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Hubbles Vs. Dark energy

  1. Jul 5, 2010 #1
    So Hubbles observations showed that the further away a galaxy is the faster it is moving meaning that older galaxies are moving away faster from us than younger, closer ones. But dark energy says that the rate of expansion is increasing,meaning the closer, younger galaxies would be traveling faster than the farther, older ones. So. Which one is correct?
     
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  3. Jul 5, 2010 #2

    Nabeshin

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    The dark energy picture is more correct than hubble's simple linear expansion picture. Hubble simply didn't have the quality of data to detect the accelerating expansion, and indeed it's not until the late 90's that we finally did. I wouldn't really say hubble was wrong though -- the situation is rather analogous to Newtonian and Einsteinian mechanics. Newton wasn't really wrong, the domain of applicability of his theory was just smaller than Einstein's.
     
  4. Jul 5, 2010 #3
    So does that mean as we look farther away from our galaxy the expansion speeds up to a certain point of time/distance the expansion starts slowing down as we look further back? Meaning Hubble was right with his data, he could see the universe expansion increasing as he looked further out, he just couldn't see far enough to see where the universe started slowing down?
     
  5. Jul 5, 2010 #4

    Ich

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    No.
    1. At any given (cosmological) time, the so-called recession speed of a galaxy is exactly proportional to its distance. The proportionality factor is called H.
    2. H is changing with time, getting less and less. "Accelerated expansion" means that H decrases slower than it would if all galaxies were freely floating.
    3. Combine this with light travel time to get a recession speed - distance at emission chart. These are more complicated. Look athttp://www.astro.ucla.edu/~wright/cosmo_01.htm" [Broken].
     
    Last edited by a moderator: May 4, 2017
  6. Jul 5, 2010 #5
    Okay so Hubble's Constant isn't constant then? How did Hubble miss that? is the change in H as the farther you go away so slight that he was unable to look far enough away to see a change in H?
     
  7. Jul 6, 2010 #6

    Ich

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    You know, I gave you the link for a reason. Have a look at Hubble's data and decide for yourself.
    Hint:1 Mpc~3Mly. Age of the universe ~13700 My.
     
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