Institute for Advanced Study / Princeton University Joint Astrophysics Colloquium

Neutrinos are the second most abundant particle in the known Universe yet they remain mysterious. While they played an important role in the early Universe, today they contribute at most 1-2% of the energy budget and leave only faint signatures. A major goal of the current decade of experiments is to measure the neutrino contribution to the energy budget at high significance, thereby determining the neutrino mass scale and perhaps even the ordering of masses. I will describe the physical effects of neutrino mass, highlighting the distinct roles played geometry and structure on constraints, and how some dataset combinations give a peculiar preference for “negative neutrino mass,” while others hint at a detection. I will also discuss novel astrophysical probes of neutrino mass that may ultimately help resolve current conundrums and contribute to validating any  detection of relic neutrinos in the late Universe.