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Shapiro Effect and Gravitational Lensing

  1. Jun 2, 2004 #1
    I have been searching for alternatives to BBT and the doppler effect to explain everything, and have been dissapointed to find a lot of crackpots out there. I have recently found this website:

    http://www.geocities.com/newastronomy/Index.htm

    and the thing makes all kinds of sense (to my limited intellect)

    But, there are a few problems I have with the explanation of "extra" gravity from stars and the explanation of neutron stars.

    Are there any real physicists out there that are willing to debunk these ideas?
    I've seen physicists "ruling out" the Shapiro Effect for redshifts on their websites, but their explanations were always "over my head". Can anyone do it in semi-plain english??

    Also, what about his ideas about gravitational lensing ? I think it's pretty cool and makes a little too much sense. Am I blind?? :confused:
     
  2. jcsd
  3. Jun 4, 2004 #2

    hellfire

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    I have not read the whole webpage, but only the part describing the hypothesis of cosmological redshift due to the Shapiro effect.

    As far as I know, a remote observer would indeed measure a modification of the speed of light when light passes through a gravitational potential, since it experiences a time-delay wrt to a trayectory through empty space.

    But I am not sure that this will produce a redshift. To calculate the redshift due to gravitation one has to make use of the formula for gravitational redshift derived from a Schwarschild spacetime. This will lead to a prediction of redshift as well as blueshift when light falls into and comes out from potentials.

    May be I am missing something.

    Regards.
     
  4. Jun 4, 2004 #3
    i think the gravitational lensing ideas on this webpage havent' been totally thought out, mathwise especially.

    wouldn't there be at least a little distortion? smudging, arcing, that type of thing?

    and OH! I guess I didn't read carefully. The shapiro effect is on the SPEED of the light? hmm, i guess I was under the assumption that light in a vacuum has ONE speed, period. I thought it reduced the energy! here i was thinking everyone thinking doppler effect and expanding space were retarded.

    I think this webpage is just some bozo like me, who doesn't do this for a living, but tries to wrestle with the concepts without doing any of the math.
     
  5. Jun 5, 2004 #4

    hellfire

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    Yes, locally always c, but seen from far away (wrt a potential) one will measure a differend speed as c.

    Regards.
     
  6. Jun 8, 2004 #5
    again, i thought that light in a vacuum went c
    in ALL inertial reference frames and wrt any other reference frame
     
  7. Jun 13, 2004 #6

    Chronos

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    if you use 'c' as the local reference frame, it solves every objection to what is observed. this is not an arbitrary measure. as a predictive model, it has flaws. the singularity at the beginning of time breaks down the math of all currently known models.
     
  8. Jun 14, 2004 #7

    hellfire

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    This is true in a globally flat spacetime, but I think a Schwarschild spacetime is usually assumed in order to calculate the gravitational redshift and the Shapiro effect. In a Schwarschild spacetime there is a dependence of the speed of light with the gravitational potential when measured by distant observers (but not when measured in a local experiment). Regards.
     
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