  The age of the universe in the Big Bang model can be calculated from three
parameters: Hubble's constant, h; the mass density of the universe, Omega_m;
and the cosmological constant, Omega_lambda. Recent observations of the cosmic
microwave background and six other cosmological measurements reduce the
uncertainty in these three parameters, yielding an age for the universe of 13.4
+/- 1.6 billion years, which is a billion years younger than other recent age
estimates. A different standard Big Bang model, which includes cold dark matter
with a cosmological constant, provides a consistent and absolutely
time-calibrated evolutionary sequence for the universe.
