Dark matter

I review the evidence for the "missing mass" and discusses several of the proposed candidates: baryons, neutrinos, axions and WIMPs. Baryonic dark matter, the simplest hypothesis, is not consistent with a flat universe and standard big bang light element nucleosynthesis. The non-detection of time of flight delay in the arrival time of the neutrinos from SN1987a rules out the electron neutrino as a galactic dark matter candidate. Observations of dwarf galaxy may rule out any neutrino species as a viable dark matter candidate. Baryonic dark matter, black holes, axions and WIMPs may be detected or ruled out by current and future experiments.