New findings charting the cosmic growth of the universe support Einstein’s theory of gravity


April 11, 2023

(Nanowerk News) For thousands of years, humans have been fascinated by the mysteries of the cosmos.

Unlike ancient philosophers who imagined the origin 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 general theory of relativity.

Now, researchers from the Atacama Cosmological Telescope Collaboration (ACT) have created groundbreaking new images that reveal the most detailed maps of dark matter spread across a quarter of the sky, extending deep into the cosmos. What’s more, it confirms Einstein’s theory of how massive structures grow and bend light, over the 14 billion year life of the universe.

“We have mapped invisible dark matter across the sky to the greatest distances, and clearly see the features of this invisible world hundreds of millions of light years across, said Blake Sherwin, professor of cosmology at the University of Cambridge, where he leads the group. ACT researcher. “It looks like the predictions of our theory.” ACT Lensing Map The researchers used the Atacama Cosmological Telescope to create this new map of dark matter. The orange areas show where there is more mass; purple where there is less or no. Its hallmark is hundreds of millions of light years away. The whitish bands show where light contaminated from dust in our Milky Way galaxy, measured with the Planck satellite, obscures deeper views. 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 a silhouette, but instead of just being black in a silhouette, you have the texture and wisps of dark matter, as if light is flowing through a curtain of fabric that has lots of knots and bumps in it,” said Suzanne Staggs, ACT director and Professor of Physics. Henry DeWolf Smyth of Princeton. “The famous blue and yellow CMB image is a snapshot of what the universe was like in one epoch, about 13 billion years ago, and it now gives us information about all the epochs since.” (Image: ACT Collaboration)

Despite making up 85% of the universe and influencing its evolution, dark matter is difficult 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, more than 160 collaborators who have built and collected data from the National Science Foundation’s Atacama Cosmological Telescope in the highlands of the Chilean Andes observed the light that emanated 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’s known as cosmic microwave background radiation (CMB).

The team tracked how the gravitational pull of massive, heavy structures including dark matter warped the CMB on its 14 billion-year journey to us, much like how a magnifying glass bends light as it passes through its lens.

“We have created a new mass map using the distortion of light left over from the Big Bang,” said Mathew Madhavacheril, assistant professor in the Department of Physics and Astronomy at the University of Pennsylvania. “Amazingly, it provides measurements showing that the ‘dirtiness’ of the universe, and its rate of growth after 14 billion years of evolution, is exactly what you’d expect from our standard cosmological model based on Einstein’s theory. gravity.”

Sherwin added, “Our results also provide new insights into the ongoing debate that some have called the ‘Crisis in Cosmology’,” explaining that this crisis stems from recent measurements using a different backlight, emitted from stars. in the galaxy than CMB . This has produced results showing dark matter is not clumpy enough under the standard model of cosmology and raised concerns that the model may be broken. However, the team’s recent results from ACT were able to correctly judge that the large blob seen in this image is the correct size.

“When I first saw them, our measurements matched so well with the underlying theory that it took me a while to process the results,” says Cambridge Ph.D. student Frank Qu, part of the research team. “It will be interesting to see how these possible discrepancies between the different measurements will be resolved.”

“The CMB lensing data rival more conventional visible-light surveys of galaxies in their ability to track the sum of what’s out there,” said Suzanne Staggs, director of the ACT and Henry DeWolf Smyth Professor of Physics at Princeton University. “Together, CMB lensing and the best optical surveys clarify the evolution of all the mass in the universe.”

“When we proposed this experiment in 2003, we didn’t know all the information that could be retrieved from our telescopes,” said Mark Devlin, the Reese Flower Professor of Astronomy at the University of Pennsylvania and co-director of the ACT. “We are indebted to the ingenuity of theorists, the many people who built new instruments to make our telescopes more sensitive, and the new analytical techniques our team came up with.”

The ACT, which has been in operation for 15 years, will be decommissioned in September 2022. However, more papers presenting the results of the final series of observations are expected to be submitted soon, and the Simons Observatory will carry out future observations at the same location, with the new telescope. is scheduled to enter service in 2024. The new instrument will be able to map the sky almost 10 times faster than the ACT.


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