Summary in Seconds: The accelerating expansion of the Universe, discovered in 1998, remains one of modern cosmology’s greatest mysteries. While the standard ΛCDM model attributes this acceleration to a cosmological constant, alternative explanations—including dynamic dark energy and possible modifications to Einstein’s general relativity—are being actively explored. Using data from large-scale surveys such as the Dark Energy Survey, researchers test gravity on cosmic scales through theoretical extensions like Horndeski models and phenomenological parameters (μ and η) that capture potential deviations from Einstein’s equations. Recent analyses suggest a mild (3-sigma) tension between observations and general relativity, particularly in how large-scale structures have