Cosmic Neutrino Time Delay Relative to Photons

By solving the Friedmann-Robertson-Walker (FRW) geodesic equations for a free test particle with finite mass, we extend the widely used time-of-flight delay expression, which is just valid locally in the neighbourhood of our Galaxy, to the cosmic distance scale. If neutrino masses are known, this may provide a potential method to determine a large scale geometry of the Universe.