Age of the Universe

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Hayden, Jul 19, 2018.

  1. Seattle Valued Senior Member

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    Our time horizon is 13.8 billion but our Observable Universe is much larger than 13,8 billion light years.
     
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  3. nebel Valued Senior Member

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    absolutely, our horizon stretches in all directions, see line 9 in the sketch above. Photons from the near BB background radiation, come from all directions, beyond that, its opaque, there was nothing radiating.
     
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  5. Write4U Valued Senior Member

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    Please Register or Log in to view the hidden image!


    https://astronomynow.com/2015/07/01/is-the-universe-ringing-like-a-crystal-glass/

    I have not yet seen mention of a wavelike expansion of the universe. This would be David Bohm's Pilot Wave model and would also agree with the general wavelike motion in physics.

    This would mean that the universe alternately expanded and contracted wih a wavelength of about 7 cycles per approx. 14 billion years.

    Any thoughts?
     
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  7. nebel Valued Senior Member

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    well, this is Hayden's thread, and his namesake produced some really soul stirring reverberations, pressure waves.
    What he thinks of the photons of his OP object being subjected to stretching and shrinking, and evidence for it?
     
  8. Gawdzilla Sama Valued Senior Member

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    We need to get Alan Guth signed up here. 'Cause we're being asked to conduct a graduate seminar in astrophysics.
     
  9. nebel Valued Senior Member

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    Yeah nothing will stop a discussion faster than the presence of somebody that knows what they are talking about. yet
    This discussion is about movement through TIME, age, and size gets in the way. All matter in the universe has moved through time the same distance, which would form a hollow sphere in time. so: we are presently in mattertime since the Big Beginning, looking back at the light that comes from the past. (see the "alma" thread).
     
    Last edited: Jul 20, 2018
  10. Hayden Registered Senior Member

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    Do we have any agreement (by all proponents of Big Bang) on the spatial size of the universe at the end of inflation? If yes, what was the size of our universe at the end of inflation? And spatially how big was the universe at t = 400 million years?

    I am just trying to figure out if the light had sufficient path to travel from t = 400 million years till today?
     
  11. Q-reeus Valued Senior Member

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    No. The model dependent estimates aka guestimates vary enormously. Try a search using e.g. "number of e-folds in inflationary regime". You will quickly find out the number has for a long time and still remains up for grabs. Many inflationary models have been weeded out thanks to Planck survey data, but many alternatives still remain.
    See above. Some claim it always was and always will be infinite in size. Which gets back to a link I gave in post #4 this thread:
    http://www.sciforums.com/threads/can-infinity-ever-be-more-than-a-mathematical-abstraction.160948/
    As far as as GR-based LCDM model, you were given a formula to work from back in #8. So plug in the accepted parameters and find out.
    Obviously some light must have. What's so special about 400 million years?
     
  12. Seattle Valued Senior Member

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    What kind of "path" are you looking for?
     
  13. Write4U Valued Senior Member

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    If I understand the thrust of your question, the answer may be that what we see as a bounded area is the background "afterglow" of the BB and it's chaotic inflation during the first 400 million years. This is area and specific time frame is identified and depicted in the illustration of the bell.

    I read that one of the clues of a small beginning lies in the wave lenghts which are received from that time frame and are missing the longest wavelengths, which indicates a relatively smaller size of the universe at that time than at present.
     
  14. Seattle Valued Senior Member

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    The CMB is from the first 400 thousand years. The only special thing about 400 million years is that's about the time the first stars and galaxies were forming.
     
  15. Gawdzilla Sama Valued Senior Member

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    And first SMBHs according to some. (The "direct to black hole" school of thought.)
     
  16. Hayden Registered Senior Member

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    It has relevance depending on the size at the end of inflation.

    Say at t = 400 million years (the oldest galaxy as recorded recently), the universe was of size x (extremes). At this time the expansion rate could not have been faster than the speed of light, in the worst case scenario assuming that this galaxy was at one extreme of the universe, then the time taken to reach the other extreme would be (x+continued expansion)/c, how this could be around 13 billion years, it all depends on x and that in turn depends on the size after inflation.
     
  17. Seattle Valued Senior Member

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    The expansion rate can be faster than the speed of light. Nothing travels though space faster than the speed of light. Space itself can expand at any rate.

    Are you arguing that there hasn't been enough time for the light to reach us? That's not true, because it has reached us.

    Are you arguing that the light should have reached us long ago? It probably did, we just found it.
     
  18. Gawdzilla Sama Valued Senior Member

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    And long ago, could be before we had telescopes able to see it.
     
  19. Write4U Valued Senior Member

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    Isn't that why we call it the "afterglow"?
    The light may have begun to reach us many millions of years ago and what we see today is the dying embers of that great event and which may have lasted another many millions of years before that background glow will have become too faint for us to see it today, when it gets here. Who can tell?

    We know of more recent stars which have burnt out long ago, but their light is just reaching us today.
     
    Last edited: Jul 21, 2018
  20. Gawdzilla Sama Valued Senior Member

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    We're on two different tracks here. I agree with what you're saying.
     
  21. Hayden Registered Senior Member

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    Assuming that at t = 400 million years, the universe was of 800 million light years size (extremes).

    Now a photon emitted at one extreme could not have taken 13 billion years even to reach the other extreme, it would have reached much earlier.
     
  22. Seattle Valued Senior Member

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    It was much bigger than that but for the sake of this discussion it doesn't matter if it was only 900 million light years in diameter.

    No one is discussing how long it took the first photon from that galaxy to cross the Universe. We are talking about how long it took the photon that we are currently viewing to reach us and the distance that it had to travel and how far away that galaxy is now (if it still exists).
     
  23. Hayden Registered Senior Member

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    That is the worst case scenario and I do not even know what it means for a photon to cross the universe.

    If a light is emitted at point A, then how could it take 13 billion years to reach a point which is less than 900 million light years away at that instant?
     

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