XPost: sci.physics.relativity, alt.usage.english   
   From: ram@zedat.fu-berlin.de   
      
   David Canzi  wrote or quoted:   
   >Has anybody calculated how much refraction by the Sun's atmosphere   
   >would bend a ray of star light, and was the result of that calculation   
   >close to the observed bending?   
      
     Found this in the internet:   
      
   |Could the displacement of star images near the sun be caused   
   |by refraction in the atmosphere of the Sun, not by general   
   |relativity?   
   |   
   |No. Long wavelength electromagnetic radio waves are, in fact,   
   |refracted by the plasma in the solar photosphere, chromosphere   
   |and corona, but this effect can be accounted for, leaving a   
   |frequency-independent bending of the amount predicted by   
   |general relativity.   
   |   
   |In 1974-75 a series of radio observations were made of the   
   |occultation by the sun of the quasars 3C273 and 3C279 by   
   |astronomers Fomalont and Sramek. The measurements were made at   
   |2.7 and 8.1 gigacycles. Because refraction from the solar   
   |corona varies with the square of the observing frequency as   
   |n^2 - 1, where n is the plasma index of refraction, it is   
   |possible from a 2-frequency observation to eliminate most of   
   |the effects caused by refraction in the solar atmosphere.   
   |General relativity predicts that the 'lensing' of light by a   
   |gravitational field does NOT depend on the frequency of the   
   |light, unlike lensing of light by optical means.   
   |   
   quoted from the internet.   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)