• Translation

What do you think about the multiverse? The question wasn't entirely out of the blue for our impromptu lecture at the dinner table, but it took me by surprise. It's not that I've never been asked about the multiverse before, but explaining a theoretical construct is one thing, but explaining how you feel about it is quite another. I can voice all the standard arguments and main questions about the multiverse, I can navigate the facts and technical details, but I get lost in the results.

Physicists are not used to talking about how they feel about something. We are for solid knowledge, quantitative assessments and experiments. But even the best of impartial analyzes only begin after we have decided which way to go. In a nascent field, there is usually a choice of possibilities, each of which has its own merits, and often we choose one of them instinctively. This choice is determined by emotional reasoning, standing above logic. The position you associate yourself with is, as Stanford University physicist Leonard Susskind says, “more than just scientific facts and philosophical principles. This is a matter of good taste in science. And, like all disputes about tastes, it involves aesthetic feelings.

I myself do string theory, and one of its features is the possibility of the existence of many logically consistent versions of universes different from ours. The process that created our universe can create both, leading to an infinite number of universes where everything that can happen happens. The sequence of reasoning begins in a familiar place, and I can follow the whorls that the equations dance on the page to this conclusion, but although I imagine the multiverse as a mathematical construct, I can't believe it would suddenly pop out of realm of theories and manifest itself in reality. How can I pretend I don't have a problem with endless copies of myself roaming parallel worlds making decisions both similar and different from mine?

I am not the only one who is ambivalent. Debate over the multiverse has been heated, and it remains a source of controversy among the most prominent scientists of our time. The multiverse debate is not just a discussion of the particulars of a theory. It's a fight over identity and outcomes, over what an explanation is based on, what evidence is made of, how we define science, and whether it all makes sense.

Whenever I talk about the multiverse, I have an answer to one of the inevitable questions. Whether we live in a universe or a multiverse, these classifications refer to scales beyond the imagination. Regardless of the outcome, life around us will not change. So what's the difference?

There is a difference because where we are affects who we are. Different places lead to different reactions, from which different possibilities arise. One object may look different on different backgrounds. We are defined by the space we inhabit in more ways than we realize. The universe is the limit of expansion. It contains all the places of action, all the contexts in which we can represent being. It represents the sum total of possibilities, the totality of all that we can be.

Measurement makes sense only in a reference system. Numbers are obviously abstract until they are assigned units, but even such vague definitions as "too far", "too small", "too strange" imply some kind of coordinate system. Too far implies a reference point. Too small refers to the scale. Too weird implies context. Unlike the always-declared units of measurement, the frame of reference for assumptions is rarely defined, yet the values ​​assigned to things—objects, phenomena, experiences—are calibrated along these invisible axes.

If we find that everything we know and can learn is in just one of the pockets of the multiverse, the whole foundation on which we have placed our grid will shift. The observations won't change, but the conclusions will. The existence of other bubble universes is possible and will not affect the measurements we make, but it may affect how we interpret them.

The first thing that strikes you about the multiverse is its immensity. She is more than anything that humanity has dealt with - such exaltation is implied in the name itself. It would be understandable if the emotional reaction to the multiverse came from a sense of self-understatement. But the size of the multiverse is perhaps the least controversial of its properties.

Gian Judis, head of CERN theorists, speaks for physicists when he claims that just looking at the sky clears our brains. We already imagine our scope. If the multiverse exists, then, as he says, "the problem of pitting me against the immensity of the universe will not change." Many are even reassured by such a cosmic perspective. Compared to the universe, all of our problems and life's dramas are reduced so much that "whatever happens here doesn't matter," says physicist and author Lawrence Krauss. "It's very comforting to me."

From stunning photographs taken by the telescope. Hubble, before Octavio Paz's "vast night" poems and Monty Python's "galactic song", there is a romanticism associated with our Lilliputian scale. At some point in our history, we have come to terms with our infinite smallness.

Is it because of our fear of scale that we are so reluctant to accept the concept of a multiverse, including worlds that are outside our field of vision and are destined to be there? This is, of course, a very common complaint I hear from my colleagues. The South African physicist George Ellis, who strongly objects to the multiverse, and the British cosmologist Bernard Carr, who is equally strongly pro-multiverse, discussed these issues in several charming conversations. Carr believes that their point of divergence relates to "what properties of science must be considered inviolable." Experiments are a common indicator. Comparative observations are a valid substitute. Astronomers are not able to control galaxies, but survey them by the millions, in various forms and states. Neither method fits the multiverse. Does it lie, then, outside the scientific field?

Susskind, one of the fathers of string theory, gives us hope. In empirical science, there is a third approach: to draw conclusions about invisible objects and phenomena from what we are able to see. For example, it will suffice to take subatomic particles. Quarks are forever bound into protons, neutrons, and other compound particles. “They are, so to speak, hidden behind a veil,” says Susskind, “but now, although we have not seen a single isolated quark, no one will seriously question the correctness of the theory of quarks. It's part of the foundation of modern physics."

As the universe expands at an accelerating rate, the galaxies currently on the horizon of the field of view will soon disappear behind it. We do not believe that they will go into oblivion, just as we do not believe that the ship will be disintegrated, hiding behind the horizon. If the galaxies known to us can exist in remote regions beyond the field of view, who's to say that something else can't be there? Things we have never seen and never will see? As soon as we acknowledge the possibility of the existence of regions that are outside our horizon, the consequences grow exponentially. British Astronomer Royal Martin Rees likens this line of reasoning to disgust therapy. When you acknowledge the presence of galaxies beyond our current horizon, you "start with a small spider very far away", but before you know it, you will unleash the possibility of a multiverse inhabited by infinite worlds, perhaps very different from yours - that is, "find a tarantula crawling over you."

The inability to directly control objects has never been my personal criterion for determining the suitability of a physical theory. If there is anything that worries me about the multiverse, I'm sure it has nothing to do with it.

The multiverse is challenging another concept we hold dear: uniqueness. Could this be causing problems? As cosmologist Alexander Vilenkin explains, no matter how large the observed region is, as long as it is finite, it can be in a finite number of quantum states. And the description of these states uniquely determines the content of the region. If there are infinitely many of these regions, then the same state will necessarily be reproduced somewhere else. Even our words will be accurately reproduced. Since the process continues indefinitely, there will also be an infinite number of our copies.

“Having these copies makes me depressed,” says Vilenkin. – Our civilization has many negative features, but at least we could declare its uniqueness – as a work of art. And now we can't even say that." I understand what he means. This worries me too, but I'm not sure that it is this thought that underlies my dissatisfaction. As Vilenkin says wistfully, "I'm not arrogant enough to tell reality what it should be."

The main riddle of the debate lies in the strange irony. Although the multiverse enlarges our concept of physical reality to an almost unimaginable size, it is claustrophobic in that it draws the line between our knowledge and our ability to acquire knowledge. Theorists dream of a world without self-will, described by self-sufficient equations. Our goal is to find a logically complete theory, severely limited by self-sufficiency, and taking only one form. Then for us, who do not even know where or why this theory came from, its structure will not look random. All the fundamental constants of nature will come "out of mathematics, the number pi and twos," says Berkeley physicist Raphael Busso.

This is the attraction of Einstein's General Theory of Relativity - the reason why physicists around the world exclaim for its unusual immortal beauty. Symmetry considerations dictate the equations so clearly that theory seems inevitable. This is what we wanted to repeat in other areas of physics. And so far we haven't succeeded.

For decades, scientists have been looking for physical reasons why the fundamental constants must take exactly the values ​​that they have, but so far no reason has been found. And in general, if we use the available theories to calculate the possible values ​​of some of the known parameters, the results are ridiculously far from the measured values. But how to explain these parameters? If there is only one single universe, then the parameters that govern it must be clothed with a special meaning. Either the process that governs the choice of parameters is random, or there is some kind of logic in it, or even a thoughtful purpose.

None of the options look attractive. We scientists spend our lives searching for laws because we believe that everything happens for a reason, even if it is unknown to us. We look for patterns because we believe in some order in the universe, even if we can't see it. Pure chance does not fit into this worldview.

But I also don’t want to talk about a reasonable plan, because this implies the existence of a certain force that preceded the laws of nature. This force must choose and judge what, in the absence of such a clear, balanced and severely limited structure as, for example, GR, implies arbitrariness. There is something frankly unsatisfactory about the idea that there may be several logically consistent universes, of which only one has been chosen. If that were the case, then, as cosmologist Dennis Sciama says, one would have to think that "there is someone who studies such a list and says, 'No, we will not have such a universe, and we will not have such a universe. There will only be this one'" .

Personally, this option, with all its implications about what could be, upsets me. Various scenes come to mind: abandoned children in an orphanage from some forgotten movie, when one of them is adopted; faces of people feverishly striving for a dream, but not achieving it; miscarriages in the first trimester. Such things that were almost born, but could not, torment me. Unless there is a theoretical constraint that excludes all but one of the possibilities, such a choice seems cruel and unfair.

In such a carefully crafted creation, how to explain unnecessary suffering? Because these philosophical, ethical, and moral issues do not belong to the realm of physics, most scientists avoid discussing them. But the Nobel laureate Steven Weinberg spoke on their behalf: “Are there traces of a generous creator in our life - everyone will answer this question for themselves. My life has been amazingly happy. But still, I saw how my mother died painfully from cancer, how Alzheimer's disease destroyed the personality of my father, and how many cousins ​​and second cousins ​​were killed in the Holocaust. Signs of the presence of a benevolent creator are very well hidden.

In the face of pain, it is much easier to accept randomness than the callous disregard or deliberate atrocity that is present in a meticulously designed universe.

The multiverse promised to distract us from these terrible thoughts, to give us a third option that would overcome the dilemma of explanation.

Of course, physicists did not invent the multiverse for this. She came from other considerations. The theory of cosmic inflation was supposed to explain the wide-ranging smoothness and lack of curvature of the universe. “We were looking for a simple explanation for why the universe is like a big ball,” says Stanford physicist Andrei Linde. “We didn’t know that something would go to this idea in the load.” The burden was realizing that our Big Bang was not unique, and that, in fact, there must be an infinite number of such explosions, each of which creates a space-time that is not connected to ours.

Then came string theory. So far, it is the best candidate for a unified theory of everything. Not only does she achieve the impossible—the reconciliation of gravity and quantum mechanics—but she simply insists on it. But for a scheme that reduces the incredible diversity of the universe to a minimal set of building blocks, string theory suffers from a humiliating problem: we don't know how to determine the exact values ​​of the fundamental constants. According to current estimates, there are potential opportunities - an immeasurably huge number, for which we do not even have a name. String theory enumerates all the forms that the laws of physics can take, and inflation provides an opportunity for their implementation. With the birth of each new universe, an imaginary deck of cards is shuffled. The hand dealt determines the laws that govern the universe.

The multiverse explains how the constants from the equations took on their inherent values ​​without involving randomness or reasonable choice. If there are many universes in which all possible laws of physics are implemented, we get exactly these values ​​when measuring, because our universe is located exactly in this place of the landscape. There is no deeper explanation. Everything. This is the answer.

But by freeing us from the old dichotomy, the multiverse leaves us in an uneasy state. The question we've been wrestling with for so long may not have a deeper answer than "that's how it works." Perhaps this is the best we can do, but we are not used to such answers. He doesn't strip the veils or explain how things work. Moreover, he shatters the theorists' dream by arguing that a unique solution cannot be found, since it does not exist.

Some people don't like this answer, others think it can't even be called an answer, and others just accept it.

It seems to Nobel laureate David Gross that the multiverse "smells like angels." He says that accepting the multiverse is like giving up, accepting that you will never understand anything, because everything observable can be reduced to "historical accident". Fellow Nobel Prize winner Gerard 't Hooft laments that he can't accept the scenario of "trying all the solutions until you find one that fits our world." He says, “Physicists have not worked this way in the past, and we can still hope that we will have better evidence in the future.”

Princeton cosmologist Paul Steinhardt calls the multiverse a "theory of anything" because it admits everything and explains nothing. “Scientific theory has to be selective,” he says. “Her strength lies in the sheer number of possibilities. If it includes all possibilities, then it does not exclude anything, and its power is zero. Steinhardt was one of the early proponents of inflation, until he realized that inflation leads to a multiverse, and creates a space of possibilities, instead of making specific predictions. He has since become one of the most vocal critics of inflation. In a recent episode of Star Talk, he introduced himself as a champion of multiverse alternatives. “What is it about the multiverse that annoys you so much? - the host joked. “She destroyed one of my favorite ideas,” Steinhardt replied.

Physicists had to deal with truth, absolute concepts, predictions. Either things are like this or they are not. Theories should not be flexible or inclusive, they should be restrictive, rigorous, excluding options. For any situation, you want to be able to predict the probable - and ideally, the only and inevitable - outcome. The multiverse does nothing for us.

The debate over the multiverse often turns into a noisy debate, where skeptics accuse the proponents of the idea of ​​betraying science. But it is important to realize that no one chose this state of affairs. Everyone wants a universe organically arising from beautiful deep principles. But from what we know, there is no such thing in our universe. She is who she is.

Is it necessary to argue against the idea of ​​a multiverse? Should she stay on the sidelines? Many of my colleagues are trying to present it in a more favorable light. Logically speaking, an infinite number of universes is easier to work with than just one—there are fewer things to explain. In the words of Scyama, the multiverse "satisfies Occam's razor in a way, because you want to minimize the number of random constraints you put on the universe." Weinberg says that a theory that is free from arbitrary assumptions and not subjected to "careful adjustments to fit observations" is beautiful in itself. It may turn out that this beauty is similar to the beauty of thermodynamics, with the statistical beauty that explains the state of a macroscopic system, but not each of its individual components. “When looking for beauty, you can't be sure where you'll find it, or what kind of beauty you'll find,” Weisenberg says.

Many times when I pondered these complex intellectual problems, my thoughts returned to the simple and beautiful wisdom of the Little Prince from the work of Antoine de Saint-Exupery, who, considering his favorite rose to be the only one of all the worlds, found himself in a rose garden. Bewildered by this betrayal and distressed by the loss of importance - his rose and himself - he weeps. In the end, he realizes that his rose is "more important than hundreds of others" because she is his.

There may be nothing special about our universe other than the fact that it is ours. Isn't that enough? Even if all our lives and everything that we can know turn out to be insignificant on the scale of the cosmos, they are still ours. There is something special about the here and now, that something is mine.

Several times in recent months I have replayed in my mind my conversation with Gian Giudis. I found confidence in how relaxed he was about the sheer number of possible universes and the seemingly random choices made by ours. Maybe the multiverse is just letting us know that we're working on the wrong things, he says. Perhaps, like Kepler with the orbits of the planets, we are trying to find a deeper meaning in the numbers than there is.

Since Kepler knew only about the existence of the solar system, he believed that some important information was hidden in the shape of the orbits of the planets and in the distances between them, but it turned out that this was not so. These values ​​were not fundamental, they were simply environmental data. At the time, this may have seemed regrettable, but from the point of view of general relativity, we no longer feel a sense of loss. We have a great explanation for gravity. It's just that in this explanation, the values ​​associated with the orbits of the planets are not fundamental constants.

Perhaps, Judis says, the multiverse implies something similar. Maybe we need to let go of what we're clinging to. Maybe we need to think broader, regroup, change the questions we ask nature. According to him, the multiverse can open "extremely satisfying, enjoyable and eye-expanding possibilities."

Of all the arguments for the multiverse, this is my favorite. In any scenario, in any physical system, there are infinitely many questions that can be asked. We try to unravel the problem down to its foundations and ask the most basic questions, but our intuition is built on what has gone before, and it is possible that we are based on paradigms no longer relevant to the new areas we are trying to explore.

The multiverse is more like a key than a closed door. From my point of view, the world is tinged with hope and filled with opportunity. He is no more wasteful than an arbor full of roses.

• Translation

What do you think about the multiverse? The question wasn't entirely out of the blue for our impromptu lecture at the dinner table, but it took me by surprise. It's not that I've never been asked about the multiverse before, but explaining a theoretical construct is one thing, but explaining how you feel about it is quite another. I can voice all the standard arguments and main questions about the multiverse, I can navigate the facts and technical details, but I get lost in the results.

Physicists are not used to talking about how they feel about something. We are for solid knowledge, quantitative assessments and experiments. But even the best of impartial analyzes only begin after we have decided which way to go. In a nascent field, there is usually a choice of possibilities, each of which has its own merits, and often we choose one of them instinctively. This choice is determined by emotional reasoning, standing above logic. The position you associate yourself with is, as Stanford University physicist Leonard Susskind says, “more than just scientific facts and philosophical principles. This is a matter of good taste in science. And, like all disputes about tastes, it involves aesthetic feelings.

I myself do string theory, and one of its features is the possibility of the existence of many logically consistent versions of universes different from ours. The process that created our universe can create both, leading to an infinite number of universes where everything that can happen happens. The sequence of reasoning begins in a familiar place, and I can follow the whorls that the equations dance on the page to this conclusion, but although I imagine the multiverse as a mathematical construct, I can't believe it would suddenly pop out of realm of theories and manifest itself in reality. How can I pretend I don't have a problem with endless copies of myself roaming parallel worlds making decisions both similar and different from mine?

I am not the only one who is ambivalent. Debate over the multiverse has been heated, and it remains a source of controversy among the most prominent scientists of our time. The multiverse debate is not just a discussion of the particulars of a theory. It's a fight over identity and outcomes, over what an explanation is based on, what evidence is made of, how we define science, and whether it all makes sense.

Whenever I talk about the multiverse, I have an answer to one of the inevitable questions. Whether we live in a universe or a multiverse, these classifications refer to scales beyond the imagination. Regardless of the outcome, life around us will not change. So what's the difference?

There is a difference because where we are affects who we are. Different places lead to different reactions, from which different possibilities arise. One object may look different on different backgrounds. We are defined by the space we inhabit in more ways than we realize. The universe is the limit of expansion. It contains all the places of action, all the contexts in which we can represent being. It represents the sum total of possibilities, the totality of all that we can be.

Measurement makes sense only in a reference system. Numbers are obviously abstract until they are assigned units, but even such vague definitions as "too far", "too small", "too strange" imply some kind of coordinate system. Too far implies a reference point. Too small refers to the scale. Too weird implies context. Unlike the always-declared units of measurement, the frame of reference for assumptions is rarely defined, yet the values ​​assigned to things—objects, phenomena, experiences—are calibrated along these invisible axes.

If we find that everything we know and can learn is in just one of the pockets of the multiverse, the whole foundation on which we have placed our grid will shift. The observations won't change, but the conclusions will. The existence of other bubble universes is possible and will not affect the measurements we make, but it may affect how we interpret them.

The first thing that strikes you about the multiverse is its immensity. She is more than anything that humanity has dealt with - such exaltation is implied in the name itself. It would be understandable if the emotional reaction to the multiverse came from a sense of self-understatement. But the size of the multiverse is perhaps the least controversial of its properties.

Gian Judis, head of CERN theorists, speaks for physicists when he claims that just looking at the sky clears our brains. We already imagine our scope. If the multiverse exists, then, as he says, "the problem of pitting me against the immensity of the universe will not change." Many are even reassured by such a cosmic perspective. Compared to the universe, all of our problems and life's dramas are reduced so much that "whatever happens here doesn't matter," says physicist and author Lawrence Krauss. "It's very comforting to me."

From stunning photographs taken by the telescope. Hubble, before Octavio Paz's "vast night" poems and Monty Python's "galactic song", there is a romanticism associated with our Lilliputian scale. At some point in our history, we have come to terms with our infinite smallness.

Is it because of our fear of scale that we are so reluctant to accept the concept of a multiverse, including worlds that are outside our field of vision and are destined to be there? This is, of course, a very common complaint I hear from my colleagues. The South African physicist George Ellis, who strongly objects to the multiverse, and the British cosmologist Bernard Carr, who is equally strongly pro-multiverse, discussed these issues in several charming conversations. Carr believes that their point of divergence relates to "what properties of science must be considered inviolable." Experiments are a common indicator. Comparative observations are a valid substitute. Astronomers are not able to control galaxies, but survey them by the millions, in various forms and states. Neither method fits the multiverse. Does it lie, then, outside the scientific field?

Susskind, one of the fathers of string theory, gives us hope. In empirical science, there is a third approach: to draw conclusions about invisible objects and phenomena from what we are able to see. For example, it will suffice to take subatomic particles. Quarks are forever bound into protons, neutrons, and other compound particles. “They are, so to speak, hidden behind a veil,” says Susskind, “but now, although we have not seen a single isolated quark, no one will seriously question the correctness of the theory of quarks. It's part of the foundation of modern physics."

As the universe expands at an accelerating rate, the galaxies currently on the horizon of the field of view will soon disappear behind it. We do not believe that they will go into oblivion, just as we do not believe that the ship will be disintegrated, hiding behind the horizon. If the galaxies known to us can exist in remote regions beyond the field of view, who's to say that something else can't be there? Things we have never seen and never will see? As soon as we acknowledge the possibility of the existence of regions that are outside our horizon, the consequences grow exponentially. British Astronomer Royal Martin Rees likens this line of reasoning to disgust therapy. When you acknowledge the presence of galaxies beyond our current horizon, you "start with a small spider very far away", but before you know it, you will unleash the possibility of a multiverse inhabited by infinite worlds, perhaps very different from yours - that is, "find a tarantula crawling over you."

The inability to directly control objects has never been my personal criterion for determining the suitability of a physical theory. If there is anything that worries me about the multiverse, I'm sure it has nothing to do with it.

The multiverse is challenging another concept we hold dear: uniqueness. Could this be causing problems? As cosmologist Alexander Vilenkin explains, no matter how large the observed region is, as long as it is finite, it can be in a finite number of quantum states. And the description of these states uniquely determines the content of the region. If there are infinitely many of these regions, then the same state will necessarily be reproduced somewhere else. Even our words will be accurately reproduced. Since the process continues indefinitely, there will also be an infinite number of our copies.

“Having these copies makes me depressed,” says Vilenkin. – Our civilization has many negative features, but at least we could declare its uniqueness – as a work of art. And now we can't even say that." I understand what he means. This worries me too, but I'm not sure that it is this thought that underlies my dissatisfaction. As Vilenkin says wistfully, "I'm not arrogant enough to tell reality what it should be."

The main riddle of the debate lies in the strange irony. Although the multiverse enlarges our concept of physical reality to an almost unimaginable size, it is claustrophobic in that it draws the line between our knowledge and our ability to acquire knowledge. Theorists dream of a world without self-will, described by self-sufficient equations. Our goal is to find a logically complete theory, severely limited by self-sufficiency, and taking only one form. Then for us, who do not even know where or why this theory came from, its structure will not look random. All the fundamental constants of nature will come "out of mathematics, the number pi and twos," says Berkeley physicist Raphael Busso.

This is the attraction of Einstein's General Theory of Relativity - the reason why physicists around the world exclaim for its unusual immortal beauty. Symmetry considerations dictate the equations so clearly that theory seems inevitable. This is what we wanted to repeat in other areas of physics. And so far we haven't succeeded.

For decades, scientists have been looking for physical reasons why the fundamental constants must take exactly the values ​​that they have, but so far no reason has been found. And in general, if we use the available theories to calculate the possible values ​​of some of the known parameters, the results are ridiculously far from the measured values. But how to explain these parameters? If there is only one single universe, then the parameters that govern it must be clothed with a special meaning. Either the process that governs the choice of parameters is random, or there is some kind of logic in it, or even a thoughtful purpose.

None of the options look attractive. We scientists spend our lives searching for laws because we believe that everything happens for a reason, even if it is unknown to us. We look for patterns because we believe in some order in the universe, even if we can't see it. Pure chance does not fit into this worldview.

But I also don’t want to talk about a reasonable plan, because this implies the existence of a certain force that preceded the laws of nature. This force must choose and judge what, in the absence of such a clear, balanced and severely limited structure as, for example, GR, implies arbitrariness. There is something frankly unsatisfactory about the idea that there may be several logically consistent universes, of which only one has been chosen. If that were the case, then, as cosmologist Dennis Sciama says, one would have to think that "there is someone who studies such a list and says, 'No, we will not have such a universe, and we will not have such a universe. There will only be this one'" .

Personally, this option, with all its implications about what could be, upsets me. Various scenes come to mind: abandoned children in an orphanage from some forgotten movie, when one of them is adopted; faces of people feverishly striving for a dream, but not achieving it; miscarriages in the first trimester. Such things that were almost born, but could not, torment me. Unless there is a theoretical constraint that excludes all but one of the possibilities, such a choice seems cruel and unfair.

In such a carefully crafted creation, how to explain unnecessary suffering? Because these philosophical, ethical, and moral issues do not belong to the realm of physics, most scientists avoid discussing them. But the Nobel laureate Steven Weinberg spoke on their behalf: “Are there traces of a generous creator in our life - everyone will answer this question for themselves. My life has been amazingly happy. But still, I saw how my mother died painfully from cancer, how Alzheimer's disease destroyed the personality of my father, and how many cousins ​​and second cousins ​​were killed in the Holocaust. Signs of the presence of a benevolent creator are very well hidden.

In the face of pain, it is much easier to accept randomness than the callous disregard or deliberate atrocity that is present in a meticulously designed universe.

The multiverse promised to distract us from these terrible thoughts, to give us a third option that would overcome the dilemma of explanation.

Of course, physicists did not invent the multiverse for this. She came from other considerations. The theory of cosmic inflation was supposed to explain the wide-ranging smoothness and lack of curvature of the universe. “We were looking for a simple explanation for why the universe is like a big ball,” says Stanford physicist Andrei Linde. “We didn’t know that something would go to this idea in the load.” The burden was realizing that our Big Bang was not unique, and that, in fact, there must be an infinite number of such explosions, each of which creates a space-time that is not connected to ours.

Then came string theory. So far, it is the best candidate for a unified theory of everything. Not only does she achieve the impossible—the reconciliation of gravity and quantum mechanics—but she simply insists on it. But for a scheme that reduces the incredible diversity of the universe to a minimal set of building blocks, string theory suffers from a humiliating problem: we don't know how to determine the exact values ​​of the fundamental constants. According to current estimates, there are potential opportunities - an immeasurably huge number, for which we do not even have a name. String theory enumerates all the forms that the laws of physics can take, and inflation provides an opportunity for their implementation. With the birth of each new universe, an imaginary deck of cards is shuffled. The hand dealt determines the laws that govern the universe.

The multiverse explains how the constants from the equations took on their inherent values ​​without involving randomness or reasonable choice. If there are many universes in which all possible laws of physics are implemented, we get exactly these values ​​when measuring, because our universe is located exactly in this place of the landscape. There is no deeper explanation. Everything. This is the answer.

But by freeing us from the old dichotomy, the multiverse leaves us in an uneasy state. The question we've been wrestling with for so long may not have a deeper answer than "that's how it works." Perhaps this is the best we can do, but we are not used to such answers. He doesn't strip the veils or explain how things work. Moreover, he shatters the theorists' dream by arguing that a unique solution cannot be found, since it does not exist.

Some people don't like this answer, others think it can't even be called an answer, and others just accept it.

It seems to Nobel laureate David Gross that the multiverse "smells like angels." He says that accepting the multiverse is like giving up, accepting that you will never understand anything, because everything observable can be reduced to "historical accident". Fellow Nobel Prize winner Gerard 't Hooft laments that he can't accept the scenario of "trying all the solutions until you find one that fits our world." He says, “Physicists have not worked this way in the past, and we can still hope that we will have better evidence in the future.”

Princeton cosmologist Paul Steinhardt calls the multiverse a "theory of anything" because it admits everything and explains nothing. “Scientific theory has to be selective,” he says. “Her strength lies in the sheer number of possibilities. If it includes all possibilities, then it does not exclude anything, and its power is zero. Steinhardt was one of the early proponents of inflation, until he realized that inflation leads to a multiverse, and creates a space of possibilities, instead of making specific predictions. He has since become one of the most vocal critics of inflation. In a recent episode of Star Talk, he introduced himself as a champion of multiverse alternatives. “What is it about the multiverse that annoys you so much? - the host joked. “She destroyed one of my favorite ideas,” Steinhardt replied.

Physicists had to deal with truth, absolute concepts, predictions. Either things are like this or they are not. Theories should not be flexible or inclusive, they should be restrictive, rigorous, excluding options. For any situation, you want to be able to predict the probable - and ideally, the only and inevitable - outcome. The multiverse does nothing for us.

The debate over the multiverse often turns into a noisy debate, where skeptics accuse the proponents of the idea of ​​betraying science. But it is important to realize that no one chose this state of affairs. Everyone wants a universe organically arising from beautiful deep principles. But from what we know, there is no such thing in our universe. She is who she is.

Is it necessary to argue against the idea of ​​a multiverse? Should she stay on the sidelines? Many of my colleagues are trying to present it in a more favorable light. Logically speaking, an infinite number of universes is easier to work with than just one—there are fewer things to explain. In the words of Scyama, the multiverse "satisfies Occam's razor in a way, because you want to minimize the number of random constraints you put on the universe." Weinberg says that a theory that is free from arbitrary assumptions and not subjected to "careful adjustments to fit observations" is beautiful in itself. It may turn out that this beauty is similar to the beauty of thermodynamics, with the statistical beauty that explains the state of a macroscopic system, but not each of its individual components. “When looking for beauty, you can't be sure where you'll find it, or what kind of beauty you'll find,” Weisenberg says.

Many times when I pondered these complex intellectual problems, my thoughts returned to the simple and beautiful wisdom of the Little Prince from the work of Antoine de Saint-Exupery, who, considering his favorite rose to be the only one of all the worlds, found himself in a rose garden. Bewildered by this betrayal and distressed by the loss of importance - his rose and himself - he weeps. In the end, he realizes that his rose is "more important than hundreds of others" because she is his.

There may be nothing special about our universe other than the fact that it is ours. Isn't that enough? Even if all our lives and everything that we can know turn out to be insignificant on the scale of the cosmos, they are still ours. There is something special about the here and now, that something is mine.

Several times in recent months I have replayed in my mind my conversation with Gian Giudis. I found confidence in how relaxed he was about the sheer number of possible universes and the seemingly random choices made by ours. Maybe the multiverse is just letting us know that we're working on the wrong things, he says. Perhaps, like Kepler with the orbits of the planets, we are trying to find a deeper meaning in the numbers than there is.

Since Kepler knew only about the existence of the solar system, he believed that some important information was hidden in the shape of the orbits of the planets and in the distances between them, but it turned out that this was not so. These values ​​were not fundamental, they were simply environmental data. At the time, this may have seemed regrettable, but from the point of view of general relativity, we no longer feel a sense of loss. We have a great explanation for gravity. It's just that in this explanation, the values ​​associated with the orbits of the planets are not fundamental constants.

Perhaps, Judis says, the multiverse implies something similar. Maybe we need to let go of what we're clinging to. Maybe we need to think broader, regroup, change the questions we ask nature. According to him, the multiverse can open "extremely satisfying, enjoyable and eye-expanding possibilities."

Of all the arguments for the multiverse, this is my favorite. In any scenario, in any physical system, there are infinitely many questions that can be asked. We try to unravel the problem down to its foundations and ask the most basic questions, but our intuition is built on what has gone before, and it is possible that we are based on paradigms no longer relevant to the new areas we are trying to explore.

The multiverse is more like a key than a closed door. From my point of view, the world is tinged with hope and filled with opportunity. He is no more wasteful than an arbor full of roses.

There is a theory according to which there are many universes where we live a completely different life: each of our actions is associated with a certain choice and, making this choice in our Universe, in a parallel one, the “other me” makes the opposite decision. How justified is such a theory from a scientific point of view? Why did scientists resort to it? Let's try to understand our article.

Multi-world concept of the universe
For the first time, the theory of a probable set of worlds was mentioned by the American physicist Hugh Everett. He offered his solution to one of the main quantum mysteries of physics. Before proceeding directly to the theory of Hugh Everett, it is necessary to understand what this mystery of quantum particles is, which has been haunting physicists around the world for more than a dozen years.

Imagine an ordinary electron. It turns out that as a quantum object, it can be in two places at the same time. This property is called the superposition of two states. But the magic doesn't end there. As soon as we want to somehow specify the location of the electron, for example, we try to knock it down with another electron, then from quantum it will become ordinary. How is this possible: the electron was both at point A and at point B, and suddenly jumped to B at a certain moment?

Hugh Everett offered his interpretation of this quantum riddle. According to his many-world theory, the electron continues to exist in two states at the same time. It's all about the observer himself: now he turns into a quantum object and is divided into two states. In one of them, he sees an electron at point A, in the other - at B. There are two parallel realities, and it is not known which of them the observer will find himself in. The division into reality is not limited to two: their branching depends only on the variation of events. However, all these realities exist independently of each other. We, as observers, fall into one, it is impossible to get out of which, as well as move to a parallel one.

From the point of view of this concept, the experiment with the most scientific cat in the history of physics, Schrödinger's cat, is also easily explained. According to the many-worlds interpretation of quantum mechanics, the unfortunate cat in the steel chamber is both alive and dead at the same time. When we open this chamber, we seem to merge with the cat and form two states - alive and dead, which do not intersect. Two different universes are formed: in one, an observer with a dead cat, in the other, with a live one.
It should be noted right away that the multi-world concept does not imply the existence of many universes: it is one, just multi-layered, and each object in it can be in different states. Such a concept cannot be considered an experimentally confirmed theory. So far, this is just a mathematical description of the quantum puzzle.

Hugh Everett's theory is supported by Howard Wiseman, a physicist at Griffith University in Australia, Dr. Michael Hall of the Griffith University Center for Quantum Dynamics, and Dr. Dirk-Andre Deckert of the University of California. In their opinion, there really are parallel worlds and are endowed with different characteristics. Any quantum riddles and patterns are a consequence of the “repulsion” of neighboring worlds from each other. These quantum phenomena arise so that each world is not like the other.

As with the many-worlds concept, string theory is difficult to prove experimentally. In addition, the mathematical apparatus of the theory is so difficult that for each new idea, a mathematical explanation must be sought literally from scratch.

Hypothesis of the mathematical universe
Cosmologist, professor at the Massachusetts Institute of Technology Max Tegmark in 1998 put forward his "theory of everything" and called it the hypothesis of the mathematical universe. He solved the problem of the existence of a large number of physical laws in his own way. In his opinion, each set of these laws, which are consistent from the point of view of mathematics, corresponds to an independent universe. The universality of the theory is that it can be used to explain the whole variety of physical laws and the values ​​of physical constants.

Tegmark proposed to divide all the worlds according to his concept into four groups. The first includes worlds that are outside our cosmic horizon, the so-called extra-metagalactic objects. The second group includes worlds with other physical constants, different from the constants of our Universe. In the third - the worlds that appear as a result of the interpretation of the laws of quantum mechanics. The fourth group is a certain set of all universes in which certain mathematical structures are manifested.

As the researcher notes, our Universe is not the only one, since space is limitless. Our world, where we live, is limited by space, the light from which reached us 13.8 billion years after the Big Bang. We will be able to know for sure about other universes in at least another billion years, until the light from them reaches us.

Stephen Hawking: Black holes are the way to another universe
Stephen Hawking is also a proponent of the multiple universe theory. One of the most famous scientists of our time in 1988 for the first time presented his essay "Black Holes and Young Universes". The researcher suggests that black holes are the road to alternative worlds.
Thanks to Stephen Hawking, we know that black holes tend to lose energy and evaporate, releasing Hawking radiation, which received the name of the researcher. Before the great scientist made this discovery, the scientific community believed that everything that somehow fell into a black hole disappeared. Hawking's theory refutes this assumption. According to the physicist, hypothetically, any thing, object, object that falls into a black hole flies out of it and enters another universe. However, such a journey is a one-way movement: there is no way to return back.

From all this it follows that the passage through a black hole is unlikely to be a popular and reliable way of space travel. First, you will have to get there by moving in imaginary time and not caring that your real-time story ends sadly. Second, you wouldn't actually be able to choose a destination. It's like flying on some airline that's in your head,
– writes the researcher.

Parallel universes and Occam's razor
As we can see, it is still impossible to prove the theory of multiple universes with complete certainty. Opponents of the theory believe that we have no right to talk about an infinite set of universes, if only because we cannot explain the postulates of quantum mechanics. This approach runs counter to the philosophical principle of William of Ockham: "One should not multiply things unnecessarily." Proponents of the same theory say: it is much easier to assume the existence of many universes than the existence of one ideal.

Whose argumentation (supporters or opponents of the theory of the multiverse) is more convincing - you decide. Who knows, maybe it is you who will be able to guess the quantum riddle of physics and propose a new universal “theory of everything”.

And if you are concerned about the structure of our Universe and are attracted by the secrets of physics, we advise you to read our article about the computer simulation hypothesis.

The science

The universe we live in is not the only one of its kind. In fact, it is just one unit of an infinite number of universes, the totality of which is called Multiverse.

The claim that we exist in the Multiverse may seem like a fabrication, but behind it are real scientific explanations. A huge number of physical theories, independently of each other, indicate that the Multiverse really exists.

We invite you to familiarize yourself with the most famous scientific theories confirming the fact that our Universe is just a particle of the Multiverse.

1) Infinity of universes

Scientists aren't exactly sure what shape spacetime has yet, but it's likely this physical model has a flat shape(as opposed to a spherical or donut shape) and extends indefinitely. If spacetime is infinite, it must repeat itself at some point. This is due to the fact that particles can line up in space and time in certain ways, and the number of these ways is limited.

So if you look far enough you will be able to stumble upon another version of yourself Or rather, an infinite number of options. Some of these twins will do what you do, while others will wear different clothes, have different jobs, make different choices in life.

The size of our universe is hard to imagine. Particles of light cover the distance from its center to the edge in 13.7 billion years. That's how many years ago the Big Bang took place. Space-time beyond this distance can be considered as a separate universe. Thus, numerous universes exist side by side, representing an infinitely gigantic patchwork quilt.

2) Bubble Giant Universe

In the scientific world, there are other theories of the development of universes, including a theory called Chaotic inflation theory . According to this theory, the universe began to expand rapidly after the Big Bang. This process was reminiscent balloon inflation which is filled with gas.

The chaotic theory of inflation was first proposed by cosmologist Alexander Videnkin. This theory suggests that some parts of space stop while others continue to expand, thus allowing the formation of an isolated "bubble universe".

Our own universe is just a small bubble in the vast expanse of space, in which there are an infinite number of such bubbles. In some of these bubble universes the laws of physics and fundamental constants may differ from ours. These laws might seem to us more than strange.

3) Parallel universes

Another theory that stems from string theory is that there is a notion of parallel universes. The idea of ​​the existence of parallel worlds is connected with the possibility that there are many more dimensions than we can imagine. According to our ideas, today there are 3 spatial dimensions and 1 temporal.

Physicist Brian Green from Columbia University describes it like this: "Our universe is one 'block' of a huge number of 'blocks' floating in space with many dimensions."

Also according to this theory, the universes are not always parallel and are not always out of our reach. Sometimes they can nestle into each other, causing repeated Big Bangs that bring the universes back to their original position again and again.

4) Child universes - another theory of the formation of universes

The theory of quantum mechanics, which is based on the concepts of the tiny world of subatomic particles, suggests another way to form multiple universes. Quart mechanics describes the world in terms of probabilities, while avoiding drawing final conclusions.

Mathematical models, according to this theory, can assume all possible outcomes of a situation. For example, at an intersection where you can turn right or left, the real universe forms two child universes, in one of which you can go to the right, and in the other - to the left.

5) Mathematical universes - the hypothesis of the origin of the universe

Scientists have long debated whether mathematics is a useful tool for describing the universe, or whether it is itself a fundamental reality and our observations are but imperfect representations of the true mathematical nature.

If the latter is true, perhaps the specific mathematical structure that shapes our universe is not the only option. Other possible mathematical structures may exist independently in separate universes.

"Mathematical structure is something that you can describe completely independently of our knowledge and concepts,- He speaks Max Tegmark, professor at the Massachusetts Institute of Technology, the author of this hypothesis. - Personally, I believe that somewhere there is such a universe that can exist completely independently of me and will continue to exist even if there are no people in it.

One model of potential multiple universes is called the multiple worlds theory. The theory may seem strange and unrealistic, so much so that it belongs in science fiction films and not in real life. However, there is no experiment that can irrefutably discredit its validity.

The origin of the parallel universe hypothesis is closely related to the introduction of the idea of ​​quantum mechanics in the early 1900s. Quantum mechanics, a branch of physics that studies the microcosm, predicts the behavior of nanoscopic objects. Physicists have had difficulty fitting the behavior of quantum matter to a mathematical model. For example, a photon, a tiny beam of light, can move vertically up and down while moving horizontally forward or backward.

This behavior contrasts sharply with objects visible to the naked eye - everything we see moves either as a wave or a particle. This duality theory of matter has been called the Heisenberg Uncertainty Principle (HOP), which states that the act of observation affects quantities such as velocity and position.

In relation to quantum mechanics, this observational effect can affect the shape - particle or wave - of quantum objects during measurements. Future quantum theories, such as Niels Bohr's Copenhagen interpretation, used the GNG to state that an observable object does not retain its dual nature and can only be in one state.

In 1954, a young student at Princeton University named Hugh Everett proposed a radical proposal that differed from the popular models of quantum mechanics. Everett did not believe that observation raises a quantum question.

Instead, he argued that the observation of quantum matter creates a split in the universe. In other words, the universe creates copies of itself, taking into account all probabilities, and these duplicates will exist independently of each other. Every time a photon is measured by a scientist in one universe, for example, and analyzed as a wave, the same scientist in another universe will analyze it as a particle. Each of these universes offers a unique and independent reality that co-exists with other parallel universes.

If Everett's Many Worlds Theory (TMT) is correct, it contains many implications that will completely transform our perception of life. Any action that has more than one possible outcome causes the universe to split. Thus, there are an infinite number of parallel universes and infinite copies of each person.

These copies have the same faces and bodies, but different personalities (one may be aggressive and the other passive) as they each have individual experiences. The infinite number of alternate realities also suggests that no one can achieve unique achievements. Every person - or another version of that person in a parallel universe - has done or will do everything.

In addition, from TMM it follows that everyone is immortal. Old age will not cease to be a sure killer, but some alternate realities may be so scientifically and technologically advanced that they have developed anti-aging medicine. If you die in one world, another version of you in another world will survive.

The most disturbing consequence of parallel universes is that your perception of the world is not real. Our "reality" at this point in one parallel universe will be completely different from the other world; it is only a tiny fiction of infinite and absolute truth. You may believe that you are reading this article at the moment, but there are many copies of you that are not being read. In fact, you are even the author of this article in a distant reality. So does winning a prize and making decisions matter if we can lose those awards and choose something else? Or live, trying to achieve more, if we can actually be dead elsewhere?

Some scientists, such as the Austrian mathematician Hans Moravec, have tried to debunk the possibility of parallel universes. Moravec developed in 1987 the famous experiment called quantum suicide, in which a gun is pointed at a person, connected to a mechanism that measures the quark. Each time the trigger is pulled, the quark's spin is measured. Depending on the result of the measurement, the weapon either shoots or it doesn't.

Based on this experiment, a gun will or will not shoot a person with a 50 percent chance for each scenario. If TMM is not correct, then the probability of human survival decreases after each measurement of a quark until it reaches zero.

On the other hand, TMM claims that the experimenter always has a 100% chance of surviving in some kind of parallel universe, and the person is faced with quantum immortality.

When a quark is being measured, there are two possibilities: the weapon can either fire or not. At this point, TMM claims that the universe is splitting into two different universes to account for two possible endings. The weapon will fire in one reality but fail in another.

For moral reasons, scientists cannot use Moravec's experiment to disprove or confirm the existence of parallel worlds, as test subjects can only be dead in that particular reality and still alive in another parallel world. In any case, the many worlds theory and its startling implications defy everything we know about the universe.