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Red shift

  1. Apr 3, 2003 #1
    Can anyone explain to me the red shift
     
  2. jcsd
  3. Apr 3, 2003 #2
    Red shift occurs as a result of the doppler effect. When a source that emits waves moves towards you the waves emitted by the object arrive earlier than they would if the object was not moving and therefore waves arrive closer together (light moves towards the blue end of the spectrum). If the source is moving away from you the waves get more stretched out (the light moves towards the red end of the spectrum).
     
  4. Apr 3, 2003 #3

    russ_watters

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    You know how the pitch of a train horn changes as it passes you? Thats the doppler effect. Same effect for light just that higher frequencies are toward blue and lower ones toward red.
     
  5. Apr 3, 2003 #4

    Phobos

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    In astronomy, there are 3 kinds of redshift...
    (1) Doppler (see above)
    (2) Gravitational (from light climbing out of a strong gravity field)
    (3) Cosmological (expanding space stretching light waves)
     
  6. Apr 4, 2003 #5
    Is the red shift visible then and how do I go about seing it?
     
  7. Apr 4, 2003 #6
    I don't think you can go about observing a shift in light in everyday life. It's observed from stars in distant galaxies moving away from us at very high velocities. you would probably need a relative velocity of around 0.10c so that the Doppler factor for EM waves, sqrt((c+u)/(c-u)) gives a noticeable shift in wavelength.
    So unless you've got the tools to measure the wavelength of light received from far-away stars, and compare with what the true wavelength should be, you might have to settle for sound :smile:.
     
  8. Apr 4, 2003 #7
    My other question is that ive heard a lot about stars going super nova, do you know when I can view these?
     
    Last edited: Apr 4, 2003
  9. Apr 4, 2003 #8

    russ_watters

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    It doesn't happen very often and its not all that predictable - so if there is a good one you might be able to see it after reading about it in the newspaper. They're generally visible for a week or so if they get bright enough.
     
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