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 uncovered new evidence suggesting that two of its most mysterious ingredients – dark matter and neutrinos – may not be as isolated as once thought.
The findings could reshape our understanding of how the cosmos evolved, and hint that the standard picture of the Universe may be incomplete.
The elusive nature of dark matter and neutrinos
Dark matter is believed to account for roughly 85% of all matter in the Universe, yet it cannot be seen directly. Its presence is inferred from its gravitational influence on galaxies and cosmic structures.
Neutrinos, by contrast, are subatomic particles with an almost negligible mass that rarely interact with ordinary 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 embedded in the widely accepted Standard Model of Cosmology, known as Lambda-CDM, which is rooted in Einstein’s General Theory of Relativity.
However, new research suggests this long-standing framework may be missing a crucial piece of the puzzle.
A tension in the cosmic timeline
The study addresses a persistent problem in cosmology: measurements of the early Universe do not perfectly align with observations of the Universe today.
Data from the infant cosmos predicts that matter should have clustered more strongly over billions of years than astronomers currently observe.
This discrepancy, often referred to as a ‘cosmological tension,’ does not overthrow existing theory but raises questions about whether all relevant physics has been accounted for.
The new research proposes that subtle interactions between dark matter and neutrinos could have slowed the growth of cosmic structures, helping to reconcile early- and late-universe measurements.
Combining data from across cosmic history
To investigate this possibility, researchers combined observations spanning nearly the entire age of the Universe.
Information about the early Universe was drawn 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 Cosmology Telescope in Chile.
These datasets were then compared with observations of the more recent Universe. Scientists analysed galaxy distributions and large-scale structures mapped by the Dark Energy Camera on the Victor M. Blanco Telescope, as well as extensive surveys from the Sloan Digital Sky Survey. Together, these sources provided an unprecedented view of how matter has evolved over time.
The analysis revealed patterns consistent with weak interactions between dark matter and neutrinos. While neither substance can be observed directly, their influence appears to be imprinted on the way galaxies and clusters formed across cosmic history.
The impacts of potential dark matter–neutrino interactions
If dark matter and neutrinos do interact, even minimally, the implications are profound. Such interactions could help explain why matter today appears slightly less clumped than predicted by early-universe models.
More broadly, the findings suggest that dark matter may have properties beyond those assumed in the simplest cosmological models.
For particle physicists, this opens a new avenue of investigation. Understanding how neutrinos interact with dark matter could provide valuable clues about the fundamental nature of both, potentially guiding future laboratory experiments designed to detect dark matter directly.
Next stages of research
The results are not yet definitive, but they offer a clear roadmap for future research.
Upcoming telescopes, next-generation cosmic microwave background experiments and advanced weak lensing surveys, which track how gravity subtly bends light from distant galaxies, will provide more precise measurements of how mass is distributed across the Universe.
With more detailed data, scientists will be able to test whether the apparent interaction between dark matter and neutrinos holds up under closer scrutiny.
If confirmed, it would represent one of the most significant advances in cosmology in recent years, reshaping theories of cosmic evolution and bringing researchers closer to understanding the invisible forces that govern the Universe.
