gravitational lensing

[telscope@xxxxxxxxxx (Peter Abrahams)]

A recent post referred to gravitational lensing of light from distant
galaxies, and asked whether multiple images of the galaxy would be stereo
pairs.  Such questions boggle the mind and leave me speechless at the reach
of the unfettered imagination.
If the earth, a galaxy, and a more distant galaxy are all in a line, the
light from the distant galaxy would normally be blocked by the nearer one.
However, the gravity from the near galaxy bends the light rays from the
distant one, and focuses them -- on to the earth, if all angles & distances
are right.  Because there are many billions of galaxies, this far-fetched
scenario has been observed -- more than several times, less than many times.  
I do not believe they would be a stereo pair.  
--The images are extremely faint, fuzzy and small.
--They are smeared, and are not a likeness.  The smearing is symmetrical,
and the images make right and left hand pairs.
--The more distant galaxy is an enormous distance behind the nearer galaxy.
The stereo base is the width of the near galaxy, probably small compared to
the intergalactic distance.
That does raise the question, what if it were close.  Probably the
distortions would then be extreme, and probably the light cannot be
refracted to more than a shallow angle.
I would like to be wrong on this one.
If there has been a more hair-raising question posted to Photo3d than this
one, please repost it, I could use the excitement.
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telscope@xxxxxxxxxx (Peter Abrahams)          
the history of the telescope, 
     the prism binocular, and the microscope


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