Over the past 13.8 billion years, the universe has grown into a vast, intricate web of galaxies, stars, and cosmic structures.
But according to new research, the way matter has spread out across the universe is less “clumpy” than scientists expected.
This surprising discovery, led by researchers Joshua Kim and Mathew Madhavacheril from the University of Pennsylvania, offers new clues about how the universe has evolved—and raises intriguing questions about forces shaping it today.
The study, published in the Journal of Cosmology and Astroparticle Physics and on the preprint server arXiv, combines data from two cutting-edge sources.
The first is the Atacama Cosmology Telescope (ACT) in Chile, which studies light from the universe’s earliest days, about 380,000 years after the Big Bang.
This ancient light, known as the Cosmic Microwave Background (CMB), is like a “baby picture” of the universe.
The second source is the Dark Energy Spectroscopic Instrument (DESI) in Arizona, which maps the current structure of the universe by studying millions of galaxies.
By layering these datasets together, the researchers were able to trace how matter has changed over billions of years.
“It’s like stacking old and new photos of the universe to see how its structures have evolved,” says Joshua Kim, lead author of the study.
This innovative approach offers a kind of “cosmic CT scan,” letting scientists examine slices of the universe’s history and track how matter clumped together over time.
One key focus of the study is something called “gravitational lensing,” a phenomenon first predicted by Einstein over a century ago.
As light from the early universe travels through space, it gets bent and warped by massive structures like galaxy clusters. By analyzing this bending, scientists can infer how matter is distributed across the cosmos.
The researchers compared these findings with DESI’s map of galaxies, which acts like a “high school yearbook photo” of the universe, showing how galaxies are spread out in recent times. Together, these datasets revealed a small but curious mismatch.
The universe appears slightly less clumpy than predicted by early models, especially over the past four billion years.
This discrepancy is measured using a metric called Sigma 8 (σ8), which tracks the clumpiness of matter. Lower-than-expected values suggest that the universe’s growth and evolution may have slowed down in ways current theories don’t fully explain.
While the difference isn’t large enough to confirm new physics, it hints that forces like dark energy—the mysterious driver of the universe’s accelerating expansion—might be playing a bigger role in shaping cosmic structures than we thought.
Future studies with advanced telescopes like the Simons Observatory aim to refine these measurements. For now, the results remind us that the universe is full of surprises, and we’re only beginning to understand its complex and ever-changing nature.
Source: University of Pennsylvania.
