A quarter-century after the discovery of the accelerated expansion of the universe, the constraints on dark energy that powers this acceleration have become very good, but the physical nature of dark energy remains elusive. I will present and discuss cosmological results from the measurement of baryon acoustic oscillations (BAO) in the three years of observations from the Dark Energy Spectroscopic Instrument. These results, when combined with other data, have indicated a possible new anomaly in the behavior of dark energy, which has caused both excitement and consternation in the field of cosmology. I will discuss these findings and their implication for our understanding of the physics of the universe.