Talk:Gravitational lens

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 Definition:  A lens formed when light from a very distant, bright source (such as a quasar) is 'bent' around a massive object (such as a cluster of galaxies) between the source object and the observer. [d] [e]
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 Workgroup category:  Physics [Categories OK]
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Initial version

Just finished an initial version (with home-made images :-) ) which should contain most of the basic information. Feel free to comment... --Jori 15:26, 26 February 2007 (CST)

A few thoughts:

Albert Einstein published a new expression, differing only by a factor of two from the Newtonian result

I wouldn't call a factor of two an "only". The difference is enormous compared to, say, the Lorentz factor for objects moving at classical speeds. In fact, isn't the huge difference the point of the section? Had the factor been, say, 1.01, Einstein's theory would not have been verified (at that time). Are there actually instances in which the Newtonian value is useful? The article could be a bit more explicit about whether the Eddington measurement did or did not render the classical approximation useless. With the "only" in there, I get the impression that it didn't.

d is the impact parameter of the light ray

I have no idea what an impact parameter is. A short definition wouldn't hurt.

Also, in the "thin lens approximation" section, there are a few undefined variables. The text should be comprehensible without looking at the image.

Instead of "Note that the distances are", I'd write "The distances are", since I don't see how one could note this (without prior knowledge) from the information given in the preceding text.

Fredrik Johansson 15:37, 8 March 2007 (CST)

Thanks for your feedback Fredrik. You're definitely right: the "only" gives the wrong impression. The history section also needs some more work (and references), currently it only contains the facts I could remember. The "thin lens approximation" section is going to be replaced by a "lensing formalism" section, which will also describe the time delay function, lensing potential etc. Anyway, I'm glad I'm not the only one reading the page :)
Jori Liesenborgs | Talk 15:40, 9 March 2007 (CST)

New 'lensing formalism' section

I removed the 'thin lens approximation' section and replaced it with a (hopefully) more complete 'lensing formalism' section.

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