What it is
The Dark Energy Spectroscopic Instrument measured baryon acoustic oscillations from more than 14 million galaxies and quasars gathered over three years of operation. On its own the data fits the standard flat Lambda-CDM model, but the parameters it prefers sit in mild 2.3 sigma tension with the cosmic microwave background. Combining the galaxy and Lyman-alpha measurements with CMB and supernova data, the analysis finds a 4.2 sigma preference for dark energy whose equation of state evolves across cosmic time rather than staying constant.
Why it matters
A constant dark energy (the cosmological constant) is the backbone of the standard model of cosmology, so a 4.2 sigma pull toward a time-varying alternative is the strongest hint yet that the model is incomplete. The signal draws on the largest BAO sample assembled to date, 14 million tracers, giving it statistical weight earlier surveys could not reach. If it holds, the accelerating expansion of the universe is driven by something that changes, reshaping predictions for the cosmic fate.
Underlined numbers link to their source. Every metric and quoted figure is listed under Sources and data below.
Filed undercosmology, dark energy, DESI, baryon acoustic oscillations, Lambda-CDM
Watch
A short explainer of this result.