  We present a new technique to measure neutrino masses using their flow field
relative to dark matter. Present day streaming motions of neutrinos relative to
dark matter and baryons are several hundred km/s, comparable with their thermal
velocity dispersion. This results in a unique dipole anisotropic distortion of
the matter-neutrino cross power spectrum, which is observable through the
dipole distortion in the cross correlation of different galaxy populations.
Such a dipole vanishes if not for this relative velocity and so it is a clean
signature for neutrino mass. We estimate the size of this effect and find that
current and future galaxy surveys may be sensitive to these signature
distortions.
