Hubble Tension Tops 5 Sigma as Riess Defends 73 vs 67 Expansion Rates
Updated
Updated · Quanta Magazine · Jul 23
Hubble Tension Tops 5 Sigma as Riess Defends 73 vs 67 Expansion Rates
1 articles · Updated · Quanta Magazine · Jul 23
Summary
Five-sigma significance has pushed the Hubble tension past the usual physics threshold for a real discrepancy, with local measurements near 73 and early-universe predictions near 67 kilometers per second per megaparsec.
Riess said a decade of cross-checks has not resolved the gap: Hubble and James Webb support the local result, while Planck and other cosmic microwave background analyses keep pointing to the lower value.
The mismatch matters because Lambda-CDM has otherwise explained the universe to roughly 1% precision, so the conflict could reflect either hidden measurement systematics or missing physics linking the Big Bang to today’s expansion.
Riess pointed to other possible cracks in the standard model, including DESI hints that dark energy may evolve and evidence the nearby universe is less clumpy than expected.
New observatories — Vera Rubin, Euclid and NASA’s Nancy Grace Roman, due in September — are expected to sharpen measurements of dark energy and the recent expansion history.