Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Accelerated expansion: is the jury still out?

  1. Feb 21, 2005 #1

    Chronos

    User Avatar
    Science Advisor
    Gold Member
    2015 Award

    I thought this was interesting:

    High Redshift Supernovae: Cosmological Implications
    http://arxiv.org/abs/astro-ph/0502247

    ... it appears that the problem of whether there is an acceleration in the Universe, and if so what its strength is, is not definitely solved and that much work is still needed before reaching the final conclusion.
     
  2. jcsd
  3. Feb 21, 2005 #2

    ohwilleke

    User Avatar
    Gold Member

    The gist of the argument (from the abstract): "We also discuss the possibility and the consequences of the fact that SNIa may not be "perfect" standard candles, in the sense of having properties in the early Universe that are systematically different from those they have at the present times."
     
  4. Feb 22, 2005 #3

    Garth

    User Avatar
    Science Advisor
    Gold Member

    Nino goes on to say that as the SNIa luminosity is calibrated from local galaxies, these would tend to be the older systems, whereas the distant SNIa would tend to be the younger ones. Hence
    Remember the problems calibrating the Cepheid Variable 'standard candle'? A error of factor of about three was introduced because it was not realised that there were two types of Cepheid Variables, belonging to Population I and Population II stars respectively.

    Methinks we may be making the same mistake again here!

    Just a thought!

    Garth

    BTW Chronos thank you for that very interesting link.
     
    Last edited: Feb 22, 2005
  5. Feb 22, 2005 #4

    Chronos

    User Avatar
    Science Advisor
    Gold Member
    2015 Award

    I share those sentiments, Garth. I've never been comfortable with the notion the universe suddenly changed speed. The explanations offered appear large and jagged [hard to swallow]. As long as I'm on a roll, there is room to doubt the Cepheid yardstick is fully calibrated:

    Population II standard candle calibration ...
    http://arxiv.org/abs/astro-ph/0303035

    The Status of the Distance Scale
    http://arxiv.org/abs/astro-ph/9911296

    Supernova type Ia luminosities, their dependence on second parameters, and the value of H_0
    http://arxiv.org/abs/astro-ph/0004063
     
    Last edited: Feb 22, 2005
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Accelerated expansion: is the jury still out?
Loading...