Looking Back with Neutrinos

We briefly discuss the history of suggestions for time- of-flight effects due to non-zero neutrino mass and a recent proposal that such effects can be used to determine the parameters of cosmology. With neutrinos there is potentially a much deeper ``look back time’’ than with photons. We note a new point, that if future large scale neutrino detection arrays see long-time secular variations in counting rate, this could be due to highly redshifted bursts originating in the early universe.