Korean Researchers Challenge Nobel-Winning Theory, Say Universe Is Slowing Down
- Yul So
- Oct 22
- 2 min read
Oct 22, 2025
Yul So
A team from Yonsei University has released research that disputes the 2011 Nobel Prize–winning theory that the universe is expanding at an accelerating rate.
According to the study, the universe is no longer accelerating but is instead entering a slower expansion phase. The researchers also found that dark energy, once thought to be constant, appears to weaken over time.
Professor Lee Young-wook and his colleagues at Yonsei University’s Department of Astronomy and the Center for Galaxy Evolution published their findings in the Monthly Notices of the Royal Astronomical Society. Their results are based on a revised analysis of Type Ia supernova brightness data. They discovered that a supernova’s brightness depends on the age of the star system where it explodes. Supernovae from younger stars appear dimmer, while those from older stars are brighter, even after standard corrections.
After adjusting for this “age bias,” the data no longer fit the standard cosmological model, which assumes dark energy is constant. Instead, it matched better with the Dark Energy Spectroscopic Instrument (DESI) model, which suggests dark energy changes over time.
When combined with data from baryon acoustic oscillations and cosmic microwave background observations, the results showed very high statistical confidence, supporting the idea that the universe is already in a decelerating phase. Professor Lee said this could mark a major shift in cosmology if confirmed. He added that future surveys, such as the upcoming LSST project, could provide even stronger evidence with tens of thousands of new supernova discoveries.
The study was conducted with Research Professor Jung Chul, researchers Son Jun-hyuk and Park Seung-hyun, and Professor Cho Hye-jeon of Yonsei University.
