One of the most intriguing questions in cosmology is why our universe is expanding faster and faster. Different methods of measuring this expansion have produced inconsistent results, leading to a puzzle known as the cosmic tension problem.
Some researchers have proposed different solutions, such as changing gravity or introducing new forms of dark energy. But a recent paper suggests a more radical idea: what if there is a mirror universe that interacts with ours via gravity?
The newspaper, published in the magazine Physics Review Letters is based on the work of a team of physicists from the University of New Mexico and the University of California, Davis.
They noticed that when they fit some cosmological models to the observed expansion rates, some dimensionless parameters remained constant. This implied that there existed a hidden symmetry in the universe that could be explained by the existence of a mirror world.
A mirror world is not a new concept in physics. It has previously been proposed to take into account the imbalance between matter and antimatter in our universe.
According to this idea, there is another universe identical to ours, except that everything is reversed: left and right, matter and antimatter, time and space. The two universes would interact only through gravity, which would be weaker than in either individual universe.
“We find that uniform scaling of the gravitational free-fall velocity and the photon-electron scattering velocity leaves most dimensionless cosmological observations virtually invariant,” the researchers write in the abstract of their study.
Therefore, they add: “A dark sector in the mirror world allows effective scaling of the gravitational free fall while respecting the measured average photon density today.”
The authors of the paper applied this idea to the cosmic tension problem and found that it worked remarkably well. By introducing a mirror world with its own dark sector, they were able to reconcile the two expansion rate measurements without violating any laws or principles of physics.
They also showed that their model could be tested by future observations of gravitational waves and cosmic microwave background radiation.
The idea of a mirror universe is provocative and has many challenges. First, it requires a refinement of the initial conditions of both universes to ensure their symmetry.
Second, it raises many philosophical questions about the nature of reality and identity. If a mirror universe exists, does it have its own inhabitants? Are they aware of us? Do they have free will? Are they our evil twins or our soulmates?
These questions may seem far-fetched, but they are not irrelevant to cosmology. As our understanding of the universe grows, so does our need for new frameworks and perspectives to interpret it.
