The thermodynamical history of the universe

A predestrian walk is offered in the early universe. It is argued that the universe has departed from its original thermal equilibrium as a consequence of its mechanical instability. This transient deviation from the state of maximum entropy has made the creation of protons and galaxies possible. It is shown that several puzzling astrophysical phenomena can be explained by assuming a nonvanishing rest mass for the heaviest stable neutrino in the region of 30 eV.