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Did the universe have a begining?

  1. Apr 7, 2015 #1

    wolram

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    I think it is correct to say the farthest light we can see is about Z=7' it would be remiss of us to think astronomers will not find light from higher values of Z in the future.

    My question is how old IS the univeres.

    http://phys.org/news/2015-02-big-quantum-equation-universe.html

    (Phys.org) —The universe may have existed forever, according to a new model that applies quantum correction terms to complement Einstein's theory of general relativity. The model may also account for dark matter and dark energy, resolving multiple problems at once
     
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  3. Apr 7, 2015 #2

    wabbit

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    There was a fairly long discussion about that paper not long ago in this forum, in the following thread : https://www.physicsforums.com/threads/ali-and-das-cosmology-from-quantum-potential.797183

    As to your question, I don't think anyone knows. It may have existed forever (not just in the Ali & Das view, but in lots of quantum cosmology models), or just for 14bn years. "At least 14 bn years" seems to be fairly well established though. And also that going back that far it was in a hot, dense state.

    But as to seing light emitted in the past, this is limited to less than 14 bn years, see http://en.wikipedia.org/wiki/Cosmic_microwave_background.
     
    Last edited: Apr 7, 2015
  4. Apr 7, 2015 #3

    phinds

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    correct.

    incorrect. The CMB IS the farthest back we can see "light". It is possible that with better detectors we might some day be able to see gravity waves and/or neutrinos from earlier than 400,000 years, but not electromagnetic radiation.
     
  5. Apr 7, 2015 #4
    I thought that it was considered unlikely that we could ever observe anything prior to what now is CMB.
    'Unlikely' does not mean impossible though, but until it ever does become possible, events prior to the recombination event. are all speculative, some guesses being more reasonable based on physics we know about with high confidence.
    However there is a lot of uncertainty of the physics prior to recombination.
    Best guess appears to be that the observable universe was approximately 379,000 years old when it occurred.
     
  6. Apr 7, 2015 #5

    phinds

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    In terms of direct observation, the CMB is only a restriction for how far back we can see electromagnetic radiation ("light"). With better detectors it is possible that some day we may be able to detect gravity waves and/or neutrinos considerably farther back.
     
  7. Apr 7, 2015 #6

    phinds

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    Ha! Beat you to it by 3 seconds !
     
  8. Apr 7, 2015 #7

    wabbit

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    Right:) bowing to the master I deleted that post. I'll be faster next time! :)

    Maybe it s a bad idea to delete posts though, I do that when I see a duplicate reply but it does break links. Not sure what's the preference here at pf.
     
  9. Apr 7, 2015 #8

    phinds

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    Yeah, you shouldn't delete posts ... it messes up the thread unless you catch it before anyone responds to it and even then you're not entirely safe because someone could be typing a response while you are deleting it.
     
  10. Apr 7, 2015 #9

    wabbit

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    OK noted, thanks. This is what happened here, quoted while deleting. Better just leave it then.

    Just wanted to add something: neutrinos also have their limiting time, similar to light. The temperature must be low enough (well, "low" is relative here) so that neutrinos decouple from matter. According to http://en.wikipedia.org/wiki/Cosmic_neutrino_background, this however happened not 380k years after the "big bang", but just two seconds - so we do gain a significant window. Still, no neutrinos from before that.
     
  11. Apr 7, 2015 #10

    Chronos

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    An efficient neutrino telescope would answer a lot of questions about the early universe. Unfortunately, neutrinos have a 'plays well with matter' grade barely above that of dark matter. They are very antisocial so collecting enough of them to generate a useful image of the early universe is hugely challenging.
     
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