  In this essay we extend the standard discussion of neutrino oscillations to
astrophysical neutrinos propagating through expanding space. This extension
introduces a new cosmological parameter $I$ into the oscillation phase. The new
parameter records cosmic history in much the same manner as the redshift z or
the apparent luminosity D_L. Measuring $I$ through neutrino oscillations could
help determine cosmological parameters and discriminate among different
cosmologies.
