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I Perlmutter presentation : pb on the age of the Universe

  1. Aug 6, 2017 #1
    I just watched a presentation about the acceleration of the Universe by Perlmutter. At this moment in the video he points the correct line for the scale factor of the Universe.

    Aaaaand that lines starts around 15 billion years ago, not 14 billion. So I thought maybe the latest estimations of the age of the Universe are now closer to 15 billions, but internet says the Planck mission gives an age of the Universe of around 13,8 billion years. So, why the line Perlmutter points as correct is the one starting 15 billion years ago, and not the next line starting a bit after 14 billions years ago ?

    A very similar figure (but with less data points) is also available here on the Supernova Cosmology Project official website.
  2. jcsd
  3. Aug 6, 2017 #2


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    AFAIK, that bunch of curves were based on calculations prior to the latest observations by plugging a variety of possible parameters into the Friedman equations. All it says is that the data is more or less consistent with the original 15 Gyr 'starting point' (age) value. The latest Plank data refined those parameters so that the calculations now indicate a 13.8 Gyr age for the universe, within relatively narrow tolerances.
  4. Aug 6, 2017 #3
    But that conference has been given after 2011 (because they tell about the Nobel Prize that Perlmutter received in 2011). I'd think he'd have updated his figures by then, but well, I can't see a better explanation than the one you gave anyway. Thank you.
  5. Aug 6, 2017 #4


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    Taking into consideration that the talk was not about the age of universe, it was perhaps a little sloppy of Perlmutter to say that the best-fit from observations falls within the thickness of the green curve, given where it starts.

    AFAIK, you need quite large deviations from Planck's reported parameters to get to an age of 15 Gyr - something like Lambda 75% or more contribution to the critical density.
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