  An electron neutrino can have the quantum phase of an electron, i.e. share
its internal clock, if the neutrino takes a path in space-time that is not in
the direction of its energy-momentum. Each flavor neutrino would then have a
different internal clock; a muon neutrino would have a muon clock and a tau
neutrino would have a tau clock. Perhaps surprisingly, there is some evidence
suggesting neutrinos have such clocks. If muon neutrinos travel on space-like
paths then some atmospheric muon neutrinos would take such paths backwards into
outer space and not be observed. These are lost at the source and have nothing
to do with oscillations or flavor-changing in flight. The expected depletion of
source muon neutrinos is shown here to be 9%, which accounts for half of the
missing muon neutrino source flux reported by Super-Kamiokande. Since there is
no depletion in the electron neutrino flux source reported at SK and SN1987A
electron neutrinos seem to have traveled at the speed of light, the electron
neutrino travels on a light-like path. Accelerator-based experiments could be
arranged to confirm the reverse motion of muon neutrinos.
