Physics Colloquium

Astronomers have mapped the visible universe for thousands of years, but with the discovery of dark matter in the last century we realized most of the universe is hidden from our eyes, and these maps are highly incomplete. The
relatively new phenomenon known as gravitational lensing is a tool for connecting the map of luminous stars and galaxies to that of the hidden dark matter. Lensing is unique in its' ability to measure this connection over an
enormous range of scales, from the scale of the dark halos surrounding galactic disks to the largest structures in the universe. I will show new results from the Sloan Digital Sky Survey that for the first time explore this entire range of scales with high precision. With this huge dynamic range we simultaneously test two fundamental predictions of the Cold Dark Matter theory: universal dark halo density profiles and the large scale correlation function of the mass field. With these measurements we also measure non-parametrically the total mass and total light in huge volumes, and infer the mean matter density in the universe. I will discuss the upcoming Dark Energy Survey, with which we will extend these measurements back in time, exploring the evolution of structure in the universe and the nature of the dark energy.