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 H ₀ t ₀ 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, H ₀ t ₀ < 1; in an accelerating Universe with the same Ω _m = 0.26, but dominated by vacuum energy with Ω _V ≥ 1 - Ω _m , H ₀ t ₀ ≥ 1. If the first globular clusters formed 109 years after the Big Bang, then with 95% confidence H ₀ t ₀ =1.0 ± 0.3. The classical Einstein-de Sitter cosmological model has H ₀ t ₀ = ⅔.