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Ask about the 1919 experiment

  1. Oct 21, 2009 #1
    Hi all,

    I rememeber that in 1919, scientists did an experiment to verify the relativity theory but do not know what they do in detail. Could anyone explain to me pls.

    Thanks
     
  2. jcsd
  3. Oct 21, 2009 #2

    russ_watters

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    You remember? J/K. In 1919 there was a test of gravitational time dilation during an eclipse.
     
  4. Oct 21, 2009 #3

    mgb_phys

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    Einstein's theory of General relativity says that gravity bends light
    gravitational_bending_l.jpg

    If you observe the shift in apparent position of a distant star when there is / is not a massive object in the way you can test the theory.

    The tricky part is that the only suitably massive body is the sun and it's rather difficult to observe a star very close to the sun in daytime. The eclipse was just a convenient way of blocking the light from the sun during the measurement.

    The important result was that the shift predicted by GR was twice the shift predicted by Newton's gravity (if you used Special Relativity to assign an equivalent 'mass' to a photon). In fact it looks like the results were really a bit too close to call because of some optical effects to do with the edge of the sun's atmosphere.

    Since then we have tested it to about 0.1% using modern telescopes
     
  5. Oct 21, 2009 #4

    JesseM

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    It was a test of the bending of starlight--can that also be seen as an indirect test of gravitational time dilation or did you misspeak? Anyway, here are some articles:

    http://www.esa.int/esaSC/SEM7I9R1VED_index_0.html
    http://www.simonsingh.net/1919_Eclipse.html [Broken]
    http://ircamera.as.arizona.edu/NatSci102/text/lightbend.htm [Broken]
     
    Last edited by a moderator: May 4, 2017
  6. Oct 21, 2009 #5
    Thanks to all for very fast responses. It's clear now.
    (I meant remember reading)
     
  7. Oct 21, 2009 #6

    russ_watters

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    Misspeak - I meant to say gravitational lensing....which, perhaps is not exactly the same thing either.
     
  8. Oct 22, 2009 #7

    mgb_phys

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    I thought you were making a joke about him remembering an event 90years ago.
     
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