Scenarios for the future of the universe. The evolution of the universe, its various models

The future of the Universe is a question considered within the framework of physical cosmology. Various scientific theories have predicted many possible futures, among which there are opinions about both destruction and the infinite life of the Universe.

After the theory of the creation of the Universe through the Big Bang and its subsequent rapid expansion was accepted by most scientists, the future of the Universe became a matter of cosmology, considered from different points of view depending on the physical properties of the Universe: its mass and energy, average density and expansion rate.

The Universe continues its evolution even today, as its parts evolve. The time of this evolution for each type of objects differs by more than an order of magnitude. And when the life of objects of one type ends, then for others everything is just beginning. This allows us to divide the evolution of the Universe into epochs. However, the final form of the evolutionary chain depends on the rate and acceleration of the expansion: with a uniform or almost uniform rate of expansion, all stages of evolution will be passed and all energy reserves will be exhausted. This development is called heat death.

If the speed continues to increase, then, starting from a certain moment, the force that expands the Universe will first exceed the gravitational forces that keep galaxies in clusters. Behind them, galaxies and star clusters will disintegrate. And finally, the most closely related star systems will be the last to disintegrate. After some time, electromagnetic forces will not be able to keep the planet and smaller objects from disintegrating. The world will again exist in the form of individual atoms. At the next stage, individual atoms will also decay. It is impossible to say exactly what will follow this: at this stage, modern physics ceases to work.

The above scenario is the Big Rip scenario.

There is also an opposite scenario - the Big Compression. If the expansion of the Universe slows down, then in the future it will stop and contraction will begin. The evolution and appearance of the Universe will be determined by cosmological epochs until its radius becomes five times smaller than the current one. Then all the clusters in the Universe will form a single megacluster, but the galaxies will not lose their individuality: the birth of stars will still occur in them, supernovae will flare up and, possibly, biological life will develop. All this will come to an end when the Universe shrinks another 20 times and becomes 100 times smaller than it is now; at that moment the Universe will be one huge galaxy.

The temperature of the relict background will reach 274 K and ice will begin to melt on terrestrial planets. Further compression will lead to the fact that the radiation of the relic background will eclipse even the central luminary of the planetary system, burning out the last sprouts of life on the planets. And soon after that, the stars and planets themselves will evaporate or be torn to pieces. The state of the Universe will be similar to what it was in the first moments of its birth. Further events will resemble those that took place at the beginning, but rewinded in reverse order: atoms decay into atomic nuclei and electrons, radiation begins to dominate, then atomic nuclei begin to decay into protons and neutrons, then the protons and neutrons themselves decay into separate quarks, there is a great unification. At this moment, as in the moment of the Big Bang, the laws of physics known to us cease to work, and it is impossible to predict the future fate of the Universe.

Cosmological epochs
Let us introduce the concept of a cosmological decade (η) as a decimal index of the degree of the age of the Universe in years:

The era of stars (6 This time is already without any energy sources. Only the residual products of all processes occurring in past decades have survived: photons with a huge wavelength, neutrinos, electrons and positrons. The temperature is rapidly approaching absolute zero. From time to time, positrons and electrons form unstable positronium atoms, their long-term fate is complete annihilation.

In the scientific world, it is generally accepted that the Universe originated as a result of the Big Bang. This theory is based on the fact that energy and matter (the foundations of all things) were previously in a state of singularity. It, in turn, is characterized by the infinity of temperature, density and pressure. The singularity state itself defies all the laws of physics known to the modern world. Scientists believe that the Universe arose from a microscopic particle, which, due to unknown reasons, came into an unstable state in the distant past and exploded.

The term "Big Bang" began to be used since 1949 after the publication of the works of the scientist F. Hoyle in popular science publications. Today, the theory of the “dynamic evolving model” has been developed so well that physicists can describe the processes occurring in the Universe as early as 10 seconds after the explosion of a microscopic particle that laid the foundation for everything.

There are several proofs of the theory. One of the main ones is the relic radiation, which permeates the entire Universe. It could have arisen, according to modern scientists, only as a result of the Big Bang, due to the interaction of microscopic particles. It is the relic radiation that makes it possible to learn about those times when the Universe looked like a blazing space, and there were no stars, planets and the galaxy itself. The second proof of the birth of everything that exists from the Big Bang is the cosmological redshift, which consists in a decrease in the frequency of radiation. This confirms the removal of stars, galaxies from the Milky Way in particular and from each other in general. That is, it indicates that the Universe expanded earlier and continues to do so until now.

A Brief History of the Universe

• 10 -45 - 10 -37 sec- inflationary expansion


• 10 -6 sec- the emergence of quarks and electrons


• 10 -5 sec- the formation of protons and neutrons


• 10 -4 sec - 3 min- the emergence of nuclei of deuterium, helium and lithium


• 400 thousand years- formation of atoms


• 15 million years- continued expansion of the gas cloud


• 1 billion years- the birth of the first stars and galaxies


• 10 - 15 billion years- the emergence of planets and intelligent life


• 10 14 billion years- termination of the process of birth of stars


• 10 37 billion years- depletion of the energy of all stars


• 10 40 billion years- evaporation of black holes and the birth of elementary particles


• 10 100 billion years- completion of the evaporation of all black holes

The Big Bang theory has become a real breakthrough in science. It allowed scientists to answer many questions regarding the birth of the universe. But at the same time, this theory gave rise to new mysteries. Chief among them is the cause of the Big Bang itself. The second question to which modern science has no answer is how space and time appeared. According to some researchers, they were born together with matter, energy. That is, they are the result of the Big Bang. But then it turns out that time and space must have some kind of beginning. That is, a certain entity, constantly existing and not dependent on their indicators, could well initiate the processes of instability in a microscopic particle that gave rise to the Universe.

The more research is done in this direction, the more questions arise for astrophysicists. The answers to them await mankind in the future.

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 20th 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 billion 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 emergence of our world, created at the end of the 20th century, made it possible to make significant progress in resolving these issues, and the general picture of the first moments of the Universe is already well drawn today, although many problems are still waiting in the wings.

Scientific view of the creation of the world

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 arose, 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 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, everything cools down over time, 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 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 Russian physicists E. Gliner and A. Starobinsky, as well as the American A. Gus, a new phenomenon was described - a super-rapid 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.

The essence of inflation

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 hardly perceives 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 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 at an 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 be used 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 10 27 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 being 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 terrainseveral 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.

In response to tricky questions

Today, our universe is made up of a large number of stars, not to mention 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 cm 3. 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, because 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.

These dangerous antiparticles

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 the relict radiation is precisely the 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 consequence, the cooling of the radiation, this energy rapidly decreased. Now the energy of relic radiation is about ten thousand times (10 4 times) less than the energy contained in massive elementary particles.

Gradually, the temperature of the universe dropped to 10 10 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.

The birth of galaxies

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 must 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, the 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 come to explain the principle of galaxy formation. After all, in order for the gravitational forces to compress matter, an initial germ is needed a region with increased density. If matter is uniformly distributed in space, then gravity, like Buridan's donkey, does not know in which direction to act. 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.

happy present

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 1014 billion light years, is separated from our "now" just by those same 1014 billion years.

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, it 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.

Vacuum energy origin and consequences

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 being sought is the energy of the vacuum itself.

In the view of people 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 kind of "new essence" 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 with 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 1020 billion years, only a few neighboring galaxies will remain at the disposal of mankind, including our 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 is also 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 will probably be even more different from us in appearance and capabilities 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 weakly 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 far exceed the size of the modern Universe (about 10 90 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 on 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 ...

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 research suggests 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.

Sergey Rubin, Doctor of Physical and Mathematical Sciences

The future of the Universe is one of the main questions of cosmology, the answer to which depends, first of all, on such characteristics and properties of the Universe as its mass, energy, average density, and expansion rate.

What do we know about the universe?

To begin with, it is necessary to define the very concept of "Universe", which takes place both in astronomy and philosophy. In the field of astronomy, the Universe is called the Metagalaxy or simply the astronomical Universe. However, from a theoretical point of view, which is taken into account by most models and scenarios for the development of the Universe, it is a colossal system that goes beyond the limits of possible observation.

One of the most important properties of the Universe, which was discovered relatively recently, is an almost uniform and isotropic expansion, which also turned out to be accelerated. Depending on the duration of this expansion, the history of the universe may take one of two proposed scenarios.

In the first case, the expansion will continue indefinitely, along with this, the average density of matter in the Universe will rapidly fall, approaching zero. In short, everything will begin with the collapse of clusters of galaxies, and will end with the fission of a proton into quarks.

The second scenario takes into account the postulates of the general theory of relativity (GR), which says that with a significant increase in the density of matter, space-time is bent. If the expansion nevertheless begins to slow down, then most likely at some point it will turn into a contraction. Then the Universe will begin to shrink, and the average density of its matter will grow rapidly. With such a course of events, according to GR, space-time will gradually curve until the Universe closes on itself, like the surface of an ordinary sphere, but with more dimensions than we used to imagine.

Cosmological epochs of the Universe

In an attempt to predict the future fate of the astronomical universe, scientists have divided its existence into the following stages:

Despite the fact that the matter of the Universe is gradually annihilating, the space itself can evolve according to four hypothetical scenarios:

1. If over time the expansion of the Universe slows down, and then turns into contraction, then the final stage of its life will be the Big Crunch. As a result, all matter collapses and returns to its original state - a singularity.
2. Another scenario is that the average density of matter in the Universe is precisely determined and is such that the expansion gradually slows down.
3. The most probable, in view of modern results of observations, model. It implies a uniform expansion of the universe, by inertia.
4. The rapid growth of the expansion rate of the Universe, which will lead our world to the so-called.