Researchers from the Université de Genève and collaborating institutions have revealed that dark matter, despite being invisible, behaves much like ordinary matter under certain conditions. Their study, published in Nature Communications on November 16, 2025, explores whether dark matter follows the same rules that govern visible matter in the cosmos.
The team sought to determine if dark matter interacts with gravity in the same way as ordinary matter does. They compared the motion of galaxies as they move through gravitational wells, which are regions where massive objects distort space-time. The findings suggest that dark matter adheres to established physical laws, although the possibility of a hidden fifth force remains a point of investigation.
Investigating Dark Matter’s Behavior
Dark matter is believed to be five times more prevalent than visible matter in the universe. The challenge for scientists lies in its elusive nature; it neither emits nor reflects light, making direct observation difficult. The current study aimed to assess whether dark matter experiences gravitational wells similarly to ordinary matter, which is influenced by known forces such as gravity, electromagnetism, and the strong and weak nuclear forces.
“To answer this question, we compared the velocities of galaxies across the universe with the depth of gravitational wells,” explained Camille Bonvin, associate professor in the Department of Theoretical Physics at UNIGE and co-author of the study. “If dark matter is not subject to a fifth force, then galaxies—predominantly composed of dark matter—will fall into these wells like ordinary matter, governed solely by gravity.” This hypothesis serves as the foundation for their analysis.
By applying this comparative method to modern cosmological data, the researchers discovered that dark matter behaves in a manner consistent with Euler’s equations, which describe the motion of fluids, including gases and liquids. This finding indicates that dark matter does not deviate significantly from the expected behavior of ordinary matter as it moves through gravitational wells.
Implications and Future Research
Despite these conclusions, the team acknowledges that their findings do not completely eliminate the possibility of an undiscovered force acting on dark matter. Nastassia Grimm, the study’s first author and a former postdoctoral researcher at UNIGE, noted, “If such a fifth force exists, it cannot exceed 7% of the strength of gravity; otherwise, it would have been detected in our analyses.” This finding offers a clearer understanding of dark matter’s role in the cosmos but leaves room for further exploration.
The next steps for researchers involve investigating whether this potential fifth force truly influences dark matter. Upcoming experiments, such as the Large Synoptic Survey Telescope (LSST) and Dark Energy Spectroscopic Instrument (DESI), are expected to yield data that can detect forces as weak as 2% of gravity. Isaac Tutusaus, a researcher at ICE-CSIC and IEEC, emphasized that these experiments should provide deeper insights into dark matter’s behavior, further informing our understanding of the universe.
This ongoing research highlights the complexities of dark matter and its fundamental role in shaping the cosmos. As scientists continue to probe these mysteries, each discovery adds another layer to our understanding of the universe and its invisible components.
