Some people reject "metaphysical" concepts (an offensive word from a physicist's point of view!). Among them is the concept of the “multiverse” - a hypothetical set of all possible real-life parallel universes (including the one in which we are located). The internationally recognized British cosmologist and astrophysicist believes that the multiverse is entirely within the purview of science, although it is still only a hypothesis.


There is a point of view that - although it is hypothetical - I find very attractive. This is the idea that our Big Bang was not the only one. Individual universes may have cooled differently, and in the end they are governed by different laws and determined by different numbers. This hypothesis does not seem "parsimonious" - indeed, perhaps nothing seems more extravagant than the appeal to multiple universes - but it flows naturally from some (even speculative) theories and opens up a new vision of our Universe as just one "atom" of the infinite multiverse.

Andrei Linde and other scientists have already proven that some assumptions, consistent with everything we know, indicate the existence of many universes that appeared after separate “big bangs” and became disconnected regions of space-time. We will never be able to observe these universes directly; we cannot even reliably say whether they exist “before”, “after” or “simultaneously” with our Universe.

The initial assumptions that predict multiple universes are still speculative, but if they can be strengthened and linked to a theory that convincingly explains what we can observe, then we will have to take other (unobservable) universes seriously, just as we trust that , what our current theories say about quarks inside atoms or what is hidden inside black holes.

If there really are many universes, the next question is how diverse they are.

The answer depends on the characteristics of physical laws at a deeper and more general level than what we currently understand. Perhaps some “ultimate theory” will provide a generalized formula for all our six numbers. If this happens, then other universes, even if they exist, are, in essence, repetitions of ours, and the obvious “tuning” will be no more a mystery than our Universe is mysterious. We are still at a loss to say how a set of numbers created in the extreme conditions of the Big Bang fell into a narrow gap that allows such interesting consequences 10 billion years later.

But there is another possibility. The overarching laws found throughout the multiverse may be more lenient. The power of forces and the mass of elementary particles may not be the same everywhere, but take on different values ​​in each universe. Then what we call the “laws of physics”, from the point of view of the multiverse, will be just regulations, applicable only within our own Universe, and the result of its early history.

Stars and planets might still exist, but they would be smaller and evolve faster. They would not provide the long enough periods of time that evolution requires. And gravity would crush anything large enough to develop into a complex organism.

The "recipe" for any "interesting" universe must include at least one very large number: it is clear that not many things can happen in a universe that is so limited that it can only accommodate a few particles.

Every complex object must consist of a large number of atoms. It takes a lot of time to evolve along the path of complexity—many, many times longer than it takes for a single atomic event.

Some theorists favor the simplest universe with sufficient intergalactic dark matter (which contradicts the best evidence today).

If in fact there are many universes, described by different "cosmic numbers", then we will find ourselves in one small and atypical subgroup.

The seemingly “designed” features of our Universe should not surprise us any more than we are surprised by the fact that we are in it at all.

We live on a planet with an atmosphere orbiting at a certain distance from its progenitor star, although in fact this is a very “special” and atypical place. A randomly chosen place in space will be very far from any star; Moreover, most likely, it will be located somewhere in the intergalactic void, millions of light years away. years from the nearest galaxy.

If no other universe is mathematically consistent with the laws of physics, we will have to accept that the “tuning” is an inexorable fact and was done by the will of Providence. On the other hand, a universal theory may allow for the existence of a multiverse whose evolution is marked by regularly recurring “big bangs.” Then the underlying physical laws of the multiverse may allow for a variety of individual universes.

Illustration: Shutterstock

Even before Everett and his idea of ​​multiple universes, physicists were stumped. They had to use one set of rules for the subatomic world, which is subject to quantum mechanics, and a different set of rules for the large-scale everyday world that we can see and touch. The complexities of moving from one scale to another twist the brains of scientists into bizarre shapes.

For example, in quantum mechanics, particles do not have certain properties unless someone is looking at them. Their nature is described by the so-called wave function, which includes all possible properties that a particle can have. But in a single universe, all these properties cannot exist at the same time, so when you look at a particle, it takes on one state. This idea is metaphorically depicted in Schrödinger's cat paradox - where a cat sitting in a box is both alive and dead until you open the box to check. Your action turns the cat into a warm and alive cat or into a stuffed cat. However, .

In the multiverse, you don't have to worry about killing the cat with your curiosity. Instead, every time you open a window, reality splits into two versions. Unclear? I agree. But somewhere out there there may be another version of the event that just happened before your eyes. It didn't happen somewhere else.

It remains to be seen what reasons scientists have found to tie this incredible theory to facts.

So reality can be infinite

In a 2011 interview, Columbia University physicist Brian Greene, who wrote the book Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos, explained that we are not entirely sure how big the universe is. It may be very, very big, but it is finite. Or, if you go from Earth in any direction, space can stretch on forever. This is roughly how most of us imagine it.

But if space is infinite, it must be a multiple universe with infinite parallel realities, according to Green. Imagine that the universe and all the matter in it are equivalent to a deck of cards. Just as there are 52 cards in a deck, there will be exactly the same number of different forms of matter. If you shuffle the deck long enough, the cards will eventually return to the original order. Likewise, in an infinite universe, matter will eventually repeat itself and organize itself in a similar way. A multiple universe, the so-called multiverse, with an infinite number of parallel realities, contains similar but slightly different versions of everything that is, and thus provides a simple and convenient way to explain repetition.

This can explain how the Universe begins and ends

Humans have a particular passion - and it is related to the brain's ability to form patterns - we want to know the beginning and end of every story. Including the history of the universe itself. But if the Big Bang was the beginning of the universe, what caused it and what existed before it? Will the universe end and what will happen after it? Each of us has asked these questions at least once.

The multiverse can explain all these things. Some physicists have suggested that the infinite regions of the multiverse could be called brane worlds. These branes exist in multiple dimensions, but we cannot detect them because we can only perceive three dimensions of space and one of time in our own braneworld.

Some physicists believe that these branes are like slabs piled together like sliced ​​bread in a bag. Most of the time they are separated. But sometimes they collide. Theoretically, these collisions are catastrophic enough to cause repeated "big bangs" - so that parallel universes start over, over and over again.

Observations suggest multiple universes may exist

The European Space Agency's Planck Orbiting Observatory collects data on the cosmic microwave background, or CMB, background radiation that is still glowing from the first and hottest stage of the universe.

Her research also led to possible evidence for the existence of a multiverse. In 2010, a team of scientists from the UK, Canada and the US discovered four unusual and unlikely circular patterns in the CMB. Scientists have suggested that these marks may be “bruises” that were left on the body of our Universe after a collision with others.

In 2015, ESA researcher Rang-Ram Hari made a similar discovery. Hari took the CMB model from the observatory's celestial image, and then removed everything else we know about it - stars, gas, interstellar dust, and so on. At this point the sky should have become mostly empty except for background noise.

But it didn't. Instead, in a certain range of frequencies, Hari was able to detect scattered spots on the map of space, areas that were about 4,500 times brighter than they should have been. Scientists have come up with another possible explanation: these areas are imprints of collisions between our Universe and a parallel one.

Hari believes that unless we find another way to explain these markings, "we will have to conclude that Nature can play dice after all, and we are just one random universe among many others."

The universe is too big to exclude the possibility of the existence of parallel realities

There is a possibility that multiple universes exist, although we have not seen parallel realities, because we cannot disprove its existence.

This may seem like a clever rhetorical trick at first, but consider this: even in our world, we have found many things we never knew existed, and these things have happened - the 2008 global crisis is a good example. Before him, no one thought that this was even possible. David Hume called these kinds of events "black swans": people will assume that all swans are white until they see black swans.

The scale of the Universe allows us to think about the possibility of the existence of multiple universes. We know that the universe is very, very large, perhaps infinite in size. This means that we will not be able to discover everything that exists in the universe. And since scientists have determined that the Universe is approximately 13.8 billion years old, we can only detect the light that managed to reach us during this time. If a parallel reality is located further than 13.8 light years from us, we may never know about its existence, even if it existed in the dimensions distinguishable by us.

Multiple universes make sense from an atheistic perspective

As Stanford University physicist Andrei Linde explained in a 2008 interview, if the physical world obeyed slightly different rules, life could not exist. If protons were 0.2% more massive than they are now, for example, they would be so unstable that they would decay into simple particles instantly without forming an atom. And if gravity were a little more powerful, the result would be monstrous. Stars like our sun would compress tightly enough that they would burn out their fuel within a few million years, giving planets like Earth no chance to form. This is the so-called “fine-tuning problem.”

Some see in this precise balance of conditions evidence of the participation of an omnipotent force, a supreme being who created everything, which greatly angers atheists. But the possibility of the existence of a multiverse, in which this force will simply be in a separate reality with all the factors necessary for life, suits them quite well.

As Linde said, “For me, the reality of multiple universes is logically possible. We can say: perhaps this is some kind of mystical coincidence. Perhaps God created the universe for our benefit. I don’t know anything about God, but the universe itself could reproduce itself an infinite number of times in all possible manifestations.”

Time travelers can't disrupt history

The popularity of the Back to the Future trilogy has made many people fascinated by the idea of ​​time travel. Since the film's release, no one has yet developed a DeLorean that can travel back and forth in time, decades or centuries. But scientists believe that time travel may be at least theoretically possible.

And if it is possible, we could find ourselves in the same position as Back to the Future protagonist Marty McFly - at the risk of unintentionally changing something in the past, thereby changing the future and the course of history. McFly accidentally prevented his parents from meeting and falling in love, thereby successfully removing himself from family photographs.

However, a 2015 paper suggested that the existence of a multiverse does not make such troubles necessary. “The existence of alternative worlds means that there is no single chronology that can be disrupted,” wrote Georg Dworsky. On the contrary, if a person goes back in time and changes something, he will simply create a new set of parallel universes.

We could be a simulation for an advanced civilization

All these topics about parallel universes that we have discussed so far have been extremely interesting. But there is something else interesting.

In 2003, philosopher Nick Bostrom, director of the Future of Humanity Institute at the University of Oxford, wondered whether everything we perceive as reality - particularly our separate parallel universe - could simply be a digital simulation of another universe. According to Bostrom, it would take 10 36 calculations to create a detailed model of all human history.

A well-developed alien civilization - creatures whose technological level would make us look like Paleolithic cave dwellers - could well have enough computing power to do all this. Moreover, modeling each individual living person will not require any absolutely dizzying electronic resources, so there can be much more computer-simulated creatures than real ones.

All this could mean that we live in a digital world, like something out of The Matrix.

But what will happen if this advanced civilization is itself a simulation?

People have thought about multiple universes since time immemorial.

It will be extremely difficult to prove this. But here one cannot help but recall the old sayings attributed either to Picasso or to Susan Sontag: if you can imagine something, it must exist.

And there is something in this. After all, long before Hugh Everett was sipping his cognac, countless people throughout human history have imagined different versions of the multiverse.

Ancient Indian religious texts, for example, are filled with descriptions of multiple parallel universes. And the ancient Greeks had a philosophy of atomism, which stated that there are an infinite number of worlds scattered in the same infinite void.

The idea of ​​multiple worlds was also raised in the Middle Ages. The Bishop of Paris argued in 1277 that the Greek philosopher Aristotle was wrong when he said there was only one possible world because it called into question the omnipotent power of God to create parallel worlds. The same idea was resurrected in the 1600s by Gottfried Wilhelm Leibniz, one of the pillars of the scientific revolution. He argued that there are many possible worlds, each with distinct physics.

All this fits into our scheme of knowledge about the Universe

As strange as the concept of the multiverse may seem, in some ways it fits into the progress of modern history and the way people see themselves and the universe.

In 2011, physicists Alexander Vilenkin and Max Tegmark noted that people in Western civilization were gradually calming down as they discovered the nature of reality. They started with a mindset that the Earth was the center of everything. It turned out that this is not so, and that ours is only a tiny part of the Milky Way.

The multiverse must take this idea to its logical conclusion. If the multiverse exists, it means that we are not the chosen ones and that there are infinite versions of ourselves.

But some believe that we are only at the very beginning of the path to expanding consciousness. As Stanford University theoretical physicist Leonard Susskind wrote, perhaps a couple of centuries from now philosophers and scientists will look back on our time as “a golden age in which the narrow, provincial conception of the universe of the 20th century gave way to a bigger and better multiverse of staggering proportions.”

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The universe we live in may not be the only one. Essentially, our Universe can only be one of an infinite number of universes that form a “multiverse.”
Some experts believe that the existence of hidden universes is more likely than not.

Here are five of the most plausible scientific theories that suggest we live in a multiverse.

1. Infinite Universes

Scientists are not yet sure what shape spacetime has, but most likely it is flat (as opposed to spherical or even donut-shaped) and stretches indefinitely. But if spacetime is infinite, then it must start repeating itself at some point, because there are a finite number of ways particles can be arranged in space and time.

So if you could look far enough, you would see another version of yourself - an infinite number of versions, in fact. Some of these twins will be doing exactly what you are doing right now, while others will be wearing a different sweater this morning, and the third and fourth will have completely different careers and lifestyles.

Since it extends only as far as light has a chance to reach 13.7 billion years after the big bang (13.7 billion light years), spacetime beyond this distance can be considered its own, separate universe. Thus, many universes exist next to each other in a giant mosaic of universes.

Space-time can stretch to infinity. If this is true, then everything in our Universe is bound to repeat itself at some point, creating a patchwork of infinite universes.

2. Sub-universes

The theory of quantum mechanics, which rules the tiny world of subatomic particles, offers another way for multiple universes to arise. Quantum mechanics describes the world in terms of probability, without concrete results. And the mathematics of this theory suggests that all possible outcomes of a situation occur in their own separate universes. For example, if you reach a crossroads where you can go right or left, the universe gives birth to two daughter universes: one in which you go right, one in which you go left.

“And in every Universe, there is a copy of you, as a witness to one or another result. Thinking that your reality is the only reality is wrong.”

—Written by Brian Randolph Green in Hidden Reality.

3. Bubble Universe

In addition to the multiple universes created by an infinitely expanding space-time, other universes may arise due to the so-called “eternal inflation” theory. The concept of inflation is that the universe expands rapidly after the Big Bang, like an inflating balloon. Eternal inflation, first proposed by Tufts University cosmologist Alexander Vilenkin, suggests that parts of space stop inflating while other regions continue to inflate, thereby giving rise to many isolated “bubble universes.”

Thus our own universe, where inflation has ended, allowing stars and galaxies to form, is just a small bubble in a vast sea of ​​space, some of which is still inflating, and which contains many other bubbles, like our Universe. And in some of these bubble universes, the laws of physics and fundamental constants might be different from ours, making some universes truly strange places.

4. Mathematical Universes

Scientists debate whether mathematics is simply a useful tool for , or whether mathematics itself is a fundamental reality and our observations of the universe are simply an imperfect perception of its true mathematical nature. If the latter case is the case, then perhaps the particular mathematical structure that makes up our universe is not the only choice, and in fact all possible mathematical structures exist as their own separate universes.

“A mathematical structure is something that can be described in such a way that it depends entirely on human baggage,” said Max Tegmark of the Massachusetts Institute of Technology, who proposed the seemingly crazy idea.

“I truly believe that this existing universe can exist independently of me, and will continue to exist even if there were no people.”

5. Parallel Universes

Another idea that emerges from string theory is the concept of "braneworlds" - parallel universes that float beyond the reach of our own, proposed by Paul Steinhardt of Princeton University and Neil Turok of the Perimeter Institute for Theoretical Physics in Ontario, Canada. The idea comes from the possibility of many other dimensions in our world than the three-dimensional space and one time we know. In addition to our 3D brane space, other 3D branes can float in higher dimensional space.

Three decades ago, the so-called inflation theory began to spread in the scientific world. At the center of this concept is the idea of ​​a special form of matter, called “false vacuum”. It has very high energy characteristics and high negative pressure. The most amazing property of a false vacuum is repulsive gravity. A space filled with such a vacuum can quickly expand in different directions.

Spontaneously arising vacuum “bubbles” spread at the speed of light, but practically do not collide with each other, because the space between such formations expands at the same speed. It is assumed that humanity lives in one of many such “bubbles”, which are perceived as an expanding Universe.

From an ordinary point of view, multiple “bubbles” of a false vacuum are a series of other, completely self-sufficient bubbles. The catch is that there are no direct material connections between these hypothetical formations. Therefore, unfortunately, it will not be possible to move from one universe to another.

Scientists conclude that the number of universes that look like “bubbles” can be infinite, and each of them expands without any restrictions. In universes that never intersect with the one where the solar system is located, an infinite number of options for the development of events are formed. Who knows, maybe in one of these “bubbles” the history of the Earth is exactly repeated?

Parallel universes: hypotheses require confirmation

It is possible, however, that other universes, which can conventionally be called parallel, are based on completely different physical principles. Even the set of fundamental constants in “bubbles” may differ significantly from those provided in the native Universe of humanity.

It is quite possible that life, if it is a natural result of the development of any matter, in a parallel universe can be built on principles that are incredible for earthlings. What then could be the Mind in neighboring universes? Only science fiction writers can judge this for now.

It is not possible to directly test the hypothesis about the existence of another universe or even many such worlds. Researchers are working to collect “circumstantial evidence,” looking for workarounds to confirm scientific assumptions. So far, scientists have only more or less convincing guesses based on the results of studying cosmic microwave background radiation, which sheds light on the history of the origin of the Universe.

Parallel universes - theory or reality? Many physicists have been struggling to resolve this issue for many years.

Do parallel universes exist?

Is our Universe one of many? The idea of ​​parallel universes, once relegated solely to science fiction, is now becoming increasingly respected among scientists - at least among physicists, who usually take any idea to the very limits of what can be contemplated. In reality, there are a huge number of potential parallel universes. Physicists have proposed several possible forms of the "multiverse", each of which is possible according to one or another aspect of the laws of physics. The problem that follows directly from the definition itself is that people will never be able to visit these universes to verify that they exist. So the question is, how can we use other methods to test the existence of parallel universes that cannot be seen or touched?

The birth of an idea

It is assumed that at least some of these universes are inhabited by human counterparts who live similar or even identical lives to people from our world. Such an idea touches your ego and awakens your fantasies - which is why multiverses, no matter how distant and unprovable they may be, have always received such widespread popularity. You might see ideas about multiverses most clearly in books like The Man in the High Castle by Philip K. Dick and movies like Beware the Closing Doors. In fact, there is nothing new about the idea of ​​multiverses, as religious philosopher Mary-Jane Rubenstein clearly demonstrates in her book Worlds Without End. In the mid-sixteenth century, Copernicus argued that the Earth was not the center of the Universe. Decades later, Galileo's telescope showed stars beyond his reach, giving humanity its first glimpse of the vastness of space. Thus, at the end of the sixteenth century, the Italian philosopher Giordano Bruno reasoned that the Universe could be infinite and contain an infinite number of inhabited worlds.

Universe-matryoshka

The idea that the universe contained many solar systems became quite common in the eighteenth century. In the early twentieth century, Irish physicist Edmund Fournier D'Alba even proposed that there might be an infinite regression of "nested" universes of different sizes, both larger and smaller. From this point of view, a single atom can be considered as a real inhabited solar system. Modern scientists deny the assumption of the existence of a nesting doll multiverse, but instead they have proposed several other options in which multiverses can exist. Here are the most popular among them.

Patchwork Universe

The simplest of these theories stems from the idea that the Universe is infinite. It is impossible to know for sure whether it is infinite, but it is also impossible to deny it. If it is still infinite, then it should be divided into “flaps” - regions that are not visible to each other. Why? The fact is that these regions are so far from each other that light cannot travel such a distance. The Universe is only 13.8 billion years old, so any regions that are 13.8 billion light years apart are completely cut off from each other. According to all data, these regions can be considered separate universes. But they don't stay in this state forever - eventually the light crosses the boundary between them and they expand. And if the Universe actually consists of an infinite number of “island universes” containing matter, stars and planets, then there must be worlds identical to Earth somewhere.

Inflationary multiverse

The second theory grows out of ideas about how the universe began. According to the dominant version of the Big Bang, it began as an infinitesimal point that expanded incredibly quickly in a hot ball of fire. A fraction of a second after the expansion began, the acceleration had already reached such an enormous speed that it far exceeded the speed of light. And this process is called “inflation”. Inflationary theory explains why the Universe is relatively homogeneous at any given point. Inflation expanded this fireball to cosmic proportions. However, the original state also had a large number of different random variations, which were also subject to inflation. And now they are preserved as cosmic microwave background radiation, the faint afterglow of the Big Bang. And this radiation permeates the entire Universe, making it less uniform.

Cosmic natural selection

This theory was formulated by Lee Smolin from Canada. In 1992, he proposed that universes could evolve and reproduce just like living things. On Earth, natural selection favors the emergence of "useful" traits, such as faster running speed or special placement of the thumbs. In a multiverse there must also be certain pressures that make some universes better than others. Smolin called this theory “cosmic natural selection.” Smolin's idea is that the "mother" universe can give life to "daughter" ones that form within it. The mother universe can only do this if it has black holes. A black hole is formed when a large star collapses under its own gravitational force, pushing all the atoms together until they reach infinite density.

Brane multiverse

When Albert Einstein's theory of general relativity began to gain popularity in the twenties, many people discussed the "fourth dimension." What could be there? Perhaps a hidden universe? This was nonsense; Einstein did not envision the existence of a new universe. All he said was that time is the same dimension, which is similar to the three dimensions of space. All four are intertwined with each other, forming a space-time continuum, the matter of which is distorted - and gravity is obtained. Despite this, other scientists began to discuss the possibility of other dimensions in space. Hints of hidden dimensions first appeared in the work of theoretical physicist Theodore Kaluza. In 1921, he demonstrated that by adding new dimensions to Einstein's equation of general relativity, an additional equation could be obtained that could be used to predict the existence of light.

Many-Worlds Interpretation (Quantum Multiverse)

The theory of quantum mechanics is one of the most successful in all of science. It discusses the behavior of very small objects such as atoms and their constituent elementary particles. It can predict phenomena ranging from the shape of molecules to how light and matter interact - all with incredible accuracy. Quantum mechanics considers particles in the form of waves and describes them with a mathematical expression called the wave function. Perhaps the strangest feature of the wave function is that it allows a particle to exist in multiple states simultaneously. This is called superposition. But superpositions break down as soon as an object is measured in any way, since measurements force the object to choose a specific position. In 1957, American physicist Hugh Everett suggested that we stop complaining about the strange nature of this approach and just live with it. He also assumed that objects did not switch to a specific position when they were measured - instead, he believed that all possible positions embedded in the wave function were equally real. Therefore, when an object is measured, a person sees only one of many realities, but all other realities also exist.