Recent results on supernovae as standard candles (Riess et al. 1998; Perlmutter et al. 1999) and on CMB anisotropy (Lineweaver 1998) indicate that ΩM ≍ 0.3-0.4, Ωv ≍ 0.6-0.7, ΩM + Ωv ≍ 1. By definition, ΩM = ρM/ρcr, ΩV = ρv/ρcr, where ρM is the matter density, ρv is the vacuum density; the critical density ρcr = 3H2/8πG; H is the Hubble parameter, G is the gravitational constant. In the standard Friedmann-Lemaître cosmologies, these results seriously constrain the non-dimensional cosmological constant (as defined below): Δ ≫ 1, meaning that the Universe expands forever. If a scalar field is present, the future evolution may be different.