Talk:Gravitational lens

From Wikipedia, the free encyclopedia

	Physics Portal This article is within the scope of WikiProject Physics, which collaborates on articles related to physics.
Start	This article has been rated as Start-Class on the assessment scale.
Mid	This article is on a subject of Mid importance within physics.
Help with this template This article has been rated but has no comments. If appropriate, please review the article and leave comments here to identify the strengths and weaknesses of the article and what work it will need.

Draft for missing parts:

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
   1. Magnification -> study the source of the light
   2. Another use of these lensing systems is the study of the distribution of masses that are doing the deflection.
   3. 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?
   4. 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.

-- looxix 20:32 Apr 13, 2003 (UTC)

Now covered astronomical applications, and the way it affects any radiation. EddEdmondson 11:44, 31 Mar 2004 (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 Mar 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

Kjetil!. It is an absolutly extrodinary picture but a bit too complex for the discussion.

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.

Is the page ready to have the 'expert' template removed? Kjetil/his article are 'expert', IMO. Someone just needs to edit.

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)

[edit] 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)

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.