Findings support Einstein’s theory of gravity
Atacama Cosmology Telescope collaboration research into mapping the universe’s cosmic growth supports Einstein’s theory of gravity
Scientists say the discovery has culminated in a significant breakthrough in understanding the evolution of the universe.
For millennia, humans have been fascinated by the mysteries of the cosmos.
Unlike ancient philosophers imagining the universe’s origins, modern cosmologists use quantitative tools to gain insights into the universe’s evolution and structure.
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 across a quarter of the entire sky, extending deep into the cosmos.
What’s more, it confirms Einstein’s theory of how massive structures grow and bend light, over the entire 14-billion-year lifespan of the universe.
Blake Sherwin, professor of cosmology at the University of Cambridge, where he leads a group of ACT researchers, said: “We have mapped the invisible dark matter across the sky to the largest distances, and clearly see features of this invisible world that are hundreds of millions of light-years across.
“It looks just as our theories predict.”
Interacts with gravity
Despite making up 85% of the universe and influencing its evolution, dark matter has been hard to detect because it doesn’t interact with light or other forms of electromagnetic radiation. As far as we know dark matter only interacts with gravity.
To track it down, the more than 160 collaborators who have built and gathered data from the National Science Foundation’s ACT in the high Chilean Andes observe light emanating following the dawn of the universe’s formation; the Big Bang – when the universe was only 380,000 years old.
Cosmologists often refer to this diffuse light that fills our entire universe as the ‘baby picture of the universe’, but formally, it is known as the cosmic microwave background radiation (CMB).
The team tracks how the gravitational pull of large, heavy structures including dark matter warps the CMB on its 14-billion-year journey to us, just as a magnifying glass bends light as it passes through its lens.
Mathew Madhavacheril, assistant professor in the Department of Physics and Astronomy at the University of Pennsylvania, said: “We’ve made a new mass map using distortions of light left over from the Big Bang.
The crisis in cosmology
“Remarkably, 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 you’d expect from our standard model of cosmology based on Einstein’s theory of gravity.”
Sherwin added: “Our results also provide new insights into an ongoing debate some have called ‘The Crisis in Cosmology.”
This crisis stems from recent measurements that use a different background light, one emitted from stars in galaxies rather than the CMB.
These have produced results that suggest the dark matter was not lumpy enough under the standard model of cosmology and led to concerns that the model may be broken.
However, the team’s latest results from ACT were able to precisely assess that the vast lumps seen in this image are the exact right size.
Cambridge PhD student Frank Qu, part of the research team, said: “When I first saw them, our measurements were in such good agreement with the underlying theory that it took me a moment to process the results.
“It will be interesting to see how this possible discrepancy between different measurements will be resolved.”
Suzanne Staggs, director of ACT and Henry DeWolf Smyth Professor of Physics at Princeton University, said: “The CMB lensing data rivals more conventional surveys of the visible light from galaxies in their ability to trace the sum of what is out there.
“Together, the CMB lensing and the best optical surveys are clarifying the evolution of all the mass in the universe.”
Image 1: Researchers used the Atacama Cosmology Telescope to create this new map of the dark matter. The orange regions show where there is more mass; purple where there is less or none. The typical features are hundreds of millions of light years across. The whitish band shows where contaminating light from dust in our Milky Way galaxy, measured by the Planck satellite, obscures a deeper view. The new map uses light from the cosmic microwave background (CMB) essentially as a backlight to silhouette all the matter between us and the Big Bang. “It’s a bit like silhouetting, but instead of just having black in the silhouette, you have texture and lumps of dark matter, as if the light were streaming through a fabric curtain that had lots of knots and bumps in it,” said Suzanne Staggs, director of ACT and Princeton’s Henry DeWolf Smyth Professor of Physics. “The famous blue and yellow CMB image is a snapshot of what the universe was like in a single epoch, about 13 billion years ago, and now this is giving us the information about all the epochs since.” © ACT Collaboration.
Image 2: Research by the Atacama Cosmology Telescope collaboration has culminated in a groundbreaking new map of dark matter distributed across a quarter of the entire sky, reaching deep into the cosmos. Findings provide further support to Einstein’s theory of general relativity, which has been the foundation of the standard model of cosmology for more than a century, and offer new methods to demystify dark matter. © Debra Kellner.
