region in the age-$w$ plane obtained for $\Omega_b h^2=0.02$, $0.05<\Omega_m<0.4$, and $0.5<h<0.9$. It is clear from the plot that an independent and accurate age determination of the universe will provide a measurement of $w$. Thus by using only the [*WMAP*]{} observation of $\ell_1$ and an independent estimate of the age of the universe, we can place constraints on $w$, largely independent of other cosmological parameters.

Results from the ages of globular clusters
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The ages of the oldest globular clusters (GCs) provide a lower limit to the total age of the universe. Numerous star-forming galaxies have now been observed up to redshift $z=6.6$ [e.g., @Kodaira+03]. Since the oldest GCs contain the oldest stellar populations in galaxies, it is reasonable to assume that GCs too have formed at redshift $z>6$. Furthermore, since small halos are easily destroyed after reionization [e.g., @Bullocketal01], GCs likely formed prior to the reionization epoch. Under this assumption, the [*WMAP*]{} recent estimate of the reionization redshift $z_{\rm reion}\sim
17$ [@KogutWMAP03] implies that the ages of the oldest globular cluster do not significantly underestimate the age of the universe.

Globular cluster ages can reliably be estimated in several different ways: from the luminosity of the main-sequence turn-off (if 