David Gerdes

Arthur F. Thurnau Professor of Physics

University of Michigan

Dark Energy and the Accelerating Universe

Me with DECamI am an Arthur F. Thurnau Professor in the Physics Department at the University of Michigan. I'm an observational cosmologist who uses the tools of optical astronomy to address one of the most alluring mysteries in science: the accelerating expansion of the universe. This expansion appears to be caused by a property of space itself called dark energy, which makes up nearly 75% of the energy in the universe. Dark energy earned its discoverers the 2011 Nobel Prize in Physics, but we actually know very little about it. Can dark energy be described by a cosmological constant, as Einstein proposed? Or does it depend on time, which would imply some new underlying dynamics? Maybe even general relativity itself needs to be modified. To address these questions, I'm working with an international team of scientists on the Dark Energy Survey (DES). We have built a new 570-Megapixel camera, DECam, to carry out a survey of 5000 square degrees (about one-eighth of the sk), using the 4-meter Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. During 525 nights of observing beginning in 2013, DES will observe 300 million galaxies and discover about 4000 Type Ia supernovae. DECam, in essence, is a time machine that allows us to look over eight billion years into the past and observe how the universe has evolved to its present state. By making this "time lapse movie" of the past eight billion years of cosmic expansion, we'll learn how the tug-of-war between gravity and dark energy has shaped the growth large-scale structure in the universe. I'm especially interested in how this interplay has affected the properties of galaxy clusters.