In this final chapter we consider the promising future directions in globular cluster research. This discussion is driven by those areas where we feel that theoretical and observational progress can have the greatest impact, both in solving currently open questions about globular cluster systems themselves and producing significant advances in other astrophysical fields. To this extent, this chapter is a wish list for the future. The most exciting developments in astrophysics are invariably unexpected, but we feel that offering some speculation on the nature of future advances is useful. We organize this chapter along the lines of the earlier text, starting with globular clusters in the Milky Way and progressing to the distant extragalactic globular cluster systems.
Milky Way globular clusters
In terms of its impact on other areas of astrophysics and cosmology, the age of Milky Way globular clusters is one of the most important topics of current and future research. There are two primary reasons for this interest. First, globular cluster ages provide a lower limit to the age of the universe, so that when combined with other observable cosmological parameters they provide constraints on the geometry and mass density of the universe. Current age estimates already provide important limits on cosmological models, so reducing uncertainties in these estimates is a key goal. Second, the age distribution of Milky Way globular clusters provides critical constraints on the formation history and formation models of the Milky Way.