1993 Nobel prize in Physics.<br /><br />David Palmer & Samar Safi-Harb<br />for Ask an Astrophysicist

 

[search]

The Nobel Prize in Physics 1993<br />Two stars for general relativity<br /><br />On 2 July 1974 the first signals were discovered from a binary pulsar, two neutron stars that orbit each other. It turned out that they could be used to demonstrate the existence of gravitational radiation. It seems that Einstein was right...<br /><br />Demonstration of gravitational waves<br />A very important observation was made when the system had been followed for some years. This followed theoretical predictions made shortly after the original discovery of the pulsar. It was found that the orbit period is declining: the two astronomical bodies are rotating faster and faster about each other in an increasingly tight orbit. The change is very small. It corresponds to a reduction of the orbit period by about 75 millionths of a second per year, but, through observation over sufficient time, it is nevertheless fully measurable. This change was presumed to occur because the system is emitting energy in the form of gravitational waves in accordance with what Einstein in 1916 predicted should happen to masses moving relatively to each other. According to the latest data, the theoretically calculated value from the relativity theory agrees to within about one half of a percent with the observed value. The first report of this effect was made by Taylor and co-workers at the end of 1978, four years after the discovery of the binary pulsar was reported.

 

[chesh]

The entire situation is a lot more complicated than it seems. Currently there is severe stress in the field of gravity research brought about by several problems, which may or not be related.<br /><br />First, Hulse and Taylor did NOT get a Nobel in physics for finding gravity waves. They got the Nobel in 1974 for showing that PSR 1913+16 obeyed Relativity rules for a decaying orbit of the NS and its companion star in a way consistent with Relativity. Gravity waves have YET to be directly observed.<br />www.astro.cornell.edu/academics/courses/astro201/psr1913.htm<br /><br />Current serious problems in physics are NOT finding anything which corroborates the current dictum that forces are mediated by particles, implying gravity waves & gravitons(both moving at Cee), Higgs Bosons(mediating that property called mass), the non-existence (undetectability) of quarks and gluons, which do NOT account for leptons(electrons, etc.), BTW, a huge gap & problem for the quark schema.<br /><br />Then there is the problem of quantizing gravity, which has not been successfully done. AND the problem of Dark matter, which is an effect which seems to exist, but for which NO matter can be detected. Again, in gallops the same Headless Horseman all around gravity research. (Who IS that guy? is very often heard these days in physics.) These problems may quite well be related on a fundamental basis.<br /><br />These problems do seem to be hovering in the neighborhood around the issue of what is the nature of gravity and mass, which are inextricably linked. Mass affects gravity. Gravity will have an effect on mass, and space/time.<br /><br />If one looks at the fundamental particles, there is not ONE single quantity in the physics or maths (altho it's measured in MeV's)) which contributes the mass. <br /><br />MASS has in effect been left out. This is a VERY peculiar omission and implies a very seriousl

 

[bonzelite]

GR, STR, and all "relativistic effects" are not proof of relativity whatsoever! therefore, gravitational waves cannot possibly be corroborated to exist by a set of theories that are in all likelihood incorrect! <br /><br />this thread belongs to Phenomena with Tachyons.

 

[bonzelite]

brilliant and thank you! :<br /><br />"One further problem is, that because gravity would seem to be propagated at cee, light speed, then how does it get outside of a black hole? Gravity effects are all around the BH, and this seems to contradict the hypothesis that gravitons and gravity waves must get out. But the physics precludes this. <br /><br />If nothing can be propagated OUTSIDE of a black hole due to the immense gravitational field, then how do gravitons and gravity waves get out, when light and no matter cannot? This puts gravity into a peculiar position with respect to the rest of physics, meaning, it may be an animal of an entirely different kind. "

 

[chesh]

It's very peculiar this quality/quantity called mass/gravity. We wait for the Large Hadron Collector, going on line this year, which should be able to create the massive energies needed to make a Higgs Boson. But it does NOT make any sense that a massive particle many fold times the mass of the proton(938 MEV's), should mediate proton mass. This is peculiar. Or that of a neutrino, of 5-10 MEV's.

 

[search]

If you would read the post you would notice that I separated the issue into:<br />The hard way and the easy way. In the easy way the post (copy of the link) states that they found gravity waves.<br /><br />The first mistake is that "gravity waves" is a term used in hydrodynamics. The correct term is "gravitational waves" or "gravitational radiation".<br /><br />In reality their observation was an indirect demonstration of gravitation waves. The issue however as many perpectives. One should remember that until proven otherwise in science (either you, me or anyone else agrees or not) it is the Standard Model that rules and GR sets the standards.<br /><br />So to make it simple:<br />Although gravitational radiation has not yet been directly detected, it has been indirectly shown to exist. This was the basis for the 1993 Nobel Prize in Physics, awarded for measurements of the Hulse-Taylor binary system.<br /><br />http://nobelprize.org/nobel_prizes/physics/laureates/1993/press.html <br /><br /><font color="yellow">The problem is that Quantum mechanics is incomplete--it does NOT address gravity. That's a massive hole in QM. Einstein and most physicists have been acutely aware of this and trying to create a Unified Field Theory which would unite the models of relativity and QM. So far all have failed. String theory is a notable recent failure. </font><br /><br />Einstein has nothing to do with Quantum Mechanics except that he provided a lots of information and despised it and yes he tried the unification but when the weak force and strong force were not known yet.<br /><br />Quantum Mechanics is about Werner Heisenberg, Max Planck, Louis de Broglie, Niels Bohr, Erwin Schrödinger, Max Born, John von Neumann, Paul Dirac, Albert Einstein, Wolfgang Pauli and others.<br /><br />It is hard to talk about failure of String Theory when it is yet to be proved or disproved.<br /><br />In what I

 

[bonzelite]

"In reality their observation was an indirect demonstration of gravitation waves. The issue however as many perpectives. One should remember that until proven otherwise in science (either you, me or anyone else agrees or not) it is the Standard Model that rules and GR sets the standards. "<br /><br />gravity waves have not been detected whatsoever, nor has GR been proven, nor is it necessarily correct. until relativisitc effects are proven, gravity waves cannot be real things. and indirect detection of them is based upon theoretical assumptions only. <br /><br />gravity wave = Leprechaun = Yeti <br /><br />relativistic effects = unproven

 

[yevaud]

<i>nor has GR been proven</i><br /><br />Gravity Probe "B" and numerous other *verified* experiments and observations. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[search]

Some info<br />LIGO <br /><br />The website<br />Laser Interferometer Gravitational Wave Observatory

 

[bonzelite]

this is an erroneous conclusion:<br /><br />"This change was presumed to occur because the system is emitting energy in the form of gravitational waves in accordance with what Einstein in 1916 predicted should happen to masses moving relatively to each other."<br /><br />the "system emitting energy in the form of gravitational waves" is completely unfounded.

 

[bonzelite]

"Gravity Probe "B" and numerous other *verified* experiments and observations.".... are based entirely upon assumptions that relativistic effects are due to "relativity" as explained in GT and STR --both of which are erroneous theories not based in real events that happen in outer space. <br /><br />if you want to <i>believe</i> relativistic effects are corroborations of relativity theory, then that is a personal matter. you may pray quietly, then.

 

[SpeedFreek]

You keep saying GR is unproven, and yet it stands up to any way we can find to experimentally test it. Why is this? It is true that we may not understand the full picture and that GR doesn't seem to work when applied to our understanding of the motion of stars within galaxies. But does that mean GR is incorrect, or just that it is unfinished? GR, STR and QM may in the end all be correct in themselves, but seen in a different context within any Grand Unified Theory.<br /><br />The aspects of GR that we can think up ways to test experimentally all seem to confirm the accuracy of the system GR describes.<br /><br />CERN is basically one long test of GR, and GR seems to pass the test. The gravitational time-dilation predicted by GR is confirmed by the adjustments we have to make to the internal clocks of GPS satellites.<br /><br /> A list of tests of GR <br /><br />If I want to believe that clocks tick slower in orbit, I will, because clocks tick slower in orbit.<br /><br />General Relativity = Passes every test we can think up so far. <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[search]

<font color="yellow">gravity waves have not been detected whatsoever, nor has GR been proven, nor is it necessarily correct. until relativisitc effects are proven, gravity waves cannot be real things. and indirect detection of them is based upon theoretical assumptions only.</font><br /><br />"Gravitational" waves have not been "directly" detected.<br /><br />GR has not been disproved.<br /><br />GR is not 100% correct but so are not any other heory and still is the most correct so far. QM is also extremely accurate but cannot deal with large things.<br /><br />Theoretical yes, assumption no since proof is a requirement for theories in science and assumptions do not require proof.

 

[search]

<font color="yellow">this is an erroneous conclusion: <br /><br />"This change was presumed to occur because the system is emitting energy in the form of gravitational waves in accordance with what Einstein in 1916 predicted should happen to masses moving relatively to each other." <br /><br />the "system emitting energy in the form of gravitational waves" is completely unfounded.</font><br /><br />Tell that to the Nobel Prize jury panel...<img src="/images/icons/wink.gif" />