  We study gravitational lensing of the cosmic neutrino background. This signal
is undetectable for the foreseeable future, but there is a rich trove of
information available. At least some of the neutrinos from the early universe
will be non-relativistic today, with a closer surface of last scattering
(compared to the cosmic microwave background) and with larger angles of
deflection. Lensing of massive neutrinos is strongly chromatic: both the
amplitude of lensing and the cosmic time at which the potential is traversed
depend on neutrino momentum, in principle giving access to our entire causal
volume, not restricted to the light cone. As a concrete example, we focus on
the case where the cosmic neutrino background would be strongly lensed when
passing through halos of galaxy clusters and galaxies. We calculate the
Einstein radius for cosmic neutrinos and investigate the impact of neutrino
mass.

Cosmology and Nongalactic Astrophysics