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The temperature of empty space What now?

  1. Aug 20, 2004 #1
    Following Hubble's discovery of the expanding universe, George Gamow postulated that the universe began as a big bang & calculated the temperature of empty space to be around 3 degrees Kelvin. In the early 60's this temperature was confirmed.

    We now know that rate of expansion is accelerating. My question is, what impact does this have on the temperature of empty space? Does theory still predict abount 3 degrees Kelvin?
     
  2. jcsd
  3. Aug 21, 2004 #2

    Chronos

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    None whatsoever. Eventually, expansion will cool it, but, it will never fall much below the currently measured temperature. The universe is already very near the limit imposed by the uncertainty principle.
     
  4. Aug 22, 2004 #3
    There are two things that come to mind when I consider that the acceleration might change the Standard Big Bang theory. First, it wasn't part of the SBB model, and it wasn't predicted. This seems pretty big to me. Second, the expansion is a big part of the dynamical properties (like temperature) of the universe. That it can be ignored really surprises me.

    I would think the acceleration would imply that the universe must be much younger than thought & further implies that the rate of cooling must have been much faster -- to get to the measured value of about 3 degrees. To me both seem to disagree with SBB theory.

    If you have to insert inflation to justify your comment, then for me to buy it, you'd have to explain why, today, nothing can go faster than c.
     
  5. Aug 22, 2004 #4

    Nereid

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    Jack,

    Seems you are confused on a whole lot of things:
    - 'wasn't part of SBB, wasn't predicted': this applies to lots of things; the key question is "with the new data, is the SBB still consistent?" and the answer is YES! (OK, some adjustments are needed, but that happens all the time; the SBB isn't derived from only a few universal constants)
    - as far as having an effect on the expansion, temperature would rank just about near the bottom. I mean, why not be surprised that the discovery of neutrino oscillation didn't make a bigger splash in cosmology? Or, why consider just the CMBR temperature (and not the relict neutrino temperature)?
    - 'acceleration -> younger universe'; it all depends on the numbers! Hand-waving 'much faster' and 'much younger' don't mean a thing ... when you crunch the numbers, using 'dark energy', the revised models are entirely consistent with the observations. Of course, as Garth has said, this consistency is model dependent, but that's life in cosmology ( :tongue2: )
    - 'nothing can go faster than c': please read the Lineweaver articles to which marcus has posted links; this is one of the least well understood aspects (by folk such as me and you) -'c' as a speed limit has its limits; wrt the expansion of the universe, it needs careful treatment.
     
  6. Sep 18, 2004 #5

    Garth

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    In addition to Nereid's excellent post, just a small correction: If the universe is accelerating rather than decelerating its age is older than previously thought. As it was going slower in the past it would have taken longer to "get to here" than previously thought! [There are some pretty mature galaxies at the edge of the visible universe that raise questions about how long they have had to form]

    Garth
     
  7. Sep 18, 2004 #6

    turbo

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    Too true! Assuming the Standard Model is accurate, we see a tremendous amount of structure and organization already in the infancy of the 13.7Gy Universe. Will the Large Binocular Telescope (a long-baseline light bucket pair with adaptive optics) show us more distant galaxies and quasars? Of course we have an infrared-optimized space telescope waiting in the wings as well, ready to probe for more highly-redshifted stuff. 13.7Gy may face some serious observational challenges in the next few years.
     
    Last edited: Sep 18, 2004
  8. Sep 18, 2004 #7

    marcus

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    Jack, I did not know Gamow came so close. Are you sure he did not guess something else besides 3 kelvin? Like, say, 5 kelvin, or 10 kelvin?
    Not to question the brilliance of the man's achievement and insight. But did he actually nail it that close? I do not know and could use a link to the history.

    Your question is interesting because it makes one ask "how would someone in 1950-1955 predict the temp of the CMB, knowing only the Hubble parameter and perhaps having some independent rough guess as to the age of the universe?"
     
  9. Sep 18, 2004 #8

    Chronos

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    Gamow predicted around 5K, which ain't bad. Another lesser known fellow, Andrew McKeller, made an even closer prediction of 2.3K in 1941. See
    http://aether.lbl.gov/www/science/CMBTimeLine.html
     
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