--- title: "New Paper Claims Everyone Is Wrong, Universe’s Expansion Is Slowing Down" description: "In a controversial new paper, researchers argue that the acceleration of the universe's expansion has slowed down." date: "2025-11-08" modified: "2025-11-08" authors: - name: "Victor Tangermann" job_title: "Senior Editor" link: "https://futurism.com/authors/victor" url: "https://futurism.com/space/universe-expansion-slowing-down" categories: - "Astronomy" - "Astrophysics" - "Dark Matter" - "Off-World" - "Space" --- # New Paper Claims Everyone Is Wrong, Universe’s Expansion Is Slowing Down ![In a controversial new paper, researchers argue that the acceleration of the universe's expansion has slowed down.]() *Getty / Futurism* By observing the brightness of distant dying stars, astronomers [have long come to believe]() that the expansion of the universe is accelerating. In fact, that apparent reality is deeply built into cosmological models: a mysterious force that influences the universe on the largest scales, dubbed [dark energy](), is believed to explain the acceleration. However, not everybody agrees with this widely accepted scientific consensus. In a [controversial new paper](), published in the journal *Monthly Notices of the Royal Astronomical Society*, a team led by Yonsei University astronomer Young-Wook Lee argues that once we take into consideration the age of these dying stars, the expansion acceleration suddenly disappears. In fact, Lee and his colleagues suggest the expansion started to decelerate 1.5 billion years ago, and could even reverse entirely in the future, resulting in a "big crunch" that effectively turns the concept of a Big Bang on its head, as [*New Scientist* reports](). It's a contentious new take on cosmology that's bound to draw plenty of skepticism from the scientific community. If confirmed, however, it would have colossal implications for our understanding of the universe — and, ultimately, its fate. For decades, scientists have posited that type Ia supernovae, which result from white dwarf stars exploding in a binary system, can stand in as "standard candles" to allow us to measure the cosmos. That's because scientists believe they are all equally bright. By using the inverse-square law, scientists have measured the distance to these exploded remnants, resulting in the consensus that the universe's expansion is accelerating. Simply put, the dimmer the supernova appears in observations, the further away it's believed to be from us. However, Lee argues that this conclusion is wrong and that the brightness isn't actually the same for each of these dying stars. The team argues that once you consider the age of each of these supernovae, the perceived acceleration goes away. The team used a sample of 300 galaxies to model the brightness of type Ia supernovae, and found that their dimming arose from "stellar astrophysics effects," and not just distance. "Our study shows that the universe has already entered a phase of decelerated expansion at the present epoch and that dark energy evolves with time much more rapidly than previously thought," Lee said in a [statement](). "If these results are confirmed, it would mark a major paradigm shift in cosmology since the discovery of dark energy 27 years ago." Not everybody is convinced of the findings. Space Telescope Science Institute physicist Adam Riess, who received the Nobel Prize in physics for the discovery of dark energy through the measurement of type Ia supernovae in 2011, told *New Scientist* that it's not easy to determine the age of these dying stars since there's a lot we still don't know about their evolution. "The theory behind this is weak because of a lack of certainty about how the \[star\] forms," he said. "It’s definitely interesting," University of Durham cosmologist Carlos Frenk, who was not involved in the research, [told *The Guardian*](). "It’s very provocative. It may well be wrong." However, "it’s not something that you can dismiss," he added. "They’ve put out a paper with tantalising results with very profound conclusions." Fortunately, researchers are hoping that observations by the Vera C. Rubin Observatory in Chile could shed more light on the matter by creating a map of tens of thousands of type Ia supernovae. "Within the next five years, with the Vera C. Rubin Observatory discovering more than 20,000 new supernova host galaxies, precise age measurements will allow for a far more robust and definitive test of supernova cosmology," said colead and Yonsei University researcher Chul Chung in the statement. **More on the expansion of the universe:** [*An Important Force of the Universe Appears to Be Changing, Scientists Find*]() ## Author I've been at Futurism since 2017, where my role has evolved to encompass design, writing, and increasingly editing. I've always been fascinated by space exploration and advanced transportation, which I've leaned into by interviewing luminaries in those fields while closely following the dimensions of policy and regulation that allow next-generation projects to succeed -- or, sometimes, to fail. I'm also keenly interested in the effects of generative AI on society, policies, and democratic institutions, as well as clean energy, physics and biology, and the vagaries of tech leadership. My work for Futurism has been cited by publications including Ars Technica, Gizmodo, PC Magazine, Jalopnik, Fox News, and the New York Post. I spent my childhood living in locations including Manila, the Philippines, and Geneva, Switzerland, attended McGill University, and now live in Toronto, Canada. Before Futurism I worked at AskMen and a small photography studio. In my free time, I'm an avid gardener, foodie, and craft beer lover, as well as a maker of artisanal hot pepper sauces. I have a magnificent dog named Freida. ### Author social links [Bluesky]()