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Why the discrepancy between telescopes and big bang?

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  1. Aug 4, 2013 #1
    I am wondering why it is that we can look into Hubble's Deep Field and see galaxies 13.7 billion light years away, and 13.7 billion years ago, yet Big Bang theory tells us that 13.7 billion years ago all matter in the universe was very close together. Shouldn't we be seeing in HST that the oldest possible objects are closer, not further away? Or am I missing something here?
     
  2. jcsd
  3. Aug 4, 2013 #2
    Note that the universe is expanding while the light is traveling. Also note that because space itself expands the "speed" of the expansion varies depending on how far apart the two points you consider are.
     
  4. Aug 4, 2013 #3

    CWatters

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    As ModusPwnd said... It appears space time expanded faster than the speed of light. That doesn't mean stars moved through space faster than light, it means space itself expanded. Google universe expanding faster than light.
     
  5. Aug 4, 2013 #4

    mathman

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    http://hubblesite.org/newscenter/archive/releases/2012/37/image/a/

    You misinterpreted the results. The telescope sees galaxies that are 13.2 billion years old, not 13.7.
     
  6. Aug 4, 2013 #5

    russ_watters

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    We do see objects closer together in distant HST images!
     
  7. Aug 5, 2013 #6
    I can't get enough of those HST images with all the galaxies, but is the telescope telling us that 13.7 billion years ago those galaxies were 13.7 billion light years away and in every direction, rather than clumped together as the theory says. How does Big Bang theory account for that?
     
  8. Aug 5, 2013 #7

    russ_watters

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    Seeing them in every direction doesn't mean they weren't clumped together. Every direction you look is into the past and the arrangement of galaxies is denser the further away we look.

    Think about it this way: In the entire sky, there are only a few hundred nearby galaxies, but a tiny chunk of the sky in the HDF shows 10,000 distant ones.

    [Edit] I suspect this is a geometry issue. The limit of our vision represents an expanding sphere, so more recent views are of a smaller chunk of the universe. But picking a tiny sphere will show that that isn't representative of the true size of the universe: if we look only at celestial objects 2 seconds or less old, the only object in that sphere is the moon, 400,000 km away. But that doesn't mean the universe was only 800,000 km across 2 seconds ago or that the moon was the only thing in it!
     
    Last edited: Aug 5, 2013
  9. Aug 5, 2013 #8
    I was just asking about this yesterday. There weren't many galaxies around 500 Million years after the BB, but if we choose a timeframe say 3B years after the BB with the corresponding red shift it should be possible to estimate the mean distance between galaxies then, and compare that with relatively close galaxies in roughly the present timeframe. I would think that there should be a difference. However it may not be very accurate because there may be new galaxies just coming into existence then as well as mergers during this time.
     
  10. Aug 5, 2013 #9

    mathman

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    Observed galaxies are 13.2 billion light years away, not 13.7!
     
  11. Aug 6, 2013 #10
    I appreciate all the answers but I still don't understand how the BB explains that the HST imaged the oldest galaxies ever seen and they were 13-plus billion light years away, 13-plus billion years ago which is right around the time the theory says the bang happened. I am pretty certain the next great telescope that replaces HST will find them even further out in space and further back in time. To my admittedly untrained mind it seems unlikely, unless someone trained in these things can convince me otherwise, that a telescope will ever be invented that shows galaxies further back in time and spatially closer. But isn't that exactly what must happen to eliminate the discrepancy between telescopes and BB?
     
  12. Aug 6, 2013 #11

    mathman

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    There is no discrepancy! 13.2 billion years is 500 million years less than 13.7 billion years, giving plenty of time for galaxies to form. The cmb is estimated to be radiation from about 300,000 years after the big bang.
     
  13. Aug 6, 2013 #12

    mathman

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  14. Aug 7, 2013 #13
    That's a great description:

    http://www.astronomy.com/News-Observ...rk Ages.aspx


    Scott: For a visual representation in answer to your question, check out the first illustration here:


    http://en.wikipedia.org/wiki/Chronology_of_the_universe

    Don't pay any attention to the surface borders.....nor the 'point' size of the big bang....
    there is no easy way to represent that the big bang happened everywhere at some point
    in time.....instead think of the stars as close together on the left,as illustrated, more spread out to the right, and with all the illustration space unconstrained.....
     
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