  We thoroughly explore the cosmic gravitational focusing of cosmic neutrino
fluid (C$\nu$F) by dark matter (DM) halo using both general relativity for a
point source of gravitational potential and Boltzmann equations for continuous
overdensities. Derived in the general way for both relativistic and
non-relativistic neutrinos, our results show that the effect has fourth power
dependence on the neutrino mass and temperature. With nonlinear mass dependence
which is different from the cosmic microwave background (CMB) and large scale
structure (LSS) observations, the cosmic gravitational focusing can provide an
independent cosmological way of measuring the neutrino mass and ordering. We
take DESI as an example to illustrate that the projected sensitivity as well as
its synergy with existing terrestrial neutrino oscillation experiments and
other cosmological observations can significantly improve the neutrino mass
measurement.
