Nobel laureate defends accelerating universe theory against growing challenges

A quarter-century-old pillar of modern cosmology — that the universe's expansion is accelerating, driven by a mysterious "dark energy" — is facing renewed scrutiny from multiple research groups whose reanalyses of supernova data suggest the evidence may not be as solid as once thought.

Tata Institute Study Questions Dark Energy

A team led by Professor Emeritus Subir Sarkar of the University of Oxford, along with researchers Animesh Sah and Mohamed Rameez of the Tata Institute of Fundamental Research in Mumbai, published a letter in Monthly Notices of the Royal Astronomical Society in June arguing that the Pantheon+ catalogue of more than 1,700 Type Ia supernovae no longer supports accelerating expansion once a correction for the age of supernova progenitor stars is applied. Their analysis suggests cosmic expansion is instead slowing down.phys+2

The correction hinges on growing evidence that the intrinsic brightness of Type Ia supernovae — long treated as reliable "standard candles" for measuring cosmic distances — depends on the age of the stars that produce them. Younger progenitors tend to yield dimmer supernovae, and failing to account for this could cause astronomers to overestimate distances and mistakenly infer acceleration. "If this effect is not accounted for, it can lead to the erroneous conclusion that the expansion rate is accelerating," Sarkar said, according to the University of Oxford.physics.ox+1

Schmidt Weighs In on Yonsei Challenge

The debate intensified on Sunday when Nobel laureate Brian Schmidt addressed a parallel challenge at the Nobel Prize Dialogue Seoul 2026, held at COEX Auditorium in Seoul. A team led by Professor Lee Young-wook at Yonsei University has argued since November 2025 that a hidden age bias in supernova measurements undermines the case for cosmic acceleration. Schmidt, who shared the 2011 Nobel Prize in Physics for discovering accelerating expansion, said plainly: "I do not think the analysis by the Yonsei University research team is correct".dongascience+1

The back-and-forth has played out in the pages of the same journal. A rebuttal paper titled "Still Accelerating," co-authored by Schmidt and fellow laureate Adam Riess, appeared in June, and Lee's group responded on August 27 with a paper titled "Still Not Accelerating". Schmidt nonetheless welcomed the exchange. "This is how science operates," he said. "It is good that these things happen, and in the end, science will decide the correct answer".chosun+2

What Comes Next

Not everyone is convinced the standard model is in trouble. A team at the University of Southampton, led by Phil Wiseman and including Riess, has argued that conventional corrections already account for brightness variations tied to host-galaxy properties and that "the evidence supporting the accelerating expansion of the universe remains unshaken". Both sides now look to the Vera C. Rubin Observatory's Legacy Survey of Space and Time, which will observe hundreds of thousands of supernovae, as the dataset that could settle the question.phys+2