Many netizens have probably seen some slightly ridiculous words like this on the Internet. Maybe everyone thinks that the parallel universe is a kind of thing invented by science fiction writers. In fact, the first time I saw the parallel universe was in the Hollywood sci-fi film The Wanted Universe starring Jet Li. In the story, Jet Li in the parallel universe kills himself in all other parallel universes, so as to gain the energy of the murdered person and strengthen himself. In the end, the world of the protagonist came to kill him, and the brain hole was quite big.
But in fact, like the sci-fi elements in many sci-fi works, the parallel universe was originally proposed as a scientific hypothesis. So far, scientists have proposed more than one parallel universe, but there are many kinds. So is there another you in the parallel universe under every parallel universe theory? Let's take a brief look at some common parallel universes and their backgrounds.
Non-scientific Pluralism in Science and Parallel Universe in Interpretation
The first time I saw the description of parallel universe in serious popular science works was in Cao Tianyuan's popular science book "Does God roll dice?" History of quantum physics. This may also be the place where parallel universes first appeared in science.
The story begins with an experiment a hundred years ago. At that time, when scientists were studying a famous optical experiment-Young's double-slit experiment, they found that when light passed through two slits, light and dark stripes would be projected on the screen behind the slits. This experiment has been going on for hundreds of years. It is not surprising that this is the characteristic of waves. Maxwell has proved that light is an electromagnetic wave, so it is not surprising that it will interfere.
If the following background knowledge is boring, you can skip it directly and continue reading from the next paragraph in bold. )
But the problem is that Einstein put forward the light quantum hypothesis in a Nobel Prize-winning paper in 1905, using light as particles to explain the photoelectric effect phenomenon discovered by physicists before. So something strange happened. Is light both a wave and a particle? Light is both a wave and a particle, because these two characteristics are clearly proved by experiments, which seems irrefutable: Young's double-slit interference experiment proves that light is a wave, and photoelectric effect and Compton scattering experiment of light with different frequencies prove that light is a particle. What about Elvin? Schrodinger and Werner? Carl. Heisenberg used wave mechanics and matrix mechanics to describe the behavior of waves and particles respectively. See you later, Louis? Victor? De Broglie put forward the hypothesis of matter wave, which holds that all matter particles have the characteristics of wave. Davidson and Lester? The diffraction phenomenon of electrons was found in the experiment, and the diffraction law was consistent with X-ray. So far, the wave-particle duality of matter particles has been established. According to the new explanation of quantum mechanics, light? Wave? It is a probability amplitude, which is a variety of possible combinations in human terms.
After explaining the experimental background, we continue to talk about the previous double-slit experiment: in the double-slit experiment, people use a special method to try to let photons pass through the double slit one by one, so as to observe the patterns appearing on the screen. The method is to weaken the light source until only one photon passes through the slit at a time, and the back of the slit is imaged with photosensitive film. When the exposure time is short, people see some scattered light spots in the photos, which shows that photons really hit the film one by one. But when the exposure time of the film was delayed long enough, something magical happened: the interference pattern like double-slit interference of light beam appeared on the film again! Does this mean that a photon can also interfere? Because the interference pattern shows that a photon passes through two slits at the same time, because only in this way can interference be generated and an interference pattern be formed.
Then the question comes: how does a photon pass through two slits at the same time? Copenhagen School consists of a bunch of founders of quantum mechanics (Bohr, Born, Heisenberg, Dirac, Pauli, etc. ) put forward a new theory. The most reasonable? Interpretation of Copenhagen. They think that before the light reaches the screen and is measured, it is not a solid particle, but a probability cloud, which exists in all possible places, including those two slits, that is, in all possible superposition States! So it does pass through two slits at the same time and interfere with itself, and finally it is measured by a solid particle hitting the photosensitive film.
This explanation is obviously unacceptable, because it means that matter particles are unreal before being measured, so physicists represented by Einstein attacked them, but they failed to give a better explanation.
Until 1957, Hugh of Princeton University, USA? Everett III put forward a hypothesis in his doctoral thesis: the multi-world hypothesis. In this crazy hypothesis, he pointed out that it may not be photons, but the universe!
In his explanation, the universe is in all possible superposition States. In the double-slit interference experiment, when photons pass through the double slit, the superimposed universe splits and produces two parallel universes. In a parallel universe, photons pass through the left slit, while in another parallel universe, photons pass through the right slit. The superimposed universe is real, and so is each divided parallel universe. Photons always pass through one after another. In this way, the authenticity of the physical world is preserved.
However, for most physicists and ordinary people, this assumption is even crazier than the Copenhagen explanation! ? I can't believe I split the universe at a glance? So for a long time, this assumption has not been widely accepted.
So as an explanation of physical theory, can this hypothesis be verified by experiments? Sorry: No, because this theory points out that when two parallel universes split, they have nothing to do with each other. They are like two parallel lines, which have no intersection.
In other words, this is an unprovable hypothesis. Although it was put forward by a doctor of physics, it does not meet the standard of scientific theory, because there is no falsifiability.
I accidentally wrote it too long, but I think this is the most important parallel universe hypothesis, so I will try my best to be simple.
No, the parallel world of Hubble volume.
This is based on two facts: 1, the universe is expanding, and 2, the speed of light is a finite value. Therefore, there is a Hubble volume and an unobservable universe in our universe, but they are isomorphic with our universe. Our Hubble volume refers to the sphere centered on us, which is the farthest distance we can see. Its radius is about 65.438+0.38 billion light years, but due to the expansion of the universe, its actual radius has now expanded to about 46.5 billion light years. For the universe 46.5 billion light-years away, it is currently unobservable and has nothing to do with us. According to our Hubble volume radius, our universe can also be divided into n disjoint small universes.
Because we are the same universe and have the same physical laws, and because the universe is isotropic, when the universe is big enough to be divided into enough small universes, there is a possibility that the particles in a small universe are arranged like our Hubble volume, so two identical small universes are produced. In that small universe, it is possible to evolve an identical you, but he has nothing to do with you.
However, because the size of our universe is limited, it is impossible to have infinite small universes, so the possibility of having exactly the same particle arrangement at such a macro scale is basically zero.
In addition, due to the limitation of the speed of light, such a small universe is also unobservable, that is, unverifiable.
The negative energy universe under the conservation of energy
Conservation of energy is an eternal physical law, but it brings an ultimate question: how did our universe come from? Our universe is full of energy, and it was born in a limited time, so how is its energy generated?
According to quantum mechanics, virtual particle pairs can be randomly generated in a vacuum and generally annihilated immediately after being generated. But there is a possibility that two virtual particles are separated by a large enough distance. Theoretically, when virtual particle pairs are separated by more than twice their wavelength, they will no longer be annihilated. When virtual particle pairs cannot be annihilated, they will become real particles. Therefore, it is pointed out that it is very likely that two big bang singularities were produced at the beginning, which were produced in a huge energy fluctuation. For some unknown reason, they separated instantly and did not annihilate immediately, so they had positive energy and negative energy respectively, and then they expanded into a macro universe. In this way, it is possible to form our universe and produce a parallel universe full of negative energy, in which there may be a negative energy you.
But obviously, such a negative energy universe is also unobservable, because the moment you observe it means destruction.
The world back in time, the universe in the white hole.
In Carl? Decades after Schwarzenegger proposed the black hole, it was suggested that there might be a kind of celestial white hole opposite to the black hole. According to the general theory of relativity, black holes can only enter but not exit, and white holes can only exit but not enter. However, scientists can't find the mechanism of the natural formation of white holes, unlike black holes that can be produced by the collapse of celestial bodies. So it was suggested that the other end of the black hole is likely to be connected with the white hole, and the two are connected through the wormhole, and the black hole is sucked into the white hole and ejected.
However, according to general relativity, the boundary visual interface of a black hole is a unidirectional film. When it crosses the horizon, the space-time in the black hole will be reversed, and all objects falling into the black hole will fall into the black hole from the space direction and become singularities in the time direction. That is to say, the process of matter falling into the black hole singularity is a chronological process, but on the contrary, the process of matter ejected from the white hole singularity becomes an inverse process, which is somewhat inconsistent with our physical laws, because our cosmic time is obviously one-way, and there is no inverse process. So some people continue to open their brains wide and put forward that the white hole is in another universe, and the time of that universe is going backwards.
However, such a universe may not be called a parallel universe, but a mirror universe. After all, even in the opposite direction of time.
For such a universe, don't ask anything, asking is impossible to falsify.
Parallel space-time under the ultimate theory
In the process of pursuing unity, a strange theory called string theory was born. By increasing the spatial dimension, scientists can incorporate more interactions into the same theory. After the development from string theory to superstring theory, scientists unified four kinds of interactions in nature in ten-dimensional space-time, but found five different superstring theories, all of which seemed right. Later physicist Edward? Witten unified the five superstring theories by adding another spatial dimension.
However, someone soon discovered the problem. After adding a spatial dimension, the space becomes ten dimensions. But even space can't derive chirality, which is inconsistent with the real world.
Later, Witten himself came up with a simple idea: unreasonable, crossing time and space; Not enough brain holes, parallel universe. ? Yes, he moved out of the parallel universe! By defining the tenth spatial dimension as a parallel spatial dimension connecting two nine-dimensional spaces, the space returns to the odd dimension again, which perfectly solves the chiral problem. In the end, this theory is called M theory, which is the ultimate theory that is most likely to unify all interactions.
Three-dimensional movies floating in high-dimensional space
At first, the high-dimensional space of string theory is curled up under Planck's length, but with the development of the theory, because there are three kinds of interaction forces that cannot be separated from the three-dimensional space (only gravity can penetrate into the high-dimensional space), we may not see the high-dimensional space even macroscopically, because our daily observation means are locked in the three-dimensional space.
In this way, a macro high-dimensional space may exist, and the visible universe may only be a three-dimensional space film floating in the high-dimensional space. So what makes you think that there is only one 3D movie in this high-dimensional space? Another brain hole has appeared: in this high-dimensional space, there may be countless three-dimensional movie universes floating, but unlike the previous parallel universes, these floating three-dimensional movies may collide (it is theoretically believed that this collision has produced BIGBANG). Even if they don't collide, the matter on the two three-dimensional films can produce gravitational interactions, which are theoretically observable in our universe. Some people think this can explain the problem of dark matter.
Because there can be an infinite number of three-dimensional movie universes, it is possible that there is a universe with exactly the same arrangement and combination as our universe, and there is another parallel universe of yours, but like the previous small universe, this parallel universe? What about you? this is nothing to do with you.
The universe is not unique? Bubble universe
In fact, all the parallel universes in front can be considered as coming from the same universe, because they have the same origin. However, it has also been suggested that there may not be only one universe at all, but countless universes, each with different physical laws and different evolution processes. Some may not expand at all, and some may expand; Some may have only one power, while others may have eight. Anyway, it is the famous saying of folk science: anything is possible!
Since there are countless different universes, it is naturally possible to have two universes with exactly the same arrangement and combination.
Unconsciously wrote thousands of words, completely beyond the original plan. I thought about whether to divide it into two parts. Think about it and forget it. It is not good to be apart. How do you feel after seeing so many parallel universes? Or what other parallel universe hypotheses do you know? You can leave a message to discuss it. (^_^)