Baryon Acoustic Oscillations (BAO) are regular, periodic fluctuations in the density of visible baryonic matter in the universe, caused by acoustic sound waves in the early universe plasma. These oscillations left an imprint at a characteristic scale of roughly 150 megaparsecs in the distribution of galaxies today, serving as a "standard ruler" for measuring cosmic distances and the expansion history. Recent measurements from the Dark Energy Spectroscopic Instrument (DESI) collaboration have found BAO scale measurements that disagree with predictions from the Planck satellite's CMB observations when both are fitted within the Lambda-CDM framework, with DESI suggesting different values for the matter density and dark energy equation of state than Planck infers (DESI Collaboration 2024; Aghamousa 2016). Lambda-CDM struggles with this tension because the model assumes the BAO scale is set by the sound horizon at the drag epoch (when photons decoupled from baryons) and should be a fixed standard ruler throughout cosmic history, leaving no room for the systematic discrepancies observed between early-universe (CMB) and late-universe (galaxy survey) measurements unless there are unaccounted systematic errors or new physics that modifies the expansion history in unexpected ways.