The Four Kinds of the Multiverse: Which One Are We in?

What is the multiverse?Is it science fiction or science fact? And if so, how many alternate universes could there be? We are unlikely to ever know the answers to these questions: our ability to know, alas, is limited. But if you believe the results of Young's experiment, then such elementary particles as photons can be in two places at the same time. But only if someone is watching them. In addition, physicists managed to prove that light can be both a wave and a particle at the same time, which is scientifically called wave-particle duality. Such contradictions and anomalies in quantum mechanics underlie both the development of science and science fiction, whether in prose or on the screen. So, the heroes of the Marvel movie comics, like the heroes of the animated series Rick and Morty, now and then travel between worlds. Agree, the very idea of ​​the existence of other versions of yourself is breathtaking, and such eminent scientists as Andrei Linde, Michio Kaku and Stephen Hawking are seriously considering the existence of the Multiverse.

The multiverse is made up of many separate and distinct universes.

Surprisingly, many of the best scientific modelsthe birth of our universe actually depends on the existence of many worlds. These other universes can be almost identical to ours, or they can be unimaginably different from each other, for example, due to other laws of physics. But even if the existence of multiverses cannot be proved, the very idea opens up many interesting and even stupefying possibilities.

Every collapsing black hole could hold the seeds of a new expanding universe, Sir Martin Rees, UK Chief Astronomer Royal.

Secrets of the multiverse

Before diving into the theory of the Multiverse,Let us recall that any conversations and scientific research in this area are hypothetical, and many physicists refuse to seriously consider the existence of parallel worlds. So, even in the days of Einstein, the topic of the multiverse was considered very eccentric, and once productive physicists who had reached old age and were ready to move away from serious matters could deal with it. As for Einstein himself, after 1935 he was mainly concerned with general relativity (GR), electromagnetism, and the search for a unified theory of everything.

Black holes, according to Stephen Hawking, may be the gateway to parallel universes

The reason for the interest of the famous physicist is simple - general relativitygorgeous. But at the same time, it is like a Trojan horse. Just a few simple assumptions describe the basic characteristics of the cosmos, including the Big Bang. Even the theory of inflation can be adjusted to a solution by fitting a chosen cosmological constant into the equations of the early universe. These equations, among other things, give us a convincing theory of the creation and death of the universe. But it is worth looking inside the Trojan horse, as we will find black holes, space-time tunnels (wormholes) and even time machines. All this is beyond common sense and Einstein denied the very possibility of their existence and detection.

Black holes can become passages to anytime. If we had to jump into a black hole, then it is assumed that we would appear in a different part of the universe and in a different time era ... Black holes can be the gateway to Wonderland. But are there Alices and white rabbits there? — Carl Sagan.

But as we know today, black holesreally exist. We recently reported on a stunning discovery - a snapshot of the shadow of a black hole at the very heart of our Galaxy. Earlier in 2019, the world gazed in admiration at the image of the black hole at the center of Messier 87, the largest supergiant elliptical galaxy in the constellation Virgo.

Black holes are gates to a parallel universe

But that's not all:In 2017, an international team of scientists proved the existence of gravitational waves, the source of which was the collision of two supermassive black holes at a distance of about 1.3 billion light-years from Earth. All these discoveries, one after another, reaffirmed the postulates of general relativity. In addition, deviations and anomalies in the calculations are an integral part of the theory, which really implies the possibility of the existence of the Multiverse. These worlds can be interconnected by space-time tunnels.

Read more about what gravitational waves are, as well as when and how they were discovered by my colleague Artem Sutyagin, a must-read.

Evidence for the existence of the multiverse

Since we are residents of the 21st century, we know aboutthe structure of the Universe is much more than the physicists of the last century. The planets, stars and galaxies known today span 93 billion light years. Modern telescopes, both on the ground and in space, have made it possible to see what Einstein and his colleagues thought was barely possible. Moreover, the development of quantum mechanics, which describes the interaction of elementary particles with incredible accuracy, has shown that the multiverse is not such an invention, and alternative worlds can be near ours, but go unnoticed. Even the theory of inflation claims that the universe underwent an incredible superluminal expansion at the time of its birth, and its postulates suggest the existence of a multiverse. The highly controversial string theory also adds charm to this amazing story.

The observable universe in one image

Moreover, over the years, researcherssuggested that alternate versions of ourselves exist within the Multiverse. It's just that "other" we can live in a completely different physical reality, since the laws of nature are not necessarily the same for every universe. For this reason, the Swedish-American cosmologist and astrophysicist Max Tegmark from the Massachusetts Institute of Technology proposed to consider four types of parallel universes.

Interesting fact
Cosmology embraces the entire universe from birthto death with secrets and intrigue at every turn. Some physicists believe that there may be different particles, different forces, even a different number of dimensions of space compared to what we see around us.

So let's say our universe collided withanother and we intend to prove it. One possibility is traces that other universes may have left in the form of swirls in the cosmic microwave background—thermal radiation left over from the Big Bang. Another way can be gravitational waves - the so-called ripples in space-time, which appeared shortly after the birth of the universe.

Gravitational waves can also provideevidence to support the theory of cosmic inflation, which predicts that gravitational waves left over from the Big Bang could produce tiny curls in the CMB, some physicists believe.

A shot from a very strange and crazy film "Everything is everywhere and at once." Recommend to watch

According to Tegmark, who wrote an article on the subject inScientific American review many years ago, there are four levels of the multiverse. In the paper, the author considers theories, including parallel universes, which form a natural four-level hierarchy of the Multiverse, allowing for an increasing variety. Just like in the movie "Everything is everywhere at once," where in one of the worlds people had huge sausages instead of fingers.

Well, to understand why some physicistsbelieve that we live in the Multiverse, read this article. In it, astrophysicist Andrei Linde explains what physical laws testify to the reality of many worlds.

Four kinds of multiverses

Assuming the existence of infinite universes,The cosmologist divided the Multiverse into four types. The first assumes the existence of an infinite universe in which all possible variants of events take place, including a copy of our Earth. At the second level, the basic laws of physics operate in the same way as in our universe, but the fundamental constants are different: for example, there may be four spatial dimensions, not three. The third level represents many different worlds and is the most popular representation of the multiverse.

Some physicists believe the discovery of black holes could indicate the existence of a multiverse.

At the same time, each choice of a person can lead toto a split in the universe, which will then lead us to endless parallel realities. And, finally, the fourth level demonstrates the multiverse, in which completely different laws of physics operate. In the article, Tegmark describes the four kinds of multiverses as follows:

• Level I: The general prediction of cosmological inflation is an infinite universe with the Hubble constant realizing all initial conditions, including an identical copy of you at a distance of about 101029 meters.
• Level II: In many models, inflation can lead to multiple Level I multiverses that have different physical constants, sizes, and particle abundances.
• Level III: In unitary quantum mechanics, other branches of the wave function do not add anything qualitatively new. Ironically, these quantum parallel universes have historically been the most controversial.
• Level IV: Various fundamental equations in physics are based on other mathematical structures.

The author of the theory also notes that a common featureof all four types of multiverses is the simplest and most elegant theory, which by default takes into account the existence of parallel worlds. And despite the many anomalies and theories and hypotheses put together, the very fact of thinking about the multiverse gives us a great opportunity to think about the nature of science and our existence. And if scientists at some point can detect characteristic curls in the CMB, or catch the ripples of space-time that arose after the Big Bang, our understanding of the world, space and the Universe will have to be seriously revised.

Doctor Strange in the Multiverse of Madness. Have you already looked?

Unfortunately (or fortunately, who knows)today there is no evidence for the existence of the Multiverse. So we can be content with the works of science fiction writers and films in which the characters discover an endless string of worlds. The main thing is not to forget about the scientific component of the multiverse, since at the most basic level our world is a mathematical structure, in which there may be a thinking observer - that is, you. You can read the text in full here.

"The idea of ​​the objective existence of mathematicalThe forms underlying the concept of the Level 4 Multiverse is not so much a matter of philosophy as of conventional science, as it is falsifiable and leads to testable predictions. No matter how you calculate pi, the result will be the same, because it exists before any calculation and independently of them. This is a testable prediction. And where such predictions begin, philosophy ends and normal science begins,” says Alexander Panov, Doctor of Physical and Mathematical Sciences and Leading Researcher at the N.N. Skobeltsyn (SINP) MSU

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Author of four types of Multiverse Max Tegmark

But there is something new.As the results of a recent study published in the journal Physical Review Letters show, the invisible "mirror world" of elementary particles can interact with ours only through gravity and may be the key to solving the main mystery of modern cosmology - the problem of the Hubble constant, which determines the rate of expansion of the Universe today. . It can even be said that scientists do not fully understand what exactly is happening with our Universe today.

Ultimately, the authors of the scientific work came tointeresting conclusion: perhaps there is a mirror universe, very similar to ours, but invisible to us, except for its gravitational influence on our world. Science is amazing, you see. As for the Hubble constant, you can learn more about the main mystery of modern cosmology here.