Astronomy Colloquium

I will discuss how sound waves racing through the cosmos during the first million years of the Universe provide a robust method formeasuring the low-redshift cosmologicaldistance scale and thereby the properties of dark energy.  The distance that the sound can travel can be computed to high precision and creates a signature in the late-time clustering of matter that serves as a standard ruler.  Galaxy clustering results from the Sloan Digital Sky Surveyand SDSS-III
reveal this feature and allow us to measure distancesto high accuracy, including a new 1% measurement to z=0.57.