Recent research has revealed that dark matter, the enigmatic substance that comprises much of the universe, adheres to gravitational laws on vast cosmic scales. This discovery may diminish the likelihood of a fifth fundamental force of nature, although it does not completely eliminate the possibility that such a force exists. The findings were published on November 3, 2023, in the journal Nature Communications.
Traditionally, matter is understood to be composed of atoms, which consist of protons, neutrons, and electrons. These particles interact with the four known fundamental forces: electromagnetism, gravity, the strong nuclear force, and the weak nuclear force. Dark matter has remained elusive, primarily because it does not interact with light in the same way as ordinary matter, making it nearly invisible. Scientists can only infer its existence through gravitational effects, which influence the behavior of galaxies and other cosmic structures.
Investigating Dark Matter’s Behavior
To understand if dark matter is influenced by an unknown fifth force, researchers from the University of Geneva (UNIGE) conducted a study to determine if dark matter behaves similarly to ordinary matter in cosmic gravity wells. These wells are formed when massive bodies warp the fabric of spacetime, as described by Albert Einstein’s theory of general relativity. The depth of these wells dictates the strength of the gravitational influence they exert.
Camille Bonvin, a researcher at UNIGE, explained the methodology: “To answer this question, 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—mostly composed of dark matter—will fall into these wells like ordinary matter, governed only by gravity.”
Should a fifth force exist, it would alter the dynamics of how galaxies move within these wells. The study compared the depths of these wells to the velocities of galaxies to test for the presence of such a force.
Findings and Implications
The research confirmed that dark matter does indeed respond to gravitational wells in the same manner as ordinary matter. While the findings do not definitively exclude the presence of a fifth fundamental force, they suggest that if such a force exists, it cannot exceed 7% of the strength of gravity. As Nastassia Grimm, team leader and researcher at the Institute of Cosmology and Gravitation at the University of Portsmouth, stated, “These conclusions do not yet rule out the presence of an unknown force. But if such a fifth force exists, it cannot exceed this threshold.”
The implications of this research help clarify the behavior of dark matter, a component that accounts for approximately five times more matter in the universe than ordinary matter. While the study does not provide conclusive evidence for or against a fifth force, it sets important parameters for future investigations.
Looking ahead, Isaac Tutusaus, a researcher at the University of Toulouse, highlighted that upcoming experiments, such as the Legacy Survey of Space and Time at the Vera C. Rubin Observatory and the Dark Energy Spectroscopic Instrument, will be capable of detecting forces as weak as 2% of gravity. These initiatives are expected to yield further insights into the elusive nature of dark matter.
This latest study not only enhances our understanding of dark matter but also serves as a stepping stone for future research aimed at uncovering the universe’s most profound mysteries.