The Hubble Constant

Abstract

With the completion of the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale, it is interesting to form the dimensionless quantity H0t0 by multiplying the Hubble Constant by the age of the Universe. In a matter dominated decelerating Universe with a density exceeding 0.26 of the critical value, H0t0 < 1; in an accelerating Universe with the same Omega_m = 0.26, but dominated by vacuum energy with Omega_V >= 1 - Omega_m, H0t0 >= 1. If the first globular clusters formed 10^9 years after the Big Bang, then with 95% confidence H0t0 = 1.0 +-0.3. The classical Einstein-de Sitter cosmological model has H0t0 = 2/3.