Dark Matter Displays Normal Behavior in Groundbreaking Study

Researchers at the Université de Genève have made significant strides in understanding dark matter, revealing that it may behave similarly to ordinary matter in a recent study published on November 16, 2025. By analyzing how galaxies move through cosmic gravitational wells, the team found that dark matter appears to follow established physical laws, like the movement of visible matter. Despite this breakthrough, the possibility of a previously unknown fifth force influencing dark matter remains.

The study addresses a fundamental question in modern cosmology: does dark matter adhere to the same physical rules as visible matter? Dark matter is notoriously difficult to study due to its invisible nature; it neither emits nor reflects light. To explore this, the researchers aimed to determine if dark matter moves in accordance with the same gravitational principles that govern ordinary matter.

The research team, led by Camille Bonvin, an associate professor in the Department of Theoretical Physics at UNIGE, examined the velocities of galaxies in relation to the depth of gravitational wells. These wells are created by massive objects that distort space. Ordinary matter, including planets and stars, falls into these wells based on established principles such as Einstein’s general relativity and Euler’s equations. The question was whether dark matter exhibited the same predictable behaviors.

To gather data, Bonvin explained, “If dark matter is not subject to a fifth force, then galaxies—mostly composed of dark matter—will fall into these wells like ordinary matter, governed solely by gravity.” Conversely, if a fifth force exists, it would alter how galaxies behave, leading to different motions. By comparing the galaxies’ velocities to the wells’ depths, the researchers tested for the presence of this potential force.

The findings indicated that dark matter indeed sinks into gravitational wells in a manner consistent with Euler’s equations, suggesting it behaves similarly to ordinary matter. Nastassia Grimm, the study’s lead author and a former postdoctoral researcher at UNIGE, noted, “At this stage, these conclusions do not yet rule out the presence of an unknown force. But if such a fifth force exists, it cannot exceed 7% of the strength of gravity—otherwise, it would already have appeared in our analyses.”

This research marks a crucial step in refining our understanding of dark matter’s role in the universe. The next phase of inquiry aims to determine whether a subtle fifth force truly affects dark matter’s behavior. As Isaac Tutusaus, a researcher at ICE-CSIC and IEEC, pointed out, “Upcoming data from the newest experiments, such as LSST and DESI, will be sensitive to forces as weak as 2% of gravity. They should therefore allow us to learn even more about the behavior of dark matter.”

The implications of this work extend beyond theoretical physics. Understanding dark matter is essential for mapping the universe and predicting cosmic phenomena. Even though dark matter is believed to be five times more prevalent than ordinary matter, researchers are just beginning to unlock its mysteries. This study is a significant step forward in the quest to understand the cosmos and our place within it.