  Increasing improvements in the independent determinations of the Hubble
constant and the age of the universe now seem to indicate that we need a small
non-vanishing cosmological constant to make the two independent observations
consistent with each other. The cosmological constant can be physically
interpreted as due to the vacuum energy of quantized fields. To make the
cosmological observations consistent with each other we would need a vacuum
energy density, $ \rho_v \sim (10^{-3} eV)^4 $ today ( in the cosmological
units $ \hbar=c=k=1 $ ). It is argued in this article that such a vacuum energy
density is natural in the context of phase transitions linked to massive
neutrinos. In fact, the neutrino masses required to provide the right vacuum
energy scale to remove the age Vs Hubble constant discrepancy are consistent
with those required to solve the solar neutrino problem by the MSW mechanism.
