  Supernovae provide a unique opportunity for large scale parity violation
because they are dominated by neutrinos. We calculate the parity violating
asymmetry A of neutrino emission in a strong magnetic field. We assume the
neutrinos elastically scatter many times from slightly polarized neutrons.
Because of multple interactions, A grows with the optical thickness of the
proto-neutron star and may be much larger than previous estimates. As a result,
the neutron star could recoil at a significant velocity.
