Scientists may be closing in on one of cosmology’s most enduring mysteries.
University of Sheffield experts investigating the deepest workings of the universe have discovered new evidence suggesting that two of the universe’s most mysterious components, dark matter and neutrinos, may not be as isolated as once thought.
The discovery could reshape our understanding of how the universe evolved and suggest that the standard picture of the universe may be incomplete.
The elusive nature of dark matter and neutrinos
Dark matter is thought to make up about 85% of all matter in the universe, but it cannot be seen directly. Its existence is inferred from its gravitational influence on galaxies and cosmic structures.
In contrast, neutrinos are subatomic particles of negligible mass that rarely interact with normal matter, making them notoriously difficult to detect despite being abundant throughout the universe.
For decades, cosmologists have assumed that dark matter and neutrinos exist independently. This assumption is built into the widely accepted standard model of cosmology, known as lambda CDM, which is rooted in Einstein’s theory of general relativity.
But new research suggests this long-standing framework may be missing a key piece of the puzzle.
Tension in the cosmic timeline
This research addresses a persistent problem in cosmology: measurements of the early universe do not perfectly match observations of the universe today.
Data from the infant Universe predicts that matter should have clustered more strongly over billions of years than astronomers currently observe.
This contradiction, often referred to as a “cosmological tension,” does not overturn existing theory, but it does raise questions about whether all the relevant physics has been accounted for.
A new study proposes that subtle interactions between dark matter and neutrinos may have slowed the growth of cosmic structure and helped bring measurements of the early and late universe into line.
Combine data from across the history of the universe
To investigate this possibility, the researchers combined observations spanning nearly all ages of the universe.
Information about the early Universe comes from measurements of the cosmic microwave background (CMB), the faint afterglow of the Big Bang, captured by both the European Space Agency’s Planck satellite and the ground-based Atacama Space Telescope in Chile.
These datasets were compared with more recent observations of the universe. Scientists analyzed the distribution and large-scale structure of galaxies mapped by the Victor M. Blanco Telescope’s Dark Energy Camera, as well as extensive surveys by the Sloan Digital Sky Survey. Taken together, these sources have provided an unprecedented perspective on how matter has evolved over time.
The analysis revealed a pattern consistent with a weak interaction between dark matter and neutrinos. Although neither substance can be observed directly, their influence appears to be imprinted on the way galaxies and galaxy clusters form throughout the history of the universe.
Impact of potential dark matter and neutrino interactions
Even minimal interactions between dark matter and neutrinos can have serious effects. Such interactions may help explain why matter today appears to be slightly less clumped than predicted by early cosmological models.
More broadly, this discovery suggests that dark matter may have properties beyond those assumed in the simplest cosmological models.
For particle physicists, this opens up new avenues of research. Understanding how neutrinos interact with dark matter provides valuable clues about the fundamental nature of both and could guide future laboratory experiments designed to directly detect dark matter.
Next stage of research
Although the results are not yet conclusive, they provide a clear roadmap for future research.
Upcoming telescopes, the next generation of the Cosmic Microwave Background Experiment, and advanced weak-lensing surveys that track how light from distant galaxies is subtly bent by gravity will provide more precise measurements of how mass is distributed throughout the universe.
More detailed data will allow scientists to test whether the apparent interaction between dark matter and neutrinos holds up under closer scrutiny.
If confirmed, it would be one of the most important advances in cosmology in recent years, reshaping the theory of cosmic evolution and bringing researchers closer to understanding the invisible forces that govern the universe.
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