Unseen mass

In this paper, the author discusses the so-called unseen mass in the universe, in view of different values of cosmological quantities like mass density and M/L. First, he gives a summary of what is widely accepted in this domain. Then he discusses the possible candidates that may contribute to the unseen mass: neutrinos and particles predicted by theoretical physicists; baryons; and mass of Population III. Some theoretical and observational constraints on the mass of Population III are discussed. Next, the author summarizes some evolutionary models on the large-scale segregation of luminous and unseen material. These models give rise to voids which contain more gas than apparent clusters and a more homogeneous distribution of the baryonic component. (Auth.)