Cosmic CT Scan: A Universe That Evolved More Complicated Than Expected

Aim your imagination towards the cosmos, a vast expanse of mysteries and wonders. Researchers today have unveiled a groundbreaking technique that offers a unique perspective on this universe. By merging data from the Atacama Cosmology Telescope (ACT) and the Dark Energy Spectroscopic Instrument (DESI), scientists have constructed a “cosmic CT scan” that charts the universe’s development over billions of years.

The Cosmic CT Scan Unveiled

This extraordinary visualization allows researchers to view the universe as a growing, complex entity. Starting with the ancient Cosmic Microwave Background (CMB) — often referred to as the universe’s baby picture — ACT provides a snapshot of the cosmos just 380,000 years old. Meanwhile, DESI contributes data from more recent cosmic periods, focusing on the distribution of luminous red galaxies. This dual-source approach has enabled scientists to understand how the universe grew and changed from infancy to present day.

“This process is like a cosmic CT scan, where we can look at different slices of cosmic history and track how matter clumped together at different epochs,” explained Mathew Madhavacheril, co-leader of the research team and a member of the University of Pennsylvania. “It gives us a direct look into how the gravitational influence of matter changed over billions of years.”

Delving into Ancient Cosmic Light

The CMB, a faint glow filling the universe, has traveled for nearly 13.8 billion years. ACT’s wide coverage of the sky captures the universe’s infancy, painting a picture of its early stages. As this light journeyed through cosmic expansion and the gravity wells of galaxy clusters, it was stretched and warped, a phenomenon known as gravitational lensing.

Decades of expansion have cooled the CMB to minus 454 degrees Fahrenheit (minus 270 degrees Celsius). Gravitational lensing bends this light, much like a glass lens distorts light in an empty swimming pool. Einstein first proposed the concept of gravitational lensing in his general theory of relativity.

The Evolution of a Complex Universe

DESI’s Year 1 data supplements the cosmic narrative, focusing on modern structure formation. By mapping millions of galaxies, primarily luminous red galaxies, DESI provides a recent cosmic blueprint. Combining ACT and DESI’s data sets is akin to flipping through a photo album that shows the universe from infancy to adulthood, revealing how gravity has shaped spatial structures over time.

Joshua Kim, a graduate researcher in the Madhavacheril Group, illustrates the combined approach: “ACT, covering approximately 23% of the sky, paints a picture of the universe’s infancy. DESI, through its mapping of luminous red galaxies, provides a more recent record. The interplay between these datasets reveals a transformation from early clumps to a more intricate cosmic structure.”

A Hint of Discrepancy

Despite the remarkable alignment with Einsteinian predictions, researchers observed a small inconsistency. The calculated amount of clumpiness in the universe around four billion years ago doesn’t entirely match theoretical models. This deviation, though subtle, could signal a need for new physics or deeper understanding of current models. Further research, spurred by new and more precise instruments, may unravel these cosmic mysteries.

Madhavacheril concludes: “We did see a hint for a small discrepancy in the amount of expected clumpiness in recent epochs. It might indicate that the universe’s structural growth has slowed in ways current models don’t fully explain. However, it’s exciting because it opens up new avenues for research in astrophysics.”