Talk:Gravitational wave

Quantum gravity, wave-particle aspects, and graviton

This is a page about GRAVITATIONAL WAVES. And suddendly, this paragraph is obviously about GRAVITY. Confusion in some minds? see https://kn0l.wordpress.com/la-gravite-est-elle-instantanee/ (in french) — Preceding unsigned comment added by 163.47.106.116 (talk) 01:12, 12 January 2017 (UTC)

Einstein’s Field Equations in Wave Form

In the Advanced Mathematics section, could someone kindly provide a reference to a proof of the claim that solutions of $\Box {\bar {h}}^{\alpha \beta }=-16\pi \tau ^{\alpha \beta }$ are waves traveling with velocity $1$?

Leonard Huang (talk) 19:36, 25 February 2017 (UTC)

External links

Dr Baker Jr's collaborator's work in HFGW finds a reference in the main article. His site GravWaves has a detailed account of the history and development of GW research. He is a pioneer in the HFGW field, however, this article is not restricted to LFGW; the article is called Gravitational waves. The US patents form an integral part of the technology researched to find applications for HFGW; therefore, they are very relevant for a general reader. The edits which added the links were started months back by another editor and there was no objection by the current editors who were very much observant even then. Now, why this war-like situation? In a Wikipedia article, a general account of the subject is given which includes technology and other educative pages from the internet. GW is a developing field, hence, all possibilities and potentials are to be respected and presented. Please, enlighten me, how taking away technology possibilities of HFGW would enrich the article? My request is to give what I discussed here a thought. Thanks User:Mandot —Preceding undated comment added 11:42, 13 September 2017 (UTC)

Where has it been reported in reliable sources WP:RS to achieve notability WP:N? Weburbia (talk) 11:56, 13 September 2017 (UTC)

A story in Hindustan Times by Manoj Sharma (talk) User:Mandot —Preceding undated comment added 12:21, 13 September 2017 (UTC)

References

Abusive language in Edit summary of External links

All editors watching this page please note that User:Deacon Vorbis is repeatedly indulging in abusive language usage on Edit summary. You may see the recent edits and reverts. The link of a US patent was added by me more than 2 months back. Nobody objected to it, there are more than 350 editors watching this page. Today, I noticed a group of editors led by User:Deacon Vorbis arbitrarily deciding that the link does not belong here. It is a US patent of a relevant technology also reported in national newspapers. It teaches a method to modulate the invariant mass of an object which creates gravitational waves. Why shouldn't it belong here? The man who holds a patent has a Wikipedia page on his works. The use of obscene and abusive words clearly show bias of this group of editors. They are behaving like dictators who suddenly decide to remove some relevant links in a motivated manner. The use of abusive language by Wikipedia editors has indeed lowered the dignity of Wikipedia Cottonmother —Preceding undated comment added 14:19, 13 September 2017 (UTC)

First, see the definition at wikt:my ass#Interjection. While it's mildly vulgar, it's by no means abusive. As well, the patent links (as well as the the company link) are promotional and do not belong on the page; see WP:ELNO for more info. The fact that they went unnoticed for a couple months is irrelevant to their appropriateness. In fact, I was alerted to it by a rather dubious comment made on a phys.org article, so I decided to investigate. Moreover, the patents constitute WP:FRINGE material and so also don't belong.

While I appreciate your confidence in my influence, I can assure you that I lead no other editors, let alone a whole group! --Deacon Vorbis (talk) 14:48, 13 September 2017 (UTC)

Going by your logic, even LIGO findings are fringe, as they are unconfirmed and repeatedly challenged by many. As another user pointed out above, this field is still getting defined. A US patent by known researchers is as good as LIGO findings -- unless you count money invested. I find your "investigations" and judgement as motivated. It is indeed uncanny that you took such offense and started using unmentionable body-part expletives; and then suddenly to rescue you, 3 more editors showed up repeatedly. When I edited and added the Pal patent link on 12 July 2017, it was deleted by some unregistered user on 14 July 2017, very soon it was reinstated back immediately by user:TwoTwoHello. This fact clearly shows that the link was being observed by many editors and was found good enough; therefore, contrary to your assertions, my edit of 12 July 2017 did not go unnoticed at all, rather it was approved by the community. You are now trying to hide behind false modesty. Your extreme reaction in using expletives brands you as a dubious editor with a motivated following. Rest of the editors may comment. Therefore the edit shall be undone. I am sorry, you may soon find yourself isolated in a Quixotic corner. Cottonmother — Preceding unsigned comment added by Cottonmother (talk • contribs) 15:57, 13 September 2017 (UTC)

Please sign your talk page comments with four tildes: ~~~~.

First, I have to say that asses are most definitely not unmentionable. I mention them all the time in fact. And we all have one (even if we shouldn't go waving them around). Moreover, my use of "my ass" is hardly extreme, nor does it mark me as "dubious" (whatever that means), nor does it give me a motivated following (whatever that means, too).

Second, I'm confused about your LIGO comments; they're really irrelevant to the discussion at hand, which is the appropriateness of the links in question. Please read WP:PATENTS for some more info here. That doesn't apply exactly, since these are external links rather than sources, but it does give some good insight into why they're not appropriate.

Third, your link was not deleted by an IP and restored by TwoTwoHello. The IP's edit was merely a small bit of vandalism which was undone by TwoTwoHello. Your claim is demonstrably false. The fact that it wasn't noticed at the time is irrelevant to its appropriateness now. --Deacon Vorbis (talk) 16:24, 13 September 2017 (UTC)

Pray, tell me in clear terms why "they" are not appropriate? From your statement no.2, "That doesn't apply exactly, since these are external links rather than sources, but it does give some good insight into why they're not appropriate." Wikipedia is replete with references to patents, as links and otherwise. If the referred IP address link removal was a small bit of vandalism, going by that logic, you folks are repeatedly indulging in the same vandalism of the same amount, and a whole series of it. To top it all, you are reporting my edits as an act of war. I accept that you people have formed a group to assault a valid edit. However, I repeatedly request you not to act as ring leaders. These times are very testy; there is no point in venting LIGO's frustration on a user. If you accuse something of being from the fringe, then you also know even Big Bang came from the fringe. — Preceding unsigned comment added by Cottonmother (talk • contribs) 17:03, 13 September 2017 (UTC)

Are you saying that you have a WP:COI here?TR 17:53, 13 September 2017 (UTC)

(edit conflict) Per WP:ELNO #13, this patent shouldn't be included in the external link section of the article. It possibly could be included in the article itself as long as WP:PATENTS is satisfied and it's not just thrown in for the sake of it. — nihlus kryik  (talk) 17:57, 13 September 2017 (UTC)

That about covers it, but my own take is they are not good references, being primary sources, and not good external links, being legalistic technical gobbledygook, intended for lawyers as much as scientists. Certainly of no interest to the typical reader of one of our articles. The only time a patent should be linked to is when it is the discussed in the article, so its relevance is established, and properly sourced.--JohnBlackburne^words_deeds 18:33, 13 September 2017 (UTC)

"Mathematics" section

The current mathematics section is somewhat of a relic of an old version of this page from before any experimental confirmation of the topic. Since then this page has grown significantly, and has become of interest to a much wider audience. I think it might be better to relegate the rather technical (and textbooky) material of this section to other more relevant pages. What do others think?TR 15:08, 22 September 2017 (UTC)

The article should presumably be split. The "textbooky" material is simplified to the point of being misleading. Historically, the linearized solutions had a bad reputation, and not just because it was unclear if they were physical or coordinate. Consider the "elevator light" paradox. Fix, relative to a freely falling elevator, an electric charge. Does it radiate, as per Maxwell? Yes, from outside the elevator, no from inside. The resolution is that the equivalence principle is purely local, but radiation is global. Linearized gravity is appropriate for analyzing detector response, but it isn't very good for the generation and prediction of actual gravitational waveforms. 129.68.81.72 (talk) 18:18, 24 September 2017 (UTC)

Linearized gravity already exists as an article and covers most of the content of the "mathematics" section here anyway. Any additional content can be merged there.TR 21:52, 24 September 2017 (UTC)

No, the additional content, generation/prediction, would be fully non-linear. Adding it to linearized gravity would make no sense. 129.68.81.72 (talk) 23:05, 24 September 2017 (UTC)

Radiation pattern of binary system

It would be helpful if the article described the radiation pattern of the binary systems discussed. The purple diagram shows omnidirectional radiation in the orbital plane. From symmetry, I would guess this was +polarized. Can this radiate angular momentum? Is there also circular-polarized radiation in the polar directions? If so, is the power radiation pattern a sphere (isotropic)? Is the angular-momentum radiation pattern a doughnut, a sphere or a dumbbell? Thanks, --catslash (talk) 18:52, 25 September 2017 (UTC)

I think going in to this would be too much detail for this particular article. (This would be more suitable for something like binary black hole, or something...). To answer your questions:

1. Yes on the equator the waves have a "+" polarization.
2. Yes, this can (and does) radiate angular momentum.
3. Away, from the equator there is a mix of polarizations. At he poles you get something close to circular polarization.
4. The power radiation spectrum is not isotropic but varies across the sphere. Typically this pattern is expanded in spin-weighted spherical harmonics of spin weight -2. The dominant modes are l=|m|=2 modes. Plotting the squares of these should give you a good idea of the angular distribution on the sphere.
5. The distribution of the angular momentum emission is almost identical.

Hope this helps.TR 13:00, 26 September 2017 (UTC)

Many thanks for such a clear and comprehensive answer. --catslash (talk) 13:37, 26 September 2017 (UTC)

Secondary effects

An anonymous comment under the #Poincaré first predicted gravitational waves before Einstein section above says "Gravitational waves don't produce any gravity or gravitational effects." Is this true? Surely if gravitational waves carry energy they must create a gravitational effect of their own? Not detectable in front of the wave, any more than a sonic boom can be heard in front of the aircraft producing it, but detectable behind and to the sides. If this is not the case, the overall curvature of space-time would change every time black holes collide, which appears absurd. Do these secondary gravitational effects contribute materially to the question of dark matter, or is the cumulative effect of billions of years worth of waves still negligible?--Keith Edkins ( Talk ) 17:25, 9 October 2017 (UTC)

Only part of an answer, but once a gravitational wave passes, then space can be permanently shifted (expanded). Each time black holes collide they give out about 5% of there mass in waves. If there are heirarchical mergers, say 27 in a row, a black hole 35,000,000 times bigger is made and 75% is radiated as gravitational waves. So it could appear as hot dark "matter". But already pulsar observations have ruled out such a high level of low frequency waves. But not only that, for every particle acceleration or photon emission there will also be a gravitation wave. These however will be extremely minute and high frequency. Graeme Bartlett (talk) 11:53, 10 October 2017 (UTC)

I agree with Keith Edkins that gravitational waves must transport mass-energy just as a photon does, and when absorbed by a system they increase the mass of that system, and furthermore as Keith suggests they constitute mass within intergalactic space, possibly explaining some fraction of "missing mass" observations. It should be possible to do a back-of-envelope calculation of the extent of mass (baryonic matter) acceleration from the big bang to present and determine the amount of mass-energy generated in gravitational radiation and see if this is of the same order as CDM mass estimates. I do not know why Graeme Bartlett calls this "hot dark matter" or why quasar observations "rule out" such an effect. I also expect that absorption of gravitational waves by orbiting systems should cause them to outspiral.

Spope3 (talk) 01:15, 11 November 2017 (UTC)

If there was enough gravitational waves out there, there would be some mass, and possibly gravitational effects. \It would be dark and free flowing, and thus "hot". See https://arxiv.org/abs/1310.4569 for the use of pulsar timing to put a limit on the magnitude of gravitational waves there are out there. An article here is Pulsar timing array. Graeme Bartlett (talk) 08:22, 18 January 2018 (UTC)

Graeme Bartlett - thanks. I agree on the definition of "hot". Thanks. I think the pulsar timing measurements are not indicative of the mass-energy of the gravitons that comprise the GWB; they instead measure the strain cause by such waves between the instrument and the pulsar. These will be very different when there are a large number of small sources contributing to the GWB. Sources that contribute to the strain may combine destructively, whereas the mass-energy of any one graviton is always positive and so these combine additively. Simplistically I would expect the mass-energy to scale with the number of sources, and the magnitude of the strain with the square root of this number. Spope3 (talk) 21:57, 12 February 2018 (UTC)

The pulsar timing is only sensitive to the really low frequency waves, perhaps from supermassive black hole mergers. It is very difficult to absorb gravitational waves, and the average orbiting system will absorb very little. Also the existing detectors are not sensitive to those really low frequencies or high supersonic frequencies either. But they already rule out a certain level of power in the audio frequency range. Graeme Bartlett (talk) 03:56, 13 February 2018 (UTC)

Yes, there's no question that there are negative results from the pulsar timing study you referenced (Shannon) and also more extensive studies from the NanoGrav Collaboration (Mingarelli - here: https://arxiv.org/abs/1508.03024 ). The question is what is being ruled out. As I described above, at some point the central limit theorem figures into the negative outcome -- the GWB as measured by strain is combination of a large number of sources and so does not measure directly the mass-energy in the background. The link between these two is model-dependent. This is described in much more detail in Mingarelli - sections 1.2 and 1.3 of the introduction. But yes the results are so far negatvie. Spope3 (talk) 19:00, 14 February 2018 (UTC)

Directional sensitivity of the Interferometer ?

The interferometer has two perpendicular arms, so when the wavefront of a passing gravitational wave is parallel to one arm and perpendicular to the other (as shown in the illustration), then the instrument is sensitive to the passing of the wave. Per the current text, this "is precisely the motion to which an interferometer is most sensitive". But what happens to the sensitivity if the wave happens to come from an equal (45 degree) angle to both arms? Would a wave from this direction be detectable at all? Is there some trigonometric relation between the sensitivity and angles between 0 and 45 degrees ? Similarly, what about a wave perpendicular to both arms, i.e. a wavefront parallel to the plane spanned by the two arms? Would a wave from this direction be detectable at all? I think the article could be expanded to cover such limitations. Further, I am guessing one reason interferometers suitable for detecting gravitational waves are being built on different parts of the Earth is exactly to try to avoid such blind (or deaf?) spots. Some information related to this would also be interesting. Lastly, I am thinking that the (millisecond scale) delay between the detections in different interferometers is what allows for the (coarse) localization of the source of the wave. This additional advantage of having multiple, well separated detectors would also be good to point out. Thanks! Lklundin (talk) 20:05, 21 October 2017 (UTC)

I read that direction can also be established by the time difference when the wave hits separate detectors (separate locations). That is one of the additional attractiveness of having India-Ligo (Indian Initiative in Gravitational-wave Observations) go online "far" from the USA and European detectors. Cheers, BatteryIncluded (talk) 20:14, 21 October 2017 (UTC)

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Gravitational wave astronomy

In this section: The sources of gravitational waves described above are in the low-frequency end of the gravitational-wave spectrum (10−7 to 105 Hz). An astrophysical source at the high-frequency end of the gravitational-wave spectrum (above 105 Hz and probably 1010 Hz) generates[clarification needed] relic gravitational waves that are theorized to be faint imprints of the Big Bang like the cosmic microwave background.[54]

It seems to me that high and low frequency ranges are mentioned incorrectly. The "waves described above" are in the high-frequency end; gravitational waves originating form the Big Bang have long wavelengths, low frequencies. Bookaneer (talk) 12:22, 3 November 2017 (UTC)

Effects of Passing, probable error

In the Effects of Passing section of this page, there is a paraphrased reference to LIGO's sensitivity that compares it to measuring the distance between us and the nearest star to an accuracy of one human hair. That is the *limit* of LIGO's ability to sense the gravity waves, but it is not necessarily the actual size of the waves. Unless gravity waves AND the sensitivity of LIGO are exactly identical, this section needs corrected. — Preceding unsigned comment added by 40.0.40.10 (talk) 08:13, 7 November 2017 (UTC)

Completely agree. There isn't enough here to say why there shouldn't be doubt about the whole phenomenon if the measurements are essentially beyond anything conventionally considered measurable, like e.g. quarks. Quarks are flatly stated to be undetectable. This apparently is in the same domain. At some point, in consideration of the huge sums of public money that are spent on these things, a better job of explaining them, including to yourselves, will be in order. I am dubious of the current model of gravitation, of gravitational waves, quarks, etc. because they present the image of science that has veered off from a need confirm reality and instead live within theory as if it were.

That is to say there isn't enough here, wiki isn't everything so will look elsewhere in re why an effect that is comparable to measuring a quark should be confirmation of gravity waves. 98.4.124.117 (talk) 06:52, 15 April 2018 (UTC)

Proof

Are the recent laser interferometer tests proof of a '"fabric" of reality," and is this simple three-word term, as are the two main ideas in it, aside from being a nice title for a book, rather or not quite eloquent and useful in the way of describing where gravitational waves live and their effects? Regards, Inowen (nlfte) 00:52, 18 January 2018 (UTC)

"Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation"

This part is junk. Either the writer means gravitational waves are a kind of radiation, which they arent; they are distortions in spacetime, or energy within gravitation waves is transformed in accord with a gravitational principle, which is technical and does not belong in the introduction. -Inowen (nlfte) 02:39, 12 September 2018 (UTC)

This does look OK to me. Just as light being a distortion in the electromagnetic field, does not preclude it from being radiation. Graeme Bartlett (talk) 00:57, 17 September 2018 (UTC)

Are gravitational waves real?

Moved to Wikipedia:Reference desk/Science#Are gravitational waves real?

The article leaves no doubt that gravitational waves as "disturbances of spacetime" are real, at least since they have been discovered experimentally (by measurement). I admit that the LIGO experiment has measured real effects; but did these effects say to the experimenter "Hello, here we are, and we are disturbances of spacetime"? I doubt this. Rather the identification of the measured effects as demonstrating the existence of "gravitational waves in the sense of Einstein's general relativity" evidently requires to presuppose Einstein's theory which predicts the existence of spacetime and of these waves as disturbances of it. Without the presupposed ART nobody would ever have understood some unidentified waves in this very sense. The suspicion then is well-founded that the identification results from a logical mistake, say of begging the question, and therefore is unjustified. Ed Dellian2003:D2:9703:5941:A81D:7A1B:AD26:ABD0 (talk) 11:39, 5 November 2018 (UTC)

Discussion moved; please continue there. –Deacon Vorbis (carbon • videos) 15:32, 5 November 2018 (UTC)

Time Dilation

This article should cover the expected effects on gravitational time dilation, not just space. 77.86.117.208 (talk) 09:48, 13 November 2018 (UTC)