Raymond & Beverly Sackler Lecture in Astrophysics

Sound waves propagating through the plasma of the Universe only 400,000 years after the Big Bang now offer some of our most precise measures of the composition and history of the Universe. In the last decade, we have been able to detect the fossil imprint of these sound waves using maps of the distribution of galaxies from the Sloan Digital Sky Survey. I will give an overview of the cosmological role of the sound waves and our observational program then describe what the results tell us about the shape of the Universe and the evolution of dark energy.