Title: Dark Energy, Clusters, and Lensing

Abstract: Dark energy is the dominant component in the universe, but there are frustratingly few methods of detecting and analyzing it. One of the most promising is the abundance of clusters of galaxies as a function of mass and redshift. I explain why, and why mass determination is so crucial to this method. One way to measure cluster masses is gravitational lensing: the deflection of light originating behind the cluster. I present some results, obstacles, and projections.