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Are SN 1a light curves evidence of universal expansion?

  1. Nov 27, 2012 #1
    All, Based on pointers that I have received from a number of people on the forum, I have been reading about the support that the time dilation of supernovae (type 1a) light curves provides to the standard model– thanks to all and a special thanks to GerogeJones.

    The material seems to fall into two categories – pro and against the relationship. The “pro” material seems (very honest, but) very selective in the fine-tuning of the model and the data used. On the other hand, the “against” material makes a number of references to people and models that I don’t have much faith in.

    On this basis, and respecting the views of people on the forum, can I ask your opinion on this subject: do you think that the time dilation of SN 1a light curves is good evidence of expansion? (Please note, I'm not asking about your views of expansion, just your views of the SN 1a light curve evidence.)


    Regards,


    Noel.
     
  2. jcsd
  3. Nov 27, 2012 #2

    Bobbywhy

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    Gold Member

    Since I am not a Cosmologist my opinion is based on what others say. I agree with Ned Wright’s answer here:

    “Has the time dilation of distant source light curves predicted by the Big Bang been observed?

    This time dilation is a consequence of the standard interpretation of the redshift: a supernova that takes 20 days to decay will appear to take 40 days to decay when observed at redshift z=1. The time dilation has been observed, with 5 different published measurements of this effect in supernova light curves. These papers are:
    • Leibundgut etal, 1996, ApJL, 466, L21-L24
    • Goldhaber etal, in Thermonuclear Supernovae (NATO ASI), eds. R. Canal, P. Ruiz-LaPuente, and J. Isern.
    • Riess etal, 1997, AJ, 114, 722.
    • Perlmutter etal, 1998, Nature, 391, 51.
    • Goldhaber etal, ApJ in press.

    These observations contradict tired light models of the redshift.”
    http://www.astro.ucla.edu/~wright/cosmology_faq.html

    Cheers,
    Bobbywhy
     
  4. Nov 27, 2012 #3

    Chronos

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    Expansion is widely accepted in the scientific community. Einstein anticipated this with his field equations and added a fudge factor called the cosmological constant to maintain a static universe - which was the prevailing opinion of his time. Hubble decided the issue with his pioneering work on galactic redshifts, prompting Einstein to disavow his cosmological constant as his greatest blunder. Little did he know he would be vindicated about a century later. The big surprise was the discovery that the rate of expansion was accelerating. This conclusion was drawn from supernova light curves by Perlmutter and Reiss. They received the Nobel for this work.
     
  5. Nov 27, 2012 #4
    Thanks guys. I agree completely with the logic, but (my reading of) more recent papers seem less convinced of the observational backup, and this surprised and disappointed me.

    Regards,

    Noel.
     
  6. Nov 27, 2012 #5

    Bobbywhy

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    Lino (Noel), Will you please post the referenced papers you mentioned? Share your doubts. Thank you.

    Cheers,
    Bobbywhy
     
    Last edited: Nov 27, 2012
  7. Nov 27, 2012 #6
    Bobby, I don't have a lot of the references to hand, and I apologize that I don't have specific notes on the problems (that I had) in specific cases. (Final apology) I also apologize about the way that I am referencing the papers here without links (again, I don't have notes, or even a decent method for reviewing and keeping notes).

    I should printout that I am not saying that there isn't a relationship, I just hoped/expected that the relationship was a lot stronger / less arguable then it appears. Personally, I strongly agree with the logic that you (& Chronos) setout ... I'm just very surprised by the amount of debate / uncertainty / opportunities for observational disagreement!

    Anyway, (all references / reading based on arxiv) my primary reading has been on Perlmutter and Riess (which unsurprisingly is pro, but which then seem to be interpretated / updated (?) by later work). I have read about 10-12 other papers such as:
    1112.1328v1 - New interpretations ...by Vlahovic (I didn't like a number of the supporting references)
    1210.3428v1 - On the rates on type 1a .. by Quimby / .. / Wheeler (whose name attracted me to it) / ... (I thought that there was a significant amount of data selection / filtration filtration)
    0602500v1 - Magnitude-redshift relationship ... by Brynjolfsson (I didn't like the number of model assumptions used)
    0104382 - Timestretch parameterization of type 1a SN ... by Goldhaber etc al (I thought there was a lot of data selection / refinement)

    I should stress that this is just a selection but most of what I read falls into one of these categories.

    Regards,

    Noel.
     
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