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Why do physicists believe we live in a multiverse?

Despite scientific progress and recentachievements of mankind, our knowledge of the universe is extremely small. The reason, in part, is that we can hardly imagine concepts (or concepts) such as infinity or the Big Bang, as well as what came before it. In search of answers to critical questions, scientists consider even the most controversial and controversial theories. One of these is the theory of the Multiverse. Some of the founders of the theory of inflation, including the Stanford University physicist Andrei Linde, put forward the idea that quantum fluctuations during inflation spawned not only galaxies, but entire universes. In this article, you will learn why the theory of the Multiverse is worth paying attention to.

If the multiverse theory is correct, what does this mean for each of us?

According to the cosmological model, hotUniverse, the evolution of the Universe begins with the state of a dense hot plasma, which consists of elementary particles and proceeds with the further expansion of the Universe.

Content

  • 1 Popular theory
  • 2 Geek Picnic Online 2020
  • 3 Inflationary model of the Universe
  • 4 Universe from nothing
  • 5 What is the Multiverse?
  • 6 Reality or Fantasy?

Popular theory

Before diving into the intricacies of the fascinating theory of the Multiverse, let me remind you that inflationary model of the universe Is a hypothesis about physical condition and lawexpansion of the young universe (shortly after the Big Bang), which contradicts the cosmological model of a hot universe. The fact is that this generally accepted model is not without drawbacks, many of which were solved in the 1980s as a result of the construction of an inflationary model of the Universe.

It is noteworthy that no matter how distant the science ofThe universe did not seem to an inexperienced reader, popular culture, together with scientists, did a truly amazing job. So, in the last years of his life, the outstanding theoretical physicist Stephen Hawking worked on topics that most researchers - by their own admission - “have a headache”: Hawking, in collaboration with physicist Thomas Hertog from the Catholic University of Leuven in Belgium, worked on the already famous article dedicated to the problem of the Multiverse.

As often happens in the era of fake newsand misinformation, due to the fact that Hawking and Hertog's work was hosted on the Airxiv preprint server (on this server, scientists exchange draft articles before they are published in peer-reviewed scientific journals), this has generated many baseless reports that Stephen Hawking predicted the end of the world and at the same time suggested a way to detect alternative universes.

You might be wondering: Who is Stephen Hawking? Part one: the rise of a legend

In fact, the study itself,published later in the Journal of High Energy Physics, not nearly as sensational. The paper deals with a paradox: if the Big Bang spawned infinite universes with an inexhaustible number of variations in the laws of physics, then how can scientists hope to answer fundamental questions about why our universe looks exactly the way it looks?

In the photo British theoretical physicist, cosmologist and astrophysicist, writer Stephen Hawking

When the universe emerged, which happened about 13.8 billion years ago, it underwent an inflationary-exponential expansion in a very short period of time. In this process, tiny quantum fluctuations in space have been magnified to cosmic proportions, creating the seeds of structures that will become galaxies and light up the universe. However, and this is even more surprising, physicist AndreyLinde assumes that inflation is still happening. A few years ago, in an interview with The Washington Post, he compared space to an ever-growing piece of Swiss cheese.

Cheese-like pocket universesthese are places where local inflation has stopped, allowing matter to condense and stars and galaxies to form. We may well live in one of these pockets, divorced from the endless alternative universes that exist around us, and are blissfully ignorant.

Andrei Linde, professor at Stanford University, the founder of the theory of inflationary expansion of the Universe, which provides for the existence of a multiple universe, or Multiverse.

And yes, if this idea surprises you too much,you are not alone. Some cosmologists are seriously wary of "eternal inflation" - and the Multiverse that could emerge from it. First, if the various pocket universes are disconnected, how can we even verify that they exist? Secondly, the infinite multiverse defies mathematical analysis, making it difficult to use the model to understandhow everything works and interacts in space. There are really a lot of questions, so let's try to understand this fascinating and popular theory.

Geek Picnic Online 2020

The multiverse theory today is sopopular, which became the main topic of a large European popular science festival (traditionally open air) dedicated to modern technologies, science and creativity Geek Picnic Online 2020. Among the invited 122 speakers were Professor Linde - his lecture in Russian can be viewed here, as well as Irish science fiction writer Ian MacDonald. According to the organizers of the festival in the official public of the event on Vkontakte, MacDonald's lecture will be published later.

Screenshot of Andrey Linde's lecture on the Multiverse

As Linde explains, according to the Bolshoi theoryexplosion, after its birth the universe was very small, but at some point it began to expand. At the same time, there was much more energy in the early universe than today. Some of this energy was subsequently spent on the expansion of the Universe. However, the main question is where all this energy came from.

Imagine that in the evening your pockets are empty, and onthere is a billion dollars in them in the morning, says Linde. But in real life, nothing like this happens. It is important to understand that all the processes due to which the Universe was born began spontaneously.

Today we see only a small part of the universe. Scientists call the observable universe "Observable universe".

Inflationary model of the universe

At the very beginning, when the size of the universe is notexceeded and a centimeter, there were approximately 10 to 90 degrees of areas that did not touch each other in any way. But why and how, in this case, they suddenly "realized" that it is time for the universe to expand? In fact, this is a well-known cosmological problem called horizon problem (horizon problem). It arises from the difficulty of explaining the observed homogeneity of causally disconnected regions of space in the absence of a mechanism that sets the same initial conditions.

So, if you try with a telescopelook into the past, we will see the light of the Big Bang, which took 13.8 billion years to reach us. However, Linde points out that we see the universe in a limited way. Viewing angle is easiest to imagine by stretching both arms left and right - the point is that we are in the center and do not see what is outside the fingertips of both hands. Moreover, neither the right nor the left hand "has a clue of what the other is doing."

The observable Universe is most easily represented as a sphere, beyond which there is unknown. The image shows the observable universe on a logarithmic scale.

The next equally important question isthe reason our universe does not rotate. Let me remind you that all massive space objects from planets to the Sun rotate, even supermassive black holes in the nuclei of galaxies. At the same time, in whatever direction the observer from the Earth looks - up, down, left or right - he will see equal distances. Scientists call it isotropy - the same physical properties in all directions, as well as symmetry with respect to the choice of direction.

It turns out that our Universe is really so strange that It is impossible to answer a huge number of questions using the Big Bang theory alone. Indeed, how to explain that the Universe being in a vacuum continues to expand with acceleration? After all, in a vacuum there are no particles at all!

Vacuum - space without substance. In applied physics, a vacuum is understood as a medium consisting of gas at a pressure significantly below atmospheric.

The answer lies in particle physics. For example, Lawrence Krauss, a theoretical physicist and president of the Origins Project Foundation, wrote a book dedicated to this issue, and it is called “Everything from nothing. How the Universe arose, ”we recommend reading. Andrei Linde, in turn, believes that some particles in a vacuum have an energy charge and can appear as a result of the decay of the vacuum.

The universe from nothing

So let's imagine one cubic meter inthe form of a box filled with sweets, with the condition that 1000 sweets are placed in one cubic meter. But what happens if this cubic meter becomes 10 times larger? The answer seems to be simple - there will still be 1000 candies inside. But due to the fact that the volume has grown a thousand times, there will be only one candy per cubic meter. It seems logical, but reality has its own rules: one cubic meter contains a constantly expanding vacuum.

At some point, its volume becomes one thousandtimes more than the original, after which the vacuum disintegrates. As a result, the energy density inside one imaginary box is the same as before the expansion - the vacuum has not changed, although our box has increased 10 times. Sounds like some kind of magic, doesn't it? As Linde himself explains, when the universe expands in a constant vacuum, the energy of matter increases exponentially, unlike the energy of gravity. As a result, the vacuum disintegrates releasing “1000 candies” - protons, electrons and other particles, and their number becomes proportional to the volume of the Universe.

Thus, if exponential growthcontinues, the number of particles also increases. Constant expansion, meanwhile, does not tell us a word about the shape of the universe. Although you and I really don't care what shape it is, because from the perspective of an observer, the universe appears flat. Exactly so - in a more or less simplified presentationlooks like the theory of an inflationary universe, first put forward by Alan Guth, an American physicist and cosmologist in 1981. It is noteworthy that at the end of his scientific work, Guth writes something like this:

There is a small problem thatis that the decay of a vacuum - the process necessary for the appearance of matter - is very similar to a vat of boiling water. What does boiling water look like? That's right - a bubble here, a bubble there, and so on.

Guth also claims that these bubblescollide in a boiling Universe and make all the processes occurring in it chaotic and ... useless. But how can this be? Guth's attempts to find an answer to this question attracted the attention of other scientists. As a result, two works were published at once - the first, written by Alan Guth in co-authorship with Eric Weinberg in 1981, and the second is the very work of Stephen Hawking in co-authorship with Thomas Hertog.

It is noteworthy that both articles came to the same andto the same conclusion - the theory of an inflationary universe is not consistent. However, Guth contacted Andrei Linde, as a result of which a professor at Stanford University created a new model of an inflationary universe, for which he was awarded the George Gamow Prize. But what does the multiverse have to do with it?

It is possible that after death, our consciousness goes into an alternative universe. Read more in the material of my colleague Ramis Ganiev

Linde believes that our universe is similar toa ballerina who, having ceased to rotate, spread her arms in different directions and froze in place. This certainly seems impossible, since it violates all known laws of physics. However, the use of a new model of an inflationary universe allows us to learn a lot about the universe. About who and why first put forward the theory of the Multiverse, read our material.

What is the Multiverse?

So we come to the most interesting - whyGeek Picnic 2020 speaker Andrei Linde, and with him the science fiction writer Ian MacDonald, believe that we live in the Multiverse? A Stanford University professor believes the multiverse is the answer to the question of ... what color is our universe. If it is black, then it must be proved,just as if we believed that its color is white or yellow. Remember the bubbling vat? Imagine that if our Universe is white, and Professor Linde thinks so, other bubbles can be black, red, yellow, blue, green, and so on. So we live in the Multiverse.

According to the professor, being in the white areaspace (white Universe), we do not see its other areas (red, purple, brown, etc.). In turn, in each universe there must be an observer who will try to explain why his universe, for example, is red. Thus, we simply cannot exclude the possibility of the existence of red, yellow, blue, blue and other universes.

And if all of the above seems to you notdizzy enough, imagine that Russia is the only country we know of. In an attempt to understand why Russia is arranged the way it is, scientists will seek answers to questions about its nature and origin. Scientists from China, Great Britain, India, USA and any other country will do exactly the same. The main condition in this example sounds like this - residents of different countries do not know about each other's existence. So is the Multiverse - being in the white universe, we do not know that there are, for example, red, black and green.

We know so little about the Universe that we cannot rule out that it may be a hologram.

Returning to the Beginning of Beginnings - the Big Bang,Linde compares the birth of the Universe from nothing (as a result of vacuum decay) with different states of one substance - H2O. Water, as you know, can be in three states - liquid, gaseous (steam, fog) and solid (snow, ice, hail), which means that the vacuum itself, which gave rise to the Universe, can have different states. From this, as you probably already understood - and the conclusion follows about the plurality of worlds.

Speaking about the Multiverse, it is important to understand that no matter how amazing, incomprehensible, chaotic and sometimes insane this theory may seem to us, from the point of view of physics, the existence of the Multiverse is possible. Partly for this reason, scientists also workover the "theory of everything" - a theory that could fully answer all questions of modern physics, including the existence of the Multiverse. According to Professor Linde, physicists who study string theory are closest. But that's a completely different story.

Interesting: A Quadrillion Ways to Create Our Universe Discovered in String Theory

Reality or Fantasy?

Since humanity is at the very beginningthe path of knowing ourselves, and then the Universe, we must test even the most insane theories. This is because today there are many more questions than answers, and the truth is often hidden where we are afraid to look. This is why science fiction is a great thought experiment that might help us better understand the universe.

Speaking at Geek Picnic Online 2020 Science Fiction YenMacDonald, the author of such works as "Brazil", "Wolf Moon", "House of the Dervish" and others, spoke about why he believes that we live in the Multiverse. According to the writer, the very idea of ​​the Multiverse is relevant to the world in which we live today. The word "Multiverse" contains many concepts and we simply cannot select everything at once. Everyone, according to MacDonald, chooses something specific for themselves, such as sports, science fiction or fashion. And this is both good and bad.

In the photo, science fiction writer Ian MacDonald

It's easier for us to unite and form communities,but at the same time, our life is sealed in these private universes, and we do not know what happens outside of them. Social, cultural, political and economic, we live in separate parallel worlds that sometimes share common spaces (e.g. cities, streets, public spaces)

Ian McDonald, Geek Picnic Online 2020

Agree, developing MacDonald's thought we are earlyor later we will come to the reflections of theoretical physicists about the structure of the Universe. And also, of course, about our society, about which MacDonald allowed himself to reflect in his works.

Do you think there is a multiverse and why? We will wait for an answer in the comments to this article, as well as in our Telegram chat

As for theoretical physics, inIn the above-mentioned work of Hawking and Hertog, the researchers rely on an idea developed back in the 1980s, known as the "Holographic Universe" two dimensions, this is done to facilitate calculations). As a result, the researchers managed to put at least some order in the vast, incomprehensible and not afraid of this word, the crazy theory of the Multiverse.

The boiling bubbles that Linde talked about canrepresent as pocket universes (as discussed at the beginning of the article) with the only difference that there are fewer universes in this model and they have certain fundamental qualities, which greatly facilitates their analysis. It is important to understand that the work of the outstanding British theoretical physicist (we are talking about Stephen Hawking) and his colleagues are not limited to a single, unique Universe, but their discoveries involve a significant reduction of the Multiverse to a much smaller range of possible universes. This means that instead of 1000 candies in an imaginary box, physicists consider 10.

Perhaps there are worlds in which you and I do not exist

The Washington Post newspaper in an article onHawking and Hertog's paper cites University of North Carolina cosmologist Katie Mack that the proposed model is not yet fully developed. "It's more of a simplified version of something to just watch and try to figure out what's going on," says Mack. So it comes as no surprise that Hawking's latest work is dependent on concepts that have not yet received widespread acceptance and the latest mathematical tools.

Interesting: The Standard Model: An Amazing Theory of Almost Everything

It is also important to understand that this work is not the solution to all problems in the universe. Of course, she intrigues, captures and makes us think in unusual categories. The multiverse theory is a potential path that can be followed even though scientists have no idea where or where it will lead them. “Stephen Hawking was human,” says Linde. "He was not a genius who says extremely correct things on a daily basis and struggled with the same scientific problems that all physicists struggle with."

Well, it remains for you and me to try to understand at least a little the theory of the Multiverse and wait for new, revolutionary discoveries in the field of theoretical physics. Hopefully this will happen very soon. And you?