  There is a puzzling contradiction: direct observations favor a low-mass
density universe, but the only model which fits universe structure over more
than three orders of magnitude in distance scale has a mix of hot (neutrino)
and cold dark matter consistuting a critical density universe. If all present
indications for neutrino mass are valid, that hot dark matter is shared by two
neutrino species (nu_mu and nu_tau). These results also require at least one
light sterile neutrino to exist to explain the solar nu_e deficit (nu_e ->
nu_s), so that nu_mu -> nu_tau accounts for the atmospheric neutrino anomaly,
with anti-nu_mu -> anti-nu_e being observed in the LSND experiment. This
experiment, when analyzed appropriately, does not conflict with any others and
is compatible with the mass difference needed for dark matter. Support for this
mass pattern is provided by the need for a sterile neutrino to make possible
heavy-element nucleosynthesis in supernovae.
