  Here we estimate the magnitude of the signals expected for realistic cosmic
neutrino backgrounds in detectors attempting to measure the mechanical forces
exerted on macroscopic targets by the elastic scattering of relic neutrinos. We
study effects proportional to the weak coupling constant $G_F$ and to $G_F^2$
for Dirac and Majorana neutrinos, either relativistic or non-relativistic, both
gravitationally bound or not.
