Cosmological distance measurements determine the expansion history of the Universe, providing knowledge on, e.g., the nature of dark energy. I will describe how the signature of baryon acoustic oscillations, imparted into the matter density field due early Universe physics, can be measured in the distribution of galaxies and used as a “standard ruler” that enables distance measurements. I will present a new BAO distance measurement (to be made public later this week) determined using quasars from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) and show the updated BAO distance ladder. These measurements yield >6sigma evidence for dark energy on their own and can be combined cosmic microwave background measurements to provide tight constraints on, e.g., the sum of neutrino masses. I will describe the characteristics of BAO measurement that make it especially robust to observational systematics. I will conclude with a brief description the Dark Energy Spectroscopic Instrument (DESI) experiment and forecast for how it will improve the BAO distance ladder.
