Climbing the branches of the eternal tree

In October 2020, somewhat cryptic-sounding reports appeared in the media that researchers at the Large Hadron Collider Laboratory intended to "make contact with a parallel universe." In publications on the subject, it was even considered likely that gravity from our own universe could "move" into this parallel universe.

“We predict that gravity may seep into extra dimensions, and if so, to the LHC. (…) We mean real universes in extra dimensions,” he told the media. Mir Fayzal from BAK. “Because gravity can flow from our universe into extra dimensions, such a model could be tested by finding mini black holes in the LHC.”

These posts were followed by references to a disastrous 2020. In fact, they refer to the work of Faisal and his team, published in Physics Letters B back in 2015, which is more speculative than based on any experimental results. In addition, we are not talking about "parallel universes", but only about the discovery of additional dimensions, which is not the same thing. This story, however, shows how powerful they are in the popular imagination.

However, it cannot be said that multiverse hypothesis (1) is non-scientific. Its various versions have long been proposed by the most prominent physicists and astrophysicists. While it is strongly dismissed by more rigorous scientists as unverifiable by scientific methods, it is hard to deny that the multiverse has now become a full part of the scientific debate, that is, part of science.

In our report, we are trying to present a "state of thought" about the multiverse or multiverse, because that name is also used, various interpretations, concepts and attempts to explore whether this hypothesis has any relation to reality. Although this is not a very good wording, because these theories are usually about something that does not have much in common with the reality we know.

Gurgling and branching

There are several multiverse theories that intersect and branch into different varieties.

One of the most famous speaks of superuniverse of an infinite number of universes. It is based on the assertion that we do not exactly know the shape and nature of space-time. It can be flat and contain an infinite number of universes.

Another well-known theory of multiple universes stems from the concept of "perpetual inflation". A well-known proponent of this is Tufts University cosmologist Alexander Vilenkin, who works with other well-known cosmic inflation theorists, Alan Guth and Arvind Borde. In these concepts, space-time is viewed as a single entity, in which some areas of space "bubble", inflate as a result of what we call the Big Bang. In some, the tumor persists, in others it stops. These non-bubble universes may have completely different laws of physics than those we know from ours, because the universes are unrelated.

The next version has other names multiverse hypothesis containing the set of all possible continuum universes, or daughter universe hypothesis. It has to do with the interpretation of authorship. Hugh Everett (2), which he calls the "multiverse interpretation of quantum mechanics" (MWI), everything that can happen, certainly happens in one of the branches of reality, which resembles a large tree, branching at every moment of life. For Everett, each state of superposition is equally real, but it takes place in a different parallel universe. The quantum multiverse is like an endless branching tree. This means, among other things, that we also branch out, whether we like it or not.

Another concept of the multiverse mathematical universesthis means that the basic structure of mathematics can change depending on which universe we live in. Although universes based on mathematics other than those known to us sound abstract, one can intuitively try to understand them by looking at constructions known to our mathematics as imaginary or complex numbers. Although they can describe them, but a little like from a different reality.

Another type of multiverse is described in an eleven-dimensional extension of string theory called M-theory. According to this hypothesis, our and other universes arose as a result of the collision of membranes in 11-dimensional space. Unlike the universes in the "quantum multiverse", they can be completely different laws of physics. According to the calculations of cosmologists-astrophysicists, prof. А. Linde i Dr. V. Vanchurin, from Stanford University in California, the number of such universes could be as high as 10.¹⁰ to the power of 10 and then back to the power of 7, this is a number that cannot be written in decimal form due to the number of zeros exceeding the number of atoms in the observable universe, estimated at 10⁸⁰.

According to one of the founders of the theory of inflation, Alana Guta from the Massachusetts Institute of Technology, "in a universe where there is perpetual inflation, everything that can happen will actually happen - and will actually happen an infinite number of times." And in that sense, the multiverse is predictable. Scientists, however, are not impressed, because it is more like metaphysics than physics.

Have you seen an atom? Have you seen another universe?

The idea, that, has a long history. As early as the XNUMXth century, the English theologian and philosopher Robert Grosseteste he wrote a work called "De Luce" in which he presented a cosmological model of the universe. This work, written in 1225, describes the beginning of the universe as follows: God created a point in space from which light then radiated in all directions, giving matter its three-dimensional form. As a result of the interaction of light with matter in space, a sphere should have formed, which, when the minimum density was reached, entered the state described as “perfect” and stopped expanding. Then another kind of light, called a lumen, will spread from its edge to the center, which will collect "imperfect" matter, compressing it. In the region of a less dense sphere, the remaining matter would become "perfect" and form another sphere (within the first one) radiating its light, and so on. Nine of these spheres were to be formed, and finally, the Earth was to be formed from the core of imperfect matter.

Even before that, the first proponents of the multiverse were the same ancient Greeks who assumed the existence of atoms. Leucippus i Democritus they believed that their atomic theory required an infinity of worlds. Their later successor, Epicurus from Samoshe also recognized the reality of many worlds. “There are an infinite number of worlds, both similar and unlike our world,” he argued.

In Hinduism's most important monotheistic religion, Vaishnavism (Krishnaism) teaches that there are two worlds: eternal spiritual (Kingdom of God) and material multiverse subject to cyclical creation and destruction. In each of the universes, at a certain stage of a rather complex process of creation, the first living being, whose position is known as Brahma, is born, receiving knowledge from God in the process of meditation and creating all existing forms.

Over time, Western science began to lean towards the point of view Aristotlewho argued that logic requires only one universe. He approved of it heliocentric worldview, After Copernicus however, with successive discoveries about other planets, stars, and galaxies, our understanding of the universe has finally changed. Some saw them as something other than universes when they saw them. Among those who looked at it in this way, among others, the famous philosopher Immanuel Kant. However, in the next stage of the development of science, the concepts of the multiverse were abandoned in favor of a single universe, still expanding as research progressed.

In the 80s, a new explanation emerged for how the universe began. inflationary cosmology. If the initial Big Bang that started our universe was followed by a period of extremely rapid expansion (inflation), then the same inflationary event could be repeated elsewhere in space. If the inflation theory turned out to be correct, our bubble would be just one of many that have already been discussed.

Opponents of the multiverse hypothesis are certainly wrong in saying that the idea of ​​a multiverse is not science because it cannot be tested. Proponents of the multiverse hypothesis readily recall this argument. Ernst Mach, an Austrian physicist and philosopher of the late XNUMXth century, who denied the existence of atoms, just as he opposes the plurality of universes today. "Have you ever seen them?" He had a habit of mocking atoms.

Today, atoms can be "seen" in images created by scanning in tunneling microscopes. But they do not exist in science until they are first visualized. They have been recognized scientific concepts for two and a half thousand years. Why should we treat the mutiversum theories differently from the old atoms?

A surplus of universes that, however, can provide computational power

Physicists and philosophers have been arguing about the "problem of measurement" for almost a hundred years. Various explanations and interpretations have been proposed, but most of them smacked of metaphysics, making human consciousness a necessary component of reality, or were cumbersome, requiring a special tuning of the wave function. In 1957, a graduate of Princeton, Hugh Everett III, came to the conclusion that the unfortunate electron that scientists wanted to capture in their double-slit experiments actually occupies all the positions allowed by the wave function, but in different universes.

The physicists of the time ridiculed MWI Everett's theories. When Everett tried to explain his theory to Niels Bohr at a meeting in Denmark, Bohr thought she was crazy. Only later, in the 70s and 80s, when they introduced quantum decoherence, quantum information theory i quantum computing, a return to Everett's many-world interpretation was returned. The nascent field of quantum computing promised to solve computational problems that the father of computer science, Alan Turing, would have thought impossible for computers. The question arose - where will all this additional computing power come from? MWI proponent David Deutsch has claimed that it is in parallel universes.

Everett he did not understand why the concretization of the state of a physical system should depend on an external factor, or why this factor (that is, the observer) should be somehow privileged. If anything, he expressed very similar hesitation a few years later. Evgeniy Wigner, noting that a broader view of the famous problem of Schrödinger's cat threatens with new paradoxes. Since the isolated cat can remain in superposition until the box is opened, the laboratory, together with the animal, the researcher, and all the equipment, can also form an isolated system in superposition with the rest of the universe (3). If we think about it, moving further and further along this path, we can finally begin to ask the philosophical question of a universal observer of the entire universe.

3. Paradoxes of quantum reality

For Everett, the state of each object is constantly changing. This means that the wave function describing the state of an exemplary particle should not undergo rapid reduction, and the act of observation should not be given much importance. Thus, at each subsequent observation, the state of the observer branches into a number of different states. Each of these branches represents a different measurement result and a corresponding eigenvector for the superposition. All branches exist simultaneously in superposition after each sequence of observations. Each roll of the dice brings six universes to life. In Schrödinger's famous metaphor, universe A with a live cat and universe B with a dead cat function. There is no collapse, understood as a sudden choice by the object of one of the options. Rather, the experimenter checks through the act of measurement to which of the resulting branches of reality he has reached.

From the very beginning, the idea was considered extravagant, and its methodological cost was considered by many to be too high. Nevertheless, there was no shortage of physicists willing to pay. At first, prominent individualists were on the side of the multiverse, like Bryce DeWitthowever, since the 90s, this interpretation seems to have become increasingly popular in the scientific community. Its main enthusiasts, led by Davidem German from Oxford express their surprise at the fact that Everett's multiverse is still the subject of much controversy.

However, inexplicable criticism is usually based on the claim that Hugh Everett he did not hesitate to become entangled in the multiplication of universes. Critics are usually drawn to the so-called. Occam's razor. However, there is a kind of relentless logic to Everett's multiverse, despite the massive costs it entails.

For a singular universe where things happen a finite number of times, scientists can calculate the relative probability of a particular event relative to another by comparing how many times both events happen. On the contrary, for a multiverse where everything happens an infinite number of times, such calculations are impossible, and one cannot say that something is more likely than something else. Any fact can be predicted and will definitely happen in one universe, but that says nothing about what will happen in our own universe.

Physicists are concerned about the impossibility of predicting. According to some of them, the path to solving the problem may indicate. Specifically, the cosmological picture of the eternal expansion of the multiverse can be mathematically equivalent to Everett's many-worlds interpretation. Linking the cosmological hypothesis of the multiverse with the bifurcation of quantum worlds, according to supporters of this concept, solves the problem of predictability.

"Wigner's Friend" Questions Objective (or One) Reality

One of Everett's lines of thought seems to have recently been confirmed in experiments by modern physicists. In 1961 it was already mentioned Evgeniy Wigner, a Nobel laureate, has described a thought experiment in which he and a theorist friend can simultaneously experience two different realities. Since then, physicists have used the "Friend of Wigner" thought experiment as the basis for discussing the measurement of i objective reality.

There were discussions, but last year physicists noted that in quantum technologies made it possible to recreate the "Wigner's friend" test in a real experiment, in which one could create different realities and see if they can actually occur at the same time. Massimiliano Proetti from Heriot-Watt University in Edinburgh and his teammates reported in February 2019 that they had done this experiment for the first time in history, created different realities and compared them. Their conclusion is that Wigner was right—these realities may be irreconcilable, so it is impossible to establish objective facts.

Wigner's original thought experiment is simple in principle. It starts with one unpolarized photonwhich can be horizontally or vertically polarized when measured. Before measurement, according to the laws of quantum mechanics, a photon exists in both states of polarization simultaneously in the so-called superposition. Wigner then he imagined a friend in another lab measuring the state of that photon and storing the result while he watched it from a distance. Wigner has no information about his friend's measurement results and is forced to assume that the photon and its measurement are in a state of superposition of possible measurement results. Wigner can even run an experiment to determine if such a superposition takes place. This is a kind of interference experiment that shows that the photon and its dimension are indeed in superposition. From Wigner's point of view, a "fact" is a superposition. And this fact suggests that there was no measurement.

But this contrasts sharply with the point of view of a friend who measured and recorded the polarization of a photon. A friend may even call Wigner and say that the measurement has been taken (provided that he does not reveal the result of the measurement). So these two realities contradict each other. “This undermines the objective status of the facts established by the two observers,” he commented. Project.

The experiment was carried out on the idea Časlav Brukner from the University of Vienna in Austria, who last year invented the method of using technique of entangling many particles at the same time. Proietti and his colleagues conducted this experiment using a chip with six speakers.

The experiment gives an unambiguous result. It turns out that both realities can coexist.even if the results are irreconcilable. This is in line with Wigner's predictions. The results of the experiment clearly show that there is no objective (or one) reality. This kind of confirms this, somewhat roundabout way, Everett multiverse. It should be remembered, however, that this applies to elementary particles, as in general, and as for its relationship with the macrocosm, you know, not so well. Of course, there is another way out for those who adhere to the conventional view of reality. Namely, there may be a gap in the arguments that the experimenters have overlooked. For years, physicists have tried to find such gaps and use experiments to close them. This does not mean that they always succeed.

Can string theory be tested?

string theory is an attempt to connect the two pillars of XNUMXth century physics – quantum mechanics and gravity – considering all particles as one-dimensional strings, the vibrations of which determine properties such as mass and charge. This theory was considered mathematically beautiful and for a long time was one of the main contenders for what scientists call Theory of everything. But lately, string theorists have gotten lost in their own maze of speculation. Many versions of string theory require that reality be made up of 10 or more dimensions, the three dimensions of space and time that we experience, and many more, rolled up into an extremely small point.

About twenty years ago, researchers realized that string theory allows the existence of up to 10 different universes (500), creating multidimensional landscapewhere our universe is just a tiny corner. But then scientists dealt a blow to string theory by suggesting that none of the myriad universes it describes actually contains dark energyas we know it.

4. Visualization of the multiverse in string theory

“It is becoming increasingly clear that the models proposed so far in string theory to describe dark energy suffer from mathematical problems,” he wrote. Ulf Danielsson, a theoretical physicist at Uppsala University in Sweden and co-author of a paper published 27 December 2018 in the journal Physical Review Letters.

The fundamental problem, according to Danielsson, is that the equations underlying string theory say that any universe with our version dark energy contained in it should quickly disintegrate and disappear. Together with his colleagues, he built a model in which the process that causes the decay of these dark energy-riddled universes is actually stimulates bubble inflation in many dimensions. We live on the periphery of one of these expanding bubbles, and "dark energy is imperceptibly induced by the interaction between the walls of the bubbles we live in and higher dimensions," wrote Danielsson.

Danielson is trying to find some solutions to the problem of the collapse of hypothetical universes by dark energy, but other researchers are more against it string theories unceremonious. “This is a mathematical fiction with no experimental evidence,” Sabina Hossenfelder, a physicist at the Frankfurt Institute for Advanced Study in Germany, told Live Science. Hossenfelder, whom we have already written about in MT, was critical of most of the latest discoveries and theories in the field of physics. In 2018, she published a book titled Lost in Math: How Beauty Leads Physics Astray. He writes in it, in part, "String theorists propose an infinite number of mathematical constructions that have nothing to do with observation."

However, Danielsson does not think that string theory will forever remain unverifiable. “If it turns out that string theory cannot predict dark energy like what we observe, then string theory will not only be proven, but will also be wrong,” Danielsson notes somewhat ironically.

Returning to the multiverse, this is at the heart of the string theory problem. In short, it doesn't explain anything. Some argue that all these multiple universes in string theory form its "landscape". Others believe that this is a swamp in which science is bogged down, not the landscape. “In my opinion, this is the death of a theory because it loses all predictive value,” says Princeton University physicist Paul Steinhardt. “Literally anything is possible here.”

Beyond the Big Bang

Science today approaches the multiverse in many ways, such as assuming one belongs to us and the other dominated by dark matter (5), or assuming that another symmetrical universe existed before us. Physicists have a pretty good idea of ​​the structure of the universe from a few seconds after the Big Bang to the present day. But experts have been arguing for decades about what happened first, in that first moment - when a tiny, infinitely dense grain of matter first expanded. It is assumed that then physics itself changed.

5. An illustration of the concept of the emergence of an alternative universe dominated by antimatter during the Big Bang.

Latham Boyle, Kieran Finn i Neil Turk from the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, turned this idea on its head, suggesting that the universe has always been essentially symmetrical and simpler than we think. According to them, the previous universe was a mirror image of our current one, but it was the other way around. Time in it moved backwards, and particles were antiparticles. Earlier ideas about the universe, which preceded ours, were considered rather as separate, but essentially similar to ours.

The Canadian hypothesis simplifies many things and provides a creative explanation for the problems that have plagued physics for years. First, it would make the first second of the universe fairly simple, saving experts from having to use complex multidimensionality for three decades to explain complex aspects. the quantum physics i Standard Modelwhich describes the zoo of subatomic particles that make up our universe. “Theorists came up with grand unified theories that predicted hundreds of new particles that have never been observed, supersymmetry, extra-dimensional string theory, higher-dimensional theories. And there are no observational data for any of them,” he says. Turok.

Previous mirror universe hypothesis it is associated with the concept of a great reflection, or pulsating Universe, which does not have a starting point in the form of a Big Bang, but expands and contracts in an eternal (?) oscillatory cycle (6). This is nothing but a different understanding of the multiverse, not so much in space as in time (although it is not known whether it makes sense to talk about time here).

6. Universes in a big reflection

Parallel universes of media coverage

The example given at the beginning of the publication about the alleged “erasing of a parallel universe” in experiments at the LHC is just one example of media exaggeration or even misinformation that does not contribute to a calm scientific study of the problem. Another well-known example of news coverage that is too far away is the recent reports from Antarctica about the ANITA experiments.

There was information that physicists in Antarctica found evidence the existence of a parallel universe. Experiment ANITA(), i.e. radio wave sensor placed in a balloon floating over the ice of a frosty continent (7), he discovered radio waves from under the Antarctic ice. They were associated with tau neutrinos penetrating the Earth and producing radio waves. But... these neutrinos should not be "seen" in the detector, because there is no source (known to us) that could generate particles of such high energy.

7. Before the flight Antarctic Pulse Transition Antenna (ANITA)

There have been three commonly accepted explanations for ANITA fixed: either there was an astrophysical source of these particles unknown to us, or the detector is faulty, or the interpretation of data from the detector is incorrect. A less traditional explanation is that something very exotic, unusual, and outside of the Standard Model and its CPT symmetry (charge, parity, time) is going on. Traditional explanations are excluded, incl. using the IceCube detector, also in Antarctica (8). An unknown astrophysical source was also excluded (because it is unknown).

8. Illustration of IceCube neutrino experiment

So, there is an anomaly, but where is the parallel universe? Or rather, nowhere. From a phenomenon that we cannot yet explain to another universe is very far away. Unfortunately, the media decided to take a shortcut and got lost.

Bruises after a collision with our neighbor in the universe?

As you know, the main problem of the multiverse hypothesis is testability. According to Ranga-Ram Charms, a scientist from the Planck Data Center project at the American California Institute of Technology, could test this hypothesis. In a 2015 article in the Astrophysical Journal, he details the strange anomalies found in the microwave background radiation left over from the Big Bang. These phenomena, detected by analysis of data from the Planck satellite, may be a trace, a kind of bruise after our universe collided with some other universe. After this publication, there was further evidence in the media that this cool spot in the radiation background - an area in the sky with a temperature of about 0,00015 ° C cooler than the environment - is not the result of the absence of enough environment. matter, as the opponents of the search for new universes originally assumed.

Analysis of these data in the range of 100-545 GHz by a physician Rank of Chari-Rama from the CIT Institute in Pasadena showed four anomalies with a much stronger signal than the theoretical model predicts. According to Dr. Chari, this may be evidence of a distant interaction between our newborn universe and some other universe, which should have occurred several hundred thousand years after the Big Bang, or about 13,8 billion years ago.

Many scientists automatically refuse multiverse concept teeming with universes and the laws of physics straight out of the zoo of the imagination. The multiverse does not explain anything in the traditional understanding of physics and does not provide satisfactory answers. It only transfers problems to a plane far from us and our cognitive abilities, where it is impossible to test scientific theories in any way.

However, supporters of the multiverse hypotheses do not lose heart. They point out that one cannot say that an idea that explains the nature of everything (and in the full sense of the word) explains nothing. Expanding one's horizons has always been a progress in knowledge, not the other way around, they say. Suggest that the multiverse could explain many of the fundamental mysteries of modern physics. If it existed, it would allow, for example, to answer the question why the parameters of the Universe known to us, such as electromagnetic interactions between molecules or the value of the cosmological constant, have the values ​​necessary with high precision and only small deviations for the existence of life in the universe. According to the logic of the supporters of the multiverse, these parameters are different in other universes. The one in which we live and which we have the opportunity to observe thanks to its adjustment, has simply ideal values ​​for the emergence and development of living beings like us.

As amazing as it may sound, the multiverse can explain to us why "this world is strange," the world we live in. Now it would have to be so "weird" because it's nothing but a thousand or quadrillion to the nth degree of universes.

Miroslav Usidus