For millennia, humans have been fascinated by the mysteries of the cosmos. Unlike ancient philosophers who imagined the origins of the universe, modern cosmologists use quantitative tools to gain insight into the evolution and structure of the universe. Modern cosmology dates back to the early 20th century, with the development of Albert Einstein’s theory of general relativity. Now, researchers from the Atacama Cosmology Telescope (ACT) collaboration have created a groundbreaking new image that reveals the most detailed map of dark matter distributed over a quarter of the sky, extending deep into the cosmos. Furthermore, it confirms Einstein’s theory of how massive structures grow and bend light during the 14 billion year lifetime of the universe.

“We have created a new mass map using the light distortions left over from the Big Bang,” says Mathew Madhavacheril, an assistant professor in the Department of Physics and Astronomy at the University of Pennsylvania. “Surprisingly, it provides measurements that show that both the ‘lumpiness’ of the universe and the rate at which it is growing after 14 billion years of evolution are just what we would expect from our standard model of cosmology based on Einstein’s theory. of gravity.” Sherwin adds: “Our results also provide new insights into an ongoing debate that some have called ‘The Crisis of Cosmology,'” explaining that this crisis stems from recent measurements using a different background light, one emitted by stars. in galaxies instead of the CMB. . These have produced results suggesting that dark matter was not lumpy enough according to the standard model of cosmology and raised concerns that the model could break. However, the latest results from the ACT team were able to accurately assess that the large lumps seen in this image are exactly the right size.

“When I first saw them, our measurements matched the underlying theory so well that it took me a moment to process the results,” says Cambridge Ph.D. student Frank Qu, part of the research team. “It will be interesting to see how this possible discrepancy between different measurements will be resolved.” “CMB lensing data rivals more conventional studies of the visible light of galaxies in their ability to track the sum of what’s out there,” says Suzanne Staggs, ACT Director and Henry DeWolf Smyth Professor of Physics at the University of of Princeton. “Together, the CMB lens and the best optical studies are shedding light on the evolution of all the mass in the universe.”

“When we proposed this experiment in 2003, we had no idea of ​​the total amount of information that could be extracted from our telescope,” says Mark Devlin, Reese Flower Professor of Astronomy at the University of Pennsylvania and deputy director of ACT. “We owe it to the intelligence of theorists, to the many people who built new instruments to make our telescope more sensitive, and to the new analysis techniques our team devised.” ACT, which operated for 15 years, was decommissioned in September 2022. However, more papers presenting the results of the final set of observations are expected to be forthcoming soon, and future observations will be made by Simons Observatory at the same site, with a new telescope. scheduled to start operating in 2024. This new instrument will be able to map the sky almost 10 times faster than ACT.