![]() | This ![]() It is of interest to the following WikiProjects: | |||||||||||||||||||||||
|
Draft for missing parts:
-- looxix 20:32, 13 April 2003 (UTC)
I can't understand what the top diagram represents. Some text in the caption is badly needed so can some kind person add some, please. For example, what's the golden ball in the middle? I've put the pic here until some is written. Thanks,
Adrian Pingstone 17:28, 1 March 2004 (UTC)
I agree with Adrian that the depiction is more confusing than clarifying, I would suggest removing the galaxy cluster for clarity.
Anyway, I have a detailed account of gravitational lensing, including extragalactic microlensing, in my thesis. There is a section on history that would be suitable for Wikipedia with a bit of editing. Feel free to grab anything from there, I would have submitted it myself, but I don't have the time.... Anyway, I had Sjur Refsdal on the committee and partly advising, and worked with Rudy Schild (whose page on the Twin Quasar is linked), so it has received a lot of scrutiny. Drop me a note on kk@kjernsmo.net if somebody wants the LaTeX source (it's fairly clean). -- Kjetil Kjernsmo — Preceding unsigned comment added by 80.213.226.235 ( talk) 20:48, 28 July 2004 (UTC)
Is the Shapiro effect really relevant when discussing differential time delay between signals from one source? 85.76.129.149 1 July 2005 06:27 (UTC)
Is the page ready to have the 'expert' template removed? Kjetil/his article are 'expert', IMO. Someone just needs to edit. Elvey 21:45, 6 January 2006 (UTC)
Agreed. I would be willing to help out with the sections on cosmology, particularly the weak lensing surveys. Or we could make that a seperate article, as it's a pretty important undertaking in observational cosmology. – Joke 22:34, 3 February 2006 (UTC)
Incidentally, I edit on a pretty fast computer but the animation in the article really seems to bog my web browser down. Does anyone else have this problem? Could we add a link (e.g. click for animation) or make it more efficient or something? – Joke 22:36, 3 February 2006 (UTC)
I took the liberty to edit the text on the simulation, so as to say that the bl.h. passes in front of the galaxy, relative to the observer -- got to be, right? Ulcph 18:46, 29 August 2006 (UTC)
I think using Abell 1689 as an example is not particularly interesting: other clusters like Abell 2218 and Abell 2667 probably have less arcs, but have giant spectacular ones, and one does not have to enlarge the picture to see them : they are just obvious. — Preceding unsigned comment added by 131.215.102.191 ( talk) 15:41, 28 March 2007 (UTC)
I'm going through various Wiki pages (on different subjects) removing references to them as "the Einstein effect". Einstein came up with a whole raft of different effects, and just because someone's referred to a specific effect somewhere as "the Einstein effect" in an understood context, it doesn't mean that the term can be used to identify any specific effect, where the context isn't already known. One might as well talk about "the Einstein equation" ... Which one? E=mc^2? Something to do with SR? GR? Quantum mechanics? If a term doesn't tell the reader which effect is being referred to, without that context, then I don't think we should be presenting it as if it functions as a scientific term with an understood meaning, when that context is missing. No disrespect to Einstein intended here, the problem here is that he discovered so many things: If he'd been an average scientist and only ever discovered one thing, then "the Einstein effect" might be a more meaningful phrase. But it aint. ErkDemon 01:07, 3 September 2007 (UTC)
Gravitational lensing should re-direct here. I would do it but un-sure how. If someone knows and lets me know I will take care of it. Viperix 06:50, 27 September 2007 (UTC)
I'm viewing this page on Firefox 2.0.0.12 (corporate overlords haven't updated me to FF3 yet) and the [edit] links for many of the early sections (e.g. Description, Simulation, History) are drawing to the wrong place. It varies based on the resolution of the browser, but to make a reproducable view, I put it on my non-primary, maximized to the full 1280x1024. In that configuration, [edit] for Description is in the History section, next to the Kitt Peak (National Observatory is on next line) link, [edit] for Simulation is just to the left of the top left corner of the Einstein's Cross picture (within the Explanation in terms of space-time curvature section), and the [edit]s for Applications, Explanation in terms of space-time curvature section *and* History are all where Studying the foreground lenses's [edit] link should be (it is buried a couple paragraphs down).
Viewed in IE7, the [edit] links are in the right place, but the text for the Description section is shunted down to begin just below the Wikimedia Commons sidebar. I'd assume a problem with a CSS/Javascript element not properly supported by FF2/IE7, but I haven't seen problems like this on other pages. Given the FF3 has only been out a month or so, it seems problematic that it screws up in two of the most widely used browsers (though not as badly in IE7).
Initially seen on this version of the page: http://en.wikipedia.org/?title=Gravitational_lens&oldid=230020480 —Preceding unsigned comment added by 38.117.134.222 ( talk) 21:13, 6 August 2008 (UTC)
I tried a rearrangement of the right hand templates, which seems to fix Description's [edit] link. Unfortunately, subsequent images are still disrupting most of the edit links, and I don't want to do a full restructure of the page to fix it (particularly since I'm not sure there isn't a better way of fixing it than screwing with the layout). —Preceding unsigned comment added by 38.117.134.222 ( talk) 21:33, 6 August 2008 (UTC)
Additional Note: Clicking some of the links (edit or otherwise) in FF2 triggers weird behavior, particularly if they are out place or you've been messing with the "Show/Hide" links in the two sidebars. The usual result I've seen is the page reformatting itself (moving the link and other text). This usually means the click does not actually trigger a page transition. This could be a browser problem or a Javascript issue. —Preceding unsigned comment added by 38.117.134.222 ( talk) 21:38, 6 August 2008 (UTC)
FF3 shows same problem as FF2. —Preceding unsigned comment added by 96.224.1.150 ( talk) 23:39, 6 August 2008 (UTC)
http://en.wikipedia.org/wiki/Wmap puts the density parameter within ~4% of spatial flatness
and
http://en.wikipedia.org/wiki/Photon gives an upper bound for the photon as 6 × 10−17 eV/c2
If the geometry of the universe is in fact perfectly Euclidean and the photon mass is indeed non-zero, then gravitational lensing would have no implications for the geometry of the universe, but that doesn't seem to be mentioned here. Neither is the dependence on a development of quantum gravity.
Talk to me! I've an essay due in a week on conventionalism in geometry.
SceaDS ( talk) 23:04, 6 January 2009 (UTC)
It seems to me that a significant proportion of those who read this piece will be left with a continuing confusion.
The standard description of a lens provides a quite reasonable explanation of how sn ordinary lens works on the basis of the interposition of a shaped region of matter with higher refractive index between the source and the image. In the region of a galaxy the density of the interstellar medium, presumably mostly hydrogen, is fairly obviously greater than that of deep space. Hence in the region of a galaxy there will be a roughly spherical optical lens.
Readers who imagine that the overall optical density of the universe includes ordinary optical lenses by virtue of local, approximately spherical, concentrations of gas - crude spherical lenses - will be confused as to why this aspect is entirely ignored in the explanation of gravitationsl lenses. Davy p ( talk) 03:30, 19 June 2009 (UTC)
Could also be just a big sphere of water as well... It has the same effect on light. — Preceding unsigned comment added by 24.96.226.82 ( talk) 14:57, 21 January 2014 (UTC)
Some have proposed an Occam's Razor approach to the gravitational lens situation: light has mass. —Preceding unsigned comment added by 132.228.195.207 ( talk) 17:47, 8 October 2009 (UTC)
Would it be appropriate to add some info about the proposed FOCAL mission to put a telescope at behond 500 AU where it could utilize the sun as a gravitational lens? I came across it here, but I am not an expert on the subject Ant6n ( talk) 01:02, 23 October 2009 (UTC)
As far as I can tell, the History section states that gravitational lensing was discovered in 1919, and then was first discovered in 1979. Can anyone sort this out?-- Heyitspeter ( talk) 21:28, 18 January 2010 (UTC)
Why are references to dark matter stated in such a way that implies that it is a fact? Dark matter is still controversial and mostly because it is merely a hypothetical from a theory of observation. It is not proven, nor is any of the evidence more than mathematical conjectures. References to 'dark matter' (and DE) should not stated as fact. There needs to be some grain of salt! And no - this is NOT the same as the evolution debate. Evolutionary theory has a multitude of PHYSICAL evidence behind it. Please, stay away from this topic wikipedia-moderator-trolls. We already know YOUR opinions. -- 66.223.168.45 ( talk) 00:38, 27 May 2010 (UTC)
Bruce T. Draine had pointed out in 1998 that under certain conditions, "there is considerable similarity between the gravitational lensing and gaseous lensing light curves." He wrote this in Astrophysical Journal Letters. Similar papers have followed. It seems to me that this deserves a section or perhaps a separate topic page, Gas Lensing. Davy p ( talk) 09:42, 22 August 2010 (UTC)
The modern field of gravitational lensing was founded almost single-handedly by Sjur Refsdal. The article should at least mention him. Even though it has its antecedents, imagine an article on relativity not mentioning Einstein, or gravitation not mentioning Newton. —Preceding unsigned comment added by 193.29.76.37 ( talk) 17:18, 28 January 2011 (UTC)
"Since galaxies are intrinsically elliptical and the weak gravitational lensing signal is small". Does the article mean only elliptical galaxies were considered, or that all galaxies including spiral galaxies are non-symmetrical? I presume it is not trying to say that spiral and irregular galaxies are elliptical? Aarghdvaark ( talk) 04:30, 3 February 2012 (UTC)
convex and concave — Preceding unsigned comment added by 106.204.229.164 ( talk) 09:56, 15 April 2012 (UTC)
I've removed from the section "Explanation in terms of space–time curvature" the following text:
Gravitational lensing is a static effect in which gravitational waves don't play any role. The light doesn't "intersect" a gravitational wave, it travels through a static, curved background, at least in the approximation in which the formula given in the text applies. The section would also benefit from some revision and a more extended discussion. -- 131.130.45.12 ( talk) 10:29, 24 April 2012 (UTC)
References
I recommend that a section be added to the article regarding the star GSC 3656-1328 in Cassiopeia, which brightened from approx. mag. 11.5 V to 7.5V in October-November 2006. All evidence indicates that this was a lensing event, and would be the brightest one yet observed, to the best of my knowledge. References: http://www.astronomerstelegram.org/?read=943 and http://adsabs.harvard.edu/full/2007SASS...26...57K — Preceding unsigned comment added by 74.232.81.147 ( talk) 17:34, 4 June 2013 (UTC)
As a lay person, I’ve learned to be wary of metaphor when discussing topics in science. The lede says that a Gravitational Lens is “a distribution of matter ... capable of bending (lensing) the light from the source, as it travels toward the observer.” Is this what’s intended?
What I mean is, I understand that the General Theory explains that the presence of such matter near the path of a photon causes a distortion of spacetime in the matter’s vicinity that makes the photon’s apparent source location change while it yet travels on a spacetime geodesic, i.e. along a generalized straight path through the locally distorted vicinity. Is this correct?
I also understand that the lede’s language should not necessarily assume the mechanism described in the General Theory but rather (merely) the observed phenomenon (despite the history of the development of the concept).
My question is whether the phenomenon can successfully be described as either being “like refraction” (as though the presence of the matter causes the refractive index of empty space to vary in its vicinity; this seems wrong) or alternately that the phenomenon can be predicted from Newtonian gravity by taking the photon to be deflected by the Force given by
or in any other way alternative to the General Theory.
In an associated article ( “Formalism”), I read that “exactly one half” of the true angle of deflection (circumflex-alpha) may be obtained by a “naïve application of Newtonian gravity.”
If the actual observed behavior can’t be obtained in ways such as these, why wouldn’t it be correct for the lede to say
or something like this? If this language is consistent with the General Theory, isn’t it better language? Another way of presenting my point is that I don’t like the metaphor that light “bends” in this sense, due to the effect of the presence of the lump of matter, in place of the idea that spacetime is locally distorted by the lump. In the lede, Is chauvinism in the form of a Newtonian interpretation of the phenomenon superior to chauvinism in the form of the General Theory’s interpretation? It seems to me that the language of the article is in opposition to our presentation of the idea of the geodesic. Rt3368 ( talk) 23:21, 3 July 2013 (UTC)
It might be worth having a section for Einstein Crosses. If such a section is created, the hatnote at Einstein Cross should probably be updated to point directly to the new section. (That is article on a specific quasar named The Einstein Cross, it has a hatnote pointing here for the concept of Einstein Crosses in general.) Alsee ( talk) 22:34, 18 March 2015 (UTC)
It appears to me that there was intended to be a paragraph break in the section "Description" subsection "3. Microlensing", at the third sentence, beginning "The effect is small ..." I wasn't sure, so didn't want to change it myself. Jeff Root ( talk) 17:51, 22 April 2015 (UTC)
This is a question that's been bothering me for a while. In almost all the images of lensing (e.g. File:HST-Smiling-GalaxyClusterSDSS-J1038+4849-20150210.jpg) the background object is bluer than the foreground object. Why is that?
You'd think that since distance = redshift, the lensed object would be redder. Is this a measurement effect (e.g. some UV line being shifted into the visible), a bias effect (lensing focuses blue better), or is this due to some true blueshift (which to my understand shouldn't happen because of the lensing effect, but could maybe be due to something else)?
Headbomb { talk / contribs / physics / books} 13:29, 25 May 2016 (UTC)
delete it, it's silly, but some people mention that option - but updated, because this is a mistake — Preceding unsigned comment added by 2a02:587:410c:4100:2557:aad6:bf3:8a6 ( talk) 20:34, 24 November 2016 (UTC)
In section "Explanation in terms of space–time curvature" the explanation under simulation GIF "Simulated gravitational lensing (black hole passing in front of a background galaxy)" - is misleading your reader and must by change on "Simulated gravitational lensing (black hole passing in front of a background galaxy - what could be seen if an observer stood close to a black hole, not what could be seen if an observer stood far away from a black hole)". This simulation was make of purpose for simulation of a gravitational lens effect in close proximity to the black hole not from an observational perspective in far away. From a far distance this observer will not see the shadow of the black hole at all. RustyBrain ( talk) 15:03, 5 May 2019 (UTC)
I request high-ranking moderator's intervention for the above dispute "Do not mislead readers of this article" RustyBrain ( talk) 15:03, 5 May 2019 (UTC)
Guys, please take a deep breath and calm down.
I don't know about your request for a "high ranking" moderator. WP isn't very much into rank structures. I'm an admin and I've been around a while, but I'm not very much into dispute resolution. That said, I think you are trying to resolve a content dispute here (see
here) and, from what I can see, what needs to be resolved here is a dispute involving differing points of view (see
WP:NPOV). The solution to such a dispute often involves WP policy as explained in
WP:DUE which says, "Neutrality requires that each article or other page in the mainspace fairly represents all significant viewpoints that have been published by reliable sources, in proportion to the prominence of each viewpoint in the published, reliable sources, ...". In general, as I interpret that in practical terms, if differing viewpoints exist which have been covered in published
reliable sources, those differences need to be acknowledged and the acknowledgement needs to be supported by citation of relevant sources. Perhaps the image caption needs a footnote doing that. Can editors who are parties to this dispute agree on such a footnote and on supporting sources to be cited there?
This has been mentioned above, and its relationship to the image disputed here has been questioned. That probably needs to be clarified in nonspecialist terms. Additionally, I'll ping here another editor who I see appearing in the history of the image: @
Alain r: Could you please take a look at this?
.
Wtmitchell
(talk) (earlier Boracay Bill)
13:59, 5 May 2019 (UTC)
This animate GIF https://upload.wikimedia.org/wikipedia/commons/0/03/Black_hole_lensing_web.gif is uploaded by the user /info/en/?search=User_talk:Urbane_Legend who mention /info/en/?search=User:Alain_r but NOT give the RELIABLE source of this simulation. Now you can open https://arxiv.org/pdf/1511.06025.pdf on page 27 and think again WHO IS THE AUTHOR OF THIS GIF and WHO UPLOAD IT? This animated GIF violates the WIKI rules because author publish it himself. And it will soon be shown that it does not even correspond to reality. He has spread his own counterfeit simulations to such an extent that they have almost become a common black hole and gravity lens symbol for general public and media. This person must be stopped to do so. This GIF must be totally removed from Wikipedia. RustyBrain ( talk) 14:56, 5 May 2019 (UTC)
I noticed one cite in this paper with problems. It supports the assertion, "Classical physics also predicts the bending of light, but only half that predicted by general relativity" and renders as:
Cf. Kennefick 2005 for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see Ohanian & Ruffini 1994, ch. 4.3 . For the most precise direct modern observations using quasars, cf. Shapiro et al. 2004 .
It throws an error reading Harv error: link from CITEREFKennefick2005 doesn't point to any citation.
I think that I have tracked down the Shapiro 2004 item cited there. With that worked in, this cite would render as:
Cf. Kennefick 2005 for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see Ohanian & Ruffini 1994, ch. 4.3 . For the most precise direct modern observations using quasars cf. S. S. Shapiro; J. L. Davis; D. E. Lebach; J. S. Gregory (March 26, 2004). "Measurement of the solar gravitational deflection of radio waves using geodetic very-long-baseline interferometry data, 1979-1999". Physical Review Letters. 92 (12).
However, that still leaves the Kennefick 2005 cite as an orphan. I think I've found it, but I'm not sure. If I'm right and add that to the cite, it might render as:
Cf. Kennefick, Daniel (2 February 2012), "9. Not Only Because of Theory: Dyson, Eddington and the Competing Myths of the 1919 Eclipse Expedition", in Lehner, Christoph; Renn, Jürgen; Schemmel, Matthias (eds.), Einstein and the Changing Worldviews of Physics, Springer Science & Business Media, ISBN 978-0-8176-4940-1
{{ citation}}
: External link in( help); Unknown parameter
|chapterurl=
|chapterurl=
ignored (|chapter-url=
suggested) ( help) for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see Ohanian & Ruffini 1994, ch. 4.3 . For the most precise direct modern observations using quasars, cf. S. S. Shapiro; J. L. Davis; D. E. Lebach; J. S. Gregory (March 26, 2004). "Measurement of the solar gravitational deflection of radio waves using geodetic very-long-baseline interferometry data, 1979-1999". Physical Review Letters. 92 (12).
That seems a bit double-barrelled. It might be broken up a bit.
Also, I came across another Kennefick 2005 item which might be of interest: "Einstein Versus the Physical Review" (PDF). Physics Today. 58 (9): 43–48. September 2005.
If nobody objects, I might try to work these into the article. Alternatively (better), perhaps someone who knows more about this stuff than I do might do it. Comments? Corrections? Wtmitchell (talk) (earlier Boracay Bill) 22:35, 1 June 2019 (UTC)
User Pacomc999 ( talk · contribs) twice removed (i.m.o.) properly sourced content here and here, so I restored and added two more sources
Comments welcome. - DVdm ( talk) 19:20, 9 January 2022 (UTC)
No, no, the Newtonian theory of light is absolutely not within classical physics. When people identity Newtonian physics with classical physics they do it because Newtonian mechanics are an fundamental part of classical physics. However, when it comes to light it it utterly wrong, even if it managed to predict some isolated things like this. I showed this article to two other phycisists from my masters and they were equally puzzled with the statement for the same reason. Pacomc999 ( talk) 21:40, 9 January 2022 (UTC)
Also I just realised another person pointed this out already ""(Classical physics also predicts the bending of light" > not really, only primitive physics when particles of light still had a mass, i.e. in Newton/Von Soldner theory? " so there is consensus about it being wrong Pacomc999 ( talk) 21:50, 9 January 2022 (UTC)
I’m too lazy to figure out how DatGuy0309 ( talk) 23:01, 11 July 2022 (UTC)
I’m too lazy to figure out how DatGuy0309 ( talk) 23:02, 11 July 2022 (UTC)
![]() | This ![]() It is of interest to the following WikiProjects: | |||||||||||||||||||||||
|
Draft for missing parts:
-- looxix 20:32, 13 April 2003 (UTC)
I can't understand what the top diagram represents. Some text in the caption is badly needed so can some kind person add some, please. For example, what's the golden ball in the middle? I've put the pic here until some is written. Thanks,
Adrian Pingstone 17:28, 1 March 2004 (UTC)
I agree with Adrian that the depiction is more confusing than clarifying, I would suggest removing the galaxy cluster for clarity.
Anyway, I have a detailed account of gravitational lensing, including extragalactic microlensing, in my thesis. There is a section on history that would be suitable for Wikipedia with a bit of editing. Feel free to grab anything from there, I would have submitted it myself, but I don't have the time.... Anyway, I had Sjur Refsdal on the committee and partly advising, and worked with Rudy Schild (whose page on the Twin Quasar is linked), so it has received a lot of scrutiny. Drop me a note on kk@kjernsmo.net if somebody wants the LaTeX source (it's fairly clean). -- Kjetil Kjernsmo — Preceding unsigned comment added by 80.213.226.235 ( talk) 20:48, 28 July 2004 (UTC)
Is the Shapiro effect really relevant when discussing differential time delay between signals from one source? 85.76.129.149 1 July 2005 06:27 (UTC)
Is the page ready to have the 'expert' template removed? Kjetil/his article are 'expert', IMO. Someone just needs to edit. Elvey 21:45, 6 January 2006 (UTC)
Agreed. I would be willing to help out with the sections on cosmology, particularly the weak lensing surveys. Or we could make that a seperate article, as it's a pretty important undertaking in observational cosmology. – Joke 22:34, 3 February 2006 (UTC)
Incidentally, I edit on a pretty fast computer but the animation in the article really seems to bog my web browser down. Does anyone else have this problem? Could we add a link (e.g. click for animation) or make it more efficient or something? – Joke 22:36, 3 February 2006 (UTC)
I took the liberty to edit the text on the simulation, so as to say that the bl.h. passes in front of the galaxy, relative to the observer -- got to be, right? Ulcph 18:46, 29 August 2006 (UTC)
I think using Abell 1689 as an example is not particularly interesting: other clusters like Abell 2218 and Abell 2667 probably have less arcs, but have giant spectacular ones, and one does not have to enlarge the picture to see them : they are just obvious. — Preceding unsigned comment added by 131.215.102.191 ( talk) 15:41, 28 March 2007 (UTC)
I'm going through various Wiki pages (on different subjects) removing references to them as "the Einstein effect". Einstein came up with a whole raft of different effects, and just because someone's referred to a specific effect somewhere as "the Einstein effect" in an understood context, it doesn't mean that the term can be used to identify any specific effect, where the context isn't already known. One might as well talk about "the Einstein equation" ... Which one? E=mc^2? Something to do with SR? GR? Quantum mechanics? If a term doesn't tell the reader which effect is being referred to, without that context, then I don't think we should be presenting it as if it functions as a scientific term with an understood meaning, when that context is missing. No disrespect to Einstein intended here, the problem here is that he discovered so many things: If he'd been an average scientist and only ever discovered one thing, then "the Einstein effect" might be a more meaningful phrase. But it aint. ErkDemon 01:07, 3 September 2007 (UTC)
Gravitational lensing should re-direct here. I would do it but un-sure how. If someone knows and lets me know I will take care of it. Viperix 06:50, 27 September 2007 (UTC)
I'm viewing this page on Firefox 2.0.0.12 (corporate overlords haven't updated me to FF3 yet) and the [edit] links for many of the early sections (e.g. Description, Simulation, History) are drawing to the wrong place. It varies based on the resolution of the browser, but to make a reproducable view, I put it on my non-primary, maximized to the full 1280x1024. In that configuration, [edit] for Description is in the History section, next to the Kitt Peak (National Observatory is on next line) link, [edit] for Simulation is just to the left of the top left corner of the Einstein's Cross picture (within the Explanation in terms of space-time curvature section), and the [edit]s for Applications, Explanation in terms of space-time curvature section *and* History are all where Studying the foreground lenses's [edit] link should be (it is buried a couple paragraphs down).
Viewed in IE7, the [edit] links are in the right place, but the text for the Description section is shunted down to begin just below the Wikimedia Commons sidebar. I'd assume a problem with a CSS/Javascript element not properly supported by FF2/IE7, but I haven't seen problems like this on other pages. Given the FF3 has only been out a month or so, it seems problematic that it screws up in two of the most widely used browsers (though not as badly in IE7).
Initially seen on this version of the page: http://en.wikipedia.org/?title=Gravitational_lens&oldid=230020480 —Preceding unsigned comment added by 38.117.134.222 ( talk) 21:13, 6 August 2008 (UTC)
I tried a rearrangement of the right hand templates, which seems to fix Description's [edit] link. Unfortunately, subsequent images are still disrupting most of the edit links, and I don't want to do a full restructure of the page to fix it (particularly since I'm not sure there isn't a better way of fixing it than screwing with the layout). —Preceding unsigned comment added by 38.117.134.222 ( talk) 21:33, 6 August 2008 (UTC)
Additional Note: Clicking some of the links (edit or otherwise) in FF2 triggers weird behavior, particularly if they are out place or you've been messing with the "Show/Hide" links in the two sidebars. The usual result I've seen is the page reformatting itself (moving the link and other text). This usually means the click does not actually trigger a page transition. This could be a browser problem or a Javascript issue. —Preceding unsigned comment added by 38.117.134.222 ( talk) 21:38, 6 August 2008 (UTC)
FF3 shows same problem as FF2. —Preceding unsigned comment added by 96.224.1.150 ( talk) 23:39, 6 August 2008 (UTC)
http://en.wikipedia.org/wiki/Wmap puts the density parameter within ~4% of spatial flatness
and
http://en.wikipedia.org/wiki/Photon gives an upper bound for the photon as 6 × 10−17 eV/c2
If the geometry of the universe is in fact perfectly Euclidean and the photon mass is indeed non-zero, then gravitational lensing would have no implications for the geometry of the universe, but that doesn't seem to be mentioned here. Neither is the dependence on a development of quantum gravity.
Talk to me! I've an essay due in a week on conventionalism in geometry.
SceaDS ( talk) 23:04, 6 January 2009 (UTC)
It seems to me that a significant proportion of those who read this piece will be left with a continuing confusion.
The standard description of a lens provides a quite reasonable explanation of how sn ordinary lens works on the basis of the interposition of a shaped region of matter with higher refractive index between the source and the image. In the region of a galaxy the density of the interstellar medium, presumably mostly hydrogen, is fairly obviously greater than that of deep space. Hence in the region of a galaxy there will be a roughly spherical optical lens.
Readers who imagine that the overall optical density of the universe includes ordinary optical lenses by virtue of local, approximately spherical, concentrations of gas - crude spherical lenses - will be confused as to why this aspect is entirely ignored in the explanation of gravitationsl lenses. Davy p ( talk) 03:30, 19 June 2009 (UTC)
Could also be just a big sphere of water as well... It has the same effect on light. — Preceding unsigned comment added by 24.96.226.82 ( talk) 14:57, 21 January 2014 (UTC)
Some have proposed an Occam's Razor approach to the gravitational lens situation: light has mass. —Preceding unsigned comment added by 132.228.195.207 ( talk) 17:47, 8 October 2009 (UTC)
Would it be appropriate to add some info about the proposed FOCAL mission to put a telescope at behond 500 AU where it could utilize the sun as a gravitational lens? I came across it here, but I am not an expert on the subject Ant6n ( talk) 01:02, 23 October 2009 (UTC)
As far as I can tell, the History section states that gravitational lensing was discovered in 1919, and then was first discovered in 1979. Can anyone sort this out?-- Heyitspeter ( talk) 21:28, 18 January 2010 (UTC)
Why are references to dark matter stated in such a way that implies that it is a fact? Dark matter is still controversial and mostly because it is merely a hypothetical from a theory of observation. It is not proven, nor is any of the evidence more than mathematical conjectures. References to 'dark matter' (and DE) should not stated as fact. There needs to be some grain of salt! And no - this is NOT the same as the evolution debate. Evolutionary theory has a multitude of PHYSICAL evidence behind it. Please, stay away from this topic wikipedia-moderator-trolls. We already know YOUR opinions. -- 66.223.168.45 ( talk) 00:38, 27 May 2010 (UTC)
Bruce T. Draine had pointed out in 1998 that under certain conditions, "there is considerable similarity between the gravitational lensing and gaseous lensing light curves." He wrote this in Astrophysical Journal Letters. Similar papers have followed. It seems to me that this deserves a section or perhaps a separate topic page, Gas Lensing. Davy p ( talk) 09:42, 22 August 2010 (UTC)
The modern field of gravitational lensing was founded almost single-handedly by Sjur Refsdal. The article should at least mention him. Even though it has its antecedents, imagine an article on relativity not mentioning Einstein, or gravitation not mentioning Newton. —Preceding unsigned comment added by 193.29.76.37 ( talk) 17:18, 28 January 2011 (UTC)
"Since galaxies are intrinsically elliptical and the weak gravitational lensing signal is small". Does the article mean only elliptical galaxies were considered, or that all galaxies including spiral galaxies are non-symmetrical? I presume it is not trying to say that spiral and irregular galaxies are elliptical? Aarghdvaark ( talk) 04:30, 3 February 2012 (UTC)
convex and concave — Preceding unsigned comment added by 106.204.229.164 ( talk) 09:56, 15 April 2012 (UTC)
I've removed from the section "Explanation in terms of space–time curvature" the following text:
Gravitational lensing is a static effect in which gravitational waves don't play any role. The light doesn't "intersect" a gravitational wave, it travels through a static, curved background, at least in the approximation in which the formula given in the text applies. The section would also benefit from some revision and a more extended discussion. -- 131.130.45.12 ( talk) 10:29, 24 April 2012 (UTC)
References
I recommend that a section be added to the article regarding the star GSC 3656-1328 in Cassiopeia, which brightened from approx. mag. 11.5 V to 7.5V in October-November 2006. All evidence indicates that this was a lensing event, and would be the brightest one yet observed, to the best of my knowledge. References: http://www.astronomerstelegram.org/?read=943 and http://adsabs.harvard.edu/full/2007SASS...26...57K — Preceding unsigned comment added by 74.232.81.147 ( talk) 17:34, 4 June 2013 (UTC)
As a lay person, I’ve learned to be wary of metaphor when discussing topics in science. The lede says that a Gravitational Lens is “a distribution of matter ... capable of bending (lensing) the light from the source, as it travels toward the observer.” Is this what’s intended?
What I mean is, I understand that the General Theory explains that the presence of such matter near the path of a photon causes a distortion of spacetime in the matter’s vicinity that makes the photon’s apparent source location change while it yet travels on a spacetime geodesic, i.e. along a generalized straight path through the locally distorted vicinity. Is this correct?
I also understand that the lede’s language should not necessarily assume the mechanism described in the General Theory but rather (merely) the observed phenomenon (despite the history of the development of the concept).
My question is whether the phenomenon can successfully be described as either being “like refraction” (as though the presence of the matter causes the refractive index of empty space to vary in its vicinity; this seems wrong) or alternately that the phenomenon can be predicted from Newtonian gravity by taking the photon to be deflected by the Force given by
or in any other way alternative to the General Theory.
In an associated article ( “Formalism”), I read that “exactly one half” of the true angle of deflection (circumflex-alpha) may be obtained by a “naïve application of Newtonian gravity.”
If the actual observed behavior can’t be obtained in ways such as these, why wouldn’t it be correct for the lede to say
or something like this? If this language is consistent with the General Theory, isn’t it better language? Another way of presenting my point is that I don’t like the metaphor that light “bends” in this sense, due to the effect of the presence of the lump of matter, in place of the idea that spacetime is locally distorted by the lump. In the lede, Is chauvinism in the form of a Newtonian interpretation of the phenomenon superior to chauvinism in the form of the General Theory’s interpretation? It seems to me that the language of the article is in opposition to our presentation of the idea of the geodesic. Rt3368 ( talk) 23:21, 3 July 2013 (UTC)
It might be worth having a section for Einstein Crosses. If such a section is created, the hatnote at Einstein Cross should probably be updated to point directly to the new section. (That is article on a specific quasar named The Einstein Cross, it has a hatnote pointing here for the concept of Einstein Crosses in general.) Alsee ( talk) 22:34, 18 March 2015 (UTC)
It appears to me that there was intended to be a paragraph break in the section "Description" subsection "3. Microlensing", at the third sentence, beginning "The effect is small ..." I wasn't sure, so didn't want to change it myself. Jeff Root ( talk) 17:51, 22 April 2015 (UTC)
This is a question that's been bothering me for a while. In almost all the images of lensing (e.g. File:HST-Smiling-GalaxyClusterSDSS-J1038+4849-20150210.jpg) the background object is bluer than the foreground object. Why is that?
You'd think that since distance = redshift, the lensed object would be redder. Is this a measurement effect (e.g. some UV line being shifted into the visible), a bias effect (lensing focuses blue better), or is this due to some true blueshift (which to my understand shouldn't happen because of the lensing effect, but could maybe be due to something else)?
Headbomb { talk / contribs / physics / books} 13:29, 25 May 2016 (UTC)
delete it, it's silly, but some people mention that option - but updated, because this is a mistake — Preceding unsigned comment added by 2a02:587:410c:4100:2557:aad6:bf3:8a6 ( talk) 20:34, 24 November 2016 (UTC)
In section "Explanation in terms of space–time curvature" the explanation under simulation GIF "Simulated gravitational lensing (black hole passing in front of a background galaxy)" - is misleading your reader and must by change on "Simulated gravitational lensing (black hole passing in front of a background galaxy - what could be seen if an observer stood close to a black hole, not what could be seen if an observer stood far away from a black hole)". This simulation was make of purpose for simulation of a gravitational lens effect in close proximity to the black hole not from an observational perspective in far away. From a far distance this observer will not see the shadow of the black hole at all. RustyBrain ( talk) 15:03, 5 May 2019 (UTC)
I request high-ranking moderator's intervention for the above dispute "Do not mislead readers of this article" RustyBrain ( talk) 15:03, 5 May 2019 (UTC)
Guys, please take a deep breath and calm down.
I don't know about your request for a "high ranking" moderator. WP isn't very much into rank structures. I'm an admin and I've been around a while, but I'm not very much into dispute resolution. That said, I think you are trying to resolve a content dispute here (see
here) and, from what I can see, what needs to be resolved here is a dispute involving differing points of view (see
WP:NPOV). The solution to such a dispute often involves WP policy as explained in
WP:DUE which says, "Neutrality requires that each article or other page in the mainspace fairly represents all significant viewpoints that have been published by reliable sources, in proportion to the prominence of each viewpoint in the published, reliable sources, ...". In general, as I interpret that in practical terms, if differing viewpoints exist which have been covered in published
reliable sources, those differences need to be acknowledged and the acknowledgement needs to be supported by citation of relevant sources. Perhaps the image caption needs a footnote doing that. Can editors who are parties to this dispute agree on such a footnote and on supporting sources to be cited there?
This has been mentioned above, and its relationship to the image disputed here has been questioned. That probably needs to be clarified in nonspecialist terms. Additionally, I'll ping here another editor who I see appearing in the history of the image: @
Alain r: Could you please take a look at this?
.
Wtmitchell
(talk) (earlier Boracay Bill)
13:59, 5 May 2019 (UTC)
This animate GIF https://upload.wikimedia.org/wikipedia/commons/0/03/Black_hole_lensing_web.gif is uploaded by the user /info/en/?search=User_talk:Urbane_Legend who mention /info/en/?search=User:Alain_r but NOT give the RELIABLE source of this simulation. Now you can open https://arxiv.org/pdf/1511.06025.pdf on page 27 and think again WHO IS THE AUTHOR OF THIS GIF and WHO UPLOAD IT? This animated GIF violates the WIKI rules because author publish it himself. And it will soon be shown that it does not even correspond to reality. He has spread his own counterfeit simulations to such an extent that they have almost become a common black hole and gravity lens symbol for general public and media. This person must be stopped to do so. This GIF must be totally removed from Wikipedia. RustyBrain ( talk) 14:56, 5 May 2019 (UTC)
I noticed one cite in this paper with problems. It supports the assertion, "Classical physics also predicts the bending of light, but only half that predicted by general relativity" and renders as:
Cf. Kennefick 2005 for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see Ohanian & Ruffini 1994, ch. 4.3 . For the most precise direct modern observations using quasars, cf. Shapiro et al. 2004 .
It throws an error reading Harv error: link from CITEREFKennefick2005 doesn't point to any citation.
I think that I have tracked down the Shapiro 2004 item cited there. With that worked in, this cite would render as:
Cf. Kennefick 2005 for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see Ohanian & Ruffini 1994, ch. 4.3 . For the most precise direct modern observations using quasars cf. S. S. Shapiro; J. L. Davis; D. E. Lebach; J. S. Gregory (March 26, 2004). "Measurement of the solar gravitational deflection of radio waves using geodetic very-long-baseline interferometry data, 1979-1999". Physical Review Letters. 92 (12).
However, that still leaves the Kennefick 2005 cite as an orphan. I think I've found it, but I'm not sure. If I'm right and add that to the cite, it might render as:
Cf. Kennefick, Daniel (2 February 2012), "9. Not Only Because of Theory: Dyson, Eddington and the Competing Myths of the 1919 Eclipse Expedition", in Lehner, Christoph; Renn, Jürgen; Schemmel, Matthias (eds.), Einstein and the Changing Worldviews of Physics, Springer Science & Business Media, ISBN 978-0-8176-4940-1
{{ citation}}
: External link in( help); Unknown parameter
|chapterurl=
|chapterurl=
ignored (|chapter-url=
suggested) ( help) for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see Ohanian & Ruffini 1994, ch. 4.3 . For the most precise direct modern observations using quasars, cf. S. S. Shapiro; J. L. Davis; D. E. Lebach; J. S. Gregory (March 26, 2004). "Measurement of the solar gravitational deflection of radio waves using geodetic very-long-baseline interferometry data, 1979-1999". Physical Review Letters. 92 (12).
That seems a bit double-barrelled. It might be broken up a bit.
Also, I came across another Kennefick 2005 item which might be of interest: "Einstein Versus the Physical Review" (PDF). Physics Today. 58 (9): 43–48. September 2005.
If nobody objects, I might try to work these into the article. Alternatively (better), perhaps someone who knows more about this stuff than I do might do it. Comments? Corrections? Wtmitchell (talk) (earlier Boracay Bill) 22:35, 1 June 2019 (UTC)
User Pacomc999 ( talk · contribs) twice removed (i.m.o.) properly sourced content here and here, so I restored and added two more sources
Comments welcome. - DVdm ( talk) 19:20, 9 January 2022 (UTC)
No, no, the Newtonian theory of light is absolutely not within classical physics. When people identity Newtonian physics with classical physics they do it because Newtonian mechanics are an fundamental part of classical physics. However, when it comes to light it it utterly wrong, even if it managed to predict some isolated things like this. I showed this article to two other phycisists from my masters and they were equally puzzled with the statement for the same reason. Pacomc999 ( talk) 21:40, 9 January 2022 (UTC)
Also I just realised another person pointed this out already ""(Classical physics also predicts the bending of light" > not really, only primitive physics when particles of light still had a mass, i.e. in Newton/Von Soldner theory? " so there is consensus about it being wrong Pacomc999 ( talk) 21:50, 9 January 2022 (UTC)
I’m too lazy to figure out how DatGuy0309 ( talk) 23:01, 11 July 2022 (UTC)
I’m too lazy to figure out how DatGuy0309 ( talk) 23:02, 11 July 2022 (UTC)