  The existence of big bang relic neutrinos - exact analogues of the big bang
relic photons comprising the cosmic microwave background radiation - is a basic
prediction of standard cosmology. At present, the observational evidence for
their existence rests entirely on cosmological measurements, such as the light
elemental abundances, anisotropies in the cosmic microwave background, and the
large-scale matter power spectrum. In this review, we concentrate on the
prospects of more direct, weak interaction based relic neutrino detection
techniques which are sensitive to the cosmic neutrino background near the
present epoch and in our local neighborhood in the universe. In this
connection, we emphasize the necessity to take into account the gravitational
clustering of the relic neutrinos in the cold dark matter halos of our Milky
Way and nearby galaxy clusters.
