Shulou(Shulou.com)11/24 Report--

In the new story of Marvel Universe, we see that the multiverse expands a new framework to Marvel's story world. In many movies, television or our imagination, the concept of multiverse is very common. We are surrounded by the idea of a multiverse, which provides us with a very tempting assumption that our reality is not unique.

Loki's first season Spatio-temporal change Administration (pictured on the Internet) the concept of the multiverse was not conceived in the writer's masterstroke, but derived from the blackboard formula of physicists. Of course, the scientific definition of multiverse is a little different from the concept of multiverse that we see in media such as film and television. The story of exploring the multiverse is no longer accompanied by the love and hatred of heroes and demons, but more about the exquisite interpretation of mathematical formulas. But the concept of multiverse on the media network is actually based on a reasonable scientific hypothesis. This scientific hypothesis is verifiable and has been verified.

The concept of the multiverse can be traced back to ancient times, and it originated from an open issue: in the world, there is no possibility of a world like us. (or a different concept of "universe") and in the exploration of modern physics, this term appears only in a few different fields.

The eternal explosion of the universe: the expansion of the universe makes the multiverse conjecture at least reasonable. Maybe the cosmic boom is still going on, but it's not here. According to the conjecture of the multiverse, there may be not only one universe beyond the limit of human observation, but a vast sea of bubbles made up of many bubble-like multiverses, each of which is as big as other universes. Different multiverses are forever separated in an expanding space. Picture from Designua / Shutterstock in order to define the multiverse, we first have to define the universe. In the strict definition, the universe refers to the farthest limit of space that can be observed by human beings. Our universe is so early and the speed of light is so fast that from our perspective on Earth, we feel trapped in a spherical space with a radius of about 45 billion light-years. And contains all the light that has reached the earth since ancient times.

Apart from Liuhe, there are all kinds of stars. Beyond the limits of the universe that humans can observe, there are more abundant stars and galaxies. These stars beyond the limits of the universe have nothing to do with us, and the eternal expansion of space makes us farther away. The latent dark energy in the universe accelerates the expansion of space and aggravates the phenomenon of galaxies moving away from each other. We can never observe these areas and cannot reach these spaces, so this part of the universe that exceeds the limit of human observation represents the most boring but also the least controversial version of the multiverse: an extension of our universe. it contains matter that is the same as we can observe the universe, but arranged in a different way. The universe beyond the limit of human observation is based on the prediction of the Big Bang model-it is a natural corollary of the expansion of the universe-but there will be no observations in this part of the universe, so no one really disputes it, and no one really cares about it. In other words, there is nothing special about this multiverse.

The second kind of multiverse, which is also a more exciting multiverse model, comes from the basic principles of quantum mechanics and an interpretation of "multiple worlds". This view holds that every time a probabilistic process occurs in the micro world (which actually happens all the time), the universe produces branches of different evolution processes. Each branch of the universe represents the corresponding process of a certain probability event in the micro world. For example, one microscopic particle in our universe is moving to the left, while in another "universe" it is moving to the right. However, this "multiverse" view is based on an understanding of the exact meaning of the concept of "measurement" (a very important concept) in quantum mechanics. The understanding of measurement is a very thorny debate. Furthermore, physicists are not even sure whether they can experimentally verify different conjectures about the measurements of the microscopic world-- or whether they have physical significance-- so most physicists are trying to avoid discussion of measurement.

So we're going to talk about the third kind of multiverse, that is, the multiverse theory based on the explosion of the universe, which is also the most interesting multiverse theory of all multiverse theories. because this theory is based on a possible theory of the early universe, and scientists have certain means to verify this theory. This multiverse theory may be able to realize all kinds of multiverse dreams on the big screen, or the desire for multiverse in our hearts. This multiverse theory may be confirmed by us, and this multiverse theory may be true.

The theory of multi-branch cosmic inflation can be traced back to the idea put forward by theoretical physicist Alan Guth, who first put forward the embryonic form of inflation theory in a paper in 1981. In order to reasonably explain some very confusing problems in the early cosmic model (for example, the general predictions of high-energy physicists require the existence of some novel phenomena in the universe, such as magnetic monopole, but these phenomena have not been observed so far), Guz proposed that the early universe experienced a short period of ultra-rapid expansion, which is also known as cosmic skyrocketing. This process ejects all the unipoles beyond the observational limits of the human universe, sweeping them under the cosmological carpet.

The inflation theory also happens to explain other problems in the Big Bang model of the mediocre universe, such as how the universe could form such a regular structure in a relatively short period of time. The theory of cosmic inflation explains all this well: if the universe expands rapidly to an incomparably great extent, then the universe will eventually be uniform.

This multiverse theory may make the movie's multiverse reverie come true.

But the reason behind the inflationary theory, and why most astronomers believe in it, is that it can very reasonably explain galaxies, cosmic fibers, cosmic gaps-the source of the large structure that fills the cosmic network. Within the framework of the theory of cosmic inflation, our universe expands rapidly, and the microscopic quantum system expands to a relatively macro scale, sowing the seeds of gravity in the universe, after millions of years of evolution under the influence of gravitation. our universe has formed galaxies, galaxies and richer content.

Physicists have no way of knowing where the energy in the process of cosmic inflation comes from, how long it lasted and why it stopped. However, the prediction of the statistical properties of the macrostructure of the universe by the theory of cosmic inflation coincides with the observation of human beings with great accuracy, so the theory of inflation has always been accepted by astronomers.

The last question-why the cosmic boom stopped-is still open to question. It's easy to imagine that the universe skyrocketed, a very magnificent process that happened suddenly in the early stages of the Big Bang, but it's hard to imagine that the process stopped quietly, leaving the cosmic stage and never to be seen again.

Maybe the explosion of the universe has never stopped, but has been going on quietly, but not here, not in our universe. Indeed, some physicists believe that the explosion of the universe is the natural result of the inherent randomness of quantum mechanics. This process requires only a small quantum shock of the particles, and the process of cosmic inflation does not stop in every corner of the universe at the same time. Perhaps our universe is just part of a larger region of the universe that emerges and stabilizes as a branch into a calmer phase of growth. At the same time, outside our cosmic sphere space, the cosmic surge continues, as more universes separate and stabilize from each other, causing other universes to be isolated from our universe in time and space.

The multi-branched concept map of the multiverse (pictured on the Internet), the theory of "eternal cosmic surge", extends the simple idea that "there is only something more outside our universe" to a higher level. Beyond the observable limits of human beings, there is not only one universe, but also a vast sea of universes, these universes are similar to bubbles, and each separated universe is similar in size to its neighboring universe. at the same time, different universes are separated by endless spaces. All these universes originated from a process-the original Big Bang-but the universe never stopped rising, so the number of independent universes was soon innumerable.

It is worth mentioning that in this original version of the multiverse theory born out of the explosion of the universe, the human universe follows the same set of physical laws as other universes. In other universes, the forces of nature are the same as those in our universe. For example, in each universe of the multiverse, the speed of light is the same.

But when you combine cosmic inflation theory with string theory, things go crazy. String theory was put forward in the 1860s to explain the strong interaction, and then gradually developed into a possible theory to explain everything. Over the past few decades, physicists have been looking for a grand unified theory, hoping to solve this mathematical puzzle so that it can explain everything, literally: everything. This includes forces in nature, families of particles and their masses, values of physical constants, and even spatial dimensions.

String theory indicates that our universe contains other dimensions, which are bent to very small sizes, so we can't actually observe them normally. The way these dimensions bend determines the physical phenomena we observe, but there are about 10500 ways to bend dimensions, and string theory cannot determine which one corresponds to our universe.

When you combine string theory with cosmic inflation theory, you have a chance to get all the configurations of curved dimensions-and the mechanism by which cosmic inflation makes the universe develop into a multiverse with different physical laws. In string theory, if our universe had curved dimensions of different configurations during the explosion of the universe, our universe might have been a completely different face, with different physical constants, or even different natural forces. And if the cosmic boom never stops, then perhaps different multiverses have different physical phenomena and laws, different physical constants, and even different realities.

This is the endless multiverse. This theory may solve some deep-seated problems in physics and cosmology.

For example, at the beginning of this century, physicists wanted to explain dark energy and the acceleration of the expansion of the universe. One of the strangest things about dark energy is that it is very weak-the slight acceleration that causes the universe to expand-but not exactly zero. This seems to be a fine-tuning; if dark energy had a slightly different value, the world as we know it would cease to exist.

The concept of multiverse promoted by string theory provides a way to solve the above problems. In many multiverses with different dark energy intensities, we happen to be in our universe, because we may not be able to exist in other universes at all.

The most interesting thing about the chance encounter of the multiverse is the measurable prediction of the multiverse theory. Otherwise, these multiverses can only be unrealistic ideas dreamed up by some boring physicists.

At present, there are several theories that verify the multiverse caused by the explosion of the universe. For example, if a neighboring universe is squeezed out at the beginning of the formation of our universe, then it is highly likely that the neighboring universe will collide with our universe before it leaves our universe. At the stage where we are now, the chances of collisions between multiuniverses are very small, because the cosmic explosion causes the universe to expand so fast (actually at superluminal speeds). And the Big Bang is 14 billion years old, so any other universe is far away from our universe.

But if a neighboring universe forms early and fast enough, it will be able to collide with our universe in its early days. This brief encounter can leave a detectable imprint on the microwave background of our universe. The cosmic microwave background radiation is the afterglow formed when our universe forms a stable state from the plasma air mass in about 380000 years. The afterglow is the farthest fact we can observe directly, and this is our best chance to observe such cosmic collisions.

We can be in our universe because we can't exist in other universes.

This is a verifiable and true scientific prediction. Alas, but the search for such signals has been in vain. But the inability to find a signal does not negate the concept of the entire multiverse, only in limited scenarios where our universe collides with other universes.

Because we are lack of direct experimental verification, we have to adopt an indirect verification method. We can deduce the theory and model of cosmic inflation in an attempt to confirm whether the multiverse is the universal and automatic result of all inflationary models (which is physically the most reliable or simplest case), or only part of the inflationary model derives the multiverse, or there is no inflationary model that can give the multiverse. Unfortunately, the theory of cosmic inflation needs to be based on the theory of ultra-high energy physics, but humans still lack knowledge about these aspects-that is, there is no sign that every theory of cosmic inflation can derive a multiverse theory.

We can also use the same method to demonstrate the theory of cosmic inflation. If the observations can tell us which model of cosmic inflation is correct, then we can verify whether a multiverse will be produced in a particular case, such as our universe. We cannot directly observe the cosmic surge because it occurs too early, but we can observe the effects of cosmic inflation, especially through the cosmic microwave background radiation. When astronomers first measured the small fluctuations of the cosmic microwave background radiation using NASA's cosmic background probe satellite in the 1990s, the cosmic inflation theory was the only theory that could correctly predict the statistical properties of the cosmic microwave background radiation. However, other identical observations-- and many subsequent observations-- have failed to tell us which of the many models of cosmic inflation is correct, let alone provide successful, definitive proof of the theory of cosmic inflation.

However, future cosmic observations may still provide some breakthroughs. The theory of cosmic inflation should leave traces of fluctuations in cosmic space-time, also known as gravitational waves. We have been able to use the LIGO (Laser interference gravitational Wave Observatory) to observe gravitational waves emitted by the fusion of celestial bodies, but these devices have not been able to detect low-frequency gravitational waves during the explosion of the universe. So now scientists plan to use space observation equipment, such as LISA (Laser interference Space Antenna) to directly detect these low-frequency gravitational waves, or indirectly use the traces of these low-frequency gravitational waves in the cosmic microwave background radiation to confirm their existence. Only time will tell whether these efforts will bear fruit and eventually lead us to the evidence that confirms (or negates) the explosion of the universe.

But even when we can do this-- prove that the theory of cosmic inflation is the only theory that can reasonably explain the process of the early universe, and mathematically deduce that the multiverse is an organic extension of the inflationary model of the universe-- we still don't have enough evidence to show that the multiverse exists.

Admittedly, we can test a theory in a range that we have easy access to (for example, verifying general relativity in the solar system) and based on the principles of mathematical consistency and the generality of physics, extend this theory to areas beyond the reach of humans in our universe to infer what happens in those regions (for example, what happens inside a black hole). But humans only stop there. Indeed, in the case of a black hole, we know that general relativity will fail in the singularity of a black hole, so even if we cannot enter the black hole (we cannot personally enter the event horizon of the black hole), we still understand that general relativity has its own shortcomings.

Unfortunately, we have no way of knowing whether the multiverse really exists, and we may never know.

Many people insist that despite the surge in attention to the topic of the multiverse in the early 21st century, theoretical and observational work on the multiverse has stagnated over the past decade. This is partly because of the nature of scientific research: observations of the early universe require a lot of time to plan, deploy, and make massive observations. But some of the decline in attention is due to the vague definition of the multiverse itself.

The best argument behind the multiverse theory is that it may reasonably explain why some of the basic characteristics of our universe are like this: because other forces, masses and constants make our universe unfit to live, human beings will cease to exist. This is the anthropic principle, which is regarded by its supporters as a feasible way to understand reality.

Every time we open a book or watch a movie, we create an alternate reality.

However, there are several inadequacies in the theory that people who criticize the theory pay. Do we really want our scientific argument to stop in this logical dead knot? Do all multiverses follow different physical laws? Is the human universe with a constant configuration rare or common in other multiverses? And how can we measure the configuration of cosmological constants at infinite multiverse scales without weakening the rigor of a theoretical argument full of hypotheses?

String theory-- which requires each theory to have its own unique physical laws in the multiverse-- also has its own problems. Theoretical physicists who study string theory have not yet found a solution-- or any solution. Although we now know that the way other dimensions in the universe bend determines the physical laws of our universe, we still don't understand how this works. If you give physicists who study string theory a specific parameter in other dimensions, they can't tell you what the physical laws of the universe look like under this parameter. At the same time, many versions of string theory are based on supersymmetry, but these theories now seem very rough because the large Hadron Collider has failed to find any experimental basis for string theory.

The concept of the multiverse is not lifeless, but like other ideas in science that seem very forward-looking at first, but fail to produce observations or even theoretical inspiration. The physical concept of the multiverse is in decline. Physicists no longer pay more attention to the theory of multiverse, and the arguments for the existence of multiverse are no more abundant than when the concept of multiverse was proposed decades ago. Most of the arguments for the multiverse still belong to the unknowns of physics.

But the concept of the multiverse still exists. In an endless multiverse model, all the processes that can happen will happen. In other multiverses, you can invite your sweetheart on a date or take the job. And it doesn't happen in some imaginary place or in the reality of "parallel" (no matter what the word means). All these other multiverse bubbles occupy the vast space of the entire multiverse. They exist in the same space-time field as we do.

The multiverse is incomparably far away from us, but it still has a limited distance. When you point your hand in any direction in the sky, if you extend long enough in that direction, then you will encounter another multiverse in which you are doing the same thing, pointing your finger at you. In the endless multiverse, all the possibilities of your life, and all the possibilities of the lives of others, and all the possible interactions of stars, galaxies, hydrogen molecules, and even different combinations of natural forces and physical constants, are real.

A strange view of the universe, of course, if the multiverse exists, it's really hot pants. The idea of the multiverse seduces us deeply, which means that every time we open a book or watch a movie, we interpret a different reality: every science fiction novel is an interpretation of the multiverse. The laws of physics in the sci-fi multiverse are similar to those in which humans inhabit, but there are some differences. In the multiverse, our dreams can come true, especially in the multiverse with different laws of physics. You want to fly? To arrange "you" in other multiverses. In other multiverses, maybe you are doing this! You want to eat stars for breakfast? No problem, the multiverse can also arrange for you. You want to have magic? Of course, why not?

The concept of the multiverse makes our imagination a reality. We can't get in touch and distance from each other, but it's possible in theory. And even the concept of the multiverse fades in the rigorous study of science, but we are also concerned about the possibility of the multiverse. This is not a bad thing: after all, science always moves forward in the process of realizing human dreams.

Author: PAUL M. SUTTER

Translation: * 0

Revision: there are interests in the future

Original link: Doctor Strange and the Multiverse in Science

This article comes from the official account of Wechat: Institute of Physics, Chinese Academy of Sciences (ID:cas-iop), author: PAUL M. SUTTER

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