I will describe the first observations of baryon acoustic oscillations (BAO) in the clustering of the inter-galactic medium. The analysis uses a large sample of high redshift (z = 2-3) quasars observed by the Baryon Oscillation Spectroscopic Survey (BOSS) to probe the Lyman-alpha forest. We estimate the 3D correlation function of the transmitted flux fraction and simultaneously measure the BAO standard ruler along and transverse to the line of sight using some novel fitting techniques. We interpret these measurements as constraints on the recent expansion history of the universe and the role of dark energy. I will review acoustic oscillations and previous measurements of the BAO standard ruler, then describe the unique features of a Lyman-alpha forest measurement and present the new BOSS results.