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Redshift and Hubble constant

  1. Jul 31, 2009 #1
    Which statement is true?

    A The apparent speed of recession of a galaxy is given by the product of the Hubble constant and the distance to the galaxy.

    B The further away a galaxy is, the lower its apparent speed of motion away from us.

    C A galaxy with a redshift of 5.37 is situated at a look-back time of 4.1 billion years.

    D Space is expanding uniformly so that the distance between galaxies remains constant.
     
  2. jcsd
  3. Jul 31, 2009 #2

    negitron

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    Which statment(s) do you think is/are true and why?
     
  4. Jul 31, 2009 #3
    I think statement A is true but I'm not 100% sure whether D is false and there is only one true statement.
     
  5. Jul 31, 2009 #4
    Well, to rule out C you can have a look at Ned Wrights Javascript cosmology calculator to determine the lookback time. Just plug in 5.37 for the redhshift. The light travel time is the "lookback time".

    http://www.astro.ucla.edu/~wright/CosmoCalc.html
     
  6. Jul 31, 2009 #5

    negitron

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    Well, isn't it generally true that the farther a galaxy is from us, the faster it appears to be receding?
     
  7. Jul 31, 2009 #6
    Yeah, I didn't think B or C were the answers.
    I'm still stuck between whether A or D is the right answer and I really need help.
     
  8. Jul 31, 2009 #7

    cepheid

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    Does it make any sense for the distance between things to remain constant in an *expanding* universe???

    When we say that a galaxy is moving away from us, what does that mean? Does it not mean that it is getting farther away with time?
     
  9. Sep 22, 2009 #8
    Statement A is definitely correct.
     
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