When all the time began to become regular, Hua Feng began to think about the significance of the parallel universe to this "apocalyptic catastrophe".

Parallel universes are other universes that are both similar and different from the original universe that are separated from one universe and exist parallel to the original universe.

The multiverse is a theoretically infinite or finite collection of possible universes, including everything that exists and can exist: all space, time, matter, energy, and the physical laws and constants that describe them. The various universes contained in the multiverse are known as parallel universes.

In the 50s of the 20th century, when some physicists observed quanta, they found that the quantum state was different each time they observed. And since all matter in the universe is made up of quanta, these scientists speculate that since each quantum has a different state, it is possible that the universe is not just one, but multiple similar universes. The concept of parallel universes was proposed thanks to the scientific discoveries of modern quantum mechanics.

Some scholars use the analogy when describing parallel universes, they may be in the same spatial system, but the time system is different, like two trains speeding on the same railway line, and they may be in the same time system, but the spatial system is different, like a car driving in the upper and lower passages of an overpass at the same time.

Parallel universes refer to other universes that are both similar and different from the original universe that exist parallel to the original universe. Among these universes, there are universes that were born under the same conditions as our universe, and there may be planets that are the same as the planets inhabited by humans, or planets with the same history, and there may be people who are exactly the same as humans. At the same time, in these different universes, things develop with different results: species that are extinct in our universe may be evolving and growing in another universe.

Two universes that are parallel to each other neither overlap nor intersect, can be described as "well water does not interfere with river water". Although sometimes through some accidental events, the two universes can perceive each other's existence, but generally speaking, it is still "the voice of chickens and dogs, and the old and dead do not communicate with each other".

Some scholars use the analogy when describing parallel universes, they may be in the same spatial system, but the time system is different, like two trains speeding on the same railway line, and they may be in the same time system, but the spatial system is different, like a car driving in the upper and lower passages of an overpass at the same time.

The concept of parallel universes was not originally proposed because of the paradox of time travel, it came from quantum mechanics, because quantum mechanics has an uncertainty, that is, quantum uncertainty. The concept of parallel universes was proposed thanks to the scientific discoveries of modern quantum mechanics.

Copenhagen explained

Since the twenties of the twentieth century, many physicists have come up with different "interpretations" of quantum mechanics in order to provide a reliable explanation for measurement problems and to enable people to understand the collapse of the wave function. In quantum mechanics, the state of a microscopic particle is described by a wave function. When a microscopic particle is in a certain state, its mechanical quantities (such as coordinates, momentum, angular momentum, energy, etc.) generally do not have a definite value, but have a series of possible values, each of which appears with a certain probability (when a macroscopic object is in a certain state, its mechanical quantity has a definite value). That is, the motion of microscopic particles is uncertain and probabilistic. The wave function describes the probability of the spatial distribution of microscopic particles.

The well-known "single-electron double-slit interference" experiment in physics is the embodiment of the uncertainty and randomness of the motion of microscopic particles. In this experiment, a single electron interfered after passing through a double slit.

In classical mechanics, an electron can only pass through one slit at the same time, and it is impossible for it to pass through two slits at the same time and interfere, whereas according to quantum mechanics, the state of motion of an electron exists as a wave function, and it is possible for an electron to pass through both this slit and that slit at the same time and interfere.

But when scientists try to determine which slit an electron passes through through an instrument, they will always find only one of them. Neither instrument can detect electrons at the same time, and electrons can only pass through one slit at a time.

Physicist Bohr proposed the famous "Copenhagen Interpretation": when people are not observed, there is a probability that the electron exists at both slit positions, but once it is measured, for example, the electron is measured at the left slit, and the electron has an accurate position, the probability of it at that point is 1, and the probability of the other points is 0. That is, the wave function of the electron "collapses" to that point at the moment it is measured.

Bohr introduced the observer and his consciousness into quantum mechanics, linking it to the state of motion of microscopic particles. But the observer and the explanation of the "collapse" are not very clear and convincing, and have been questioned by many scientists. For example, how collapse occurs, whether it happens in a split second, or does it not start until a photon enters a person's eye and triggers an electrical impulse signal on the retina.

Multi-Worlds Explained:

So, is there a way to bypass the so-called "collapse" and "observer" and remove the subjective component of the observer from physics, which is supposed to study objective laws?

Everett came up with a bold idea: if the wave function does not "collapse", it must increase linearly. In other words, the electrons in the above experiments are still in a superposition state of the left/right slit even after re-observation.

Everett further proposed that people's worlds are also superimposed, and when electrons pass through the double slit, it is not only the electrons that are in the superimposed state, but also the whole world. That is, when the electrons pass through the double slit, two worlds are superimposed, and in one world the electrons pass through the slit on the left, and in the other world, the electrons pass through the slit on the right.

In this way, the wave function does not need to "collapse" and randomly choose left or right, because it appears as a superposition of two worlds: people living in one world find that electrons pass through the slit on the left where they are, and in the other world, people observe electrons on the right.

In the case of "Schrödinger's Cat", Everett points out that both cats are real. There is a live cat and there is a dead cat, but they are in different worlds. The question is not whether the emitting atom in the box decays, but whether it decays and does not. When the observer looks into the box, the whole world splits into two versions of itself. The two versions are identical in all the rest of the way. The only difference is that in one version, the atom decays and the cat dies, while in the other version, the atom does not decay and the cat is still alive.

The two worlds of "the atom decays and the cat dies, and the atom does not decay and the cat is still alive" will evolve in parallel and completely independent of each other, just like two parallel worlds. Quantum processes create "two worlds", which is Everett's avant-garde "many-worlds explanation".

The advantage of this explanation is that the Schrödinger equation always holds true, the wave function never collapses, and thus it simplifies the basic theory. The problem is that the assumptions are too bizarre and the price comes from the fact that these parallel worlds are all equally real. It is no wonder that it has been said: "In the history of science, the many-world explanation is undoubtedly the boldest and most ambitious theory ever proposed." ”

Ideological Prototypes in Historical Development:

In the 5th century B.C., Democritus proposed the concept of "infinite worlds", arguing that "countless worlds" were formed by atoms moving themselves. He said: "The atoms move freely in the void, and because of their sharp, messy motion, they collide with each other, and, when they touch each other, because of their various shapes, they collude with each other, so that the world and the things in it are formed, or rather, an infinite number of worlds." ”

In the first century B.C., Lucretius pointed out that beyond our "visible world" there were "other worlds" inhabited by "other races of men and beasts." ”

In the 4th century B.C., Epicurus expressed the idea of the plurality of the world: "There are infinitely many worlds, some of which resemble our world, and some of which are not. "In all worlds, there are animals, plants, and other things that we see in this world. ”

In 1714, Leibniz proposed his concept of "possible worlds", which envisaged the existence of an infinite number of "possible worlds" beyond the confines of the necessary world (the observable universe).

He believed that the world is composed of infinite monads, and that there is no causal relationship between monads, but a certain predetermined harmonious relationship, and although the monads are independent, there are extremely high and low differences between them. Leibniz explained the emergence of a real event, such as a specific person, as the result of many combinations of monads, the results of which are related to the dominant role of the better monad in the monad. This means that the world can look different, and any event is accidental, even the entire universe.

In 1957, physicist Everett came up with his own idea for the problem of quantum measurement. He pointed out that in quantum mechanics, there are multiple parallel worlds, and in each world, the results of each quantum mechanical measurement are different, so different histories occur in different parallel universes.

The multi-world explanation is that the observation of the measuring device causes the measuring device to be broken down into two. And this decomposition goes on and on in this measurement chain. Along with this decomposition, there must be a complete cosmic replication. That is, as long as one quantum measurement occurs, then each branch of the universe, and the components in that branch, will lead to a possible measurement. Everyone in a particular branch of the universe will think that his measurements and the universe in which he lives are the only ones that exist. That is, a new universe is produced in one measurement.

There is no possibility that these new universes, which are different from each other, will not coincide unless they are identical. The publication of this theory marked the formal introduction of the concept of parallel universes.