The Hubble tension, a discrepancy in the calculated rate of the universe’s expansion, is one of the most pressing problems in cosmology. Two methods, the cosmic distance ladder and the early relic method, yield different results. The cosmic distance ladder suggests an expansion rate of 73-to-74 km/s/Mpc, while the early relic method suggests a rate of 67 km/s/Mpc. This discrepancy could potentially be explained by new, exotic physics or a change in the energy contents of the universe over time.
