How the Universe appeared: scientific approaches and versions. How did the universe come into existence? Theories and assumptions

Not many people living in modern society will be able to confidently talk about how the universe came into being. Few people today think about how it could turn into a huge colossal space that does not know definite and clear boundaries. Few people think about what can happen to the Universe in billions of years. Topics of this kind have always tormented the ancient minds of pundits, in the face of tireless researchers and philosophers who, in a fit of momentary insight, created their own masterpieces - interesting and very crazy theories regarding the history of the origin of the Universe .

Modern scientists have gone further in terms of scientific knowledge than their ancient predecessors. Many astronomers, physicists, and cosmologists along with them are convinced that the Universe could have appeared as a result of a large-scale explosion, which could not only become the ancestor of the main part of matter, but also become the basis for the formation of all the most important physical laws that determined the existence of the cosmos. This phenomenon is commonly referred to as the "Big Bang Theory".

The meaning of the theory

Its basics are extremely simple. The theory states the fact that modern matter and matter that existed in far, far away antiquity are identical to each other, since in essence they are one and the same object under study. All matter formed about 13.8 billion years ago. In those distant times, it existed in the form of a point, or a compactly formed abstract body in the form of a ball, which in turn had an infinite density and a certain temperature. This state scientists call it a "singularity". For unknown reasons, this very singularity suddenly began to rapidly expand into different sides, as a result of which the Universe appeared. This point of view is actually only a hypothesis, and one of the most common and popular today. It is accepted by science as an explanation regarding the origin of matter, basic physical laws, and the colossal structure of the universe itself. This is due to the fact that the Big Bang theory describes the reasons that influenced the expansion of the Universe, it also contains a huge number of other aspects and phenomena associated with unlimited space.

Excursion into history

The subject of the Big Bang has become relevant for science since the beginning of the last century. In 1912, an astronomer from the United States named Westo Slifer for some time made a series of observations of spiral galaxies (earlier taken for nebulae), during which the scientist was able to measure the Doppler redshift of these same galaxies. He came to the conclusion that the object of his research over a certain time interval is moving farther and farther away from the Milky Way. Science did not stand still for a long time, and already in 1922, the Soviet cosmologist and mathematician A. Fridman, relying on the works of Einstein , was able to derive his equations from the equations related to the theory of relativity. It was he who became the first scientist who was able to declare to the scientific community about the expansion of the Universe, expressing only one personal assumption.

Edwin Hubble in 1924 measured the distance from the Earth to the nearest spiral nebula, which proved that other galactic systems could be nearby. Carrying out his experiments with a powerful telescope, the scientist established the relationship formed between the distance of galaxies and the speed with which they moved away from each other.

The Church has always imposed on people the opinion that God created the world in almost a week, that is, in 6 days. This dogma of the Christian religion is actively supported to this day. However, not all church canons are convinced of this point of view.

Georges Lemaitre is considered to be the founding father of the concept of the Big Bang theory. He became the first person who raised before society the question of the origin of such a global boundless space as the Universe. He was engaged in the study of the primitive atom and its transformation of numerous fragments into celestial bodies - stars with galaxies. In 1927, the priest published his own arguments in a newspaper. When the great Einstein got acquainted with Lemaitre's thoughts, he noted that the priest had calculated absolutely everything correctly, but the master's knowledge of the holy father in the field of physics was not satisfied. The Big Bang theory was accepted only in 1933, when Einstein himself gave in under the pressure of the theses and facts of a scientific discovery, recognizing Lemaitre's version as one of the most convincing of all those he had ever encountered. Einstein himself worked on the mystery of the origin of the Universe. The scientist in 1931 wrote a manuscript in which he outlined his version of events, different from the version of Georges Lemaitre. The work of another eminent scientist, Alfred Hoyle, who worked independently of other famous researchers, was written in exactly the same direction in the 1940s.

Einstein was skeptical about one fact that had to be in the Big Bang theory, namely, the singularity of matter, in which it was before the explosion. He tried to express his own judgment regarding the infinite expansion of outer space. According to his beliefs, matter in the Universe arose from nowhere at all, it was needed to maintain cosmic density in conditions of constant expansion. According to Einstein, this process can be described using the theory of relativity, but later the scientist realized that he had made a mistake in his calculations and abandoned his discovery.

A similar theory was held by the world famous science fiction writer Edgar Allan Poe, who pondered the origin of the universe back in 1848. This man was not a physicist, therefore, all his thoughts did not carry any scientific value due to the fact that they were not fixed by any calculations. In addition, in those distant times, the necessary mathematical apparatus were not invented to allow calculating studies of this kind. Po could realize his idea only in literary work, which he did with great success, writing the poem "Eureka", which already talks about such a phenomenon as a black hole, and clearly explains Olbers' paradox. The science fiction writer himself called his literary creation a revelation that mankind had never even heard of before.
Olbers' paradox is an indirect confirmation of the Big Bang theory, it is as follows: if at night you raise your head and see some star (focusing on it with your close attention), then a mentally drawn line that originates on the earth on this very star and will end. Poe in his "Eureka" wrote about a primeval particle, which, according to him, was completely unique and individual. His literary work was subjected to severe criticism, the poem was literally blown to smithereens, it turned out to be an unsuccessful work from an artistic point of view. Modern scientists, on the contrary, are thrown into confusion, they still cannot understand how a person who does not have a scientific education could predict such facts. According to them, Edgar Allan Poe with his book was far ahead of official scientific knowledge. The discoveries of physicists and astronomers of the 20s and 30s of the last century excited the scientific world, since most scientists adhered to the view that the Universe is in a stationary position.

Already after the end of the Second World War in the society of scientists, they again began to talk about the Big Bang theory and reflect on its conceptuality. It is this version of the origin of the Universe that has been gaining momentum in popularity every year, leaving behind other variations that from time to time were offered by tireless space explorers and objects belonging to it.

Time passed, and the theory of the Big Bang increasingly firmly occupied its niche on the scientific Olympus, while the stationarity of the Universe began to be questioned altogether. In 1965, the relic radiation was discovered: a discovery of this kind, which became fundamental, finally strengthened the Big Bang, and the birth of the Universe associated with it in science. From the 60s to the 90s of the XX century, a huge number of cosmologists and astronomers carried out a whole series of research works related to the famous theory, as a result of which they discovered many problems of a theoretical nature and, accordingly, their solutions, which related to the subject of the emergence of a huge Universe from one point .
The fact that the singularity is an undeniable initial state of general relativity, as well as the cosmological state of the explosion itself, was expressed by the world-famous physicist, whose name everyone knows today, Stephen Hawking. 1981 was marked by the emergence of a theory describing the period of rapid expansion of outer space: it, in turn, allowed to solve a huge number of problematic issues, to which no one could give a specific answer before.

By the end of the 20th century, many scientists had a genuine interest, accompanied by curiosity, in such an object of study as dark energy. It has been considered as a key to unlocking the importance of many cosmological problems. Scientists were interested in why the Universe loses weight, and also why dark energy also loses its mass. A hypothesis of this kind was created long ago by the scientist Jan Oort, back in 1932.

In the last decade of the last century, telescopes were intensively created, improved and making it possible to conduct a clear survey of outer space. Satellites, stuffed with computer equipment, allow modern scientists to explore literally every millimeter of the universe, and transmit data via a satellite system directly to research centers in various states.

Where did the name come from

The author of the name for the Big Bang theory was its opponent Alfred Hoyle, an English physicist. It was he who came up with the phrase "Big Bang", but the physicist did this not to elevate Lemaitre's judgment, but, on the contrary, to humiliate him, declaring it absurd, and not the greatest phenomenon in the field of cosmology, physics and astronomy.

Chronology of events

Modern researchers, who have reliable information about the state of affairs in the universe, are reduced to a unanimous opinion, according to which everything was created from a point. The ever-increasing infinite density and finite time must have had their own beginning at a certain point. When the initial expansion took place, according to the already mentioned theory, the Universe was able to go through a cooling phase, which became a co-author of the creation of subatomic particles, and a little later, of the simplest atoms. After some time, huge clouds, consisting of the original ancient elements, thanks solely to gravity, began to form stars, which now absolutely any person can see every night, and galaxies, where, according to ufologists, parallel worlds can be located and highly developed civilizations can be concentrated alien beings. This whole mechanism, according to the researchers, started just 13.8 billion years ago: therefore, this starting point can be indicated as the age of the universe. In the course of studying a huge amount of theoretical information, conducting numerous experiments that were based on the involvement of particle accelerators and all kinds of high-energy states, surveying the distant hidden corners of outer space with a telescope, a chronological event was established that began with the Big Bang and brought the Universe to its modern form, or as it is otherwise called by physicists and astronomers - to the "state of cosmic evolution."

There is an opinion among scientists that the initial periods of the formation of outer space could last from 10-43 to 10-11 seconds from the explosion; However, there is currently no unequivocal opinion on this matter. It should be borne in mind that all the physical laws known to modern society in the distant past simply did not yet exist in the full set that is known to mankind, therefore, the very process of formation of the young Universe remains incomprehensible. This mystery is reinforced by the fact that up to the present time, including it as well, not a single experiment has been carried out in any developed state related to the study of those types of energy that existed at the time of the creation of boundless outer space. The opinions of pundits agree on one thing only: once there was a point that became a reference point, and it all started from it.

Epochal period of formation

1. The era of the singularity (Planckian). It is considered to be primary, as an early evolutionary period of the Universe. Matter was concentrated in one point, having its own temperature and infinite density. Scientists argue that this era is typical for the dominance of quantum effects belonging to the gravitational interaction over physical ones, and not a single one physical strength of all those that existed in those distant times, in its strength it was not identical to gravity, that is, it was not equal to it. The duration of the Planck era is concentrated in the range from 0 to 10-43 seconds. It received such a name due to the fact that only Planck time could fully measure its length. This time interval is considered to be very unstable, which in turn is closely related to the extreme temperature and the boundless density of matter. Following the epoch of singularity, there was a period of expansion, and with it a period of cooling, which led to the formation of the main physical forces.

From the period from 10-43 to 10-3 seconds in the boundless space, a new event occurs in the form of a collision of transitional temperatures, this, in turn, is displayed on their state. There is an opinion that the fundamental forces that are now dominant in the modern cosmic boundless space, in this moment began to rapidly move away from each other. The consequence of this process was the formation of weak gravitational forces, such a state as electromagnetism, and at the same time weak, along with strong, nuclear interactions.

From 10-36 to 10-32 seconds from the Big Bang, a very low temperature is set in the Universe, equal to 1028K, this fact, in turn, causes the separation of electromagnetic forces, which occurs in the process of strong interaction with the weak (nuclear) one.
2. The era of inflation. With the appearance in the boundless expanses of the Universe of the first forces, called by scientists only fundamental, a new era begins, lasting from 10-32 seconds (according to Planck time) to an absolutely unknown time. A huge number of cosmological models establish that in this time interval the Universe could be in a state of baryogenesis - a very high temperature affects the chaotic movement of particles in a spatial environment, occurring at an incredible speed.

This time is typical for the collision and repulsion of antiparticles - collapsing pairs of particles. Researchers tend to believe that it was then that matter dominated over its antipode, antimatter, which is today a characteristic feature of the Universe, meaning the dominant. By the end of the epoch of inflation, the Universe was formed on the basis of quark-gluon plasma and other elementary particles. It began to gradually cool down, and matter, in turn, began active formation and connection.
3. Epoch of cooling. From the moment of lowering the level of density and temperature in the Universe itself, significant changes began to occur in each particle - their energy began to decrease. A state of this kind ended only when elementary particles came to their modern form, and with them the fundamental forces. The particle energy began to drop to those parameters that today can only be obtained under laboratory conditions, in the course of numerous experiments and experiments along with them. Scientists do not doubt for a second that this time interval existed in the history of the formation of the Universe. They note that immediately after the Big Bang, the energy of particles gradually decreased, as a result of which it acquired significant dimensions. At 10-6 seconds, baryons in the form of protons and neutrons began to form from gluons and quarks. Along with this, a dissonance appeared in the form of the predominance of quarks over antiquarks, baryons over antibaryons. Due to the decrease in temperature, the production of proton-neutron pairs and, accordingly, their antipodes began to cease, protons and neutrons began to rapidly disappear, and their antiparticles completely ceased to exist. A similar process occurred again some time later. However, this time the action touched positrons and electrons.

As a result of the rapid annihilation, the particles stopped their chaotic motion, and the energy density related to the Universe began to be intensively filled with photons.

Since the expansion of the boundless space, the process of triggering nucleosynthesis has been formed. Due to the low temperature and lower energy density, the neutron and proton created the world's first deuterium (an isotope of hydrogen) by their symbiosis, and they also took a direct part in the formation of helium atoms. A huge number of protons, in turn, became the basis for creating a hydrogen nucleus.

After 379,000 years, hydrogen nuclei will combine with electrons, as a result of which atoms of the same hydrogen will appear. At a given moment in time, the separation of radiation from matter takes place; from now on, it independently fills the entire universal space. This radiation is called relic radiation, it is considered to be the most ancient source of light from all existing ones.
4. The era of structure. During the subsequent time interval of a couple of billion years, matter was already able to spread throughout the universe, and its densest regions began to actively attract each other, becoming denser. As a result of this action, clouds began to appear, consisting of gas, galaxies, stars and other space objects that can be seen today. This period is known by another name, it is customary to call it the “Hierarchical era.” This time period is due to the fact that the Universe managed to acquire a certain form. Matter began to form into various structures having various sizes:
- stars,
- galaxies,
- planets,
- galactic clusters and superclusters, separated from each other by means of intergalactic bridges and including several galaxies.

Forecasts for the future

Due to the fact that the Universe has its own point of origin, scientists periodically create hypotheses that someday there will also be a point that will cease to exist. Physicists and astronomers are also interested in the question of the expansion of the Universe from just one point, they even make predictions that it can expand even more. Or even once the reverse process may occur, in boundless space, for unknown reasons, the expansive force may cease to act, as a result of which the reverse process may occur, which consists in compression. In the 1990s, the Big Bang theory was adopted as the main model for the development of the Universe, it was at about the same time that two main ways for the further existence of cosmic boundless space were developed.

1. Big compression. At one point, the universe can reach its maximum peak in the form of a huge size, and then its destruction will begin. Such a variant of development will become possible only if the mass density of the Universe is greater than its critical density.

2. In this case, a different picture of actions will occur: the density will equal or even become lower than the critical one. The result is an expansion slowdown that will never stop. This option was called the heat death of the universe. The expansion will continue until the star formations stop actively consuming the gas inside nearby galaxies. In this case, the following will happen: the transfer from one cosmic object to another will simply stop from energy and matter. All the stars that can be seen with the naked eye every evening and night in the sky will suffer the same sad fate: they will become nothing more than a white dwarf, a black hole, or a neutron star.
Black holes have always been a nuisance, not only for cosmologists. Newly formed holes will connect with themselves, forming similar objects of a much larger size. Meanwhile, the average temperature in an infinite space can reach 0. The consequence of this situation will be the absolute evaporation of black holes, which will finally begin to emit Hawking radiation into the environment. The final stage in this case will be heat death. Modern scientists are conducting a huge amount of research concerning not only the existence of dark energy, but also its direct impact on the expansion of outer space. In the course of their research, they, in turn, found that the expansion of the universe is happening at such a rapid pace that soon humanity will not even know how boundless the boundless space really is. Of course, what kind of further path of development the planet can take, the minds of pundits cannot even imagine. They only predict the result, substantiating their choice with certain criteria. However, many of the luminaries predict such an end to the boundless space as heat death, considering it the most probable.

There is also an opinion in the scientific community that all the planets, atomic nuclei, atoms, matter and stars will burst by themselves in the distant future, which will lead to a big gap. This is another version of the death of the Universe, however, it is formed on the expansion.

Other options

Of course, the Big Bang theory is not the only one, as has been pointed out more than once above. Mankind throughout its existence had the right to its own version of the origin of the Universe.

1. In very ancient times, people thought about what kind of world they live and exist in. A religious worldview has not yet been established, and a person has already thought about how the world works, what place he himself occupies in the space surrounding him.
The ancient developed peoples connected their lives closely with religious dogmas. Who, if not a deity, could create a tree, a man, a fire? And when he can do it all, therefore, the whole world is also created by some god.
If we make a review of the life of one of the most ancient civilizations that once lived on the territory of Mesopotamia (the modern lands of Iraq, Iran, Syria, Turkey), then we can see, using the example of the antagonists of good and evil - Ahuramazda and Ahriman, that these gods, according to ancient written sources , are the direct creators of the Universe. Each ancient people associated the formation of outer space with the activity of some deity (most often the supreme one). The great thinkers of antiquity tried to understand the origin of the Universe, they understood that the gods had absolutely nothing to do with it. Cosmology was studied by Aristotle, who tried to prove that the universe has its own evolution. In the East, everyone knows the name of the doctor Avicenna, but not only medicine dominated his inquisitive mind. Avicenna was one of the first researchers who tried, with the help of reason and his own logic, to refute the divine formation of the Universe.
2. Time moves inexorably forward, and with it the rapid development of human thought takes place. The researchers of the Middle Ages (those people who were hiding from the Holy Inquisition) and the New Age, going against the authoritarian religious authorities, proved not only what the planet Earth is like, but also laid down the methods of astrological research, and a little later, astrophysical research. many philosophers have their bright heads, among which the Frenchman Rene Descartes should be singled out. Descartes attempted to use theory to understand the origin of celestial bodies, while combining all the mathematical, physical and biological knowledge that this talented person possessed. He did not achieve success in his field.
3. Until the beginning of the 20th century, people believed that the Universe had no clear boundaries in either space or time, and besides, in addition to this, it was static and homogeneous. Isaac Newton dared to speak out infinitely about outer space. The German philosopher Emmanuel Kant listened to his arguments and, based on Newtonian reasoning, put forward his own theory that the Universe has no time and no beginning at all. All the processes that took place in the universe, he attributed to the laws of mechanics.

Kant developed his theory, backed up with knowledge from biology. The scientist said that in the vastness of the Universe there can be a huge number of possibilities that give life to a biological product. A similar statement would later be of interest to a no less famous scientist - Charles Darwin.

Kant created his theory based on the experience of astronomers, who are practically his contemporaries. It was considered the only true and unshakable right up to the moment when the Big Bang theory arose.

4. The author of the famous theory of relativity, Albert Einstein, also did not stay away from the problems of the creation of the Universe. In 1917, he presented his project to the public. Einstein also thought that the Universe is stationary, he sought to prove that the cosmic boundless space should neither shrink nor expand. However, his own thoughts went against his main work (the theory of relativity), according to which Einstein's Universe both expanded and contracted at the same time.

The scientist hastened to establish that the Universe is static, he justified this by the fact that the cosmic repulsive force affects the balancing of the attraction of stars and thereby stops the movement of celestial bodies in space.

For Einstein, the Universe had a finite size, but at the same time he did not establish clear boundaries: this becomes possible only in the case of curvature of space.
5. A separate theory of the creation of the Universe is Creationism. It, in turn, is based on the fact that humanity and the Universe are founded by the creator. Of course, we are talking about Christian dogma. This theory arose in the 19th century, its supporters argued that the creation of outer space was recorded in Old Testament. At this time, knowledge from the field of biology, physics, and astronomy was formed into a single scientific trend. Darwin's theory of evolution occupied a significant place in the life of society. As a result, science went against religion: knowledge against the divine concept of the creation of the world. Creationism has become a kind of protest against innovation. Conservative Christians opposed scientific discoveries.
Creationism was known to the public in the form of two directions:

Young Earth (literal). God worked on the creation of the world for exactly 6 days, as indicated in the Bible. They claim that the world was created about 6,000 years ago.

Old Earth (metaphorical). The 6 days described in the Bible are nothing but a metaphor that was understood only by people who lived in ancient times. In fact, such a Christian concept as “day” may not include the established 24 hours, it is concentrated in an indefinite period of time (that is, without fixed clear boundaries), which in turn can be calculated in millions of years.

Old-Earth creationism accepts some scientific ideas and discoveries, its followers agree with the astrophysical age of celestial bodies, but they completely deny the existence of the theory of evolution together with natural selection, arguing that only God can influence the appearance and disappearance of biological species.

Outcome

The history of the creation of the Universe throughout the entire human existence has repeatedly undergone changes that were dictated by religious beliefs or scientific research. To date, there is one version that satisfies scientific minds. The Big Bang Theory is the most good option, accurately describing exactly how the birth of boundless space took place, what eras it lived. On its basis, scientists predict the further development of the universe.

However, as previous experience shows, not always a theory, even if it is very popular in human society, is true. Science does not stand in one place, it is constantly progressing, finding more and more new sources of replenishment of knowledge.

It is possible that one day another physicist, cosmologist or astronomer will appear in the scientific community, who will present his own theory of the creation of the Universe, which, perhaps, will turn out to be more correct than the Big Bang theory.

One of the main questions that do not come out of human consciousness has always been and is the question: “how did the Universe appear?”. Of course, there is no unequivocal answer to this question, and it is unlikely to be received in the near future, however, science is working in this direction and forming a certain theoretical model of the origin of our Universe. First of all, we should consider the main properties of the Universe, which should be described within the framework of the cosmological model.

The model must take into account the observed distances between objects, as well as the speed and direction of their movement. Such calculations are based on the Hubble law: cz = H0D, where z is the redshift of an object, D is the distance to this object, c is the speed of light.
The age of the Universe in the model must exceed the age of the oldest objects in the world.
The model must take into account the initial abundance of elements.
The model must take into account the observed large-scale structure of the Universe.
The model must take into account the observed relict background.

A Brief History of the Universe. Singularity in the view of the artist (photo)

Let us briefly consider the generally accepted theory of the origin and early evolution of the Universe, which is supported by the majority of scientists. Today, the Big Bang theory refers to the combination of the hot universe model with the Big Bang. And, although these concepts first existed independently of each other, as a result of their combination, it was possible to explain the initial chemical composition of the Universe, as well as the presence of cosmic microwave background radiation.

According to this theory, the Universe arose about 13.77 billion years ago from some dense heated object - a singular state that is difficult to describe within the framework of modern physics. The problem with the cosmological singularity, among other things, is that when describing it, most physical quantities, such as density and temperature, tend to infinity. At the same time, it is known that at an infinite density, entropy (a measure of chaos) should tend to zero, which is in no way compatible with infinite temperature.

The first 10 to -43 seconds after the Big Bang is called the quantum chaos stage. The nature of the universe at this stage of existence cannot be described within the framework of physics known to us. There is a disintegration of a continuous single space-time into quanta.

The Planck moment is the moment of the end of quantum chaos, which falls on 10 in -43 seconds. At that moment, the parameters of the Universe were equal to the Planck values, like the Planck temperature (about 1032 K). At the time of the Planck era, all four fundamental interactions (weak, strong, electromagnetic and gravitational) were combined into a single interaction. It is not possible to consider the Planck moment as a certain long period, since modern physics does not work with parameters less than the Planck ones.
stage of inflation. The next stage in the history of the universe was the inflationary stage. At the first moment of inflation, the gravitational interaction separated from a single supersymmetric field (previously including the fields of fundamental interactions). During this period, the matter has a negative pressure, which causes an exponential increase in the kinetic energy of the Universe. Simply put, during this period, the Universe began to swell very quickly, and towards the end, the energy of physical fields turns into the energy of ordinary particles. At the end of this stage, the temperature of the substance and radiation increases significantly. Along with the end of the inflation stage, a strong interaction also emerges. Also at this moment, the baryon asymmetry of the Universe arises.

[The baryon asymmetry of the Universe is an observed phenomenon of the predominance of matter over antimatter in the Universe]

The stage of radiation dominance. The next stage in the development of the Universe, which includes several stages. At this stage, the temperature of the Universe begins to decrease, quarks are formed, then hadrons and leptons. In the era of nucleosynthesis, the formation of initial chemical elements occurs, helium is synthesized. However, radiation still dominates matter.
The era of the dominance of matter. After 10,000 years, the energy of matter gradually exceeds the energy of radiation and their separation occurs. The substance begins to dominate over the radiation, a relict background appears. Also, the separation of matter with radiation significantly increased the initial inhomogeneities in the distribution of matter, as a result of which galaxies and supergalaxies began to form. Laws of the Universe came to the form in which we observe them today.

The above picture is composed of several fundamental theories and gives general view about the formation of the Universe in the early stages of its existence.

Where did the universe come from?

If the Universe originated from a cosmological singularity, then where did the singularity come from? It is not yet possible to give an exact answer to this question. Let's consider some cosmological models that affect the "birth of the Universe".

Cyclic models. Brane simulation (photo)

These models are based on the assertion that the Universe has always existed and over time its state only changes, moving from expansion to contraction and vice versa.

Steinhardt-Turok model. This model is based on string theory (M-theory), as it uses such an object as a "brane".

[Bran (from membrane) in string theory (M-theory) is a hypothetical fundamental multidimensional physical object of a dimension less than the dimension of the space in which it is located]

According to this model, the visible Universe is located inside a three-brane, which periodically, every few trillion years, collides with another three-brane, which causes a kind of Big Bang. Further, our three-brane begins to move away from the other and expand. At some point, the share of dark energy takes precedence and the rate of expansion of the three-brane increases. The colossal expansion scatters matter and radiation to such an extent that the world becomes almost homogeneous and empty. Eventually, the three-branes collide again, causing ours to return to the initial phase of its cycle, re-creating our "Universe".

The theory of Loris Baum and Paul Frampton also states that the universe is cyclical. According to their theory, after the Big Bang, the latter will expand due to dark energy until it approaches the moment of “disintegration” of space-time itself - the Big Rip. As you know, in a "closed system, entropy does not decrease" (the second law of thermodynamics). It follows from this statement that the Universe cannot return to its original state, since during such a process the entropy must decrease. However, this problem is solved within the framework of this theory. According to the theory of Baum and Frampton, in a moment before the Big Rip, the Universe breaks up into many "rags", each of which has a rather small value of entropy. Experiencing a number of phase transitions, these "patches" of the former Universe give rise to matter and develop similarly to the original Universe. These new worlds do not interact with each other, as they fly apart at a speed greater than the speed of light. Thus, scientists also avoided the cosmological singularity, which begins the birth of the Universe according to most cosmological theories. That is, at the moment of the end of its cycle, the Universe breaks up into many other non-interacting worlds, which will become new universes.
Conformal cyclic cosmology – the cyclic model of Roger Penrose and Vahagn Gurzadyan. According to this model, the universe is able to go into new cycle without violating the second law of thermodynamics. This theory is based on the assumption that black holes destroy the absorbed information, which in some way "legitimately" lowers the entropy of the universe. Then each such cycle of existence of the Universe begins with the likeness of the Big Bang and ends with a singularity.

Other Models for the Origin of the Universe

Among other hypotheses explaining the appearance of the visible Universe, the following two are most popular:

Chaotic inflation theory - Andrey Linde's theory. According to this theory, there is some scalar field, which is non-uniform throughout its volume. That is, in different regions of the universe, the scalar field has a different meaning. Then, in areas where the field is weak, nothing happens, while areas with a strong field begin to expand (inflation) due to its energy, thus forming new universes. Such a scenario implies the existence of many worlds that did not arise simultaneously and have their own set of elementary particles, and, consequently, the laws of nature.
Lee Smolin's theory suggests that the Big Bang is not the beginning of the existence of the Universe, but is only a phase transition between its two states. Since before the Big Bang the Universe existed in the form of a cosmological singularity, close in nature to the singularity of a black hole, Smolin suggests that the Universe could have arisen from a black hole.

There are also models in which the universes arise continuously, bud off from their parents and find their own place. At the same time, it is not at all necessary that the same physical laws are established in such worlds. All these worlds are "embedded" in a single space-time continuum, but they are separated in it so much that they do not feel each other's presence in any way. In general, the concept of inflation allows - moreover, forces! - to consider that in the gigantic megacosmos there are many universes isolated from each other with different arrangements.

Despite the fact that cyclic and other models answer a number of questions that the Big Bang theory cannot answer, including the problem of the cosmological singularity. Yet, together with the inflationary theory, the Big Bang more fully explains the origin of the Universe, and also converges with many observations.

Today, researchers continue to intensively study possible scenarios for the origin of the Universe, however, to give an irrefutable answer to the question “How did the Universe appear?” - is unlikely to succeed in the near future. There are two reasons for this: direct proof of cosmological theories is practically impossible, only indirect; even theoretically there is no way to get accurate information about the world before the Big Bang. For these two reasons, scientists can only put forward hypotheses and build cosmological models that will most accurately describe the nature of the Universe we observe.

The question of the origin of all things has been raised by man since ancient times. It seemed quite logical: a person constantly saw how everything in the world is born, goes through a period of formation, reaches its peak and in the end - dies ... shouldn't the world as a whole obey this law?

An ancient man, a man of the Middle Ages, had no doubt that the Universe had a beginning: it was created by God (or gods), arose from primitive chaos or even from a world egg laid by a divine bird ... The scientific worldview of the New Age rejected the very idea of the beginning of the Universe: it is infinite in time so the same as in space - therefore, it cannot have a beginning in time ... in other words, the Universe has always existed! It is difficult for a person to imagine such a thing - but in modern physics in general there is a lot of things that go beyond the scope of ordinary consciousness ...

And who would have thought that in the 20th century the idea of the beginning of the Universe would return! Yes, it has returned - of course, in the form of a rigorous scientific theory - but anyway, science said: yes, the Universe has a beginning! And whether the Creator had a hand in its creation or not - it is still a personal matter for everyone - to believe or not to believe, this is already beyond the scope of science.

The first step towards such an idea was taken in 1929, when the American astronomer E. Hubble discovered that galaxies move and move away from us at great speed, and the farther they go, the faster they move away... The Universe is not static, as previously thought - it is expanding! Theoretically, it followed that there was a certain point from which this expansion began ...

This is how the Big Bang hypothesis was born. For the first time this term was used by the English astronomer (who also showed himself as a science fiction writer) F. Hoyle (it is noteworthy that this scientist, who gave the name to the Big Bang hypothesis, did not support it himself, considering it “unsatisfactory”). In its most general form, it boils down to the following: in the past there was a certain finite moment in time when the dimensions of the Universe were equal to zero, and the density and temperature were infinite (this state is called a cosmological singularity), and from this point space-time begins to expand.

The expansion rate of the Universe allowed scientists to calculate when this historical event occurred: 13 billion 700 million years ago. It was the moment when Nothing became Something; and it is pointless to ask where the Big Bang happened - it happened everywhere, this point was the whole Universe!

So, fast forward to 13 billion 700 million years ago, when there was an infinitely dense, infinitely hot and unimaginably small (less than an atom) particle of pure energy - not even a substance yet. The earliest era about which some theoretical provisions can be built is called the Planck era (named after the German physicist M. Planck) - at that time its density was 10 to the 97th degree kg per cubic meter, and the temperature was ten to the 32nd degree K How long did this era last? 10 to the minus 43rd power of seconds (such a period of time is called Planck time) - to imagine this, you will have to divide a second into millions over and over again (and to imagine how many times the Universe has expanded during this time, you will have to multiply millions in the same way) ... At the end of the Planck era, all the forces that govern the universe arise, and the first of these is gravity, which truly decided everything. Nowadays, scientists create computer models of hypothetical Universes with different gravitation, and it turns out that if gravity were a little less than it is, nothing could form (neither stars, nor galaxies, nor anything else), if it were a little more, it would not work nothing but black holes... so maybe someone calculated our gravity? Or a happy accident in an endless series of unsuccessful (or maybe successful) Big Bangs? We don't know this...

Anyway, the universe has expanded from less than an atom to about the size of a golf ball (it's like if the same ball expanded to the size of the Earth) - you could hold it in the palm of your hand. In a fraction of a second, it expands to the size of the Earth, in another fraction - to the size of the solar system ... What does the Universe look like at this time? It is still a raging mass of energy (dense than anything we know now) - even the "bubbling cauldrons" of the stars are nothing compared to this state, the temperature is estimated at trillions of degrees (so I do not advise going there by car time: you won’t succeed in making a sufficiently reliable spacesuit - at such a temperature, any atoms will be destroyed ... in fact, they didn’t exist then).

But expanding, the Universe cooled down - and the decrease in temperature led to the emergence of subatomic particles: energy passed into matter - the first substance in the Universe! It was still unstable - particles appeared and disappeared, moving randomly at great speed (did the ancients really know this, speaking about the emergence of the Universe from chaos?). But as the temperature dropped, they moved more slowly, more orderly and ceased to turn back into energy - there was more matter (recall that at this stage the time count is still going on in fractions of a second). And here another "actor" appears on the scene - antimatter.

Antimatter was born together with matter - and does not differ from it in anything, except for the charge (antimatter has the opposite). Today, physicists create it in laboratories, and, in general, there is nothing wrong with it - until it comes into contact with matter. If you met with your counterpart, consisting of antimatter, you would be convinced that he is no different from you, and nothing terrible would happen until you decided to shake hands - then a monstrous explosion would follow ... something similar happened if it were with the Universe, if the amount of matter and antimatter in it were equal - they would destroy each other, turning into radiation, there would be no matter at all! But it happened (or was it planned?) so that for every billion particles of antimatter there were a billion and one particles of matter - and these "remnants" escaped annihilation.

And now, when matter has won the cosmic battle with antimatter - almost a second after the Big Bang - it's "time to collect stones" ... i.e. collect particles. The temperature of the universe has dropped so much that particles can combine - and this is how atoms are formed, and the first were hydrogen atoms (isn't the Bible talking about this time: “and the earth was formless and empty, and the spirit of God hovered over the water”?). In the next three minutes, two more elements appear - helium and lithium. The size of the universe is already measured in light years. And the time… for the electrons to slow down so that they can join new atoms is 380 thousand years… and the message from those times has reached us!

In 1965, two scientists in the United States (New Jersey) - A. Penzias and R. Wilson - tracked radio signals in the Universe - but an incomprehensible background noise interfered with their work ... maybe it's because of pigeon droppings on the antenna? The antenna was cleaned - but nothing changed ... when the researchers spoke about this at Princeton University, one of those present replied: “You found either the effect of pigeon droppings - or the creation of the universe!” The phenomenon discovered by A. Penzias and R. Wilson was called relic radiation - it was born, however, not at the very moment of the big bang, but at the moment when the first electrons joined atoms.

Now the Universe has ceased to be homogeneous: somewhere the temperature was higher, somewhere lower, somewhere there was less matter - somewhere more. Where there is more matter, stars and galaxies will eventually arise, and where there is less, there will be empty space ...

So, the Universe is 380 thousand years old, clouds of hydrogen and helium move in it. After 200 million years, the first stars form from them, and a billion years after the Big Bang, the first galaxies will arise ...

However, this is another story… The birth of the Universe took place!

In a certain sense, we can say that the Big Bang continues to this day - the Universe continues to expand, and this expansion is not slowing down, but rather picking up speed. Theoretically, this should lead to the fact that not only galaxies, but also atoms will fly apart, there will be nothing - thus. The big explosion, which gave rise to the Universe, will also kill it ... But what will be the end of the Universe - we do not know. It can be an expansion to complete cooling and the absence of light, it can be a change from expansion to contraction... The death of our Universe can lead to a new Big Bang - which will give rise to a new Universe. Perhaps our Universe is just another in an endless series of Universes being born and dying...

Scientists have yet to answer these and many other questions.

The model must take into account the observed distances between objects, as well as the speed and direction of their movement. Such calculations are based on the Hubble law: cz =H0D, where z is the redshift of the object, D- distance to this object, c is the speed of light.
The age of the Universe in the model must exceed the age of the oldest objects in the world.
The model must take into account the initial abundance of elements.
The model must take into account the observable .
The model must take into account the observed relict background.

Let us briefly consider the generally accepted theory of the origin and early evolution of the Universe, which is supported by the majority of scientists. Today, the Big Bang theory refers to the combination of the hot universe model with the Big Bang. And although these concepts first existed independently of each other, as a result of their combination, it was possible to explain the initial chemical composition of the Universe, as well as the presence of cosmic microwave background radiation.

According to this theory, the Universe arose about 13.77 billion years ago from some dense heated object - which is difficult to describe within the framework of modern physics. The problem with the cosmological singularity, among other things, is that when describing it, most physical quantities, such as density and temperature, tend to infinity. At the same time, it is known that at infinite density (the measure of chaos) should tend to zero, which is in no way compatible with infinite temperature.

- The first 10 -43 seconds after the Big Bang is called the stage of quantum chaos. The nature of the universe at this stage of existence cannot be described within the framework of physics known to us. There is a disintegration of a continuous single space-time into quanta.

The Planck moment is the moment of the end of quantum chaos, which falls on 10 -43 seconds. At this moment, the parameters of the Universe were equal, like the Planck temperature (about 10 32 K). At the time of the Planck era, all four fundamental interactions (weak, strong, electromagnetic and gravitational) were combined into a single interaction. It is not possible to consider the Planck moment as a certain long period, since modern physics does not work with parameters less than the Planck ones.
Stage. The next stage in the history of the universe was the inflationary stage. At the first moment of inflation, the gravitational interaction separated from a single supersymmetric field (previously including the fields of fundamental interactions). During this period, the matter has a negative pressure, which causes an exponential increase in the kinetic energy of the Universe. Simply put, during this period, the Universe began to swell very quickly, and towards the end, the energy of physical fields turns into the energy of ordinary particles. At the end of this stage, the temperature of the substance and radiation increases significantly. Along with the end of the inflation stage, a strong interaction also emerges. Also at this moment arises.
The stage of radiation dominance. The next stage in the development of the Universe, which includes several stages. At this stage, the temperature of the Universe begins to decrease, quarks are formed, then hadrons and leptons. In the era of nucleosynthesis, the formation of initial chemical elements occurs, helium is synthesized. However, radiation still dominates matter.
The era of the dominance of matter. After 10,000 years, the energy of matter gradually exceeds the energy of radiation and their separation occurs. The substance begins to dominate over the radiation, a relict background appears. Also, the separation of matter with radiation significantly increased the initial inhomogeneities in the distribution of matter, as a result of which galaxies and supergalaxies began to form. Laws of the Universe came to the form in which we observe them today.

The above picture is composed of several fundamental theories and gives a general idea of the formation of the Universe in the early stages of its existence.

Where did the universe come from?

Cyclic models

These models are based on the assertion that the Universe has always existed and over time its state only changes, moving from expansion to contraction and vice versa.

Steinhardt-Turok model. This model is based on string theory (M-theory), as it uses such an object as a "brane". According to this model, the visible Universe is located inside a 3-brane, which periodically, every few trillion years, collides with another 3-brane, which causes a kind of Big Bang. Further, our 3-brane begins to move away from the other and expand. At some point, the share of dark energy takes precedence and the rate of expansion of the 3-brane increases. The colossal expansion scatters matter and radiation to such an extent that the world becomes almost homogeneous and empty. Eventually the 3-branes collide again, causing ours to return to the initial phase of its cycle, re-creating our "Universe".

The theory of Loris Baum and Paul Frampton also states that the universe is cyclical. According to their theory, after the Big Bang, the latter will expand due to dark energy until it approaches the moment of “disintegration” of space-time itself - the Big Rip. As you know, in a "closed system, entropy does not decrease" (the second law of thermodynamics). It follows from this statement that the Universe cannot return to its original state, since during such a process the entropy must decrease. However, this problem is solved within the framework of this theory. According to the theory of Baum and Frampton, in a moment before the Big Rip, the Universe breaks up into many "rags", each of which has a rather small value of entropy. Experiencing a number of phase transitions, these "patches" of the former Universe give rise to matter and develop similarly to the original Universe. These new worlds do not interact with each other, as they fly apart at a speed greater than the speed of light. Thus, scientists also avoided the cosmological singularity, which begins the birth of the Universe according to most cosmological theories. That is, at the moment of the end of its cycle, the Universe breaks up into many other non-interacting worlds, which will become new universes.
Conformal cyclic cosmology – the cyclic model of Roger Penrose and Vahagn Gurzadyan. According to this model, the Universe is able to move into a new cycle without violating the second law of thermodynamics. This theory is based on the assumption that black holes destroy the absorbed information, which in some way "legitimately" lowers the entropy of the universe. Then each such cycle of existence of the Universe begins with the likeness of the Big Bang and ends with a singularity.

Other Models for the Origin of the Universe

Among other hypotheses explaining the appearance of the visible Universe, the following two are most popular:

The chaotic theory of inflation is the theory of Andrey Linde. According to this theory, there is some scalar field, which is non-uniform throughout its volume. That is, in different regions of the universe, the scalar field has a different meaning. Then, in areas where the field is weak, nothing happens, while areas with a strong field begin to expand (inflation) due to its energy, thus forming new universes. Such a scenario implies the existence of many worlds that did not arise simultaneously and have their own set of elementary particles, and, consequently, the laws of nature.
Lee Smolin's theory suggests that the Big Bang is not the beginning of the existence of the Universe, but is only a phase transition between its two states. Since before the Big Bang the Universe existed in the form of a cosmological singularity, close in nature to the singularity of a black hole, Smolin suggests that the Universe could have arisen from a black hole.

Results

Today, researchers continue to intensively study possible scenarios for the origin of the Universe, however, to give an irrefutable answer to the question “How did the Universe appear?” — is unlikely to happen in the near future. There are two reasons for this: direct proof of cosmological theories is practically impossible, only indirect; even theoretically there is no way to get accurate information about the world before the Big Bang. For these two reasons, scientists can only put forward hypotheses and build cosmological models that will most accurately describe the nature of the Universe we observe.

Having learned about the Big Bang theory, we ask ourselves the question, where did it come from that exploded?

The question of the origin of the Universe with all its known and yet unknown properties has been of concern to man since time immemorial. But only in the twentieth century, after the discovery of cosmological expansion, the question of the evolution of the universe began to gradually become clearer. Recent scientific data have led to the conclusion that our universe was born 15 million years ago as a result of the Big Bang. But what exactly exploded at that moment and what, in fact, existed before the Big Bang, still remained a mystery. The inflationary theory of the appearance of our world, created in the 20th century, made it possible to make significant progress in resolving these issues, the general picture of the first moments of the Universe is already well drawn today, although many problems are still waiting in the wings.

Until the beginning of the last century, there were only two views on the origin of our universe. Scientists believed that it is eternal and unchanging, and theologians said that the world was created and it will have an end. The twentieth century, having destroyed a lot of what had been created in previous millennia, managed to give its own answers to most of the questions that occupied the minds of scientists of the past. And perhaps one of the greatest achievements of the past century is the clarification of the question of how the Universe in which we live came into being, and what hypotheses exist about its future. A simple astronomical fact - the expansion of our Universe - led to a complete revision of all cosmogonic concepts and the development of a new physics - the physics of emerging and disappearing worlds. Just 70 years ago, Edwin Hubble discovered that light from more distant galaxies is "redder" than light from closer ones. Moreover, the recession speed turned out to be proportional to the distance from the Earth (Hubble's expansion law). This was discovered thanks to the Doppler effect (the dependence of the wavelength of light on the speed of the light source). Since more distant galaxies appear more "red", it was assumed that they are moving away at a faster rate. By the way, it is not stars and even individual galaxies that scatter, but clusters of galaxies. The nearest stars and galaxies are connected with each other by gravitational forces and form stable structures. Moreover, in whatever direction you look, clusters of galaxies scatter from the Earth at the same speed, and it may seem that our Galaxy is the center of the Universe, but this is not so. Wherever the observer is, he will everywhere see the same picture - all the galaxies are running away from him. But such expansion of matter must have a beginning. This means that all galaxies must have been born at the same point. Calculations show that this happened about 15 billion years ago. At the moment of such an explosion, the temperature was very high, and a lot of light quanta should have appeared. Of course, over time everything cools down, and the quanta scatter over the emerging space, but the echoes of the Big Bang should have survived to this day. The first confirmation of the fact of the explosion came in 1964, when the American radio astronomers R. Wilson and A. Penzias discovered relic electromagnetic radiation with a temperature of about 3 ° Kelvin (-270 ° C). It was this discovery, unexpected for scientists, that convinced them that the Big Bang really took place and that the Universe was very hot at first. The Big Bang theory has helped explain many of the problems facing cosmology. But, unfortunately, or perhaps fortunately, it also raised a number of new questions. In particular: What happened before the Big Bang? Why does our space have zero curvature and why is Euclid's geometry, which is studied at school, correct? If the Big Bang theory is correct, then why is the current size of our universe so much larger than the 1 centimeter predicted by the theory? Why is the Universe surprisingly homogeneous, while in any explosion the matter scatters in different directions extremely unevenly? What led to the initial heating of the Universe to an unimaginable temperature of more than 10 13 K?

All this indicated that the Big Bang theory was incomplete. For a long time it seemed that going further was impossible. Only a quarter of a century ago, thanks to the work of the Russian physicists E. Gliner and A. Starobinsky, as well as the American A. Gus, a new phenomenon was described - the superfast inflationary expansion of the Universe. The description of this phenomenon is based on well-studied sections of theoretical physics - Einstein's general theory of relativity and quantum field theory. Today it is generally accepted that this period, called "inflation", preceded the Big Bang.

When trying to give an idea of the essence of the initial period of the life of the Universe, one has to operate with such ultra-small and super-large numbers that our imagination can hardly perceive them. Let's try to use some analogy to understand the essence of the process of inflation.

Imagine a snow-covered mountain slope interspersed with heterogeneous small objects - pebbles, branches and pieces of ice. Someone on top of this slope made a small snowball and let it roll down the mountain. Moving down, the snowball increases in size, as new layers of snow with all the inclusions stick to it. And the larger the snowball, the faster it will grow. Very soon, from a small snowball, it will turn into a huge lump. If the slope ends in an abyss, then he will fly into it with ever-increasing speed. Having reached the bottom, the lump will hit the bottom of the abyss and its components will scatter in all directions (by the way, part of the lump's kinetic energy will go to heat the environment and flying snow).

Let us now describe the main provisions of the theory using the above analogy. First of all, physicists had to introduce a hypothetical field, which was called "inflaton" (from the word "inflation"). This field filled the entire space (in our case, snow on the slope). Due to random fluctuations, it took on different values in arbitrary spatial regions and at different points in time. Nothing significant happened until a uniform configuration of this field with a size of more than 10 -33 cm was accidentally formed. As for the Universe observed by us, it apparently had a size of 10 -27 cm in the first moments of its life. on such scales, the basic laws of physics known to us today are already valid, so it is possible to predict the further behavior of the system. It turns out that immediately after this, the spatial region occupied by the fluctuation (from the Latin fluctuatio - “fluctuation”, random deviations of the observed physical quantities from their average values) begins to increase very quickly in size, and the inflaton field tends to take a position in which its energy minimal (snowball rolled). Such an expansion lasts only 10 -35 seconds, but this time is enough for the diameter of the Universe to increase at least 1027 times and by the end of the inflationary period our Universe has acquired a size of about 1 cm. Inflation ends when the inflaton field reaches a minimum of energy - there is nowhere else to fall. In this case, the accumulated kinetic energy is converted into the energy of particles born and expanding, in other words, the heating of the Universe occurs. It is this moment that is called today the Big Bang.

The mountain mentioned above can have a very complex relief - several different lows, valleys below and all sorts of hills and bumps. Snowballs (future universes) are continuously born at the top of the mountain due to field fluctuations. Each lump can slide into any of the minima, thus giving rise to its own universe with specific parameters. Moreover, the universes can differ significantly from each other. The properties of our universe are amazingly adapted to ensure that intelligent life arose in it. Other universes may not have been as fortunate.

Once again, I would like to emphasize that the described process of the birth of the Universe "practically from nothing" is based on strictly scientific calculations. Nevertheless, any person who first gets acquainted with the inflationary mechanism described above has many questions.

Today our universe is made up of a large number stars, not to mention the hidden mass. And it might seem that the total energy and mass of the universe is enormous. And it is completely incomprehensible how all this could fit in the initial volume of 10-99 cm3. However, in the Universe there is not only matter, but also a gravitational field. It is known that the energy of the latter is negative and, as it turned out, in our Universe, the energy of gravity exactly compensates for the energy contained in particles, planets, stars and other massive objects. Thus, the law of conservation of energy is perfectly fulfilled, and the total energy and mass of our Universe are practically equal to zero. It is this circumstance that partly explains why the nascent Universe did not turn into a huge black hole immediately after its appearance. Its total mass was completely microscopic, and at first there was simply nothing to collapse. And only at later stages of development did local clumps of matter appear, capable of creating such gravitational fields near themselves, from which even light cannot escape. Accordingly, the particles from which stars are “made” simply did not exist at the initial stage of development. Elementary particles began to be born at that period of the development of the Universe, when the inflaton field reached a minimum of potential energy and the Big Bang began.

The area occupied by the inflaton field grew at a speed much greater than the speed of light, but this does not in the least contradict Einstein's theory of relativity. Only material bodies cannot move faster than light, and in this case, the imaginary, non-material boundary of the region where the Universe was born moved (an example of superluminal motion is the movement of a light spot over the surface of the Moon during the rapid rotation of the laser illuminating it).

Moreover, the environment did not at all resist the expansion of the region of space, covered by an ever more rapidly growing inflaton field, since it seemed to not exist for the emerging World. The general theory of relativity states that the physical picture that an observer sees depends on where he is and how he moves. So, the picture described above is valid for the "observer" located inside this area. Moreover, this observer will never know what is happening outside the region of space where he is. Another "observer", looking at this area from the outside, will not find any expansion at all. At best, he will see only a small spark, which, according to his watch, will disappear almost instantly. Even the most sophisticated imagination refuses to perceive such a picture. And yet it appears to be true. At least, this is what modern scientists think, drawing confidence in the already discovered laws of Nature, the correctness of which has been repeatedly verified.

It must be said that this inflaton field still continues to exist and fluctuate. But only we, internal observers, are not able to see this - after all, for us, a small area has turned into a colossal Universe, the boundaries of which even light cannot reach.

So, immediately after the end of inflation, a hypothetical internal observer would see the Universe filled with energy in the form of material particles and photons. If all the energy that could be measured by an internal observer is converted into a mass of particles, then we will get approximately 10 80 kg. The distances between particles increase rapidly due to the general expansion. The gravitational forces of attraction between particles reduce their speed, so the expansion of the universe after the end of the inflationary period gradually slows down.

Immediately after birth, the universe continued to grow and cool. At the same time, cooling occurred, among other things, due to the banal expansion of space. Electromagnetic radiation is characterized by a wavelength that can be associated with temperature - the longer the average wavelength of the radiation, the lower the temperature. But if space expands, then the distance between the two "humps" of the wave will increase, and, consequently, its length. This means that in expanding space, the radiation temperature must also decrease. This is confirmed by the extremely low temperature of modern relic radiation.

As it expands, the composition of the matter that fills our world also changes. Quarks unite into protons and neutrons, and the Universe turns out to be filled with elementary particles already familiar to us - protons, neutrons, electrons, neutrinos and photons. There are also antiparticles. The properties of particles and antiparticles are almost identical. It would seem that their number should be the same immediately after inflation. But then all particles and antiparticles would mutually annihilate and there would be no building material for galaxies and ourselves. And here again we are lucky. Nature made sure that there were a little more particles than antiparticles. It is thanks to this small difference that our world exists. And relic radiation is just a consequence of the annihilation (that is, mutual annihilation) of particles and antiparticles. Of course, at the initial stage, the energy of the radiation was very high, but due to the expansion of space and, as a result, the cooling of the radiation, this energy quickly decreased. Now the energy of relic radiation is about ten thousand times (104 times) less than the energy contained in massive elementary particles.

Gradually, the temperature of the universe dropped to 1010 K. By this time, the age of the universe was about 1 minute. Only now have protons and neutrons been able to combine into nuclei of deuterium, tritium and helium. This was due to nuclear reactions, which people have already studied well, detonating thermonuclear bombs and operating atomic reactors on Earth. Therefore, one can confidently predict how many and what elements can appear in such a nuclear pile. It turned out that the currently observed abundance of light elements is in good agreement with the calculations. This means that the physical laws known to us are the same in the entire observable part of the Universe and were such already in the first seconds after the appearance of our world. Moreover, about 98% of the helium existing in nature was formed precisely in the first seconds after the Big Bang.

Immediately after birth, the Universe went through an inflationary period of development - all distances rapidly increased (from the point of view of an internal observer). However, the energy density at different points in space cannot be exactly the same - some inhomogeneities are always present. Suppose that in some area the energy is slightly greater than in neighboring ones. But since all sizes are growing rapidly, then the size of this area should also grow. After the end of the inflationary period, this expanded area will have slightly more particles than the space around it, and its temperature will be slightly higher.

Realizing the inevitability of the emergence of such areas, supporters of the inflationary theory turned to the experimenters: "it is necessary to detect temperature fluctuations ..." - they stated. And in 1992 this wish was fulfilled. Almost simultaneously, the Russian satellite "Relikt-1" and the American "COBE" detected the required fluctuations in the temperature of the cosmic microwave background radiation. As already mentioned, the modern Universe has a temperature of 2.7 K, and the deviations of temperature from the mean found by scientists were approximately 0.00003 K. It is not surprising that such deviations were difficult to detect before. So the inflationary theory received another confirmation.

With the discovery of temperature fluctuations, another exciting opportunity has emerged - to explain the principle of galaxy formation. Indeed, in order for gravitational forces to compress matter, an initial germ is needed - an area with increased density. If matter is uniformly distributed in space, then gravity, like Buridan's donkey does not know which direction to take. But it is precisely the areas with an excess of energy that generate inflation. Now the gravitational forces know what to act on, namely the denser areas created during the inflationary period. Under the influence of gravity, these initially slightly denser regions will shrink and it is from them that stars and galaxies will form in the future.

The current moment of the evolution of the Universe is extremely well adapted for life, and it will last for many more billions of years. Stars will be born and die, galaxies will rotate and collide, and clusters of galaxies will fly farther and farther apart. Therefore, humanity has plenty of time for self-improvement. True, the very concept of “now” for such a huge universe as ours is poorly defined. So, for example, the life of quasars observed by astronomers, remote from the Earth by 10-14 billion light years, is separated from our "now" just by those same 10-14 billion years. And the farther into the depths of the Universe we look with the help of various telescopes, the earlier period of its development we observe.

Today, scientists are able to explain most of the properties of our universe, from 10 -42 seconds to the present and beyond. They can also trace the formation of galaxies and predict the future of the universe with some confidence. Nevertheless, a number of "small" incomprehensibility still remains. First of all, this is the essence of the hidden mass (dark matter) and dark energy. In addition, there are many models that explain why our Universe contains many more particles than antiparticles, and we would like to decide in the end on the choice of one correct model.

As the history of science teaches us, it is usually “minor imperfections” that open up further development paths, so that future generations of scientists will certainly have something to do. In addition, deeper questions are also already on the agenda of physicists and mathematicians. Why is our space three-dimensional? Why are all the constants in nature as if “fitted” so that intelligent life arises? And what is gravity? Scientists are already trying to answer these questions.

And of course, leave room for surprises. It should not be forgotten that such fundamental discoveries as the expansion of the Universe, the presence of relic photons and vacuum energy were made, one might say, by chance and were not expected by the scientific community.

Possible scenarios for the development of our world

1. Pulsating model of the Universe, in which after the period of expansion comes the period of contraction and everything ends with the Big Bang
2. A universe with a strictly adjusted average density exactly equal to the critical one. In this case, our world is Euclidean, and its expansion slows down all the time
3. Uniformly expanding by inertia Universe. Until recently, data on the calculation of the average density of our Universe testified in favor of such an open model of the world.
4. A world expanding at an ever-increasing rate. The latest experimental data and theoretical studies suggest that the Universe is expanding faster and faster, and despite the Euclidean nature of our world, most of the galaxies will be inaccessible to us in the future. And the dark energy that is today associated with some kind of internal energy of the vacuum that fills all space is to blame for such a strange arrangement of the world.

What awaits our Universe in the future? Until a few years ago, theorists had only two options in this regard. If the energy density in the universe is low, then it will expand forever and gradually cool down. If the energy density is greater than a certain critical value, then the expansion stage will be replaced by the compression stage. The universe will shrink in size and heat up. This means that one of the key parameters determining the development of the Universe is the average energy density. So, astrophysical observations carried out before 1998 showed that the energy density is approximately 30% of the critical value. And inflationary models predicted that the energy density should be equal to the critical one. Apologists of the inflationary theory were not very embarrassed. They shrugged off their opponents and said that the missing 70% "somehow will be found." And they really did. This is a great victory for the theory of inflation, although the energy found was so strange that it raised more questions than answers. It seems that the dark energy we are looking for is the energy of the vacuum itself.

In the view of people who are not connected with physics, vacuum is “when there is nothing” - no matter, no particles, no fields. However, this is not quite true. The standard definition of a vacuum is a state in which there are no particles. Since energy is contained precisely in particles, then, as almost everyone reasonably believed, including scientists, there are no particles - there is no energy either. So the vacuum energy is zero. This whole blissful picture collapsed in 1998, when astronomical observations showed that the recession of galaxies deviates slightly from Hubble's law. The shock caused by these observations among cosmologists did not last long. Very quickly began to publish articles explaining this fact. The simplest and most natural of them was the idea of the existence of positive vacuum energy. After all, vacuum, after all, simply means the absence of particles, but why can only particles have energy? The discovered dark energy turned out to be surprisingly uniformly distributed in space. Such homogeneity is difficult to achieve, because if this energy were contained in some unknown particles, the gravitational interaction would force them to gather into grandiose conglomerates, similar to galaxies. Therefore, the energy hidden in the space-vacuum, very elegantly explains the structure of our world.

However, other, more exotic, variants of the world order are also possible. For example, the Quintessence model, the elements of which were proposed by the Soviet physicist A.D. Dolgov in 1985, suggests that we are still sliding down the very hill that was mentioned at the beginning of our story. Moreover, we have been rolling for a very long time, and there is no end in sight to this process. The unusual name, borrowed from Aristotle, denotes a certain " new entity”, designed to explain why the world works this way and not otherwise.

Today, there are much more options for answering the question about the future of our Universe. And they essentially depend on which theory explaining latent energy is correct. Let us assume that the simplest explanation is true, in which the vacuum energy is positive and does not change with time. In this case, the Universe will never shrink and we will not be threatened with overheating and the Big Bang. But all good things come at a price. In this case, as calculations show, we will never be able to reach all the stars in the future. Moreover, the number of galaxies visible from the Earth will decrease, and in 10-20 billion years only a few neighboring galaxies will remain at the disposal of mankind, including ours - Milky Way, as well as neighboring Andromeda. Humanity will no longer be able to increase quantitatively, and then it will be necessary to deal with its qualitative component. As a consolation, we can say that several hundred billion stars that will be available to us in such a distant future are also quite a lot.

However, do we need stars? 20 billion years is a long time. After all, in just a few hundred million years, life evolved from trilobites to modern humans. So our distant descendants may be appearance and opportunities to be even more different from us than we are from trilobites. What promises them even more distant future, according to the forecasts of modern scientists? It is clear that stars will “die” in one way or another, but new ones will also form. This process is also not endless - in about 10 14 years, according to scientists, only faintly luminous objects will remain in the Universe - white and dark dwarfs, neutron stars and black holes. Almost all of them will also die in 10 37 years, having exhausted all their energy reserves. By this time, only black holes will remain, having absorbed all the rest of the matter. What can destroy a black hole? Any of our attempts to do this only increase its mass. But "nothing lasts forever under the moon." It turns out that black holes slowly, but radiate particles. This means that their mass is gradually decreasing. All black holes should also disappear in about 10,100 years. After that, only elementary particles will remain, the distance between which will greatly exceed the size of the modern Universe (about 1090 times) - after all, the Universe has been expanding all this time! And, of course, the vacuum energy will remain, which will absolutely dominate the Universe. By the way, the properties of such a space were first studied by W. De Sitter back in 1922. So our descendants will either have to change the physical laws of the universe, or move to other universes. Now it seems incredible, but I want to believe in the power of mankind, no matter how it, humanity, may look in such a distant future. Because he has plenty of time.

By the way, it is possible that even now we, without knowing it, are creating new universes. In order for a new universe to arise in a very small region, it is necessary to initiate an inflationary process, which is possible only at high energy densities. But experimenters have long been creating such areas by colliding particles in accelerators ... And although these energies are still very far from inflationary, the probability of creating a universe on an accelerator is no longer equal to zero. Unfortunately, we are the same “remote observer” for whom the lifetime of this “man-made” universe is too short, and we cannot penetrate into it and see what is happening there ...

Although this is not the only theory of the origin of the World. Theologians believed that the Universe was created by God, the Creator. Moreover, different peoples there were different theories, such as the biblical theory. The creation of the world took six days.

On the first day “In the beginning God created the heavens and the earth. The earth was bottomless and empty, and darkness was over the abyss…”, then God said: “Let there be light!”

On the second day, God said: “Let there be a firmament in the midst of the waters, and let it separate the water from the water!”

On the third day, God said, “Let the waters that are under the sky be gathered into one place, and let dry land appear!”

The fourth day came, God said: “Let there be lights in the firmament of heaven, to separate the day and night, and for signs and times, and days and years; and may they be lamps in the firmament of heaven to shine on the Earth! “This meant the appearance of the Sun, Moon and stars.

On the fifth day God created reptiles, animals, fish and “every feathered bird”, and on the sixth day he created the first man.

From another holy book, the Koran, you can also learn about the six-day creation of the World, about how God (Allah) created “seven heavens” and “seven lands”, and at first the heavens and earths were connected, and then separated.

Inflationary and theological theories are the most common on Earth, and there will always be supporters of one theory or another. I would like to take a closer look at the topic of the origin and evolution of stars and planets. Let's discuss in more detail what the stars are - these luminous points in the sky - in the light of the modern concept.

First, a protostar is formed. Particles of a giant moving gas and dust cloud in a certain region of space are attracted to each other due to gravitational forces. This happens very slowly, because the forces proportional to the masses of the atoms (mainly hydrogen atoms) and dust particles entering the cloud are extremely small. However, the particles gradually approach each other, the density of the cloud increases, it becomes opaque, the resulting spherical “lump” begins to rotate little by little, and the force of attraction also grows, because now the mass of the “coma” is large. More and more particles are captured, more and more density of matter. The outer layers press on the inner ones, the pressure in the depths increases, and, therefore, the temperature also rises. (This is exactly the case with gases that have been studied in detail on Earth). Finally, the temperature becomes so high - several million degrees - that conditions are created in the core of this formed body for the nuclear fusion reaction to proceed: hydrogen begins to turn into helium. You can find out about this by registering the fluxes of neutrinos - elementary particles released during such a reaction. The reaction is accompanied by a powerful flow of electromagnetic radiation, which presses (by the force of light pressure, first measured in the Earth laboratory by P. Lebedev) on the outer layers of matter, counteracting gravitational compression. Finally, the contraction stops as the pressures balance and the protostar becomes a star. To go through this stage of its evolution, a protostar needs several million years if its mass is greater than the sun's, and several hundred million years if its mass is less than the sun's. There are very few stars whose masses are less than 10 times that of the sun.

Mass is one of the important characteristics of stars. It is curious to note that double stars are quite common - they form near each other and rotate around a common center. They account for 30 to 50 percent of the total number of stars. The occurrence of binaries is probably related to the distribution of the angular momentum of the initial cloud. If such a pair forms a planetary system, then the motion of the planets can be quite intricate, and the conditions on their surfaces will vary greatly depending on the location of the planet in orbit in relation to the luminaries. It is very possible that stationary orbits, such as those that can exist in the planetary systems of single stars (and exist in the solar system), will not be at all. Ordinary, single stars in the process of their formation begin to rotate around their axis.

Another important characteristic is the radius of the star. There are stars - white dwarfs, the radius of which does not exceed the radius of the Earth, there are also such - red giants, the radius of which reaches the radius of the orbit of Mars. Chemical composition stars according to spectroscopic data, on average, this is: for 10,000 hydrogen atoms there are 1000 helium atoms, 5 oxygen atoms, 2 nitrogen atoms, 1 carbon atom, and even fewer other elements. Because of the high temperatures, the atoms ionize, so that the matter of the star is mostly hydrogen-helium plasma - a generally electrically neutral mixture of ions and electrons. Depending on the mass and chemical composition of the initial cloud, the formed star falls into one or another section of the so-called main sequence on the Hertzsprung-Russell diagram. The latter is a coordinate plane, on the vertical axis of which the luminosity of the star is plotted (i.e., the amount of energy emitted by it per unit time), and on the horizontal axis - its spectral type (characterizing the color of the star, which in turn depends on the temperature of its surface) . At the same time, “blue” stars are hotter than “red” ones, and our “yellow” Sun has an intermediate surface temperature of about 6000 degrees) (Fig. 2). Traditionally, the spectral classes from hot to cold are denoted by the letters O, B, A, F, G, K, M, with each class divided into ten subclasses. So, our Sun has a spectral type G2. The diagram shows that most of the stars are located along a smooth curve going from the upper left corner to the lower right. This is the main sequence. Our Sun is also on it. As hydrogen "burns out" in the center of the star, its mass changes slightly and the star shifts slightly to the right along the main sequence. Stars with masses of the solar order are on the main sequence of 10-15 billion years (our Sun has been on it for about 4.5 billion years). Gradually, less and less energy is released in the center of the star, the pressure drops, the core contracts, and the temperature in it rises. Nuclear reactions now take place only in a thin layer at the boundary of the core inside the star. As a result, the star as a whole begins to "swell", and its luminosity increases. The star leaves the main sequence and moves to the upper right corner of the Hertzsprung-Russell diagram, turning into the so-called "red giant". After the temperature of the shrinking (now helium) core of the red giant reaches 100-150 million degrees, a new nuclear reaction fusion - the conversion of helium into carbon. When this reaction also exhausts itself, the shell is ejected - a significant part of the mass of the star turns into a planetary nebula. The hot inner layers of the star are "outside", and their radiation "inflates" the separated shell. After several tens of thousands of years, the shell dissipates, and a small, very hot, dense star remains. Slowly cooling down, it moves to the lower left corner of the diagram and turns into a "white dwarf". White dwarfs appear to represent the final stage in the normal evolution of most stars.

But there are also anomalies. Some stars flare up from time to time, turning into new stars. At the same time, they each time lose about a hundredth of a percent of their mass. Of the well-known stars, we can mention the new one in the constellation Cygnus, which flared up in August 1975 and stayed in the sky for several years. But sometimes supernova explosions also occur - catastrophic events leading to the complete destruction of a star, in which a short time more energy is emitted than from billions of stars in the galaxy to which the supernova belongs. Such an event was recorded in Chinese chronicles in 1054: such a bright star appeared in the sky that it could be seen even during the day. The result of this event is now known to us as the Crab Nebula (Fig. 3), whose “slow” spread across the sky we have been observing in the last 300 years. The expansion velocity of its gases as a result of the explosion is about 1500 m / s, but it is very far away. By comparing the expansion rate with the apparent size of the Crab Nebula, we can calculate the time when it was a point object, and find its place in the sky - these times and places correspond to the time and place of the appearance of the star mentioned in the chronicles.

If the mass of the star left after the shell is ejected by the "red giant" exceeds the solar one by 1.2-2.5 times, then, as calculations show, a stable "white dwarf" cannot form. The star begins to shrink, and its radius reaches an insignificant size of 10 km, and the density of the matter of such a star exceeds the density of the atomic nucleus. It is assumed that such a star consists of densely packed neutrons, which is why it is called so - a neutron star. According to this theoretical model, a neutron star has a strong magnetic field, and it itself rotates at a tremendous speed - several tens or hundreds of revolutions per second. And only the pulsars discovered (precisely in the Crab Nebula) in 1967 - point sources of pulsed radio emission of high stability - have exactly the properties that one would expect from neutron stars. The observed phenomenon confirmed the concept.

If the remaining mass is even greater, then the gravitational contraction uncontrollably compresses the matter further. One of the predictions of the general theory of relativity comes into play, according to which matter will shrink into a point. This phenomenon is called gravitational collapse, and its result is a "black hole". This name is due to the fact that the gravitational mass of such an object is so great, the forces of attraction are so significant that not only any material body cannot leave the vicinity of a black hole, but even light - an electromagnetic signal - cannot be reflected or go "outside". ". Thus, it is impossible to directly observe a black hole; one can only guess about its existence from indirect effects. Moving in space towards a black hole (which we don't know anything about yet), you can find that the pattern of constellations located directly along the course begins to change. This is due to the fact that the light coming from the stars and passing near the black hole is deflected by its gravity. As you approach the hole, an empty area will appear, surrounded by luminous dots-stars, including those that have not been observed before. Light from some stars can, passing by the hole, turn around it, and then fall into the receivers of the observer. Thus, one star can give several images in different places. All this, of course, contradicts both our life experience and classical ideas, according to which light propagates in a straight line. However, in favor of the existence of black holes speaks whole line indirect astronomical observations, and the deflection of light under the influence of gravitational attraction is recorded already when the beam passes by such a “normal” object as the Sun.

Now we can move on to the topic of the formation of planets.

The motion of the planets in the solar system is ordered: they revolve around the sun in the same direction and almost in the same plane. Distances from one planet to another increase naturally. The orbits of the planets are close to circles, which allows them to revolve around the Sun for billions of years without colliding with each other.

If the motion of the planets is subject to the same order, then the process of their formation must be the same. This was shown in the 18th century. Immanuel Kant and Pierre Laplace. They came to the conclusion that in place of the planets, a nebula of gas and dust initially rotated around the Sun.

But where did this nebula come from? And how did gas and dust turn into large planetary bodies? These questions remained unresolved in the cosmogony of the 19th and early 20th centuries. The stumbling block was the problem of momentum of the planets. The mass of all planets in the system is 750 times less than the mass of the Sun. At the same time, only 2% of the total angular momentum falls on the share of the Sun, and the remaining 98% are contained in the orbital rotation of the planets.

Science took up these problems closely only in the second half of the 20th century. Almost until the end of the 80s. the early history of our planetary system had to be "recreated" only on the basis of data about itself. And only by the 90s. previously invisible objects became available for observation - gas and dust disks revolving around some young stars similar to the Sun.

The gas-dust nebula, in which the planets, their satellites, small solid bodies - meteorites, asteroids and comets, arose, is called a protoplanetary (or pre-planetary) cloud. The planets revolve around the Sun in almost the same plane, which means that the gas and dust cloud itself had a flattened, lenticular shape, which is why it is also called a disk. Scientists believe that both the Sun and the disk formed from the same rotating mass of interstellar gas - the protosolar nebula.

The initial phase of the protosolar nebula is the subject of research in astrophysics and stellar cosmogony. The study of its evolution, which led to the appearance of planets, is the central task of planetary cosmogony.

The age of the Sun is slightly less than 5 billion years. The age of the oldest meteorites is almost the same: 4.5-4.6 billion years. Equally old and early hardened parts of the lunar crust. Therefore, it is generally accepted that the Earth and other planets formed 4.6 billion years ago. The Sun belongs to the stars of the so-called second generation of the Galaxy. Its oldest stars are significantly (8-10 billion years) older than the solar system. There are also young stars in the Galaxy, which are only 100 thousand - 100 million years old (for a star this is a very young age). Many of them are similar to the Sun, and they can be used to judge the initial state of our system. Observing several dozen such objects, scientists came to the following conclusions.

The size of the pre-planetary cloud of the solar system should have exceeded the radius of the orbit of the last planet - Pluto. The chemical composition of the young Sun and the gas and dust cloud-disk surrounding it, apparently, was the same. The total content of hydrogen and helium in it reached 98%. The share of all other, heavier elements accounted for only 2%; volatile compounds prevailed among them, including carbon, nitrogen and oxygen: methane, ammonia, water, carbon dioxide. Other methods and in other branches of knowledge.

Calculations show that within the orbit of Pluto, i.e. disk with a radius of 40 AU. That is, the total mass of all the planets, together with the volatile substances lost by now, should have been 3-5% of the mass of the Sun. Such a cloud model is called a cloud of moderately low mass, and it is also confirmed by observations of circumstellar disks.

If the mass of the cloud were comparable to the mass of the central body, then a star would have to form - a companion of the Sun (or an explanation must be found for the ejection of huge excesses of matter from the solar system).

The least studied is the earliest stage - the separation of the protosolar nebula from the giant parent molecular cloud belonging to the Galaxy. In the 40s. Academician Otto Yulievich Schmidt put forward a hypothesis that has become generally accepted about the formation of the Earth and other planets from cold solid pre-planetary bodies - planetesimals. The previously widespread point of view that the planets are small remnants of the once red-hot giant gas clumps of the solar composition that have lost volatile substances has come into conflict with the sciences of the Earth.

The earth, as studies show, has never passed through a fiery-liquid, i.e. fully molten state. By investigating the evolution of the pre-planetary disk step by step, scientists have obtained a sequence of main stages in the development of the gas and dust disk that surrounded the Sun into a system of planets.

The initial size of the cloud exceeded modern size planetary system, and its composition corresponded to that observed in interstellar nebulae: 99% gas and 1% dust particles ranging in size from fractions of a micrometer to hundreds of micrometers. During the collapse, i.e. the fall of gas with dust on the central core (the future Sun), the substance was strongly heated, and interstellar dust could partially or completely evaporate. Thus, at the first stage, the cloud consisted almost entirely of gas, moreover, it was well mixed due to high turbulence - multidirectional, chaotic motion of particles.

As the disk forms, the turbulence subsides. It takes a little time - about 1000 years. In this case, the gas is cooled and solid dust particles are again formed in it. This is the first stage in the evolution of the disc.

A cooling pre-planetary cloud is characterized by very low pressure - less than ten thousandth of the atmosphere. At this pressure, the substance from the gas condenses directly into solid particles, bypassing the liquid phase. The most refractory compounds of calcium, magnesium, aluminum and titanium condense first, followed by magnesium silicates, iron and nickel. After that, only sulfur, free oxygen, nitrogen, hydrogen, all inert gases and some volatile elements remain in the gaseous medium.

In the process of condensation, water vapor becomes active, oxidizing iron and forming hydrarized compounds. The main cosmic elements - hydrogen and helium - remain in gaseous form. Their condensation would require temperatures close to absolute zero, under no circumstances attainable in a cloud.

The chemical composition of the dust grains in the preplanetary disk was determined by the temperature, which fell with distance from the Sun. Unfortunately, it is very difficult to calculate the temperature change in the preplanetary cloud. The chemical composition of the terrestrial planets shows that they consist mainly of substances condensed at high temperatures. The composition of the near part of the asteroid belt is dominated by stony bodies. As the distance from the Sun increases, the number of bodies in the asteroid belt increases, which contain minerals enriched with water and some volatile substances. They were found in meteorites, which are fragments of asteroids. Among the minor planets, apparently, there are no or very few icy bodies. Consequently, the boundary of water ice condensation should have passed behind them, no closer than the outer edge of the asteroid belt - more than three times farther from the Sun than the Earth.

At the same time, Jupiter's largest moons, Ganymede and Callisto, are half water. They are at a much greater distance from the Sun than the asteroid belt. This means that water ice condensed throughout Jupiter's formation zone. Starting from the orbit of Jupiter and further in the pre-planetary cloud, ice grains with inclusions of more refractory substances should have prevailed. In the region of the outer planets, at an even lower temperature, the dust grains contained ices of methane, ammonia, solid carbon dioxide, and other frozen volatile compounds. A similar composition currently has cometary nuclei that fly into the vicinity of the Earth from the far periphery of the solar system.

The first condensates - dust particles, ice floes - immediately after their appearance began to move through the gas to the central plane of the cloud. The larger the particles were, the faster they settled, since during their movement larger particles (unlike small ones) encounter less gas resistance per unit of their mass.

At the second stage, the formation of a thin dust layer - a dust subdisk - in the central plane of the cloud was completed. The stratification of the cloud was accompanied by an increase in particle size up to several centimeters. Colliding with each other, the particles stuck together, while the speed of their movement towards the central plane increased and growth also accelerated.

At some point, the dust density in the subdisk approached the critical value, exceeding the density of the gas by ten times. When the critical density is reached, the dust layer becomes gravitationally unstable. Even very weak seals that randomly appear in it do not dissipate, but, on the contrary, thicken with time. At first, a system of rings could form in it, which, when compacted, also lost their stability and, at the third stage of the evolution of the disk, broke up into many separate small clumps. Because of the spin inherited from the spinning disk, these clumps cannot immediately compress to the density of solids. But, colliding with each other, they unite and become more and more dense. At the fourth stage, a swarm of pre-planetary bodies about a kilometer in size is formed; their initial number reaches many millions.

The described path of formation of bodies is possible if the dust subdisk is very flat: its thickness must be many times smaller than its diameter. Such objects still exist today, such as the rings of Saturn.

Another way for the formation of pre-planetary bodies, in addition to gravitational condensation, is their direct growth during collisions of small particles. They can stick together only at low impact speeds, with a sufficiently loosened contact surface, or in the case of an increased adhesive force.

Such bodies, whichever of the two ways they may have arisen, have served building material for the formation of planets, satellites and meteoroids.

Scientists suggest that pre-planetary bodies formed at the periphery of the cloud at a very low temperature have survived to this day in the cometary cloud, where they were thrown by gravitational perturbations of the giant planets.

The formation of pre-planetary bodies in the gas and dust cloud lasted tens of thousands of years - an extremely insignificant period on the cosmogonic time scale. The further association of bodies into planets - the accumulation of planets - is a much longer process that took hundreds of millions of years. It is very difficult to restore it in detail: the subsequent geological stage, which has lasted for more than 4 billion years, has by now erased the features of the initial state of the planets.

The pre-planetary swarm was a complex system of a large number of planetesimal bodies. They had different masses and moved at different speeds. In addition to the orbital velocity common for all bodies at a given distance from the Sun, these bodies had additional individual velocities with randomly distributed directions. In the pre-planetary cloud, small particles and bodies have always been the most numerous. A smaller proportion were bodies of intermediate sizes. There were very few large bodies comparable to the Moon or Mars.

The evolution of the cloud led to the fact that it was in a few large bodies that the bulk of all planetary matter was concentrated. This hierarchy has been preserved to this day: the total mass of the planets is much higher than the total mass of all small bodies - satellites, asteroids, comets and dust particles.

Large bodies with their gravitational influence gradually increase the chaotic speeds of planetesimals. Each approach of two bodies changes the nature of their movement in circumsolar orbits. As a rule, the orbits become more elongated and more inclined towards the central plane. Thus, during this stage, there is a "buildup" of the system from a very flat disk to a thicker one. In this case, the bodies acquire the greater chaotic speeds, the smaller their mass, and vice versa.

Bodies grow very unevenly. The largest of them in any ring zone, where the orbits of other bodies intersect with its orbit, receives a privileged position and in the future can become the embryo of the planet.

The role of collisions can be explained by the example of the modern asteroid belt, where the consequences of impacts are not the same for different bodies. At the present time, the chaotic velocities of asteroids are approximately 5 km/s; with the same speeds they collide with small bodies. The impact energy during the fall of a body on the surface of an asteroid is usually so high that not only the fallen body itself is destroyed, but also part of the asteroid. An impact crater is formed, the ejecta from which scatter at speeds of hundreds of meters per second. The expanding material falls back to the surface of the asteroid only if it has sufficient gravity.

All modern belt asteroids lose mass in collisions. Only a few of the largest (with radii greater than 200 km) are at best able to maintain their mass. Similarly, collisions of planetesimals led to the growth of only the largest of them.

The inner part of the solar system is formed by the planets of the terrestrial group - Mercury, Venus, Earth and Mars. The composition of these planets indicates that their growth occurred in the absence of light gases due to stony particles and bodies containing various amounts of iron and other metals.

The main condition for the growth of bodies during collisions is their low relative velocities at the initial stage. In order for bodies to reach kilometer sizes, chaotic velocities must not exceed 1 m/s. This is possible only if there is no strong influence from outside. In the growth zone of the terrestrial planets external influences were weak, only in the zone of Mars the influence of Jupiter affected, slowing down its growth and reducing its mass. In the asteroid belt, on the contrary, the perturbing influence of the neighboring giant planet Jupiter is clearly visible. The stage of association of planetesimals into planets and their growth lasted more than 100 million years.

The period of dissipation (scattering) of gas from the zone of terrestrial planets lasted no more than 10 million years. The gas was mainly blown out by the solar wind; streams of charged particles (protons and electrons) ejected from the surface of the Sun at speeds of hundreds of kilometers per second.

The solar wind cleared of gas not only the region of the planets of the terrestrial group, but also more distant spaces of the planetary system. However, the giant planets Jupiter and Saturn have already managed to absorb a huge amount of matter, the vast majority of the mass of the entire planetary system.

How did the giant planets form? Their embryos could arise in two ways: through the gravitational instability of the gaseous masses of the pre-planetary disk or through the increasing capture of the gaseous atmosphere on the massive core of planetesimals.

In the first case, the mass of the pre-planetary cloud should have been a significant fraction of the mass of the Sun, and the composition of the giant planets should have coincided with the solar one. Neither of these correspond to the facts. Recent studies have shown that the cores of Jupiter and Saturn seem to contain elements heavier than hydrogen and helium, constituting at least 5-6% of the planet's mass. This is significantly more than one would expect from the solar abundance of chemical elements. This means that the second way is more probable: first, as with the terrestrial planets, a massive embryonic nucleus is formed from rocky and icy planetesimals, and then it builds up a hydrogen-helium shell.

The process of adding matter is called accretion. Starting from one or two masses of the Earth, the body can not only keep the gaseous atmosphere on the surface, but also capture new portions of gas at an accelerating rate if there is a gaseous medium in the path of its movement. Accretion stops only when the gas is completely exhausted. The duration of this process is much shorter than the stage of formation of the nucleus-embryo. According to the calculations of scientists, the growth of the core of Jupiter lasted tens, and the core of Saturn - hundreds of millions of years.

As long as the core, immersed in the gas, is small, it attaches only a small atmosphere that is in equilibrium. But at a certain critical mass (2-3 Earth masses), the gas begins to fall on the body at an increasing rate, greatly increasing its mass. In a stage of rapid accretion in just a few hundred years, Jupiter grew to a mass in excess of 50 Earth masses, absorbing gas from its sphere of gravitational influence. Then the accretion rate dropped, as the gas could only reach the planet by slow diffusion from the wider zone of the disk.

At the same time, Jupiter continued to grow at the expense of solid planetesimals, and those that were not absorbed by it could be thrown back by its gravity either inward, into the asteroid zone and the Mars zone, or away from the solar system. Jupiter communicated speeds to solid bodies more than the speed of release: in order to leave solar system from the orbit of Jupiter, a speed of only 18 km / s is sufficient, and a body flying from Jupiter at a distance of several of its radii accelerates to tens of kilometers per second.

Saturn formed in a similar way. But its core did not grow as fast and reached critical mass later. By this time, due to the action of the solar wind, there was less gas left than in Jupiter's zone at the beginning of its accretion. That is why, compared with Jupiter, Saturn contains several times more condensed matter and differs even more in composition from the Sun.

Uranus and Neptune grew even more slowly, and gas from the outer zone dissipated faster. When these planets reached critical mass, there was almost no gas left in their zones. Therefore, hydrogen and helium account for only about 10% of the mass of Uranus, while Neptune contains even less of them. The main components of these bodies are water, methane and ammonia, as well as oxides of heavy elements; gases enter planetary atmospheres.

The two-stage scheme for the formation of giant planets (the formation of nuclei from condensed matter and gas accretion onto these nuclei) is confirmed by facts. First, it turned out that modern masses the nuclei of Jupiter and Saturn, as well as the masses of Uranus and Neptune without their atmospheres, have similar values: 14-20 masses of the Earth, while the proportion of gases - hydrogen and helium - in them naturally decreases with distance from the Sun. Secondly, there are such "material evidence" of the early history of the giant planets as their satellites and rings. The accretion of gas onto the planets is accompanied by the formation of gas and dust disks around them, in which satellites are formed.

At the stage of rapid accretion, a huge amount of energy was released, and the upper layers of the planets became very hot. The maximum surface temperature of Jupiter and Saturn, apparently, was several thousand degrees - almost like that of stars. In the disk of Jupiter, where its satellites were formed, at close distances from the planet the temperature was higher than the condensation point of water vapor, and at more distant ones it was lower. Indeed, the nearest satellites of Jupiter, including Io and Europa, are composed of stony substances, and the more distant ones - Ganymede and Callisto - are half of water ice. At Saturn, the temperature in the disk was lower, so the ice condensed there at all distances (particles of Saturn's rings and all its close satellites are icy).

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