How Fast Is the Universe Really Expanding?

The accelerating expansion of the universe challenges fundamental cosmological models, specifically the Lambda CDM framework. Nobel laureate Adam Riess details how Type 1a supernovae serve as "standard candles" to measure cosmic distances, providing the empirical evidence that the universe's expansion is speeding up rather than decelerating due to gravity. While the Lambda CDM model successfully accounts for dark matter and dark energy, current measurements of the Hubble constant reveal a persistent "Hubble tension"—a discrepancy between early-universe predictions and local observations. This tension suggests potential cracks in the standard model, prompting ongoing investigation into whether dark energy remains constant or evolves over time. Future observations from the Nancy Grace Roman Space Telescope aim to resolve these discrepancies, potentially leading to a conceptual shift in understanding the universe’s composition and ultimate fate.