Parallel universe, science or science fiction?

Every choice Xiulian makes "creates" a branch of a parallel universe. In these parallel universes, Xiulian is not only a Kung Fu superstar, but also a chef, a Peking Opera actor, a superhero... In the Oscar-winning film "Blink", once the heroine Xiulian, played by Michelle Yeoh, connects with another self in a parallel universe, she will "download" the skills mastered by the self in that universe.

In the movie world, Xiulian travels to a parallel universe and meets another me in the world. Is the parallel universe a philosophical idealistic dream or a verifiable scientific world?

From quantum mechanics

In short, parallel universes refer to multiple universes that exist simultaneously and independently of each other. You may appear in different universes, eating skewers here and playing football there. Although it sounds outrageous, the origin of parallel universes is closely related to quantum mechanics in physics.

In the 1920s, in order to explain the microscopic phenomena observed in atomic physics experiments, Bohr, Heisenberg, Schrödinger, Dirac, Born and others established the theory of quantum mechanics. In the field of quantum mechanics, scientists hold different views on "how quantum moves". German physicist Heisenberg believes that quantum does not follow routines when it moves. At the same time, quantum is here and there. When you look at it, it stops moving. This phenomenon is called collapse. Therefore, before we observe it, you will never know what quantum is doing. This is the quantum superposition state that has been confirmed by scientific experiments.

People still have difficulty fully understanding many concepts in quantum mechanics. One of the most influential but still controversial explanations is the "many-worlds theory" proposed by American physicist Everett. According to the many-worlds theory, the universe is made up of countless parallel worlds. Assuming that there are countless worlds can avoid the so-called wave function collapse, creating a "happy ending" situation.

“Evidence” of the existence of parallel universes

"Schrödinger's cat is a thought experiment about quantum measurement, which can well explain this theory." Wu Biao, a professor at the School of Physics of Peking University, believes in the existence of parallel universes. He told reporters that according to the many-worlds theory, after the experiment, the world is divided into two: in one universe, the cat is alive; in the other universe, the cat is dead. The two universes exist in parallel and cannot perceive each other's existence. Therefore, when opening the door of the laboratory, people can only see the cat in one state.

Wu Biao believes that these two universes are equally real and exist in parallel. Since the evolution of quantum mechanics is linear, they will evolve independently and will not affect each other. Each observation will lead to the birth of a different parallel universe. Such "observations" are happening all the time in nature. When cosmic rays hit an organism, it may or may not cause a gene mutation. At this time, the world is divided into two: one parallel universe has a gene mutation, and the other parallel universe has no gene mutation. If this is the case, we may be able to imagine countless possibilities: in some universes, fish have just crawled onto land; in another universe, there may still be only single-celled organisms on Earth.

Is the universe we live in today really just a drop in the ocean? Chen Zheng, associate professor at the School of Physics and Engineering at Beijing Jiaotong University, told reporters: "According to the current parallel universe hypothesis, there are two parallel possibilities for the universe, that is, one splits into multiple, or multiple gradually 'collapses' and only one remains. The clues between these universes can only be found through quantum statistics, and there is basically no connection between matter, energy, and information in macroscopic phenomena."

A world that cannot be proven or disproven

Is the parallel universe a scientific conjecture or a scientific conclusion that can stand the test? In Wu Biao's opinion, no experiment has been able to disprove the multiverse theory.

"Parallel universes do not contradict current physical experiments, so we cannot say they are wrong; but at the same time, no experiment can prove that they are right." Wu Biao said that it can be said that parallel universes are a conjecture, and no one in the world has seen parallel universes. According to current physical theories, even if parallel universes exist, there can be no communication between them. However, if physicists unify quantum mechanics and gravity in the future, according to this new theory, parallel universes may be able to communicate.

Chen Zheng is also more inclined to believe that the parallel universe is a scientific conjecture, because it currently does not have a feasible "measurement plan". "There are two basic paths for the construction of physics. One is 'induction', which summarizes the laws from a large number of experimental observations, and then further verifies the laws through more experiments; the other is 'deduction', starting from one or several basic propositions, proposing theories and verifiable predictions through logical deduction and mathematical reasoning, and then repeatedly verifying the predictions made by the theory through experiments." Obviously, the parallel universe has not yet been supported by theory and verified by experiments.

From a radiation-filled "purgatory" to the formation of atoms after the Big Bang, to the condensation of matter to form stars and galaxies, the solar system began to form and evolve, and the Earth happened to be in the habitable zone. Is it all too coincidental? But according to the Many Worlds Theory, this is not a coincidence.