Talk:Gravitational wave

message: 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)
thread_title:  Quantum gravity, wave-particle aspects, and graviton 

message: 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)
thread_title:  Einstein’s Field Equations in Wave Form 

message: 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)
replies: text: 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)
replies: text: 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)
replies: text: 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)
thread_title:  "Mathematics" section 

message: An anonymous comment under the Talk:Gravitational wave/Archive 5#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)
replies: text: 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)

text: 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)

text: 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)

text: 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)
thread_title:  Secondary effects 

message: 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)
replies: text: 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)
replies: text: It is harder to visualize than dipole fields like EM waves. You can see from the polarization videos that it is most sensitive when the axes are parallel to the detector axes.  That is, the + mode is detected, while the 45 degree rotated X mode is not. Coming from other directions, it depends on the components along the axes. Gah4 (talk) 09:41, 1 July 2020 (UTC)
thread_title:  Directional sensitivity of the Interferometer ? 

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thread_title:  External links modified 

message: 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)
thread_title:  Gravitational wave astronomy 

message: 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)
replies: text: 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)
replies: text: This is confusing. Waves are commonly described by wavelength. That is, we say size when we should say wavelength. In the case of electromagnetic waves, there is no ambiguity. Gravitational waves have a wavelength, and also an amplitude, where the latter can also be given as a length ratio, or given an interferometer arm length, the amplitude is a length, but unrelated to wavelength. Gah4 (talk) 09:46, 1 July 2020 (UTC)
thread_title:  Effects of Passing, probable error 

message: 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)
thread_title:  Proof 

message: 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)
replies: text: 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)
thread_title:  "Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation" 

message: 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)
thread_title:  Time Dilation 

message: Hello everyone. As mentioned in the title, such operation would alter the meaning a bit and most importantly, suit the definition of the article nowadays such as: "In physics, gravitational radiation refers to the wave (or its quantum, gravitons) of the gravitational field, propagating (radiating) through space, carrying gravitational radiant energy." I would like to hear anyone's reply.
Dominic3203 (talk) 09:25, 30 January 2019 (UTC)
thread_title:  Moving Gravitational wave to Gravitational radiation for better understanding 

message: A Lagrangian point exists midway between two equal masses where their gravitational field cancel. I see no sign of cancellation between the black holes persisting in the simulation video. Is this correct? DroneB (talk) 20:41, 7 May 2019 (UTC)
thread_title:  Langrangian point between colliding black holes 

message: The article should include an explanation of the difference between spacetime and gravity. In the rod&bead experiment it is unclear why the gravitational waves would affect just the beads along the rod and not the space housing the atoms of the rod itself  (and therefore the rod) as well. Gravitational waves are disturbances in spacetime, why affect and move just the beads and not the space housing the atoms of the rod (and the space anywhere the rod may be attached for that matter)?  86.93.208.34 (talk) 00:49, 12 May 2020 (UTC)
thread_title:  Difference between spacetime and gravity 

message: The section on redshift has a few , and I might see if I can find some. In the case of light, redshift is useful as we can compare spectral lines to known lines, and compute the redshift. In the case of GW, there are no spectral lines, so there is nothing to compare. Presumably the physics requires it, but it doesn't seem so useful. Gah4 (talk) 01:53, 26 November 2020 (UTC)
thread_title:  redshift 

message: Earth-sized interferometry isn't big enough for very long primordial gravitational wave detection (it has a cut-off [frequency limit]). Write more. Ask NASA and CNSA (physicists are friendly).
::future missions  — Preceding unsigned comment added by 2A02:587:411F:F7D5:D013:D83D:B586:E11E (talk) 17:26, 30 April 2021 (UTC)
thread_title:  3 space-probe laser interferometric array for very long primordial gravitational wave detection 

message: Recently the North American Nanohertz Observatory for Gravitational Waves announced the successful culmination of 50 years of development of the idea of detecting gravitational waves by pulsar observations. Someone removed the reference to the research consortium and replaced it with the non-specific passive tense "was claimed to be detected", despite the consortium being clearly identified in the reference. This is not good Wikipedia practice! Wikilinking the consortium would have been, so I have done so in a new edit. Elroch (talk) 19:57, 1 July 2023 (UTC)
replies: text: The text about this appeared like a press release promoting North American Nanohertz Observatory for Gravitational Waves. Since this was a joint project it is WP:UNDUE to just mention one part of the collaboration. The focus of the article should be on the findings not the organisation. Graeme Bartlett (talk) 22:12, 1 July 2023 (UTC)
replies: text: It is of course entirely normal practice to credit the scientist, research group, project, organisation or collaboration that achieved and published an advance in knowledge. I am sure you will agree that the solution was to credit others contributing to the same advance, as User:Hfst has commendably done. Elroch (talk) 12:58, 4 July 2023 (UTC)
thread_title:  Don't remove information about sources of results