« For me, life is too short to worry about things beyond my control and maybe even unrealizable. So they ask: “What if the Earth is swallowed up black hole, or there will be a distortion of space-time - this is a reason for concern? My answer is no, because we will only know about it when it reaches our... our place in space-time. We get jolts when nature decides the time is right: be it the speed of sound, the speed of light, the speed of electrical impulses - we will always be victims of the time delay between the information around us and our ability to receive it»
Neil deGrasse Tyson
Time is an amazing thing. It gives us the past, present and future. Because of time, everything around us has an age. For example, the age of the Earth is approximately 4.5 billion years. About the same number of years ago, the closest star to us, the Sun, also caught fire. If this figure seems mind-blowing to you, do not forget that long before the formation of our native solar system the galaxy in which we live appeared - the Milky Way. According to the latest estimates by scientists, the age of the Milky Way is 13.6 billion years. But we know for sure that galaxies also have a past, and space is simply huge, so we need to look even further. And this reflection inevitably leads us to the moment when it all began - the Big Bang.
Einstein and the Universe
People's perception of the world around them has always been ambiguous. Someone still doesn't believe in the existence vast universe around us, some people think the Earth is flat. Before the scientific breakthrough in the 20th century, there were only a couple of versions of the origin of the world. Adherents of religious views believed in divine intervention and creation higher intelligence, those who disagreed were sometimes burned. There was another side that believed that the world around us, as well as the Universe, is infinite.
For many people, everything changed when Albert Einstein gave a speech in 1917, presenting his life's work - the General Theory of Relativity - to the general public. The genius of the 20th century connected space-time with the matter of space using the equations he derived. As a result, it turned out that the Universe is finite, unchanged in size and has the shape of a regular cylinder.
At the dawn of the technical breakthrough, no one could refute Einstein’s words, since his theory was too complex even for the greatest minds of the early 20th century. Since there were no other options, the model of a cylindrical stationary Universe was accepted by the scientific community as the generally accepted model of our world. However, she was able to live only a few years. After physicists were able to recover from Einstein’s scientific works and began to take them apart, in parallel with this, adjustments began to be made to the theory of relativity and specific calculations of the German scientist.
In 1922, an article was suddenly published in the journal Izvestia Physics Russian mathematician Alexander Friedman, in which he states that Einstein was wrong and our Universe is not stationary. Friedman explains that the German scientist’s statements regarding the invariability of the radius of curvature of space are misconceptions; in fact, the radius changes with respect to time. Accordingly, the Universe must expand.
Moreover, here Friedman gave his assumptions regarding exactly how the Universe could expand. There were three models in total: a pulsating Universe (the assumption that the Universe expands and contracts with a certain periodicity in time); the expanding Universe from mass and the third model – expansion from a point. Since at that time there were no other models, with the exception of divine intervention, physicists quickly took note of all three Friedman models and began to develop them in their own direction.
The work of the Russian mathematician slightly stung Einstein, and in the same year he published an article in which he expressed his comments regarding Friedman’s work. In it, a German physicist tries to prove the correctness of his calculations. This turned out to be rather unconvincing, and when the pain from the blow to self-esteem subsided a little, Einstein published another note in the journal Izvestia Physics, in which he said:
« In a previous post I criticized the above work. However, my criticism, as I was convinced from Friedman's letter, communicated to me by Mr. Krutkov, was based on an error in the calculations. I think Friedman's results are correct and shed new light».
Scientists had to admit that all three Friedman models of the appearance and existence of our Universe are absolutely logical and have the right to life. All three are explained with clear mathematical calculations and leave no questions asked. Except for one thing: why would the Universe begin to expand?
The theory that changed the world
The statements of Einstein and Friedman led the scientific community to seriously question the origin of the Universe. Thanks to general theory relativity had a chance to shed light on our past, and physicists did not fail to take advantage of it. One of the scientists who tried to present a model of our world was astrophysicist Georges Lemaitre from Belgium. It is noteworthy that Lemaitre was a Catholic priest, but at the same time he studied mathematics and physics, which is real nonsense for our time.
Georges Lemaitre became interested in Einstein's equations, and with their help he was able to calculate that our Universe appeared as a result of the decay of a certain superparticle, which was outside of space and time before the fission began, which can actually be considered an explosion. At the same time, physicists note that Lemaitre was the first to shed light on the birth of the Universe.
The theory of an exploded superatom satisfied not only scientists, but also the clergy, who were very dissatisfied with modern scientific discoveries, under which we had to come up with new interpretations of the Bible. The Big Bang did not come into significant conflict with religion; perhaps this was influenced by the upbringing of Lemaître himself, who devoted his life not only to science, but also to serving God.
On November 22, 1951, Pope Pius XII made a statement that the Big Bang Theory does not conflict with the Bible and Catholic dogma about the origin of the world. Orthodox clergy also stated that they view this theory positively. This theory was also relatively neutrally received by adherents of other religions, some of them even said that in their scriptures there are references to the Big Bang.
However, despite the fact that the Big Bang Theory is currently the generally accepted cosmological model, it has led many scientists into a dead end. On the one hand, the explosion of a superparticle fit perfectly into the logic of modern physics, but on the other hand, as a result of such an explosion, mainly only heavy metals, in particular iron, could be formed. But, as it turned out, the Universe consists mainly of ultra-light gases - hydrogen and helium. Something didn’t add up, so physicists continued to work on the theory of the origin of the world.
Initially, the term “Big Bang” did not exist. Lemaître and other physicists offered only the boring name “dynamical evolutionary model,” which caused yawns among students. Only in 1949, at one of his lectures, the British astronomer and cosmologist Freud Hoyle said:
“This theory is based on the assumption that the Universe arose in the process of a single powerful explosion and therefore exists only for a finite time... This idea of a Big Bang seems to me completely unsatisfactory.”.
Since then, the term has become widely used in scientific circles and the general public's understanding of the structure of the Universe.
Where did hydrogen and helium come from?
The presence of light elements has baffled physicists, and many adherents of the Big Bang Theory set out to find their source. For many years they were not able to achieve much success, until in 1948 the brilliant scientist Georgiy Gamow from Leningrad was finally able to establish this source. Gamow was one of Friedman's students, so he gladly took on the development of his teacher's theory.
Gamow tried to imagine the life of the Universe in the opposite direction, and rewinded time to the moment when it just began to expand. By that time, as we know, humanity had already discovered the principles of thermonuclear fusion, so the Friedmann-Lemaitre theory gained the right to life. When the Universe was very small, it was very hot, according to the laws of physics.
According to Gamow, just a second after the Big Bang, the space of the new Universe was filled with elementary particles that began to interact with each other. As a result of this, thermonuclear fusion of helium began, which the Odessa mathematician Ralph Asher Alfer was able to calculate for Gamow. According to Alpher's calculations, just five minutes after the Big Bang, the Universe was filled with helium so much that even staunch opponents of the Big Bang Theory will have to come to terms with and accept this model as the main one in cosmology. With his research, Gamow not only opened up new ways to study the Universe, but also resurrected Lemaître's theory.
Despite the stereotypes about scientists, they cannot be denied romanticism. Gamow published his research on the theory of the Superhot Universe at the time of the Big Bang in 1948 in his work “The Origin of Chemical Elements.” As fellow assistants, he indicated not only Ralph Asher Alpher, but also Hans Bethe, an American astrophysicist and future laureate Nobel Prize. On the cover of the book it turned out: Alpher, Bethe, Gamow. Doesn't remind you of anything?
However, despite the fact that Lemaître’s works received a second life, physicists still could not answer the most exciting question: what happened before the Big Bang?
Attempts to resurrect Einstein's stationary Universe
Not all scientists agreed with the Friedman-Lemaître theory, but despite this, they had to teach generally accepted cosmological model. For example, astronomer Fred Hoyle, who himself coined the term “Big Bang,” actually believed that there was no explosion, and devoted his life to trying to prove it.
Hoyle has become one of those scientists who in our time offer an alternative view of modern world. Most physicists are pretty cool about the claims similar people, but this does not bother them at all.
To put Gamow and his rationale for the Big Bang Theory to shame, Hoyle and like-minded people decided to develop their own model of the origin of the Universe. As a basis, they took Einstein's proposals that the Universe is stationary, and made some adjustments suggesting alternative reasons for the expansion of the Universe.
If adherents of the Lemaitre-Friedmann theory believed that the Universe arose from one single superdense point with an infinitesimal radius, then Hoyle suggested that matter is constantly being formed from points that are located between galaxies moving away from each other. In the first case, the entire Universe, with its infinite number of stars and galaxies, was formed from one particle. In another case, one point provides enough substance to produce just one galaxy.
The failure of Hoyle's theory is that he was never able to explain where the very substance that continues to create galaxies containing hundreds of billions of stars comes from. In fact, Fred Hoyle suggested that everyone believe that the structure of the universe appears out of nowhere. Despite the fact that many physicists tried to find a solution to Hoyle's theory, no one succeeded in doing this, and after a couple of decades this proposal lost its relevance.
Unanswered Questions
In fact, the Big Bang Theory also does not give us answers to many questions. For example, in the mind ordinary person We cannot comprehend the fact that all the matter around us was once compressed into one singularity point, which is much smaller in size than an atom. And how did it happen that this superparticle heated up to such an extent that an explosion reaction started.
Until the mid-20th century, the theory of the expanding Universe was never confirmed experimentally, and therefore was not widely used in educational institutions. Everything changed in 1964, when two American astrophysicists - Arno Penzias and Robert Wilson - decided to study radio signals from the starry sky.
While scanning the radiation of celestial bodies, namely Cassiopeia A (one of the most powerful sources of radio emission in the starry sky), scientists noticed some extraneous noise that constantly interfered with recording accurate radiation data. Wherever they pointed their antenna, no matter what time of day they began their research, this characteristic and constant noise always followed them. Angry before to a certain extent, Penzias and Wilson decided to study the source of this noise and unexpectedly made a discovery that changed the world. They discovered relict radiation, which is an echo of that same Big Bang.
Our Universe is cooling much more slowly than a cup of hot tea, and the CMB suggests that the matter around us was once very hot, and is now cooling as the Universe expands. Thus, all theories related to the cold Universe were left behind, and the Big Bang Theory was finally adopted.
In his writings, Georgy Gamow assumed that in space it would be possible to detect photons that have existed since the Big Bang; all that is needed is more advanced technical equipment. The relict radiation confirmed all his assumptions regarding the existence of the Universe. It was also possible to establish that the age of our Universe is approximately 14 billion years.
As always, when practical proof any theory, many alternative opinions immediately arise. Some physicists mocked the discovery cosmic microwave background radiation as evidence of the Big Bang. Even though Penzias and Wilson won the Nobel Prize for their historic discovery, there were many who disagreed with their research.
The main arguments in favor of the failure of the expansion of the Universe were inconsistencies and logical errors. For example, the explosion equally accelerated all the galaxies in space, but instead of moving away from us, the Andromeda Galaxy is slowly but surely approaching the Milky Way. Scientists suggest that these two galaxies will collide with each other in just 4 billion years. Unfortunately, humanity is still too young to answer this and other questions.
Equilibrium theory
Nowadays, physicists offer various models of the existence of the Universe. Many of them cannot stand even simple criticism, while others receive the right to life.
At the end of the 20th century, American astrophysicist Edward Tryon, together with his Australian colleague Warren Kerry, proposed a fundamental new model Universe, and did it independently of each other. Scientists based their research on the assumption that everything in the Universe is balanced. Mass destroys energy and vice versa. This principle came to be called the principle Zero Universe. Within this Universe, new matter arises at singularity points between galaxies, where the attraction and repulsion of matter are balanced.
The theory of the Zero Universe was not torn to smithereens because after some time scientists were able to discover the existence of dark matter - a mysterious substance of which almost 27% of our Universe consists. Another 68.3% of the Universe is made up of the more mysterious and mysterious dark energy.
It is due to gravitational effects dark energy and is credited with accelerating the expansion of the universe. By the way, the presence of dark energy in space was predicted by Einstein himself, who saw that something in his equations did not converge; the Universe could not be made stationary. Therefore, he introduced the cosmological constant into the equations - the Lambda term, for which he then repeatedly blamed himself and hated himself.
It so happened that the theoretically empty space in the Universe is nevertheless filled with some special field, which puts Einstein’s model into action. In a sober mind and according to the logic of those times, the existence of such a field was simply impossible, but in fact the German physicist simply did not know how to describe dark energy.
***
We may never know how and from what our Universe arose. It will be even more difficult to establish what happened before its existence. People tend to fear what they cannot explain, so it is possible that until the end of time, humanity will also believe in divine influence in the creation of the world around us.
They say that time is the most mysterious matter. No matter how much a person tries to understand its laws and learn to control them, he always gets into trouble. Taking the last step towards solving the great mystery, and considering that it is practically already in our pocket, we are always convinced that it is still just as elusive. However, man is an inquisitive creature and the search for answers to eternal questions for many becomes the meaning of life.
One of these secrets was the creation of the world. Followers of the “Big Bang Theory,” which logically explains the origin of life on Earth, began to wonder what happened before the Big Bang, and whether there was anything at all. The topic for research is fertile, and the results may be of interest to the general public.
Everything in the world has a past - the Sun, the Earth, the Universe, but where did all this diversity come from and what came before it?
It is hardly possible to give a definite answer, but it is quite possible to put forward hypotheses and look for evidence for them. In search of the truth, researchers have received not one, but several answers to the question “what happened before the Big Bang?” The most popular of them sounds somewhat discouraging and quite bold - Nothing. Is it possible that everything that exists came from nothing? That Nothing gave birth to everything that exists?
Actually, this cannot be called absolute emptiness and are there still some processes going on there? Was everything born from nothing? Nothing - complete absence not only matter, molecules and atoms, but even time and space. Rich soil for the activity of science fiction writers!
Scientists' opinions about the era before the Big Bang
However, Nothing cannot be touched, ordinary laws do not apply to it, which means you either speculate and build theories, or try to create conditions close to those that resulted in the Big Bang and make sure your assumptions are correct. In special chambers from which particles of matter were removed, the temperature was lowered, bringing it closer to space conditions. The observation results provided indirect confirmation scientific theories: Scientists studied the environment in which the Big Bang could theoretically occur, but calling this environment “Nothing” turned out to be not entirely correct. The mini-explosions that occur could lead to a larger explosion that gave birth to the Universe.
Theories of universes before the Big Bang
Adherents of another theory argue that before the Big Bang there were two other Universes that developed according to their own laws. What exactly they were is difficult to answer, but according to the theory put forward, the Big Bang occurred as a result of their collision and led to the complete destruction of the previous Universes and, at the same time, to the birth of ours, which exists today.
The theory of “compression” says that the Universe exists and has always existed; only the conditions of its development change, which lead to the disappearance of life in one region and the emergence in another. Life disappears as a result of the “collapse” and appears after the explosion. No matter how paradoxical it may sound. This hypothesis has a large number of supporters.
There is another assumption: as a result of the Big Bang, a new Universe arose from nothingness and inflated, like a soap bubble, to gigantic proportions. At this time, “bubbles” budded from it, which later became other Galaxies and Universes.
The theory of “natural selection” suggests that we are talking about “natural cosmic selection”, like the one that Darwin spoke about, only in a more large sizes. Our Universe had its own ancestor, and it, in turn, also had its own ancestor. According to this theory, our Universe was created by a Black Hole. and are of great interest to scientists. According to this theory, in order for a new Universe to appear, “reproduction” mechanisms are necessary. The Black Hole becomes such a mechanism.
Or maybe those who believe that as our Universe grows and develops is expanding, heading towards the Big Bang, which will be the beginning of a new Universe, are right. This means that once upon a time, an unknown and, alas, disappeared Universe became the progenitor of our new universe. The cyclical nature of this system looks logical and this theory has many adherents.
It is difficult to say to what extent the followers of this or that hypothesis came close to the truth. Everyone chooses what is closer in spirit and understanding. Religious world gives his answers to all questions and puts the picture of the creation of the world into a divine framework. Atheists are looking for answers, trying to get to the bottom of things and touch this very essence with their own hands. One may wonder what caused such persistence in searching for an answer to the question of what happened before the Big Bang, because practical benefit It is quite problematic to extract from this knowledge: a person will not become the ruler of the Universe; at his word and desire, new stars will not light up and existing ones will not go out. But what is so interesting is what has not been studied! Humanity is struggling to solve mysteries, and who knows, maybe sooner or later they will fall into man’s hands. But how will he use this secret knowledge?
Illustrations: KLAUS BACHMANN, GEO magazine
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12. What caused the Big Bang?
The paradox of emergence
Not one of the lectures on cosmology that I ever read was complete without the question of what caused the Big Bang? Until a few years ago I didn't know the real answer; today, I believe, he is famous.
Essentially, this question contains two questions in a veiled form. First, we would like to know why the development of the Universe began with an explosion and what caused this explosion in the first place. But for the sake of it physical problem another, deeper problem of a philosophical nature is hidden. If the Big Bang marks the beginning of the physical existence of the Universe, including the emergence of space and time, then in what sense can we talk about what caused this explosion?
From the point of view of physics, the sudden emergence of the Universe as a result of a giant explosion seems to some extent paradoxical. Of the four interactions that govern the world, only gravity manifests itself on a cosmic scale, and, as our experience shows, gravity has the nature of attraction. However, the explosion that marked the birth of the Universe apparently required a repulsive force of incredible magnitude, which could tear the cosmos to shreds and cause its expansion, which continues to this day.
This seems strange, because if gravitational forces dominate in the Universe, then it should not expand, but contract. Indeed, gravitational forces of attraction cause physical objects to shrink rather than explode. For example, a very dense star loses its ability to withstand its own weight and collapses, forming neutron star or a black hole. The degree of compression of a substance is very early universe was significantly higher than that of the densest star; Therefore, the question often arises as to why the primordial cosmos did not collapse into a black hole from the very beginning.
The usual answer to this is that the primary explosion should simply be taken as the initial condition. This answer is clearly unsatisfactory and causes confusion. Of course, under the influence of gravity, the rate of cosmic expansion has been continuously decreasing from the very beginning, but at the moment of its birth the Universe was expanding infinitely quickly. The explosion was not caused by any force - the development of the Universe simply began with expansion. If the explosion had been less strong, gravity would have very soon prevented the spread of matter. As a result, the expansion would give way to compression, which would become catastrophic and turn the Universe into something similar to a black hole. But in reality, the explosion turned out to be quite “big”, which made it possible for the Universe, having overcome its own gravity, to either continue to expand forever due to the force of the primary explosion, or at least to exist for many billions of years before being compressed and disappearing into oblivion.
The problem with this traditional picture is that it in no way explains the Big Bang. The fundamental property of the Universe is again simply interpreted as the initial condition accepted ad hoc(for this case); Essentially, it only states that the Big Bang took place. It still remains unclear why the force of the explosion was the way it was and not another. Why wasn't the explosion even stronger so that the Universe is expanding much faster now? One might also ask why the Universe is not currently expanding much more slowly or contracting at all. Of course, if the explosion were not powerful enough, the Universe would soon collapse and there would be no one to ask such questions. It is unlikely, however, that such reasoning can be taken as an explanation.
Upon closer analysis, it turns out that the paradox of the origin of the Universe is actually even more complex than described above. Careful measurements show that the expansion rate of the Universe is very close to the critical value at which the Universe is able to overcome its own gravity and expand forever. If this speed were a little less, the collapse of the Universe would have occurred, and if it were a little more, cosmic matter would have completely dissipated long ago. It will be interesting to find out how accurately the expansion rate of the Universe falls within this very narrow acceptable interval between two possible catastrophes. If at the moment of time corresponding to 1 s, when the expansion pattern was already clearly defined, the expansion rate would differ from its real value by more than 10^-18, this would be enough to completely disrupt the delicate balance. Thus, the force of the Universe's explosion corresponds with almost incredible accuracy to its gravitational interaction. The Big Bang, therefore, is not just some distant explosion - it was an explosion of a very specific force. In the traditional version of the Big Bang theory, one has to accept not only the fact of the explosion itself, but also the fact that the explosion occurred in an extremely whimsical way. In other words, the initial conditions turn out to be extremely specific.
The rate of expansion of the Universe is just one of several obvious cosmic mysteries. The other is related to the picture of the expansion of the Universe in space. According to modern observations. Universe in on a large scale extremely homogeneous with regard to the distribution of matter and energy. The global structure of space is almost the same both when observed from Earth and from a distant galaxy. Galaxies are scattered in space with the same medium density, and from every point the Universe looks the same in all directions. The primary thermal radiation filling the Universe falls on the Earth, having the same temperature in all directions with an accuracy of no less than 10-4. On its way to us, this radiation travels through space for billions of light years and bears the imprint of any deviation from homogeneity it encounters.
The large-scale homogeneity of the Universe is maintained as the Universe expands. It follows that the expansion occurs uniformly and isotropically with a very high degree of accuracy. This means that the rate of expansion of the Universe is not only the same in all directions, but also constant in different regions. If the Universe were expanding faster in one direction than in others, this would lead to a decrease in the temperature of the background thermal radiation in that direction and would change the pattern of galaxy motion visible from Earth. Thus, the evolution of the Universe did not just begin with an explosion of a strictly defined force - the explosion was clearly “organized”, i.e. occurred simultaneously, with exactly the same force at all points and in all directions.
It is extremely unlikely that such a simultaneous and concerted eruption could occur purely spontaneously, and this doubt is strengthened within the traditional Big Bang theory by the fact that the various regions of the primordial cosmos are not causally related to each other. The fact is that, according to the theory of relativity, no physical impact cannot travel faster than light. Consequently, different regions of space can become causally connected with each other only after a certain period of time has passed. For example, 1 s after the explosion, light can travel a distance of no more than one light second, which corresponds to 300 thousand km. Regions of the Universe separated by a large distance will still not influence each other after 1s. But by this time, the region of the Universe we observed already occupied a space of at least 10^14 km in diameter. Consequently, the Universe consisted of approximately 10^27 regions causally unrelated to each other, each of which, nevertheless, expanded at exactly the same rate. Even today, observing thermal cosmic radiation coming from opposite sides starry sky, we register exactly the same “fingerprints” of regions of the Universe separated by enormous distances: these distances turn out to be more than 90 times greater than the distance that light could travel from the moment of emission of thermal radiation.
How to explain such a remarkable coherence of various areas of space that, obviously, were never connected with each other? How did such a thing arise? similar behavior? The traditional answer again refers to special initial conditions. The exceptional homogeneity of the properties of the primary explosion is considered simply as a fact: this is how the Universe arose.
The large-scale homogeneity of the Universe looks even more mysterious if we consider that on small scales the Universe is by no means homogeneous. The existence of individual galaxies and galaxy clusters indicates a deviation from strict homogeneity, and this deviation is also everywhere the same in scale and magnitude. Because gravity tends to enlarge any initial accumulation of matter, the degree of heterogeneity required to form galaxies was much less during the Big Bang than it is now. However, in initial phase There must still have been some small irregularities in the Big Bang, otherwise the galaxies would never have formed. In the old Big Bang theory, these early discontinuities were also attributed to "initial conditions." Thus, we had to believe that the development of the Universe began not from a completely ideal, but from an extremely unusual state.
All that has been said can be summarized as follows: if the only force in the Universe is gravitational attraction, then the Big Bang should be interpreted as “sent from God,” i.e. without a cause, with given initial conditions. It is also characterized by remarkable consistency; in order to arrive at the present structure, the universe must have evolved properly from the very beginning. This is the paradox of the origin of the Universe.
Search for antigravity
The paradox of the origin of the Universe was resolved only in recent years; however, the basic idea of the solution can be traced back to distant history, to a time when neither the theory of the expansion of the Universe nor the Big Bang theory existed. Newton also understood how complex problem represents the stability of the Universe. How do stars maintain their position in space without support? Universal character gravitational attraction should have led to stars being pulled together into clusters close to each other.
To avoid this absurdity, Newton resorted to a very curious reasoning. If the Universe were to collapse under its own gravity, each star would "fall" towards the center of the cluster of stars. Suppose, however, that the Universe is infinite and the stars are distributed, on average, uniformly over infinite space. In this case there would be no general center, in the direction towards which all the stars could fall, - after all, in infinite universe all areas are identical. Any star would experience the influence of the gravitational attraction of all its neighbors, but due to the averaging of these influences in various directions, there would be no net force tending to move this star to a certain position relative to the entire set of stars.
When Einstein created a new theory of gravity 200 years after Newton, he was also puzzled by the problem of how the universe avoided collapse. His first work on cosmology was published before Hubble discovered the expansion of the Universe; therefore, Einstein, like Newton, assumed that the Universe was static. However, Einstein tried to solve the problem of the stability of the Universe in a much more direct way. He believed that in order to prevent the collapse of the Universe under the influence of its own gravity, there must be another cosmic force that could resist gravity. This force must be a repulsive force rather than an attractive force to compensate for the gravitational attraction. In this sense, such a force could be called “antigravitational,” although it would be more correct to talk about the force of cosmic repulsion. Einstein in this case did not just arbitrarily invent this force. He showed that in his equations gravitational field you can introduce an additional term, which leads to the appearance of a force with the desired properties.
Despite the fact that the idea of a repulsive force opposing the force of gravity is in itself quite simple and natural, in reality the properties of such a force turn out to be completely unusual. Of course, no such force has been noticed on Earth, and no hint of it has been discovered over the course of several centuries of planetary astronomy. Obviously, if the force of cosmic repulsion exists, then it should not have any noticeable effect at small distances, but its magnitude increases significantly on an astronomical scale. This behavior contradicts all previous experience in studying the nature of forces: they are usually intense at short distances and weaken with increasing distance. Thus, electromagnetic and gravitational interactions continuously decrease according to the inverse square law. Nevertheless, in Einstein's theory a force with such rather unusual properties naturally appeared.
One should not think of the force of cosmic repulsion introduced by Einstein as the fifth interaction in nature. It's just a bizarre manifestation of gravity itself. It is not difficult to show that the effects of cosmic repulsion can be attributed to ordinary gravity if a medium with unusual properties is chosen as the source of the gravitational field. Regular material environment(e.g. gas) exerts pressure, whereas the hypothetical medium discussed here should have negative pressure or tension. To more clearly imagine what we are talking about, let’s imagine that we managed to fill a vessel with such cosmic substance. Then, unlike ordinary gas, the hypothetical space environment will not put pressure on the walls of the vessel, but will tend to pull them inside the vessel.
Thus, we can consider cosmic repulsion as a kind of complement to gravity, or as a phenomenon due to ordinary gravity inherent in an invisible gaseous medium that fills all space and has a negative pressure. There is no contradiction in the fact that, on the one hand, the negative pressure seems to suck inside the wall of the vessel, and, on the other hand, this hypothetical environment repels galaxies, rather than attracts them. After all, repulsion is caused by the gravity of the environment, and not by any mechanical action. Anyway, mechanical forces are created not by the pressure itself, but by the pressure difference, but it is assumed that the hypothetical medium fills the entire space. It cannot be limited the walls of the vessel, and an observer in this environment would not perceive it as a tangible substance at all. The space would look and feel completely empty.
Despite such amazing features of the hypothetical environment, Einstein at one time declared that he had built a satisfactory model of the Universe, in which a balance is maintained between gravitational attraction and the cosmic repulsion he discovered. Using simple calculations, Einstein estimated the magnitude of the cosmic repulsion force required to balance gravity in the Universe. He was able to confirm that the repulsion must be so small within the Solar System (and even on the Galaxy scale) that it cannot be detected experimentally. For a time, it seemed that the age-old mystery had been brilliantly solved.
However, then the situation changed for the worse. First of all, the problem of equilibrium stability arose. Einstein's basic idea was based on a strict balance of attractive and repulsive forces. But, as in many cases of strict balance, subtle details also emerged. If, for example, Einstein's static universe were to expand a little, then the gravitational attraction (weakening with distance) would decrease slightly, while the force of cosmic repulsion (increasing with distance) would increase slightly. This would lead to an imbalance in favor of repulsive forces, which would cause further unlimited expansion of the Universe under the influence of all-conquering repulsion. If, on the contrary, Einstein's static universe were to shrink slightly, the gravitational force would increase and the force of cosmic repulsion would decrease, which would lead to an imbalance in favor of the forces of attraction and, as a consequence, to an ever faster compression, and ultimately to the collapse that Einstein thought he had avoided. Thus, at the slightest deviation, the strict balance would be disrupted, and a cosmic catastrophe would be inevitable.
Later, in 1927, Hubble discovered the phenomenon of the recession of galaxies (i.e., the expansion of the Universe), which made the problem of equilibrium meaningless. It became clear that the Universe is not in danger of compression and collapse, since it is expanding. If Einstein had not been distracted by the search for the force of cosmic repulsion, he would certainly have come to this conclusion theoretically, thus predicting the expansion of the Universe a good ten years earlier than astronomers managed to discover it. Such a prediction would undoubtedly go down in the history of science as one of the most outstanding (such a prediction was made on the basis of Einstein’s equation in 1922-1923 by Petrograd University professor A. A. Friedman). In the end, Einstein had to angrily renounce cosmic repulsion, which he later considered “the biggest mistake of his life.” However, this is not the end of the story.
Einstein invented cosmic repulsion to solve the non-existent problem of a static universe. But, as always happens, once the genie is out of the bottle, it is impossible to put it back. The idea that the dynamics of the Universe may be due to the confrontation between the forces of attraction and repulsion continued to live. And although astronomical observations did not provide any evidence of the existence of cosmic repulsion, they could not prove its absence - it could simply be too weak to manifest itself.
Although Einstein's gravitational field equations allow for the presence of a repulsive force, they do not impose restrictions on its magnitude. Taught by bitter experience, Einstein had the right to postulate that the magnitude of this force is strictly equal to zero, thereby completely eliminating repulsion. However, this was by no means necessary. Some scientists found it necessary to retain repulsion in the equations, although this was no longer necessary from the point of view of the original problem. These scientists believed that, in the absence of proper evidence, there was no reason to believe that the repulsive force was zero.
It was not difficult to trace the consequences of maintaining the repulsive force in the scenario of an expanding Universe. On early stages development, when the Universe is still in a compressed state, repulsion can be neglected. During this phase, gravitational attraction slowed the rate of expansion - in complete analogy with the way the Earth's gravity slows down the movement of a rocket launched vertically upward. If we accept without explanation that the evolution of the Universe began with rapid expansion, then gravity should constantly reduce the expansion rate to the value observed at present. Over time, as matter dissipates gravitational interaction weakens. Instead, cosmic repulsion increases as galaxies continue to move away from each other. Ultimately, repulsion will overcome gravitational attraction and the expansion rate of the Universe will begin to increase again. From this we can conclude that cosmic repulsion dominates in the Universe, and expansion will continue forever.
Astronomers have shown that this unusual behavior of the Universe, when the expansion first slows down and then accelerates again, should be reflected in the observed movement of galaxies. But the most careful astronomical observations have failed to reveal any convincing evidence of such behavior, although contrary statements are made from time to time.
It is interesting that the idea of an expanding Universe was put forward by the Dutch astronomer Wilem de Sitter back in 1916 - many years before Hubble experimentally discovered this phenomenon. De Sitter argued that if ordinary matter is removed from the Universe, then gravitational attraction will disappear, and repulsive forces will reign supreme in space. This would cause the expansion of the Universe - at that time this was an innovative idea.
Since the observer is unable to perceive the strange invisible gaseous medium with negative pressure, it will simply appear to him as if empty space is expanding. The expansion could be detected by hanging test bodies in different places and observing their distance from each other. The idea of expanding empty space was considered a curiosity at the time, although, as we will see, it turned out to be prophetic.
So, what conclusion can be drawn from this story? The fact that astronomers do not detect cosmic repulsion cannot yet serve as logical proof of its absence in nature. It is quite possible that it is simply too weak to be detected by modern instruments. The accuracy of observation is always limited, and therefore only the upper limit of this power can be estimated. It could be argued against this that, from an aesthetic point of view, the laws of nature would look simpler in the absence of cosmic repulsion. Such discussions dragged on for many years without leading to any definite results, until suddenly the problem was looked at from a completely new angle, which gave it unexpected relevance.
Inflation: The Big Bang Explained
In previous sections we said that if the force of cosmic repulsion exists, then it must be very weak, so weak that it would not have any significant effect on the Big Bang. However, this conclusion is based on the assumption that the magnitude of the repulsion does not change with time. In Einstein's time, this opinion was shared by all scientists, since cosmic repulsion was introduced into the theory “man-made.” It never occurred to anyone that cosmic repulsion could be called upon other physical processes that arise as the Universe expands. If such a possibility had been provided, then cosmology could have turned out to be different. In particular, a scenario for the evolution of the Universe is not excluded, which assumes that in the extreme conditions of the early stages of evolution, cosmic repulsion prevailed over gravity for a moment, causing the Universe to explode, after which its role was practically reduced to zero.
This general picture emerges from latest works to study the behavior of matter and forces at very early stages of the development of the Universe. It became clear that the gigantic cosmic repulsion was the inevitable result of the action of the Superpower. So, the “antigravity” that Einstein sent out the door came back through the window!
The key to understanding the new discovery of cosmic repulsion comes from the nature of the quantum vacuum. We have seen how such repulsion can be caused by an unusual invisible medium, indistinguishable from empty space, but possessing negative pressure. Today, physicists believe that the quantum vacuum has precisely these properties.
In Chapter 7 it was noted that the vacuum should be considered as a kind of “enzyme” of quantum activity, teeming with virtual particles and saturated with complex interactions. It is very important to understand that within quantum description vacuum plays a decisive role. What we call particles are just rare disturbances, like “bubbles” on the surface of a whole sea of activity.
At the end of the 70s, it became obvious that the unification of the four interactions requires a complete revision of ideas about the physical nature of the vacuum. The theory suggests that vacuum energy is not manifested unambiguously. Simply put, a vacuum can be excited and be in one of many states with widely varying energies, just as an atom can be excited to move to higher energy levels. These eigenstates vacuum - if we could observe them - would look exactly the same, although they have completely different properties.
First of all, the energy contained in a vacuum flows in huge quantities from one state to another. In theories Great Unification For example, the difference between the lowest and highest vacuum energies is unimaginably large. To get some idea of the gigantic scale of these quantities, let us estimate the energy released by the Sun over the entire period of its existence (about 5 billion years). Let's imagine that all this colossal amount of energy emitted by the Sun is contained in a region of space smaller in size than the Solar System. The energy densities achieved in this case are close to the energy densities corresponding to the state of vacuum in the TVO.
Along with tremendous energy differences, the various vacuum states correspond to equally gigantic pressure differences. But here lies the “trick”: all these pressures - negative. The quantum vacuum behaves exactly like the previously mentioned hypothetical medium that creates cosmic repulsion, only this time numerical values the pressures are so great that the repulsion is 10^120 times greater than the force that Einstein needed to maintain equilibrium in a static Universe.
The way is now open to explain the Big Bang. Let us assume that at the beginning the Universe was in an excited state of vacuum, which is called a “false” vacuum. In this state, there was a cosmic repulsion in the Universe of such magnitude that it would cause an uncontrolled and rapid expansion of the Universe. Essentially, in this phase the Universe would correspond to the de Sitter model discussed in the previous section. The difference, however, is that for de Sitter the Universe is quietly expanding on astronomical time scales, whereas the “de Sitter phase” in the evolution of the Universe from the “false” quantum vacuum is in reality far from quiet. The volume of space occupied by the Universe should in this case double every 10^-34 s (or a time interval of the same order).
Such superexpansion of the Universe has a number of characteristic features: all distances increase with exponential law(we have already encountered the concept of exponent in Chapter 4). This means that every 10^-34 s all regions of the Universe double their size, and then this doubling process continues in geometric progression. This type of expansion, first considered in 1980. Alan Guth of MIT (Mass. Institute of Technology, USA), was called by him “inflation”. As a result of the extremely rapid and continuously accelerating expansion, it would very soon turn out that all parts of the Universe would fly apart, as if in an explosion. And this is the Big Bang!
However, one way or another, the inflation phase must end. As in all excited quantum systems, the “false” vacuum is unstable and tends to decay. When decay occurs, repulsion disappears. This in turn leads to the cessation of inflation and the transition of the Universe to the power of ordinary gravitational attraction. Of course, the Universe would continue to expand in this case thanks to the initial impulse acquired during the period of inflation, but the expansion rate would steadily decrease. Thus, the only trace that has survived to this day from cosmic repulsion is a gradual slowdown in the expansion of the Universe.
According to the "inflationary scenario", the Universe began its existence from a state of vacuum, devoid of matter and radiation. But even if they were present initially, their traces would quickly be lost due to the enormous expansion rate during the inflation phase. In the extremely short period of time corresponding to this phase, the region of space that today occupies the entire observable Universe has grown from a billionth of the size of a proton to several centimeters. The density of any substance that originally existed would effectively become zero.
So, by the end of the inflation phase, the Universe was empty and cold. However, when inflation dried up, the Universe suddenly became extremely “hot.” This burst of heat that illuminated space is due to the enormous reserves of energy contained in the “false” vacuum. When the vacuum state decayed, its energy was released in the form of radiation, which instantly heated the Universe to approximately 10^27 K, which is sufficient for the processes in the GUT to occur. From that moment on, the Universe developed according to the standard theory of the “hot” Big Bang. Thanks to thermal energy, matter and antimatter arose, then the Universe began to cool, and gradually all its elements observed today began to “freeze out.”
So the hard problem is what caused the Big Bang? - managed to solve using the theory of inflation; empty space spontaneously exploded under the influence of repulsion inherent in a quantum vacuum. However, the mystery still remains. The colossal energy of the primary explosion, which went into the formation of matter and radiation existing in the Universe, had to come from somewhere! We cannot explain the existence of the Universe until we find the source of primary energy.
Space bootstrap
English bootstrap literally means “lacing”, figuratively - self-consistency, the absence of hierarchy in the system of elementary particles.
The universe was born in the process of a gigantic release of energy. We still detect traces of it - this is background thermal radiation and cosmic matter (in particular, the atoms that make up stars and planets), storing a certain energy in the form of “mass”. Traces of this energy also appear in the retreat of galaxies and in the violent activity of astronomical objects. Primary energy “started the spring” of the nascent Universe and continues to power it to this day.
Where did this energy come from that breathed life into our Universe? According to the theory of inflation, this is the energy of empty space, otherwise known as the quantum vacuum. However, can such an answer fully satisfy us? It is natural to ask how the vacuum acquired energy.
In general, when we ask the question of where energy comes from, we are essentially making an important assumption about the nature of that energy. One of the fundamental laws of physics is law of conservation of energy, according to which different forms of energy can change and transform into one another, but the total amount of energy remains unchanged.
It is not difficult to give examples in which the effect of this law can be verified. Suppose we have an engine and a supply of fuel, and the engine is used as a drive for an electric generator, which in turn supplies electricity to the heater. When fuel burns, the chemical energy stored in it is converted into mechanical energy, then into electrical energy, and finally into thermal energy. Or suppose that a motor is used to lift a load to the top of a tower, after which the load falls freely; upon impact with the ground, exactly the same amount of thermal energy is generated as in the example with the heater. The fact is that, no matter how energy is transmitted or how its form changes, it obviously cannot be created or destroyed. Engineers use this law in everyday practice.
If energy can neither be created nor destroyed, then how does primary energy arise? Isn't it simply injected at the first moment (a kind of new initial condition assumed ad hoc)? If so, then why does the Universe contain this and not some other amount of energy? There is about 10^68 J (joules) of energy in the observable Universe - why not, say, 10^99 or 10^10000 or any other number?
Inflation theory offers one possible scientific explanation for this mystery. According to this theory. The Universe at the beginning had virtually zero energy, and in the first 10^32 seconds it managed to bring to life the entire gigantic amount of energy. The key to understanding this miracle is to be found in wonderful fact that the law of conservation of energy in the usual sense not applicable to the expanding Universe.
Essentially, we have already encountered a similar fact. Cosmological expansion leads to a decrease in the temperature of the Universe: accordingly, the energy of thermal radiation, so large in the primary phase, is depleted and the temperature drops to values close to absolute zero. Where did all this go? thermal energy? In a sense, it was used up by the universe to expand and provided pressure to supplement the force of the Big Bang. When an ordinary liquid expands, its outward pressure does work using the energy of the liquid. When an ordinary gas expands, it internal energy is spent on doing work. IN complete opposite In this regard, cosmic repulsion is similar to the behavior of a medium with negative pressure. When such a medium expands, its energy does not decrease, but increases. This is exactly what happened during the period of inflation, when cosmic repulsion caused the Universe to expand at an accelerated rate. Throughout this period, the total energy of the vacuum continued to increase until, at the end of the period of inflation, it reached an enormous value. Once the period of inflation ended, all the stored energy was released in one giant burst, generating heat and matter on the full scale of the Big Bang. From this moment on, the usual expansion with positive pressure began, so that the energy began to decrease again.
The emergence of primary energy is marked by some kind of magic. A vacuum with mysterious negative pressure is apparently endowed with absolutely incredible capabilities. On the one hand, it creates a gigantic repulsive force, ensuring its ever-accelerating expansion, and on the other, the expansion itself forces an increase in the energy of the vacuum. The vacuum essentially feeds itself with energy in huge quantities. It contains an internal instability that ensures continuous expansion and unlimited energy production. And only the quantum decay of the false vacuum puts a limit to this “cosmic extravagance.”
Vacuum serves as a magical, bottomless jug of energy in nature. In principle, there is no limit to the amount of energy that could be released during inflationary expansion. This statement marks a revolution in traditional thinking with its centuries-old “out of nothing nothing is born” (this saying dates back at least to the era of the Parmenides, i.e. 5th century BC). Until recently, the idea of the possibility of “creation” from nothing was entirely within the purview of religions. In particular, Christians have long believed that God created the world from Nothing, but the idea of the possibility of spontaneous emergence of all matter and energy as a result of purely physical processes was considered absolutely unacceptable by scientists a dozen years ago.
Those who cannot internally come to terms with the whole concept of the emergence of “something” from “nothing” have the opportunity to take a different look at the emergence of energy during the expansion of the Universe. Since ordinary gravity is attractive, in order to move parts of matter away from each other, work must be done to overcome the gravity acting between these parts. This means that the gravitational energy of the system of bodies is negative; When new bodies are added to the system, energy is released, and as a result, gravitational energy becomes “even more negative.” If we apply this reasoning to the Universe at the stage of inflation, then it is the appearance of heat and matter that “compensates” for the negative gravitational energy of the formed masses. In this case, the total energy of the Universe as a whole is zero and no new energy arises at all! Such a view of the process of “creation of the world” is, of course, attractive, but it still should not be taken too seriously, since in general the status of the concept of energy in relation to gravity turns out to be dubious.
Everything said here about the vacuum is very reminiscent of the story beloved by physicists about a boy who, having fallen into a swamp, pulled himself out by his own shoelaces. The self-creating Universe is reminiscent of this boy - it also pulls itself up by its own “laces” (this process is referred to as “bootstrap”). Indeed, due to its own physical nature, the Universe excites in itself all the energy necessary for the “creation” and “revitalization” of matter, and also initiates the explosion that generates it. This is the cosmic bootstrap; We owe our existence to his amazing power.
Advances in inflation theory
After Guth put forward the seminal idea that the Universe underwent an early period of extremely rapid expansion, it became clear that such a scenario could nicely explain many features of Big Bang cosmology that had previously been taken for granted.
In one of the previous sections we encountered paradoxes very high degree organization and coordination of the primary explosion. One of wonderful examples This is due to the force of the explosion, which turned out to be precisely “adjusted” to the magnitude of the gravity of space, as a result of which the expansion rate of the Universe in our time is very close to the boundary value separating compression (collapse) and rapid expansion. Decisive test The inflationary scenario is precisely whether it involves a Big Bang of such a precisely defined magnitude. It turns out that due to exponential expansion in the inflation phase (which is its most characteristic property) the force of the explosion automatically strictly ensures the ability of the Universe to overcome its own gravity. Inflation can lead to exactly the rate of expansion that is actually observed.
Another " great mystery"is associated with the homogeneity of the Universe on large scales. It is also immediately solved based on the theory of inflation. Any initial inhomogeneities in the structure of the Universe should be completely erased with a tremendous increase in its size, just like the folds on a deflated hot air balloon smooth out when inflated. And as a result of an increase in the size of spatial regions by approximately 10^50 times, any initial disturbance becomes insignificant.
However, it would be wrong to talk about full homogeneity. To make it possible to appear modern galaxies and galaxy clusters, the structure of the early Universe must have had some “clumpiness”. Initially, astronomers hoped that the existence of galaxies could be explained by the accumulation of matter under the influence of gravitational attraction after the Big Bang. The cloud of gas should be compressed under the influence of its own gravity, and then break up into smaller fragments, and those, in turn, into even smaller ones, etc. Perhaps the distribution of gas resulting from the Big Bang was completely uniform, but due to purely random processes, condensations and rarefactions arose here and there. Gravity further intensified these fluctuations, leading to the growth of areas of condensation and their absorption of additional matter. Then these regions were compressed and successively disintegrated, and the smallest condensations turned into stars. Eventually, a hierarchy of structures arose: stars were united into groups, those into galaxies, and then into clusters of galaxies.
Unfortunately, if there were no inhomogeneities in the gas from the very beginning, then such a mechanism for the formation of galaxies would have worked in a time significantly exceeding the age of the Universe. The fact is that the processes of thickening and fragmentation competed with expansion of the Universe, which was accompanied by gas dispersion. In the original version of the Big Bang theory, it was assumed that the “seeds” of galaxies existed initially in the structure of the Universe at its origin. Moreover, these initial inhomogeneities had to have very specific sizes: not too small, otherwise they would never have formed, but not too large, otherwise areas of high density would simply collapse, turning into huge black holes. At the same time, it is completely unclear why galaxies have exactly such sizes or why exactly such a number of galaxies are included in the cluster.
The inflationary scenario provides a more consistent explanation of galactic structure. The basic idea is quite simple. Inflation is due to the fact that the quantum state of the Universe is an unstable state of a false vacuum. Eventually, this vacuum state breaks down and its excess energy is converted into heat and matter. At this moment, the cosmic repulsion disappears - and inflation stops. However, the decay of the false vacuum does not occur strictly simultaneously throughout all space. As in any quantum processes, the decay rates of the false vacuum fluctuate. In some areas of the Universe, decay occurs somewhat faster than in others. In these areas, inflation will end earlier. As a result, inhomogeneities are retained in the final state. It is possible that these heterogeneities could serve as “seeds” (centers) gravitational compression and, ultimately, led to the formation of galaxies and their clusters. Conducted mathematical modeling fluctuation mechanism, however, with very limited success. As a rule, the effect turns out to be too large, the calculated inhomogeneities are too significant. True, the models used were too crude and perhaps a more subtle approach would have been more successful. Although the theory is far from complete, it at least describes the nature of the mechanism that could lead to the formation of galaxies without the need for special initial conditions.
In Guth's version of the inflationary scenario, the false vacuum first turns into a "true" vacuum, or the lowest-energy vacuum state that we identify with empty space. The nature of this change is quite similar to a phase transition (for example, from gas to liquid). In this case, in a false vacuum there would be accidental education bubbles of true vacuum, which, expanding at the speed of light, would capture ever larger areas of space. In order for the false vacuum to exist long enough for inflation to do its “miraculous” work, these two states must be separated by an energy barrier through which “quantum tunneling” of the system must occur, similar to what happens with electrons (see chap.) . However, this model has one serious drawback: all the energy released from the false vacuum is concentrated in the walls of the bubbles and there is no mechanism for its redistribution throughout the bubble. As the bubbles collided and merged, the energy would eventually accumulate in the randomly mixed layers. As a result, the Universe would contain very strong inhomogeneities, and all the work of inflation to create large-scale homogeneity would fail.
With further improvement of the inflation scenario, these difficulties were overcome. IN new theory there is no tunneling between two vacuum states; instead, the parameters are chosen so that the decay of the false vacuum occurs very slowly and thus gives the Universe sufficient time to inflate. When the decay is completed, the energy of the false vacuum is released in the entire volume of the “bubble,” which quickly heats up to 10^27 K. It is assumed that the entire observable Universe is contained in one such bubble. Thus, on ultra-large scales the Universe may be extremely irregular, but the region accessible to our observation (and even much larger parts of the Universe) lies within a completely homogeneous zone.
It is curious that Guth initially developed his inflationary theory to solve a completely different cosmological problem - the absence of magnetic monopoles in nature. As shown in Chapter 9, the standard Big Bang theory predicts that in the primary phase of the evolution of the Universe, monopoles should arise in abundance. They are possibly accompanied by their one- and two-dimensional counterparts - strange objects that have a "string" and "sheet" character. The problem was to rid the Universe of these "undesirable" objects. Inflation automatically solves the problem of monopoles and other similar problems, since the gigantic expansion of space effectively reduces their density to zero.
Although the inflationary scenario has only been partially developed and is only plausible, nothing more, it has allowed us to formulate a number of ideas that promise to irrevocably change the face of cosmology. Now we can not only offer an explanation for the cause of the Big Bang, but we also begin to understand why it was so “big” and why it took on such a character. We can now begin to address the question of how the large-scale homogeneity of the Universe arose, and along with it, the observed inhomogeneities of a smaller scale (for example, galaxies). The primary explosion, in which what we call the Universe arose, has henceforth ceased to be a mystery that lies beyond the boundaries of physical science.
A universe creating itself
And yet, despite the enormous success inflation theory in explaining the origin of the universe, the mystery remains. How did the Universe initially end up in a state of false vacuum? What happened before inflation?
A consistent, completely satisfactory scientific description of the origin of the Universe must explain how space itself (more precisely, space-time) arose, which then underwent inflation. Some scientists are ready to admit that space always exists, others believe that this issue generally goes beyond the scope of the scientific approach. And only a few claim more and are convinced that it is quite legitimate to raise the question of how space in general (and a false vacuum, in particular) could arise literally from “nothing” as a result of physical processes that, in principle, can be studied.
As noted, we have only recently challenged the persistent belief that “nothing comes from nothing.” The cosmic bootstrap is close to the theological concept of the creation of the world from nothing (ex nihilo). Without a doubt, in the world around us, the existence of some objects is usually due to the presence of other objects. Thus, the Earth arose from the protosolar nebula, which in turn - from galactic gases, etc. If we happened to see an object suddenly appearing “out of nothing,” we would probably perceive it as a miracle; for example, we would be amazed if in a locked, empty safe we suddenly discovered a mass of coins, knives or sweets. In everyday life, we are accustomed to recognizing that everything comes from somewhere or from something.
However, everything is not so obvious when it comes to less specific things. What, for example, does a painting come from? Of course, this requires a brush, paints and canvas, but these are just tools. The manner in which the picture is painted - the choice of shape, color, texture, composition - is not born with brushes and paints. This is the result creative imagination artist.
Where do thoughts and ideas come from? Thoughts, without a doubt, really exist and, apparently, always require the participation of the brain. But the brain only ensures the implementation of thoughts, and is not their cause. The brain itself generates thoughts no more than, for example, a computer generates calculations. Thoughts can be caused by other thoughts, but this does not reveal the nature of the thought itself. Some thoughts may be born by sensations; Memory also gives birth to thoughts. Most artists, however, view their work as the result unexpected inspiration. If this is indeed the case, then the creation of a painting - or at least the birth of its idea - is precisely an example of the birth of something from nothing.
And yet, can we consider that physical objects and even the Universe as a whole arise from nothing? This bold hypothesis is being discussed quite seriously, for example, in scientific institutions on the east coast of the United States, where quite a few theoretical physicists and cosmology specialists are developing a mathematical apparatus that would help clarify the possibility of the birth of something from nothing. This select circle includes Alan Guth of MIT, Sydney Coleman of Harvard University, Alex Vilenkin from Tufts University, Ed Taillon and Heinz Pagels from New York. They all believe that in one sense or another “nothing is unstable” and that the physical universe spontaneously “bloomed out of nothing,” governed only by the laws of physics. “Such ideas are purely speculative,” admits Guth, “but at some level they may be correct... Sometimes they say that there is no free lunch, but the Universe, apparently, is just such a “free lunch”.
In all of these hypotheses, quantum behavior plays a key role. As we discussed in Chapter 2, the main feature of quantum behavior is the loss of strict cause-and-effect relationships. In classical physics, the presentation of mechanics followed strict adherence to causality. All details of the movement of each particle were strictly predetermined by the laws of motion. It was believed that movement was continuous and strictly defined current forces. Laws of motion in literally embodied the relationship between cause and effect. The universe was viewed as a giant clockwork mechanism, the behavior of which is strictly regulated by what is happening at the moment. It was the belief in such comprehensive and absolutely strict causality that prompted Pierre Laplace to argue that a super-powerful calculator could, in principle, predict, based on the laws of mechanics, both the history and fate of the Universe. According to this view, the universe is doomed to follow its prescribed path forever.
Quantum physics has destroyed the methodical but sterile Laplacean scheme. Physicists have become convinced that at the atomic level, matter and its movement are uncertain and unpredictable. Particles can behave "crazyly", as if resisting strictly prescribed movements, suddenly appearing in the most unexpected places for no apparent reason, and sometimes appearing and disappearing “without warning”.
The quantum world is not completely free from causality, but it manifests itself rather hesitantly and ambiguously. For example, if one atom is in an excited state as a result of a collision with another atom, it typically quickly returns to its lowest energy state, emitting a photon. The appearance of a photon is, of course, a consequence of the fact that the atom has previously passed into an excited state. We can say with confidence that it was the excitation that led to the creation of the photon, and in this sense the relationship of cause and effect remains. However, the actual moment at which a photon appears is unpredictable: an atom can emit it at any moment. Physicists are able to calculate the probable, or average, time of occurrence of a photon, but in each specific case it is impossible to predict the moment when this event will occur. Apparently for characterization similar situation It is best to say that the excitation of an atom does not so much lead to the appearance of a photon as “push” it towards this.
Thus, the quantum microworld is not entangled in a dense web of causal relationships, but still “listens” to numerous unobtrusive commands and suggestions. In the old Newtonian scheme, the force seemed to address the object with the unchallenged command: “Move!” In quantum physics, the relationship between force and object is one of invitation rather than command.
Why do we generally consider the idea of the sudden birth of an object “out of nothing” so unacceptable? What makes us think about miracles and supernatural phenomena? Perhaps the whole point is only in the unusualness of such events: in everyday life we never encounter the appearance of objects for no reason. When, for example, a magician pulls a rabbit out of a hat, we know that we are being fooled.
Suppose we actually live in a world where objects appear from time to time apparently “out of nowhere”, for no reason and in a completely unpredictable way. Having become accustomed to such phenomena, we would cease to be surprised by them. Spontaneous birth would be perceived as one of nature's quirks. Perhaps in such a world we would no longer have to strain our credulity to imagine the sudden emergence of the entire physical Universe from nothing.
This imaginary world is essentially not so different from the real one. If we could directly perceive the behavior of atoms with the help of our senses (and not through the mediation of special instruments), we would often have to observe objects appearing and disappearing without clearly defined causes.
The phenomenon closest to “birth from nothing” occurs in a sufficiently strong electric field. At a critical value of the field strength, electrons and positrons begin to appear “out of nothing” completely randomly. Calculations show that near the surface of the uranium nucleus the electric field strength is quite close to the limit beyond which this effect occurs. If there were atomic nuclei containing 200 protons (there are 92 in the uranium nucleus), then spontaneous creation of electrons and positrons would occur. Unfortunately, a kernel with such a large number protons apparently becomes extremely unstable, but there is no complete certainty about this.
The spontaneous creation of electrons and positrons in a strong electric field can be considered as a special type of radioactivity when the decay occurs in empty space, a vacuum. We have already talked about the transition of one vacuum state to another as a result of decay. In this case, the vacuum breaks down into a state in which particles are present.
Although the decay of space caused electric field, is difficult to comprehend; a similar process under the influence of gravity could well occur in nature. Near the surface of black holes, gravity is so strong that the vacuum is teeming with constantly being born particles. This is the famous radiation from black holes, discovered by Stephen Hawking. Ultimately, it is gravity that is responsible for the birth of this radiation, but it cannot be said that this happens “in the old Newtonian sense”: it cannot be said that any particular particle should appear in a certain place at one time or another as a result of the action of gravitational forces . In any case, since gravity is just a curvature of space-time, we can say that space-time causes the birth of matter.
The spontaneous emergence of matter from empty space is often spoken of as birth “out of nothing,” which is similar in spirit to birth ex nihilo in Christian doctrine. However, for a physicist, empty space is not “nothing” at all, but a very significant part of the physical Universe. If we still want to answer the question of how the Universe came into being, then it is not enough to assume that empty space existed from the very beginning. It is necessary to explain where this space came from. Thought of birth space itself It may seem strange, but in a sense this happens all around us all the time. The expansion of the Universe is nothing more than the continuous “swelling” of space. Every day the area of the Universe accessible to our telescopes increases by 10^18 cubic light years. Where does this space come from? The analogy of rubber is useful here. If the elastic rubber band is pulled out, it “becomes larger.” Space resembles superelastic in that, as far as we know, it can stretch indefinitely without breaking.
The stretching and curvature of space resemble the deformation of an elastic body in that the “movement” of space occurs according to the laws of mechanics in exactly the same way as the movement of ordinary matter. In this case, these are the laws of gravity. Quantum theory is equally applicable to matter, space and time. In previous chapters we said that quantum gravity is seen as a necessary step in the search for the Superpower. This raises an interesting possibility; if, according to quantum theory, particles of matter can arise “out of nothing,” then in relation to gravity, won’t it describe the emergence “out of nothing” of space? If this happens, then isn't the birth of the Universe 18 billion years ago an example of just such a process?
Free lunch?
main idea quantum cosmology consists in applying quantum theory to the Universe as a whole: to space-time and matter; Theorists take this idea especially seriously. At first glance, there is a contradiction here: quantum physics deals with the smallest systems, while cosmology deals with the largest. However, the Universe was once also limited to very small dimensions and, therefore, quantum effects were extremely important then. The calculation results indicate that quantum laws should be taken into account in the GUT era (10^-32 s), and in the Planck era (10^-43 s) they should probably play a decisive role. According to some theorists (for example, Vilenkin), between these two eras there was a moment in time when the Universe arose. According to Sidney Coleman, we have made a quantum leap from Nothing to Time. Apparently, space-time is a relic of this era. The quantum leap Coleman talks about can be thought of as a kind of “tunnel process.” We noted that in the original version of the inflation theory, the state of the false vacuum was supposed to tunnel through the energy barrier into the state of the true vacuum. However, in the case of the spontaneous emergence of the quantum Universe “out of nothing,” our intuition reaches the limit of its capabilities. One end of the tunnel represents the physical Universe in space and time, which gets there by quantum tunneling"out of nothing." Therefore, the other end of the tunnel represents this very Nothing! Perhaps it would be better to say that the tunnel has only one end, and the other simply “does not exist.”
The main difficulty of these attempts to explain the origin of the Universe is to describe the process of its birth from a state of false vacuum. If the newly created space-time were in a state of true vacuum, then inflation could never occur. The Big Bang would be reduced to a weak burst, and space-time would cease to exist a moment later again - it would be destroyed by the very quantum processes due to which it originally arose. If the Universe had not found itself in a state of false vacuum, it would never have been involved in the cosmic bootstrap and would not have materialized its illusory existence. Perhaps the state of a false vacuum is preferable due to its characteristic extreme conditions. For example, if the Universe arose with a sufficiently high initial temperature and then cooled, then it could even “run aground” in a false vacuum, but so far many technical questions of this type remain unresolved.
But whatever the actual situation with these fundamental problems, the Universe must one way or another way to arise, and quantum physics is the only branch of science in which it makes sense to talk about an event occurring without an apparent cause. If we are talking about space-time, then in any case it makes no sense to talk about causality in the usual sense. Typically, the concept of causality is closely related to the concept of time, and therefore any considerations about the processes of the emergence of time or its “emergence from non-existence” must be based on a broader concept of causality.
If space is truly ten-dimensional, then the theory considers all ten dimensions to be quite equal in the very early stages. It is attractive to be able to connect the phenomenon of inflation with the spontaneous compactification (folding) of seven of the ten dimensions. According to this scenario, the “driving force” of inflation is a by-product of interactions manifested through additional dimensions space. Further, ten-dimensional space could naturally evolve in such a way that during inflation, three spatial dimensions greatly expand at the expense of the seven others, which, on the contrary, shrink, becoming invisible? Thus, the quantum microbubble of ten-dimensional space is compressed, and three dimensions are thereby inflated, forming the Universe: the remaining seven dimensions remain captive in the microcosm, from where they manifest themselves only indirectly - in the form of interactions. This theory seems very attractive.
Although theorists still have a lot of work to do to study the nature of the very early Universe, it is already possible to give a general outline of the events that resulted in the Universe taking on the shape we see today. At the very beginning, the Universe spontaneously arose “out of nothing.” Thanks to the ability quantum energy Serving as a kind of enzyme, bubbles of empty space could inflate at an ever-increasing speed, creating colossal reserves of energy thanks to the bootstrap. This false vacuum, filled with self-generated energy, turned out to be unstable and began to disintegrate, releasing energy in the form of heat, so that each bubble was filled with fire-breathing matter (fireball). The inflation of bubbles stopped, but the Big Bang began. On the “clock” of the Universe at that moment it was 10^-32 s.
From such a fireball all matter and all physical objects arose. As the cosmic material cooled, it experienced successive phase transitions. With each transition, more and more different structures were “frozen out” from the primary formless material. One after another, interactions were separated from each other. Step by step the objects we now call subatomic particles, acquired the features inherent in them today. As the composition of the “cosmic soup” became more and more complex, large-scale irregularities left over from the times of inflation grew into galaxies. In the process of further formation of structures and separation of various types of matter, the Universe increasingly acquired familiar forms; the hot plasma condensed into atoms, forming stars, planets, and ultimately life. This is how the Universe “realized” itself.
Matter, energy, space, time, interactions, fields, order and structure - All these concepts, borrowed from the “creator’s price list,” serve as integral characteristics of the Universe. New physics opens up the tantalizing possibility of a scientific explanation for the origin of all these things. We no longer need to specifically enter them “manually” from the very beginning. We can see how all the fundamental properties of the physical world can come into being automatically as consequences of the laws of physics, without the need to assume the existence of highly specific initial conditions. The new cosmology claims that the initial state of the cosmos does not play any role, since all information about it was erased during inflation. The Universe we observe bears only the imprints of those physical processes that have occurred since the beginning of inflation.
For thousands of years, humanity has believed that “out of nothing nothing can be born.” Today we can say that everything came from nothing. There is no need to “pay” for the Universe - it is absolutely a “free lunch”.
The idea of the development of the Universe naturally led to the formulation of the problem of the beginning of the evolution (birth) of the Universe and its
end (death). Currently, there are several cosmological models that explain certain aspects of the emergence of matter in the Universe, but they do not explain the causes and process of the birth of the Universe itself. Of the entire set of modern cosmological theories, only the Big Bang theory of G. Gamow has been able to satisfactorily explain almost all the facts related to this problem to date. The main features of the Big Bang model have been preserved to this day, although they were later supplemented by the theory of inflation, or the theory of an inflating Universe, developed by the American scientists A. Guth and P. Steinhardt and supplemented by the Soviet physicist A.D. Linda.
In 1948, the outstanding American physicist of Russian origin G. Gamow proposed that the physical Universe was formed as a result of a gigantic explosion that occurred approximately 15 billion years ago. Then all the matter and all the energy of the Universe were concentrated in one tiny super-dense clump. If you believe mathematical calculations, then at the beginning of the expansion the radius of the Universe was completely equal to zero, and its density was equal to infinity. This initial state is called singularity - point volume with infinite density. The known laws of physics do not apply in a singularity. In this state, the concepts of space and time lose their meaning, so it makes no sense to ask where this point was. Also, modern science cannot say anything about the reasons for the appearance of this condition.
However, according to Heisenberg's uncertainty principle, matter cannot be compressed into one point, so it is believed that the Universe in its initial state had a certain density and size. According to some calculations, if all the matter of the observable Universe, which is estimated at approximately 10 61 g, is compressed to a density of 10 94 g/cm 3, then it will occupy a volume of about 10 -33 cm 3. In no way electron microscope it would be impossible to see her. For a long time, nothing could be said about the causes of the Big Bang and the transition of the Universe to expansion. But today some hypotheses have emerged that try to explain these processes. They underlie the inflationary model of the development of the Universe.
"Beginning" of the Universe
The main idea of the Big Bang concept is that the Universe in the early stages of its emergence had an unstable vacuum-like state with high density energy. This energy came from quantum radiation, i.e. as if out of nowhere. The fact is that in a physical vacuum there are no fixed
particles, fields and waves, but it is not a lifeless void. In a vacuum there are virtual particles that are born, have a fleeting existence and immediately disappear. Therefore, the vacuum “boils” with virtual particles and is saturated with complex interactions between them. Moreover, the energy contained in a vacuum is located, as it were, on its different floors, i.e. there is a phenomenon of differences in vacuum energy levels.
While the vacuum is in an equilibrium state, only virtual (ghost) particles exist in it, which borrow energy from the vacuum for a short period of time in order to be born, and quickly return the borrowed energy in order to disappear. When, for some reason, the vacuum at some initial point (singularity) became excited and left the state of equilibrium, then virtual particles began to capture energy without recoil and turned into real particles. Eventually, at a certain point in space, a huge number of real particles were formed, along with the energy associated with them. When the excited vacuum collapsed, gigantic radiation energy was released, and superforce compressed the particles into superdense matter. The extreme conditions of the “beginning”, when even space-time was deformed, suggest that the vacuum was also in special condition, which is called a “false” vacuum. It is characterized by extremely high density energy, which corresponds to an extremely high density of matter. In this state of matter, strong stresses and negative pressures can arise in it, equivalent to gravitational repulsion of such magnitude that it caused the uncontrolled and rapid expansion of the Universe - the Big Bang. This was the initial impetus, the “beginning” of our world.
From this moment the rapid expansion of the Universe begins, time and space arise. At this time, there is an uncontrollable inflation of “space bubbles”, the embryos of one or several universes, which may differ from each other in their fundamental constants and laws. One of them became the embryo of our Metagalaxy.
According to various estimates, the period of "inflation", which proceeds exponentially, takes an unimaginably short period of time - up to 10 - 33 s after the "start". It's called inflationary period. During this time, the size of the Universe increased 10 50 times, from a billionth the size of a proton to the size of a matchbox.
Towards the end of the inflation phase, the Universe was empty and cold, but when inflation dried up, the Universe suddenly became extremely "hot". This burst of heat that illuminated space is due to the enormous reserves of energy contained in the “false” vacuum. This state of vacuum is very unstable and tends to decay. When
the collapse is completed, the repulsion disappears, and inflation ends. And the energy, bound in the form of many real particles, was released in the form of radiation, instantly heating the Universe to 10 27 K. From that moment on, the Universe developed according to the standard theory of the “hot” Big Bang.
Early stage of the evolution of the Universe
Immediately after the Big Bang, the Universe was a plasma of elementary particles of all types and their antiparticles in a state of thermodynamic equilibrium at a temperature of 10 27 K, which freely transformed into each other. In this clot there were only gravitational and large (Great) interactions. Then the Universe began to expand, and at the same time its density and temperature decreased. The further evolution of the Universe occurred in stages and was accompanied, on the one hand, by differentiation, and on the other, by the complication of its structures. The stages of the evolution of the Universe differ in the characteristics of the interaction of elementary particles and are called eras. The most important changes took less than three minutes.
Hadron era lasted 10 -7 s. At this stage, the temperature drops to 10 13 K. At the same time, all four fundamental interactions appear, the free existence of quarks ceases, they merge into hadrons, the most important among which are protons and neutrons. Most significant event became a global violation of symmetry, which occurred in the first moments of the existence of our Universe. The number of particles turned out to be slightly greater than the number of antiparticles. The reasons for this asymmetry are still unknown. In the general plasma-like clump, for every billion pairs of particles and antiparticles, there was one more particle; it did not have enough pairs for annihilation. This determined the further emergence of the material Universe with galaxies, stars, planets and intelligent beings on some of them.
Lepton era lasted up to 1 s after the start. The temperature of the Universe dropped to 10 10 K. Its main elements were leptons, which participated in the mutual transformations of protons and neutrons. At the end of this era, matter became transparent to neutrinos, they stopped interacting with matter and have since survived to this day.
Radiation Era (Photon Era) lasted 1 million years. During this time, the temperature of the Universe decreased from 10 billion K to 3000 K. During this stage, the most important processes of primary nucleosynthesis for the further evolution of the Universe took place - the combination of protons and neutrons (there were about 8 times less of them).
higher than protons) into atomic nuclei. By the end of this process, the matter of the Universe consisted of 75% protons (hydrogen nuclei), about 25% were helium nuclei, hundredths of a percent were deuterium, lithium and other light elements, after which the Universe became transparent to photons, since the radiation was separated from substances and formed what in our era is called relict radiation.
Then, for almost 500 thousand years, no qualitative changes occurred - there was a slow cooling and expansion of the Universe. The Universe, while remaining homogeneous, became increasingly rarefied. When it cooled to 3000 K, the nuclei of hydrogen and helium atoms could already capture free electrons and transform into neutral hydrogen and helium atoms. As a result, a homogeneous Universe was formed, which was a mixture of three almost non-interacting substances: baryonic matter (hydrogen, helium and their isotopes), leptons (neutrinos and antineutrinos) and radiation (photons). By this time there were no longer high temperatures and high pressures. It seemed that in the future the Universe would undergo further expansion and cooling, the formation of a “lepton desert” - something like thermal death. But this did not happen; on the contrary, there was a leap that created the modern structural Universe, which, according to modern estimates, took from 1 to 3 billion years.
