Dark Matter Confirms Gravitational Laws, Challenges New Forces
Scientists have established that dark matter, the enigmatic substance that constitutes a significant portion of the universe, adheres to gravitational laws on an extensive cosmic scale. This discovery may limit the possibility of a fifth fundamental force of nature, although it does not definitively rule it out. The research, conducted by a team from the University of Geneva (UNIGE), sheds light on how dark matter interacts with gravity, an area that has puzzled researchers for years.
Traditionally, matter is composed of atoms, which consist of protons, neutrons, and electrons. These particles align with known fundamental forces: electromagnetism, gravity, the strong nuclear force, and the weak nuclear force. Dark matter, however, has remained elusive. It does not interact visibly with light or electromagnetic radiation, making it nearly invisible. Scientists infer its presence through its gravitational effects, observing how it influences light and ordinary matter.
To investigate whether dark matter behaves in accordance with the gravitational principles outlined by Albert Einstein in his 1915 theory of general relativity, researchers sought to determine if dark matter falls into cosmic gravity wells similarly to ordinary matter. These wells form when massive bodies warp the fabric of spacetime. The deeper the well, the stronger the gravitational influence.
Camille Bonvin, a researcher at UNIGE, explained the approach: “We compared the velocities of galaxies across the universe with the depth of gravitational wells. If dark matter is not subject to a fifth force, then galaxies—composed largely of dark matter—will fall into these wells like ordinary matter, governed only by gravity.”
By analysing current cosmological data, the team concluded that dark matter does indeed navigate gravity wells in the same manner as ordinary matter. While these findings suggest no evidence of a fifth fundamental force, they do not entirely eliminate the possibility.
According to Nastassia Grimm, team leader and researcher at the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK, “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 have already appeared in our analyses.”
This research does not close the door on the concept of a fifth fundamental force but refines the understanding of dark matter’s characteristics. The pursuit to uncover more about dark matter continues, with upcoming projects poised to provide further insights.
Isaac Tutusaus, a member of the research team from the University of Toulouse, highlighted the importance of future experiments. “Upcoming data from the newest experiments, such as the Legacy Survey of Space and Time conducted by the Vera C. Rubin Observatory and the Dark Energy Spectroscopic Instrument (DESI), will be sensitive to forces as weak as 2% of gravity. They should therefore allow us to learn even more about the behaviour of dark matter.”
The team’s findings were published on November 3, 2023, in the journal Nature Communications. As scientists continue to delve into the mysteries of dark matter, the implications of this research may reshape fundamental understandings of the universe’s fabric and the forces that govern it.
