Measuring Cosmic Acceleration

David Weinberg

Ohio State University

The discovery of accelerating cosmic expansion has inspired ambitious programs to measure the expansion history and growth of structure with perecent-level precision over a wide range of redshift. These programs include some of the largest cosmological surveys currently underway and some of the highest priority projects recommended by the Astro2010 decadal survey. I will summarize highlights from a nearly completed, book-length review article on "Observational Probes of Cosmic Acceleration" (Weinberg, Mortonson, Eisenstein, Hirata, Riess, Rozo, in prep.). I will pay particular attention to the complementarity of baryon acoustic oscillations (BAO) and supernovae as distance indicators, to the potential of galaxy clusters calibrated by stacked weak lensing as a probe of structure growth, and to the power of a balanced, multi-pronged observational program that combines supernovae, BAO, weak lensing, and additional methods enabled by the same data sets. The dark energy community is now searching for subtle quantitative anomalies that would have profound physical implications, distinguishing among fundamentally different theories of the energy content of the universe, the nature of gravity, and the origin of cosmic acceleration. The road from 5-percent measurements to 1-percent or sub-percent measurements is a challenging one, but we are well equipped for the journey.