In 1929 the astronomer Edwin Hubble observed that distant galaxies move away from us with velocities proportional to their distance, i.e. the universe appears to be expanding.
Our concept of 'The age of the universe' is based on the fact that we can extrapolate the Hubble expansion rate backwards in time to a 'crunch' situation, yielding a result
of about 13 billion years.
Inflation, if in fact it is true, took place in the earliest instants of the big bang. It was over and done with in an eye blink and really doesn't count in the determination of
the age of the universe.
For additional information on this subject look at:
p.s. There's also apparently some inflation going on now, but it's much, much weaker than that early burst. mike w.
(published on 05/27/07)