Talk:Gravitational lens

Missing Parts
Draft for missing parts: -- looxix 20:32, 13 April 2003 (UTC)
 * 1) note about famous un-scientific experiment
 * 2) Missing: light refraction/optical lenses/gravitational lenses
 * 3) Missing: not only visible light but generaly any radiation (this is in now)
 * 4) Missing: info about the weakness of this effect
 * 5) Missing: schema
 * 6) Missing: images (this is in now)
 * 7) Astronomical Applications
 * 8) Magnification -> study the source of the light
 * 9) Another use of these lensing systems is the study of the distribution of masses that are doing the deflection.
 * 10) This is a (classic) inverse problem: what distribution of masses can distort the light of a distant source into the picture I see in my telescope?
 * 11) Indirect method to study theses objects which may be indetectable by others means. These results may provide an estimate of the amount of dark matter there is in the Universe.
 * Now covered astronomical applications, and the way it affects any radiation. EddEdmondson 11:44, 31 March 2004 (UTC)

Top diagram
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)


 * Kjetil!. It is an absolutly extrodinary picture but a bit too complex for the discussion. — Preceding unsigned comment added by Artoftransformation (talk • contribs) 00:23, 6 November 2005 (UTC)

Shapiro effect
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)
 * Well, the delay may be tiny, but its existence has large implications. Elvey 21:45, 6 January 2006 (UTC)
 * If the Shapiro effect didn't exist then there would be no lens effect, as the time delay would become independent of the distribution of mass in the lens. The time delay surface would be parabolic and you'd see only what would be observed without a grav. lens in the way. There would be no distortion and no multiple imaging. — Preceding unsigned comment added by 84.65.36.114 (talk) 16:31, 2 February 2006 (UTC)

'Expert' template
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)


 * Article is still unsatisfactory in some respect. Will try to improve it next week. Alain Riazuelo 15:47, 7 January 2006 (UTC)


 * I want to completely rewrite this myself when I get a chance. There are some errors, misemphases, etc.  See the review paper at the Living Reviews of Relativity website, standard monographs on lensing, literature on strong and weak-field lensing, etc.  When I get a chance I might start by creating a todo list (I'll make sure to look at the comments by Iooix for this). ---CH 21:54, 3 February 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)

13MB GIF
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 agree, do we really need a 13mb (!!!!) GIF image in the main article page? Nexx au 15:55, 5 February 2006 (UTC)


 * Incredible. The animation doesn't look that cool – surely there must be a way to make it smaller? –Joke 00:02, 7 February 2006 (UTC)


 * Removed the animation from this page, and replaced it with a link. It is too heavy. There is people on slow computers and modems out there. Besides, I'm pretty sure it'd take less space as a video file (i.e ogg theora, xvid or whatever) than as a gif. I'll look into transcoding it. vidarlo 21:31, 15 April 2006 (UTC)


 * It will be an easy matter to optimise this gif to a more practical size. It'll have to sacrifice quality, but the link to the higher-quality version can stand should anyone want to see it. Then we can have the gif back in the article. I'll do it myself shortly. ▫ UrbaneLegend talk 18:44, 18 May 2006 (UTC)


 * As a suggestion, maybe cut out the front and back, I think you can kill a good number of frames that don't really add to it. --Falcorian (talk) 19:56, 18 May 2006 (UTC)


 * I was thinking just that. I've trimmed the front 10 and the back 30 frames of the animation (so only the relevant distortion and return to normal appearance is seen). Also, every second frame has then been removed, the number of colours has been reduced to 128, and the animation shrunk to 75% of original size. I don't think the loss of quality is that severe. Have a look. It's now only 714KB. ▫ UrbaneLegend talk 22:35, 18 May 2006 (UTC)
 * Looks great! --Falcorian (talk) 00:29, 19 May 2006 (UTC)
 * I'll put the reduced-size animation back in the main article. ▫ UrbaneLegend talk 09:45, 19 May 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)

Abell 1689 not the best example
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)

Delete "Einstein effect" ref.
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)
 * PS: for the benefit of any poor soul trying to search for "The Einstein effect" on Wikipedia, the existing disambiguation page (which points here as well as to some other pages) should probably sort them out. ErkDemon 01:12, 3 September 2007 (UTC)

Re-direct
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)
 * never mind figured it out. Viperix 07:51, 2 October 2007 (UTC)

Edit links - CSS/Javascript problem?
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/w/index.php?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)

Lensing due to curved space-time or non-zero photon mass?
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)

Gas Lensing
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)


 * I had noticed the absence of any discussion of temperature and density with regard to refractive index on the pages on refraction, temperature and density; the summary of the effects of temperature even omit mention of this. I had wondered at the potential effects of temperature variation in atmospheric gases on optical refraction. A corrolary is the absence of any discussion in these relativity items on effective index of refraction, ie. the correlation of apparent displacement due to spacetime curvature with an optical IOR; or, more colloquially, noting that the Eddington experiment could be easily reproduced in the absence of the eclipsed sun using an appropriate lens or glass of water, suggesting a correlating IOR. A paper that came up in a quick search can be found here: https://is.muni.cz/th/9844/prif_d/reaction_to_oponent_2.pdf. Again, like the absent details regarding temp, density and refraction, seems a bit of an oversight (regardless of the effects of variations in the density of the interstellar medium on optical refraction). 31.55.1.247 (talk) 20:17, 28 September 2016 (UTC)

Counter Theories
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)
 * That theory makes falsifiable predictions, which have been shown to be incorrect. --Falcorian (talk) 18:05, 8 October 2009 (UTC)
 * Light doesn't need to be affected by gravity, it only needs to affected by something. Why is there no mention of the possibility that plasma, although minimal, has an affect as a normal gas would, in producing light distortions around solar and gas bodies? --66.223.168.45 (talk) 00:44, 27 May 2010 (UTC)
 * Bruce T. Draine has done work on Lensing of Stars by Spherical Gas Clouds. "If the gas clouds are dust-free and approximately isothermal, they will produce magnification events with light curves which resemble those resulting from gravitational lensing by a point source. Hence it is conceivable that some of the observed microlensing events might in fact be due to gaseous rather than gravitational lenses." Davy p (talk) 09:17, 22 August 2010 (UTC)

Focal Mission
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)

History discrepancy
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)
 * The 1919 reference is confirmation that mass bends the path of light. The 1979 discovery is a Gravitational Lens. --Falcorian (talk) 05:43, 19 January 2010 (UTC)
 * I noticed the same contradiction. How could you possibly confirm the existence of gravitational lensing without discovering a gravitational lens?? A star is, of course, a gravitational lens, exactly as a galaxy is. — Preceding unsigned comment added by 201.187.75.218 (talk) 09:33, 5 October 2014 (UTC)

Dark Matter?!?
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)
 * Please be civil. You seem to have misunderstood the theory of dark matter. Dark matter is the name given to a gravitational occurrence with reliable mathematical behavior, but which has other properties that are as of yet undefined. There is no debate in the scientific community about the existence of this phenomenon; debate only exists about its specifics. This article makes no inappropriate or unfounded statements about dark matter. Somnambulent (talk) 20:17, 3 September 2010 (UTC)
 * Ouch that's a harsh reply. It's mostly the big-bang theory that requires dark matter hypothetically. Alternative theories exist. Even alternative big-bang theories that don't rely on dark matter. And one needs only read other Wikipedia articles to find this out. Give the man a break. Admit the big-bang theory is only a theory, and thus dark matter is hypothetical. Wikipedia should be a place of neutrality, not an inquisition-like institution... I'm not saying it is, I'm just saying it could become it if we don't care enough. And science shouldn't make the same mistakes as religions did in the past. Just saying... 80.215.43.88 (talk) 16:22, 25 July 2022 (UTC)

Lensing of Stars by Gas Clouds
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)

Refsdal
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)

intrinsically elliptical galaxies
"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)

lens
convex and concave — Preceding unsigned comment added by 106.204.229.164 (talk) 09:56, 15 April 2012 (UTC)

No wave!
I've removed from the section "Explanation in terms of space–time curvature" the following text:
 * Some care needs to be taken in defining this distance because gravity is not instantaneous: like light, it propagates at speed c. The path of the gravitational wave and the electromagnetic radiation intersect at specific space–time coordinates, and the lensing is determined by the component of the incident gravitational wave perpendicular to the direction of the electromagnetic radiation's motion.

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)


 * Absolutely. But many people, including in high level vulgarisation, mix up gravitational waves with some sort of propagation of gravity, often using "gravity waves" as their mental bridge between the two. In my articles https://kn0l.wordpress.com/la-gravite-est-elle-instantanee/ (in French) I show how frequent this problem has become. Einstein, who hypothesised GW, was well aware of the experimental findings of Laplace on the speed of gravity, has always avoided any prediction on gravity's speed, notably to say or write that "gravity is not instantaneous". Actually his theory, replacing the force acting at a distance by a field "already present" ("static" as you write) is an astute manner of avoiding the problem (of the propagation of this fied).
 * "(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?
 * stefjourdan--92.167.74.85 (talk) 09:14, 13 May 2021 (UTC)

Bright lensing event observed in 2006
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)

"bent light" vs. "distorted spacetime"
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
 * F = G x h x nu x M / (R^2 x c^2)
 * [R the distance from the center of distribution of the matter M]

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
 * “A gravitational lens refers to a distribution of matter ... between a distant source ... and an observer that is capable of distorting spacetime in its vicinity sufficiently that a photon passing nearby appears to the observer to have originated at a substantially different part of spacetime,”

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)

Einstein Cross
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)

Smushed paragraphs?
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)

Why are lensed galaxies blue?
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%2B4849-20150210.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)

dark matter as an intra-gravitational lensing phenomenon, not of light, but of the gravitational field, but now the crystal of our lens is spatial curvature itself and not directly the mass
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)


 * self: it's not silly, you are — Preceding unsigned comment added by 2a02:587:410c:4100:2557:aad6:bf3:8a6 (talk) 20:36, 24 November 2016 (UTC)

Do not mislead readers of this article
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 have undone your edit per wp:UNSOURCED. - DVdm (talk) 10:46, 5 May 2019 (UTC)
 * Better get the fix back. I think here you all must understand such simple things before misleading your readers. https://arxiv.org/abs/1511.06025 " Consequently, most of those recent works are motivated by actual astrophysical observational projects of our  Galactic  center  such  as  GRAVITY  [12]  or  the Event Horizon Telescope [13], see, e.g., [14–17], but some others were focused on what could be seen if an observer stood close to a black hole [18, 19] thus being less relevant from an observational perspective, but more focused on the diversity of physical effects that can arise in the vicinity of a black hole.  Our work fits within this second category." Please be clear about this fact, because it has serious implications for the media interpretation of this gravitational lens effect. They present these simulations, such as what EXTERNAL observer must see if look in black hole, which is not true. As I said external observer CAN'T see black hole shadow at all. This is why in the moment the "black hole" image of an Event Horizon Telescope is under pressure. An accretion disk can't be seen as they present to you, exactly because gravitational lens effect act different for an external observer from simulations that are make for the vicinity of a black hole. Soon we will release this simulation and the code it was made with. There will be no more doubts. And by the way https://upload.wikimedia.org/wikipedia/commons/thumb/0/02/Gravitational_lens-full.jpg/220px-Gravitational_lens-full.jpg this image also show wrong gravitational lens effect. The gravitational lens turns, distorted and blurred the images for external observer in a different manner. You imagine wrong and unscientific artistic interpretations for your riders - This is not acceptable for Wikipedia's article. PLEASE contact some of your authors to clarify this question. By doing so, you put them in a humiliating position misleading all that they are the cause of the media to present an external observer view of gravitational lens effect to the public in this wrong perspective. I make correction of article again, and until you get confirmation from them that they were referring to an external observer - DON'T UNDONE my corrections!RustyBrain (talk) 15:03, 5 May 2019 (UTC)
 * Your corrections will be undone until you get a reliable source. - DVdm (talk) 11:29, 5 May 2019 (UTC)
 * Can you read or not?! I give you one source for example, but obviously you are not able to read scientific articles. I'm already clear why your whole article is full of inaccuracies. Is here a real physicist between the moderators? Can you get him to join this conversation, please. : https://arxiv.org/abs/1511.06025 RustyBrain (talk) 15:03, 5 May 2019 (UTC)
 * You gave a source and then you say "They present these simulations, such as what EXTERNAL observer must see if look in black hole, which is not true." So you did not provide a source in the article for the content that you want to add to the article. - DVdm (talk) 11:38, 5 May 2019 (UTC)
 * These simulations are done for an observer close to Event Horizon, not for External Observer. I give you a source https://arxiv.org/abs/1511.06025 "Our work fits within this second category." but as I said you are not able to understand and read scientific articles. This is why I have request for REAL physicist moderator here, with whom I can discuss this topic normally. You don't understand even simple things. I don't make corrections I make clarifying a fact in your article.RustyBrain (talk) 15:03, 5 May 2019 (UTC)
 * You add content to the article without citing a source in the article. Your source says something about their work, not about the work in the image. Please read our policies regarding wp:reliable sources. And wp:BURDEN. - DVdm (talk) 12:04, 5 May 2019 (UTC)
 * ?! Are you with your head or forget it in your home today?! I give you a source https://arxiv.org/pdf/1511.06025.pdf . His name is Alain Riazuelo and is exactly the source of this animated GIF you published here. You can connect with him, and ask if he agree with my clarification under the simulation. He have email address in this pdf. If he disagrees, you will UNDO it. So calmly for now and stop doing things you don't understand.RustyBrain (talk) 15:03, 5 May 2019 (UTC)
 * There is no indication of the name Alain Riazuelo on the description of the uploaded image. Click the image... [[Image:Black hole lensing web.gif|thumb|right]] - DVdm (talk) 12:49, 5 May 2019 (UTC)


 * The more you write, the more you expose yourself to the rest as not very clever man. This is the user who upload this GIF https://en.wikipedia.org/wiki/User:Alain_r . 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? Stop UNDO my changes please I will complaint against you. By the way, 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. RustyBrain (talk) 15:03, 5 May 2019 (UTC)
 * The uploader of the gif is user . - DVdm (talk) 14:20, 5 May 2019 (UTC)
 * I don't understand you make some fun with me, or what?! https://en.wikipedia.org/wiki/Gravitational_lens#/media/File:Black_hole_lensing_web.gif in this link is describe "Urbane Legend (optimised for web use by Alain r) - en:Image:BlackHole_Lensing_2.gif" Give me RELIABLE SOURCE OF THIS ANIMATE GIF PLEASE, and this source to meets the requirements of Wikipedia. RustyBrain (talk) 15:03, 5 May 2019 (UTC)
 * Yes, in the link of that image, the name is present. Not in the image that is in this article. - DVdm (talk) 14:37, 5 May 2019 (UTC)
 * Give the RELIABLE SOURCE for this animate GIF, that meets the requirements of Wikipedia. And stop sending me warnings. I will not make more changes under GIF, you simple will delete it, as it violate Wiki's rules. Get it?! Now read carefully Urbane_Legend talking page, https://en.wikipedia.org/wiki/User_talk:Urbane_Legend and think again, how many more seconds will you keep this scam on the main page of Gravitational Lens.RustyBrain (talk) 14:55, 5 May 2019 (UTC)
 * Be patient, and let's see what happens after Wtmitchell's suggestion and your two requests below. - DVdm (talk) 15:13, 5 May 2019 (UTC)
 * "So Wtmitchell, you ask the person who makes several accounts to distribute his fake GIF simulation in Wikipedia, to see and answer of question: why he do it? It's "good" call. You are admin for example, please be more careful what you talk. He can't be able to answer of question you ask, because he is UNRELIABLE source and publish his own UNRELIABLE simulation, which has not been verified by anyone other than himself. Perhaps you need to make a refresher course for topics like "Self-published books" or "Personal communication" https://en.wikipedia.org/wiki/Wikipedia:Potentially_unreliable_sources " DVdm, here the moderators obviously have some problems with learning the rules of Wikipedia. What you will ask Alain Riazuelo?! He is self-publisher in ARXIV.ORG site, https://arxiv.org/pdf/1511.06025.pdf, which is UNRELIABLE SOURCE of information. Or you don't know it?! https://www.youtube.com/watch?v=UvVULEcFBVs if you have doubts that he is the man behind simulation. Unfortunately, you will soon be writing articles about him, as a man who managed to trick everyone into what a black hole looks like for an external observer. P.s. If you say me that arxiv.org is reliable source for WIKI, tomorrow I will publish PDF article with C++ code of gravitational lens effect and this paper will not be rejected. Next I will make correction in your article to put my name in it, and to make ad of my simulation PDF. RustyBrain (talk) 16:28, 5 May 2019 (UTC)
 * On your talk page you have been invited to the tea house. Do have a look. In my experience, on Wikipedia ultimately things happen by wp:CONSENSUS. You have lounched two semi-official requests. You best bet now, is to wait and see what happens in response. If nothing happens, then nothing will be changed to the article, as is explained in wp:NOCONSENSUS. Patience. And try to enjoy that cup of tea. - DVdm (talk) 16:32, 5 May 2019 (UTC)
 * Do you know I can delete this image right now and if you return it without specifying a RELIABLE SOURCE you will violate WIKI RULES?! Do you think the Wiki's rules do not apply to you?! Just dare to return the image before you point to a RELIABLE source - I will make a formal complaint from you. Let's see if the wiki will show us whether some people here are allowed to violate it rules.RustyBrain (talk) 16:46, 5 May 2019 (UTC)
 * wp:POINT - See - DVdm (talk) 16:53, 5 May 2019 (UTC)
 * You are the man who disrupt Wikipedia to illustrate a point. I delete this GIF because it does not have RELIABLE SOURCE, you return it. Think about how arrogant you are. Can you answer us: WHY YOU RETURN THIS GIF, EXACTLY, WHEN YOU DON'T HAVE EVEN THE SOURCE FROM WHERE IT IS? And notice, I don't talk only for reliable source, but source at all. Do you think that some user Urbane_Legend is source in some way?! P.s. Please, if here are more moderators to take action about this moron (excuse me, for my language, but I don't know how to call him) who only want to show me that he is with privileges here and can make what he want with articles, no matter from Wiki's rules. RustyBrain (talk) 20:15, 5 May 2019 (UTC)

Request for high-ranking moderator's intervention
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)
 * I have also put an edit warring warning on your talk page. - DVdm (talk) 12:49, 5 May 2019 (UTC)
 * And please sign all your talk page messages with four tildes ( ~ ) — See Help:Using talk pages. Thanks. - DVdm (talk) 12:56, 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:. Wtmitchell (talk) (earlier Boracay Bill) 13:59, 5 May 2019 (UTC)
 * No problem, but meanwhile they made a 3rd revert. Next stop is wp:AN3. How hard is it to make a change and add a proper source? - DVdm (talk) 14:15, 5 May 2019 (UTC)
 * So Wtmitchell, you ask the person who makes several accounts to distribute his fake GIF simulation in Wikipedia, to see and answer of question: why he do it? It's "good" call. You are admin for example, please be more careful what you talk. He can't be able to answer of question you ask, because he is UNRELIABLE source and publish his own UNRELIABLE simulation, which has not been verified by anyone other than himself. Perhaps you need to make a refresher course for topics like "Self-published books" or "Personal communication" https://en.wikipedia.org/wiki/Wikipedia:Potentially_unreliable_sources RustyBrain (talk) 15:43, 5 May 2019 (UTC)
 * Thanks, DVdm. Adding a source to an article page isn't hard; see help:Footnotes (and Template:Refn, which is probably what I would use, with the Contents of the footnote parameter there including one or more   footnotes). I can help with the mechanics of that if need be. IMO, the supporting source should (also) appear on the image page, but WP isn't very attuned to the need for support concerning images appearing as article content. Wtmitchell (talk) (earlier Boracay Bill) 16:59, 5 May 2019 (UTC)

Request for removing of Simulating Gravitational Lensing's animate GIF
This animate GIF https://upload.wikimedia.org/wikipedia/commons/0/03/Black_hole_lensing_web.gif is uploaded by the user https://en.wikipedia.org/wiki/User_talk:Urbane_Legend who mention https://en.wikipedia.org/wiki/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)
 * Please sign all your talk page messages with four tildes ( ~ ) — See Help:Using talk pages. Thanks. - DVdm (talk) 14:39, 5 May 2019 (UTC)
 * Now you will check the origin of this spam simulation GIF, and if you do not find this RELIABLE source - delete it. RustyBrain (talk) 14:58, 5 May 2019 (UTC)
 * That looks like an interesting paper; I wish I had the background to understand it, but I don't. I note that this is hosted at https://arxiv.org/. Further information I see that page says: "Submissions to arXiv should conform to Cornell University academic standards." That says that submissions "should conform" to the standards. I don't know what those standards are or whether this particular hosted item does conform. Wtmitchell (talk) (earlier Boracay Bill) 17:20, 5 May 2019 (UTC)
 * This is the problems here. You don't understand much from the topics you write on. I want exact source of the GIF. Because Alain Riazuelo is GIF source but this article is not https://arxiv.org/abs/1511.06025. RustyBrain (talk) 20:17, 5 May 2019 (UTC)
 * DVdm, you are the man who disrupt Wikipedia to illustrate a point. I delete this GIF because it does not have RELIABLE SOURCE, you return it. Think about how arrogant you are. Can you answer us: WHY YOU RETURN THIS GIF, EXACTLY, WHEN YOU DON'T HAVE EVEN THE SOURCE FROM WHERE IT IS? And notice, I don't talk only for reliable source, but source at all. Do you think that some user Urbane_Legend is source in some way?! P.s. Please, if here are more moderators to take action about this moron (excuse me, for my language, but I don't know how to call him) who only want to show me that he is with privileges here and can make what he want with articles, no matter from Wiki's rules. P.p.s And this GIF simulation is fake and Alain Riazuelo know it very well. For gravitational lens, the distance to the black hole is very important for what will see external observer. From such distance he illustrate gravitational lens effect in this GIF the image will be different for external observer. You can ask him and see what he will answer. This man was self distributed his fake simulation GIF all over the wiki articles. He must be stopped in some way.RustyBrain (talk) 20:17, 5 May 2019 (UTC)
 * You are know that here is history, aren't you?! Why you lie admins that I was making pointless changes to the article?! I was explain the reason for the changes, and admins will see it. But how you will explain to them that you restore GIF that has not source at all?! You are really very arrogant.RustyBrain (talk) 20:48, 5 May 2019 (UTC)
 * Your edit is not "pointless". Do have a look at the page wp:POINT that I provided. And please stop removing content unless there is a consensus to do so. See wp:NOCONSENSUS: "In discussions of proposals to add, modify or remove material in articles, a lack of consensus commonly results in retaining the version of the article as it was prior to the proposal or bold edit." - DVdm (talk) 21:55, 5 May 2019 (UTC)

Kennefick and Schapiro cites
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. for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see . For the most precise direct modern observations using quasars, cf.."

It throws an error reading

I think that I have tracked down the Shapiro 2004 item cited there. With that worked in, this cite would render as: "Cf. for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see . For the most precise direct modern observations using quasars cf."

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. for the classic early measurements by the Eddington expeditions; for an overview of more recent measurements, see . For the most precise direct modern observations using quasars, cf."

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:

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)

Half the value given by general relativity
User twice removed (i.m.o.) properly sourced content here and here, so I restored and added two more sources
 * Extract of page 21:
 * "What the calculation yielded was a deflection of light from distant stars by the sun’s gravity (for light just grazing the sun) through an angle of 1.7"—just twice as much as the bending one gets in Newtonian theory by treating light corpuscularly."


 * Extract of page 31:
 * "Although the bending of light can also be derived by extending the universality of free fall to light, the angle of deflection resulting from such calculations is only half the value given by general relativity."

Comments welcome. - DVdm (talk) 19:20, 9 January 2022 (UTC)


 * Hello, both of the sources you added are right. The first one talks about treating light as a particle which is not classical physics, in the sense of not according to Maxwells equations. The second is exactly right, that by extending the equivalence principle (i.e universality of free fall) you can get the result up to a factor of two. It's a very common exercise for the first class of graduate cosmology/GR because you don't have to explain what a manifold is, it is a local effect. My point is that none of this is classical physics in any way and leaves people with the wrong idea. All the best Pacomc999 (talk) 20:43, 9 January 2022 (UTC)


 * Another one (page not available on Google, extract taken from my own copy, emphasis added):
 * "Although the deflection of light was a key to establishing the correctness of general relativity, it is interesting that there is a purely Newtonian argument for light deflection. This was first predicted by Cavendish in 1784 and independently by the German astronomer J. G. von Söldner (1776–1833) in 1801. The argument relies on light behaving like a particle moving at speed c. Since the motion of a particle in a gravitational field depends only on its velocity, Cavendish and von Söldner were able to compute the simple result that the deflection would be 2M/b, exactly half of the prediction of general relativity in Eq. (11.55). Einstein himself, unaware of this previous work, derived the same result in 1908, just at the beginning of his quest for a relativistic theory of gravity. So the triumph of general relativity was not that it predicted a deflection, but that it predicted the right amount of deflection."
 * Looks classical to me. - DVdm (talk) 20:49, 9 January 2022 (UTC)
 * Looks classical to me. - DVdm (talk) 20:49, 9 January 2022 (UTC)


 * In all fairness, classical is a term that widely varies in meaning depending on the context, but the classical theory of light is wave dynamics and in particular Maxwell's equations. I am aware that Newton believed light to be a particle but this can not explain any simple light phenomena like diffraction. If you want to say something like "some of the early theories of corpuscular light predict this effect up to a factor of two" it wouldn't be wrong. That could be meaningful but in any case, it needs to be explicit that this is not classical electromagnetism. Pacomc999 (talk) 21:14, 9 January 2022 (UTC)


 * Please indent your talk page messages as outlined in wp:THREAD and wp:INDENT — See Help:Using talk pages. Thanks.
 * The article statement is
 * "Classical physics also predicts the bending of light, but only half of that predicted by general relativity."
 * I think that the cited sources adequately support that, and that no change is needed. Unless perhaps something like:
 * "Newtonian physics also predicts the bending of light, but only half of that predicted by general relativity."
 * That's even closer to the sources. - DVdm (talk) 21:26, 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)


 * Again, please indent your talk page messages as outlined in wp:THREAD and wp:INDENT — See Help:Using talk pages.
 * I think that Shutz is a pretty reliable source. And of course, wp:consensus is established by the contributors of Wikipedia, not by "other phycisists from [yoiur] masters". Comments from others? - DVdm (talk) 22:55, 9 January 2022 (UTC)


 * I think this IS an important point to leave in the article, and it's certainly more than adequately sourced. Can we write it in such a way to make clear that this is an argument using classical dynamics, but doing so with light considered (atypically for these types of dynamics) as a particle?  You could come up with a number of ways to word it, and we can discuss that here, but it definitely is appropriate content. PianoDan (talk) 01:35, 10 January 2022 (UTC)


 * Newtonian theories of light seems the best descriptor for this, rather than classical theories. &#32; Headbomb {t · c · p · b} 04:22, 10 January 2022 (UTC)
 * Yes, fine with me. - DVdm (talk) 10:35, 10 January 2022 (UTC)
 * I have made change and put Shutz in place of the removed circular source: . Thanks, user ! - DVdm (talk) 13:28, 10 January 2022 (UTC)


 * I agree with Pacomc999's point: the article should not be ambiguous, which it remains. Using qualifiers that have no clear-cut definition such as "Newtonian theory", "Newtonian physics" or "classical theory" does the reader a disservice when the details count.  We need to interpret the sources' meanings and present that, not simply echo the sources' terminology.  Something like "Treating light as corpuscles travelling at the speed of light [at infinity or at perihelion?] in Newtonian theory [...]" or "With some assumptions on the nature of light in Newtonian theory [...]".  The sources typically provide context to disambiguate simpler statements (such as earlier descriptions, although sources often make implicit assumptions too).  Assumptions such as the speed of light are not implicit in "Newtonian physics", for example and neither is the corpuscular nature of light.  I read the statement as it currently stands and I immediately run into a wall of mental questions about the unstated assumptions made for the statement to hold.  172.82.46.13 (talk) 16:36, 10 January 2022 (UTC)


 * Clarified in article: . - DVdm (talk) 17:38, 10 January 2022 (UTC)
 * That works for me. Having this in the article makes a historically significant point that is of interest.  172.82.46.13 (talk) 19:29, 10 January 2022 (UTC)

Can someone add the new JWST image?
I’m too lazy to figure out how DatGuy0309 (talk) 23:01, 11 July 2022 (UTC)

Can someone add the new JWST image to the gravitational lensing page?
I’m too lazy to figure out how DatGuy0309 (talk) 23:02, 11 July 2022 (UTC)


 * That's a good idea and is relevant here. Should we redirect this to the JSWT scientific results section here?
 * https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Scientific_results
 * This section has the image and the details about the gravitational lens view as seen in the image released by JSWT Suksane (talk) 11:57, 16 July 2022 (UTC)
 * @DatGuy0309 - Since you raised the topic about the images from the JSWT first, whats your opinion? Suksane (talk) 15:47, 16 July 2022 (UTC)