Nobel Laureates Rebut Study Claiming Universe's Expansion Is Slowing, Confirm Acceleration Continues

A University of Southampton-led team, co-authored by Nobel Prize-winning astrophysicists Adam Riess and Brian Schmidt, has published a detailed rebuttal confirming that the universe's expansion continues to accelerate, driven by dark energy. The study, appearing in the Monthly Notices of the Royal Astronomical Society, directly addresses a late-2024 paper by South Korean researchers who had argued that Type Ia supernova data indicated dark energy was weakening and cosmic expansion was decelerating. The new analysis identified two key errors in that earlier work: it incorrectly assumed the age of an exploding star matched the age of its host galaxy — a flawed shortcut that distorts brightness calculations — and it failed to apply a standard correction accounting for host galaxy mass. When both errors are corrected, the evidence for cosmic acceleration returns clearly and consistently, as illustrated by NASA's timeline of the universe showing dark-energy-driven acceleration beginning roughly five billion years ago. Lead author Dr. Phil Wiseman described the episode as a scientific misunderstanding rather than a flaw in the universe, and Riess emphasized that extraordinary claims require especially careful testing. The mystery of dark energy's fundamental nature remains entirely open, but researchers say the episode has also opened new avenues for thinking about how supernovae explode and how dark energy can be measured more precisely.