  The next generation of cosmological surveys are expected to measure a
non-zero sum of neutrino masses, even down to the minimum value of 58 meV
inferred from neutrino flavor oscillation. The implications of such a
measurement for the physics of neutrinos have been well documented; in
contrast, the cosmological implications of such a measurement have received
less attention. In this paper, we explore the impact of a neutrino mass
detection consistent with $\sum m_\nu = 58$ meV for our understanding of the
history and contents of the universe. We focus primarily on three key areas:
the thermal history of the universe, clustering of matter on diverse scales,
and the application to dark matter and dark sectors. First we show that a
detection of non-zero neutrino mass would provide a unique connection between
the cosmic neutrino background, which is detected gravitationally, and
neutrinos measured on Earth. We then discuss how the consistency of a detection
between multiple probes will impact our knowledge of structure formation.
Finally, we show how these measurements can be interpreted as sub-percent level
tests of dark sector physics.
