What To Know
- The mystery of this “missing mass” is at the heart of modern cosmology, but a new hypothesis could well revolutionize our understanding of this phenomenon.
- Concretely, instead of looking for specific particles, the researchers suggest that the solution could lie in topological defects present in the Universe that result from phase transitions in its early stages.
- a thin layer of positive mass on the inside and a thin layer of negative mass on the outside.
Dark matter, often described as the “poltergeist” of the Universe, continues to defy scientific understanding. Invisible and undetectable directly, its gravitational effects are nevertheless observable on cosmic structures such as galaxies. The mystery of this “missing mass” is at the heart of modern cosmology, but a new hypothesis could well revolutionize our understanding of this phenomenon.
The Missing Mass Problem
When only their visible matter (stars, gas) is measured, galaxies do not have enough mass to explain their gravitational cohesion. According to the laws of current physics, these galaxies should dissipate, the stars and gas dispersing into space. Despite this, they remain intact, which suggests the existence of additional, invisible matter: dark matter. This mysterious substance would represent about 85% of the mass of the Universe. Many theories have been proposed to explain the nature of dark matter, including exotic objects such as primordial black holes, axions, and WIMPs (Weakly Interacting Massive Particles). However, despite decades of research, none of these hypotheses have been confirmed and dark matter remains elusive, which brings us back to these jobs. Researchers at the University of Alabama in Huntsville are proposing an innovative alternative theory.
Dark matter (shown in blue in this composite satellite image) dominates up to 85% of the mass of most galaxies. Credits: NASA, ESA, CFHT, CXO, MJ Jee
A new perspective
Concretely, instead of looking for specific particles, the researchers suggest that the solution could lie in topological defects present in the Universe that result from phase transitions in its early stages. In detail, a topological defect is a irregularity in the structure of space-time that can form during phase transitions. Think of a phase transition as a change in the state of matter, such as when water turns to ice. In the early universe, similar transitions took place, changing the fundamental conditions and creating these defects. The researchers propose that spherical shells of high matter density could be a type of topological defect. These shells would be composed of two layers: a thin layer of positive mass on the inside and a thin layer of negative mass on the outside. The total mass of these layers would be zero, meaning they would have no no direct measurable mass. However, they could exert a gravitational force on other objects. As mentioned above, these topological shells could have formed during phase transitions. A notable example of a transition is when the Universe cooled enough to allow the strong force to bind quarks into protons and neutrons. According to the authors, this cooling could have led to the formation of these spherical shells.
Cosmic observations and implications
According to the researchers, spherical shells resulting from such transitions could create effects similar to those attributed to dark matter. For example, the gravitational lenses are phenomena where starlight is bent by the gravity of massive objects. If these topological shells exist, then they could bend light in the same way, creating gravitational lenses. Similarly, as mentioned earlier, astronomers have observed that galaxies and galaxy clusters appear to have more mass than we can see. This suggests that there is additional, invisible matter that helps hold these structures together. Again, these topological shells could explain this cohesion without resorting to traditional dark matter. Finally, the recent discovery giant arcs and other large-scale symmetrical structures in the Universe could support this hypothesis. These nearly symmetrical structures that extend over enormous distances could be the result of the formation and alignment of these topological shells. This offers a new perspective on the formation and evolution of galaxies. Although still in the exploratory phase, this hypothesis therefore opens new avenues of research. Future observations and research will determine whether these topological defects really exist and whether they can explain the gravitational effects attributed to dark matter. If this theory is confirmed, it could revolutionize our understanding of the Universe and solve one of the greatest mysteries of modern cosmology.
