Revealed properties of dark matter align with classical gravitational theory

Revealed properties of dark matter align with classical gravitational theory
by Robert Schreiber
Berlin, Germany (SPX) Nov 04, 2025
Does dark matter follow the same laws as ordinary matter? The question continues to intrigue scientists because dark matter is invisible and hypothetical, neither emitting nor reflecting light. Researchers from the University of Geneva, collaborating across several institutions, aimed to determine whether dark matter behaves similarly to ordinary matter on a cosmological scale or if additional forces are involved. Their recent study, published in Nature Communications, reveals that dark matter appears to follow established physical laws, even as the possibility of unknown interactions remains open. These findings contribute new insights into dark matter, which is estimated to be five times more abundant than ordinary matter.

Ordinary matter interacts through gravity, electromagnetism, and the strong and weak nuclear forces at the atomic level. Dark matter, by contrast, remains largely undetected except through its gravitational effects and may be subject to these same four fundamental forces or potentially a fifth, yet unidentified force.

The Geneva-led team applied rigorous analysis to compare the velocity of galaxies throughout the Universe with the depth of gravitational wells shaped by massive celestial bodies. Massive objects throughout the cosmos distort the space around them, creating gravity wells into which ordinary matter falls as predicted by theoretical frameworks like Einstein's general relativity and Euler's equations.

"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's Faculty of Science and study co-author. "If dark matter is not subject to a fifth force, then galaxies - which are mostly made of dark matter - will fall into these wells like ordinary matter, governed solely by gravity. On the other hand, if a fifth force acts on dark matter, it will influence the motion of galaxies, which would then fall into the wells differently. By comparing the depth of the wells with the galaxies' velocities, we can therefore test for the presence of such a force."

The team found that dark matter conforms to Euler's equations, behaving in gravitational wells as ordinary matter does. "At this stage, however, these conclusions do not yet rule out the presence of an unknown force. But if such a fifth force exists, it cannot exceed 7 percent of the strength of gravity - otherwise it would already have appeared in our analyses," stated Nastassia Grimm, first author and former UNIGE postdoctoral researcher, now at the University of Portsmouth.

The study marks significant progress in characterising dark matter's properties. Isaac Tutusaus, co-author from ICE-CSIC/IEEC and IRAP/University of Toulouse, observed, "Upcoming data from the newest experiments, such as LSST and DESI, will be sensitive to forces as weak as two percent of gravity. They should therefore allow us to learn even more about the behaviour of dark matter."

Research Report:Comparing the motion of dark matter and standard model particles on cosmological scales