Neutrinos: Ghost particles of the universe

Neutrinos are special among elementary particles in that they interact extremely weakly, their masses are extremely small, and they show the phenomenon of flavor oscillations, a macroscopic quantum interference effect, which allows them to convert from one type (or flavor) to another. They play a dominant dynamical role in the early universe and in core-collapse supernovae, may be responsible for the cosmic matter-antimatter asymmetry, and they carry crucial information about the highest-energy astrophysical phenomena – the field of neutrino astronomy has only just begun. We will review the role of these elusive particles in physics, astrophysics and cosmology.