This work by researchers of the Department of Theoretical Physics of UNIGE may shed new light on this research field. Whatever their findings, these astronomical observations provide revealing new insights into the elusive nature of dark matter. Taken together, the findings undermine a tantalizing and controversial hypothesis that dark matter does not actually defy gravity, as once thought. This new study has uncovered the key characteristics of dark matter. Currently, scientists think it’s at least five times more abundant than ordinary matter in the universe.
Dark matter is still one of the most enigmatic ingredients to the cosmos. It is undetectable and elusive, yet it makes up about 85% of the matter in our universe. The new research provides evidence that dark matter does behave by the same physical principles as the matter we encounter in our everyday lives. Or maybe it’s being influenced by some unknown fifth force. This fresh angle puts to bed longstanding tales that dark matter must be breaking the fundamental laws of physics.
Ordinary matter, which includes everything from planets to stars, obeys four fundamental forces: gravity, electromagnetism, and the strong and weak nuclear forces. As the study states, if a fifth force is indeed out there, it can’t be stronger than 7% of gravity’s strength. This unknown force should have a tremendous impact on the movement of galaxies, which are mostly made up of dark matter.
Dark matter might feel a fifth force, changing the way galaxies form. As they crash into gravitational wells, or regions where gravity is so strong that nothing, not even light, can escape it, their moods can take a dramatic turn. In this case galaxies wouldn’t sink into these wells like normal matter does. If dark matter does not experience this proposed fifth force, it would follow the same gravitational laws as ordinary matter, leading to predictable movements as described by Einstein’s theory of general relativity and Euler’s equations.
Nastassia Grimm, the study’s first author, former postdoctoral researcher at UNIGE’s Department of Theoretical Physics. She stressed that knowing what dark matter really is, really matters. According to co-author Camille Bonvin, an associate professor in the same department, these findings have the potential to be highly consequential. They might change everything we know about astrophysics and cosmology.
In May, their work was featured in the prestigious Nature scientific journal. This finding opens the door wide to further investigation into the still-mysterious nature of dark matter. The DOI for the publication is 10.1038/s41467-025-65100-8.