The 5-year quest by the Dark Energy Survey (DES) team is underway (3 September 2013) to solve the cosmic detective puzzle of why the expansion of the universe is speeding up rather than slowing down. Penn physicists are playing integral roles on the team and on the mission. Prof. Bhuvnesh Jain is leader of the Penn contingent and co-coordinator of the gravitational lensing group. Prof. Gary Bernstein is co-leader of the Science Verification team that has been fine-tuning the DES camera. Assoc. Prof. Masao Sako is co-coordinator of the Supernovae group working with Prof. and dept chair Larry Gladney. The survey will systematically map one-eighth of the sky in unprecedented detail, with the goal of finding out why the expansion of the universe is speeding up, instead of slowing down due to gravity. They will probe the mystery of dark energy, the force believed to be causing that acceleration. More information about the Dark Energy Survey, including the list of participating institutions, is available atwww.darkenergysurvey.org.