On Thu, Nov 15, 2012 at 05:20:14AM -0600, Roger Clough wrote:
> Hi Bruno  and Russell,
> 
> The evidence of a Big Bang is enormous. See, for example:
> 

Of course, but the big bang is not the same thing as the beginning of
the universe.

Also, the cosmic microwave background, which is the direct
observational evidence of the big bang comes from the last
scattering, when electrons and nuclei combined for the last time
into atomic matter and stayed that way. Red shift surveys can only
give information about the age of the last scattering, and even then,
interpreting it as a certain number of years can only occur within a
specific model of the universe - the Friedmann model is often used
because of its simplicity - even though we now know the universe
evolved quite differently from the Friedmann model due to things like
dark energy, which introduces far too much uncertainty to claim that
the inverse of an accurate Hubble constant is "the age of the universe"

The big bang theory gives an account of the evolution of the universe
from a quark-gluon soup to the last scattering, and gives quite a good
account of the 300,000 years before the last scattering. Accounts of
what happened prior to the quark-gluon plasma are highly speculative,
including inflation theory, and are likely to be revised as science
progresses. In some of those speculations, the actual beginning of the
universe occurred much earlier, or in the infinite past.

Actually, according to Wikipedia:

Though the universe might in theory have a longer history, the
International Astronomical Union [4] presently use "age of the
universe" to mean the duration of the Lambda-CDM expansion, or
equivalently the elapsed time since the Big Bang in the current
observable universe.


Lambda-CDM is apparently the most widely accepted model of how the
universe expanded since the big bang. I didn't realise the IAU has
defined an "age of the universe", but its anything but.


Cheers

-- 

----------------------------------------------------------------------------
Prof Russell Standish                  Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics      hpco...@hpcoders.com.au
University of New South Wales          http://www.hpcoders.com.au
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