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Why did we stop at 46.5 billion light years?

  1. Aug 25, 2012 #1
    It's been bugging me. We've looked 13.5 billion years into the past, supposedly only about 500 million years short of the big bang, at objects 46.5 billion light years away. What were the limiting factors? What stops us so close from the finish line from peeking into the very beginning?

    If it's limitations on the Hubble, couldn't we build another telescope with just a smidge more accuracy to get that glimpse? I mean.. it can't be because there was no light, I'd assume with all the heat generated at some point pre 13.5 billion light years there must have been a lot of photons being thrown about.

    Thanks!

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    Edit - This is what I found on Wiki, so shouldn't we be able to "theoretically" look back to +10 seconds given the best circumstances?

    Photon epoch
    Between 10 seconds and 380,000 years after the Big Bang
    Main article: Photon epoch
    After most leptons and anti-leptons are annihilated at the end of the lepton epoch the energy of the universe is dominated by photons. These photons are still interacting frequently with charged protons, electrons and (eventually) nuclei, and continue to do so for the next 380,000 years.
     
    Last edited: Aug 25, 2012
  2. jcsd
  3. Aug 26, 2012 #2

    Chronos

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    You have severely misunderstood modern cosmology.
     
  4. Aug 26, 2012 #3
    You sorta answered your own question. After most leptons and anti-leptons are annihilated at the end of the lepton epoch the energy of the universe is dominated by photons. These photons are still interacting frequently with charged protons, electrons and (eventually) nuclei, and continue to do so for the next 380,000 years.

    Those photons were interacting with charged protons, electrons and (eventually) nuclei until 380,000 years after the big bang. So we can't see back before that.

    Photons from that time period (380,000 +) can be detected as microwaves now. Galaxies were not fully formed at this point clearly, so galaxy formation began closer to 500 million years after the big bang.
     
  5. Aug 26, 2012 #4
    So instead of looking at that 10 second time period you mention our best alternative is to try and recreate the conditions present at that time period.
     
  6. Aug 26, 2012 #5
    Thanks for stating the obvious.
     
  7. Aug 26, 2012 #6
    I've not learned much about particle interaction, but I'm gleaning that this pre 380,000 year interaction made the photons of the time undetectable. What would this area of study be called so I can look into it? A google search for "Photon interaction with charged particles" produces a myriad of results.

    Thanks!
     
    Last edited: Aug 26, 2012
  8. Aug 26, 2012 #7
  9. Aug 26, 2012 #8

    phyzguy

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    The simple answer to your question is that we can see back to what's called the "surface of last scattering", which is ~400,000 years after the big bang. Before this, the universe was opaque to EM radiation, so we can't see any further back. It's something like trying to look into the center of the sun. There is some hope of "seeing" further back by detecting neutrinos that were emitted earlier.
     
  10. Aug 26, 2012 #9

    phinds

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    You might find "The First Three Minutes" by Weinberg informative
     
  11. Aug 26, 2012 #10
    we have seen as far in the past as we could with CoBE(actually we had done it before CoBE)
    it has detected highly red shifted light as microwave radiation there was no light in the universe before that
     
  12. Aug 26, 2012 #11

    D H

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    There was lots of light in the universe "before that".

    Imagine what things would look like inside our Sun. Even though the interior of the Sun is optically opaque, there would be light coming from everywhere. The interior is opaque because a photon inside the Sun doesn't go all that far before being absorbed thermally. Photons inside the Sun are constantly being created and absorbed by thermal processes. It takes a long time for the energy created at the center of the Sun to make its way to the Sun's surface, where it is finally emitted into empty space.

    That light coming from everywhere is what our early universe would have looked like. There was lots of light in the early universe; there was light all around. It just didn't go very far. What we see as the CMBR is the radiation that was finally freed to traverse the universe once the universe had finally cooled enough so as to become transparent.
     
  13. Aug 27, 2012 #12
    that was what i meant essentially :D
     
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