Is there anyone else in the universe. Life in the Universe and the search for its traces

1. Methanogens

In 2005, Heather Smith of the International Space University in Strasbourg and Chris McKay of NASA's Ames Research Center produced a report on the possibility of methane-based life, which they called "methanogens." Such a life form could breathe hydrogen, acetylene and ethane, exhaling methane instead of carbon dioxide. This would make it possible for life to exist on cold worlds such as Saturn's moon Titan.

Like Earth, Titan's atmosphere is mostly nitrogen, but it is mixed with methane. Titan is also the only place in the solar system where, in addition to Earth, there are many lakes and rivers (consisting of a mixture of ethane and methane). The liquid is considered essential for the molecular interactions of organic life, but until now ordinary water has been sought on other planets.

2. Silicon-based life

Silicon-based life is perhaps the most common form of alternative biochemistry depicted in popular science fiction. Silicon is so popular because it is very similar to carbon and can take four forms, just like carbon.

This opens up the possibility of a biochemical system based entirely on silicon, which is the most abundant element in the Earth's crust other than oxygen. Recently, a species of algae was discovered that uses silicon during its growth process. Full-fledged silicon life is unlikely to appear on Earth, since most free silicon is found in volcanic and igneous rocks made of silicate minerals. But the situation may be different in high temperature environments.

3. Other alternative biochemical systems

There are many other suggestions as to how life based on another element other than carbon might evolve. Like carbon and silicon, boron tends to form strong covalent molecular compounds, forming various hydride structural species in which the boron atoms are linked by hydrogen bridges. Like carbon, boron can form bonds with a nitrogen atom, resulting in compounds that have chemical and physical properties similar to alkanes, the simplest organic compounds.

All life on Earth is made of carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur, but in 2010 NASA scientists found a bacterium called GFAJ-1 that can incorporate arsenic instead of phosphorus into its cellular structure. GFAJ-1 thrives in the arsenic-rich waters of Mono Lake in California. Arsenic was considered poisonous to every living creature on the planet, but it turned out that life based on it is possible.

Ammonia has also been mentioned as a possible alternative to water for creating life forms. Biochemists have created nitrogen-hydrogen compounds using ammonia as a solvent, which can be used to create proteins, nucleic acids and polypeptides. Any ammonia-based life would have to exist at lower temperatures, at which ammonia becomes a liquid state.

Sulfur is believed to be the basis for the beginning of metabolism on Earth, and even today there are organisms that use sulfur instead of oxygen in their metabolism. Perhaps in another world evolution will develop based on sulfur. Some believe that nitrogen and phosphorus can also take the place of carbon under very specific conditions.

4. Memetic life

Richard Dawkins believes that "the development of life is about survival and reproduction." Life must be capable of reproduction and must develop in an environment where natural selection and evolution are possible. In his book The Selfish Gene, Dawkins noted that concepts and ideas develop in the brain and spread between people through communication. In many ways, this resembles the behavior and adaptation of genes. Dawkins introduced the concept of a meme, which describes a unit of transmission of human cultural evolution, analogous to a gene in genetics. When humanity became capable of abstract thinking, these memes began to develop further, regulating tribal relations and forming the basis of the first culture and religion.

5. Synthetic life based on CNC

Life on Earth is based on two information-carrying molecules - DNA and RNA, and scientists have long wondered whether it is possible to create other similar molecules. Since any polymer can store information, RNA and DNA encode heredity and the transmission of genetic information, and the molecules themselves are capable of adapting over time through evolutionary processes. DNA and RNA are chains of molecules called nucleotides, which are made up of three chemical components—a phosphate, a five-carbon sugar, and one of five standard bases (adenine, guanine, cytosine, thymine, or uracil).

In 2012, a group of scientists from England, Belgium and Denmark developed for the first time in the world xeno-nucleic acid (XNA or XNA) - synthetic nucleotides that are functionally and structurally similar to DNA and RNA. Such molecules have been developed before, but this is the first time they have been shown to be capable of reproduction and evolution.

6. Chromodynamics, weak nuclear forces and gravitational life

In 1979, scientist and nanotechnologist Robert A. Freitas Jr. announced the possibility of non-biological life. He argued that metabolism of living systems was possible based on four fundamental forces - electromagnetism, the strong nuclear force (or QCD), weak nuclear forces and gravity.

Chromodynamic life may be possible based on the strong nuclear force, which is the strongest of the fundamental forces, but only over very short distances. He suggests that such an environment could exist on a neutron star, a super-dense object that has the mass of a star but is only 10 to 20 kilometers in size.

Freitas considers life forms based on weak nuclear forces to be less likely, since weak forces operate only in the sub-nuclear range and are not particularly strong.

There may also be gravitational beings, since gravity is the most widespread and effective fundamental force in the universe. Such creatures could receive energy from the very force of gravity in the Universe.

7. Dusty Plasma Life Form

As you know, organic life on Earth is based on molecules of carbon compounds. But in 2007, an international team of scientists led by V.N. Tsytovich from the Institute of General Physics of the Russian Academy of Sciences documented that under certain conditions, inorganic dust particles can organize into spiral structures, which can then interact with each other almost identically to the processes of organic dust. chemistry. A similar process occurs in the plasma state, the fourth state of matter (besides solid, liquid and gas), in which electrons are stripped from atoms.

Tsytovich's team discovered that when electrons are separated and the plasma becomes polarized, particles in the plasma, without external influence, self-organize into spiral structures that attract each other. These helical structures can also separate, further forming copies of the original structure, similar to DNA.

8. iCHELL

Professor Lee Cronin, head of the department of chemistry at the College of Science and Technology at the University of Glasgow, has a dream - he wants to create living cells from metal. To do this, the professor is experimenting with polyoxometalates, metal atoms, combining them with oxygen and phosphorus to create bubble-like cells he calls inorganic chemical cells, or iCHELLs. By changing the composition of the metal oxide, the bubbles can be given the characteristics of biological cell membranes.

9. Gaia hypothesis

In 1975, James Lovelock and Sidney Upton wrote an article for New Scientist, "The Search for Gaia." Although life is traditionally believed to have originated on Earth, Lovelock and Upton argue that life itself takes an active role in determining and maintaining the conditions for its survival. They suggested that all life on Earth, down to the air, oceans and land, is part of a single system, which is a living super-organism capable of changing the surface temperature and composition of the atmosphere to ensure its survival.

This system is Gaia, in honor of the Greek goddess of the Earth. It exists to maintain the homeostasis by which the biosphere can exist in the Earth system. The Earth's biosphere supposedly has a number of natural cycles, and if something goes wrong with one of them, the rest compensate for it in order to maintain conditions for the existence of life. With this hypothesis it is easy to explain why the atmosphere is not composed mainly of carbon dioxide or why the seas are not too salty.

10. Von Neumann probes

The possibility of artificial life based on machines has been discussed for a long time. Today we will consider the concept of von Neumann probes. The mid-20th century Hungarian mathematician and futurist John von Neumann believed that in order to replicate the functions of the human brain, a machine would need self-awareness and a self-healing mechanism. He came up with the idea of creating self-replicating machines, which would have some kind of universal constructor that would allow them to not only build replicas of themselves, but also potentially improve or change versions, making long-term evolution possible.

Von Neumann robotic probes would be ideally suited to reach distant star systems and create factories in which they would multiply by the thousands. Moreover, moons, rather than planets, are more suitable for von Neumann probes, since they can easily land and take off from these satellites, and also because there is no erosion on the satellites. These probes will multiply from natural deposits of iron, nickel, etc., extracting raw materials to create robot factories. They will create thousands of copies of themselves, and then fly off to look for other star systems.

The universe still holds a huge number of mysteries and secrets. For example, such as .

Potentially habitable planets. Our Earth can well be used as a reference world for the existence of life. But scientists still need to consider many different conditions that are very different from ours. In which life in the Universe can be maintained in the long term.

How long has life existed in the Universe?

The earth was formed about 4.5 billion years ago. However, more than 9 billion years have passed since the Big Bang. It would be extremely arrogant to assume that the Universe needed all this time to create the necessary conditions for life. Inhabited worlds could have arisen much earlier. All the ingredients necessary for life are still unknown to scientists. But some are quite obvious. So what conditions must be met in order for there to be a planet that can support life?

The first thing you will need is the right type of star. All sorts of scenarios could exist here. A planet could exist in orbit around an active, powerful star and remain habitable despite its hostility. Red dwarfs, such as , can emit powerful flares and strip the atmosphere of a potentially habitable planet. But it is clear that a magnetic field, a thick atmosphere, and life that was smart enough to seek refuge during such intense events could very well combine to make such a world habitable.

But if the lifespan of a star is not too long, then the development of biology in its orbit is impossible. The first generation of stars, known as Population III stars, had a 100 percent chance of not having habitable planets. Stars need to at least contain some metals (heavy elements heavier than helium). In addition, the first stars lived short enough for life to appear on the planet.

Planet Requirements

So, enough time has passed for heavy elements to appear. Stars arose whose lifespan is estimated at billions of years. The next ingredient we need is the right type of planet. As far as we understand life, this means that a planet must have the following characteristics:

capable of maintaining a fairly dense atmosphere;
maintains uneven distribution of energy on its surface;
has liquid water on the surface;
has the necessary initial ingredients for the emergence of life;
has a powerful magnetic field.

A rocky planet that is large enough, has a dense atmosphere, and orbits its star at the right distance has a good chance. Considering that planetary systems are a fairly common phenomenon in space, and also that there are a huge number of stars in each galaxy, the first three conditions are quite easy to fulfill.

The star of the system may well provide the energy gradient of its planet. It can occur when exposed to its gravity. Or such a generator could be a large satellite orbiting a planet. These factors can cause geological activity. Therefore, the condition of uneven energy distribution is easily fulfilled. The planet must also have reserves of all the necessary elements. Its dense atmosphere should allow liquid to exist on the surface.

Planets with similar conditions must have arisen by the time the Universe was only 300 million years old.

Need more

But there is one nuance that needs to be taken into account. It consists in the fact that it is necessary to have sufficient quantity heavy elements. And their synthesis takes longer than it takes to produce rocky planets with the right physical conditions.

These elements must provide the correct biochemical reactions that are necessary for life. On the outskirts of large galaxies, this may take many billions of years and many generations of stars. Which will live and die in order to produce the required amount of the desired substance.

In hearts, star formation occurs frequently and continuously. New stars are born from the recycled remains of previous generations of supernovae and planetary nebulae. And the number of necessary elements can grow there quickly.

The galactic center, however, is not a very favorable place for life to arise. Gamma-ray bursts, supernovae, black hole formation, quasars and collapsing molecular clouds create an environment here that is unstable at best for life. It is unlikely that it will be able to arise and develop in such conditions.

To obtain the necessary conditions, this process must stop. It is necessary that star formation no longer occurs. That is why the very first planets most suitable for life probably did not arise in a galaxy like ours. But rather in a red-dead galaxy that stopped forming stars billions of years ago.

When we study galaxies, we see that 99.9% of their composition is gas and dust. This is the reason for the emergence of new generations of stars and the continuous process of star formation. But some of them stopped forming new stars about 10 billion years ago or more. When their fuel runs out, which can happen after a catastrophic major galactic merger, star formation suddenly stops. Blue giants simply end their lives when they run out of fuel. And they remain to slowly smolder further.

Dead galaxies

As a result, these galaxies are today called "red dead" galaxies. All their stars are stable, old and safe from the risks that regions of active star formation bring.

One of these, the galaxy NGC 1277, is very close to us (by cosmic standards).

Therefore, it is obvious that the first planets on which life could arise appeared no later than 1 billion years after the birth of the Universe.

The most conservative estimate is that there are two trillion galaxies. And so galaxies that are cosmic oddities and statistical outliers undoubtedly exist. Only a few questions remain: what is the prevalence of life, the probability of its emergence and the time required for this? Life can arise in the Universe even before reaching the billionth year. But a stable, permanently inhabited world is a much greater achievement than life that has just arisen.

For the evolution of living organisms from the simplest forms (viruses, bacteria) to intelligent beings, enormous time intervals are required, since the “driving force” of such selection is mutations and natural selection - processes that are random in nature. It is through a large number of random processes that the natural development from lower to higher forms of life is realized. Using our planet Earth as an example, we know that this time interval apparently exceeds a billion years. Therefore, only on planets orbiting sufficiently old stars can we expect the presence of highly organized living beings. Given the current state of astronomy, we can only talk about arguments in favor of the hypothesis of the multiplicity of planetary systems and the possibility of the emergence of life on them. Astronomy does not yet have rigorous proof of these most important statements. In order to talk about life, we must at least assume that fairly old stars have planetary systems. For the development of life on the planet, it is necessary that a number of general conditions be met. And it is quite obvious that life cannot arise on every planet.

We can imagine around every star that has a planetary system, a zone where temperature conditions do not exclude the possibility of the development of life. It is unlikely to be possible on planets like Mercury, the temperature of the part illuminated by the Sun is higher than the melting point of lead, or like Neptune, whose surface temperature is -200°C. However, one cannot underestimate the enormous adaptability of living organisms to unfavorable environmental conditions. It should also be noted that very high temperatures are much more “dangerous” for the life of living organisms than low ones, since the simplest types of viruses and bacteria can, as is known, be in a state of suspended animation at temperatures close to absolute zero.

In addition, it is necessary that the radiation of the star remains approximately constant over many hundreds of millions and even billions of years. For example, a large class of variable stars whose luminosities vary greatly with time (often periodically) should be excluded from consideration. However, most stars radiate with amazing consistency. For example, according to geological data, the luminosity of our Sun has remained constant over the past few billion years with an accuracy of several tens of percent.

For life to appear on a planet, its mass should not be too small. On the other hand, too much mass is also an unfavorable factor; on such planets the probability of the formation of a solid surface is low; they are usually gas balls with a density rapidly increasing towards the center (for example, Jupiter and Saturn). One way or another, the masses of planets suitable for the development of life must be limited both above and below. Apparently, the lower limit of the mass possibilities of such a planet is close to several hundredths of the Earth’s mass, and the upper limit is tens of times greater than the Earth’s. The chemical composition of the surface and atmosphere is very important. As you can see, the limits of the parameters of planets suitable for life are quite wide.

To study life, you must first define the concept of “living matter”. This question is far from simple. Many scientists, for example, define living matter as complex protein bodies with ordered metabolism. This point of view was held, in particular, by Academician A.I. Oparin, who worked a lot on the problem of the origin of life on Earth. Of course, metabolism is the most essential attribute of life, but the question of whether the essence of life can be reduced primarily to metabolism is controversial. After all, in the inanimate world, for example, in some solutions, metabolism is observed in its simplest forms. The question of defining the concept of “life” is very acute when we discuss the possibilities of life on other planetary systems.

Currently, life is defined not through the internal structure and substances that are inherent in it, but through its functions: a “control system”, which includes a mechanism for transmitting hereditary information that ensures safety to subsequent generations. Thus, due to the inevitable interference in the transmission of such information, our molecular complex (organism) is capable of mutations, and therefore of evolution.

The emergence of living matter on Earth (and, as can be judged by analogy, on other planets) was preceded by a rather long and complex evolution of the chemical composition of the atmosphere, which ultimately led to the formation of a number of organic molecules. These molecules subsequently served as “building blocks” for the formation of living matter.

According to modern data, planets are formed from a primary gas-dust cloud, the chemical composition of which is similar to the chemical composition of the Sun and stars; their initial atmosphere consisted mainly of the simplest compounds of hydrogen - the most common element in space. The majority of the molecules were hydrogen, ammonia, water and methane. In addition, the primary atmosphere should have been rich in inert gases - primarily helium and neon. Currently, there are few noble gases on Earth since they once dissipated (evaporated) into interplanetary space, like many hydrogen-containing compounds.

However, it seems that plant photosynthesis, during which oxygen is released, played a decisive role in establishing the composition of the earth’s atmosphere. It is possible that some, and perhaps even a significant, amount of organic matter was brought to Earth by the fall of meteorites and, perhaps, even comets. Some meteorites are quite rich in organic compounds. It is estimated that over 2 billion years, meteorites could have brought to Earth from 108 to 1012 tons of such substances. Also, organic compounds can arise in small quantities as a result of volcanic activity, meteorite impacts, lightning, and due to the radioactive decay of certain elements.

There is fairly reliable geological evidence indicating that already 3.5 billion years ago the earth's atmosphere was rich in oxygen. On the other hand, the age of the earth's crust is estimated by geologists at 4.5 billion years. Life must have arisen on Earth before the atmosphere became rich in oxygen, since the latter is mainly a product of plant life. According to a recent estimate by the American planetary astronomer Sagan, life on Earth arose 4.0-4.4 billion years ago.

The mechanism of increasing complexity of the structure of organic substances and the appearance in them of properties inherent in living matter has not yet been sufficiently studied, although great progress has been recently observed in this area of biology. But it is already clear that such processes last for billions of years.

Any no matter how complex combination of amino acids and other organic compounds is not yet a living organism. One can, of course, assume that under some exceptional circumstances, somewhere on Earth a certain “proto-DNA” arose, which served as the beginning of all living things. However, this is unlikely to be the case if the hypothetical “proto-DNA” was quite similar to modern DNA. The fact is that modern DNA by itself is completely helpless. It can function only in the presence of enzyme proteins. To think that purely by chance, by “shaking up” individual proteins - polyatomic molecules, such a complex machine as “praDNA” and the complex of protein-enzymes necessary for its functioning could arise - this means believing in miracles. However, it can be assumed that DNA and RNA molecules evolved from a more primitive molecule.

For the first primitive living organisms formed on the planet, high doses of radiation could pose a mortal danger, since mutations would occur so quickly that natural selection could not keep up with them.

Another question that deserves attention is: why doesn’t life on Earth arise from nonliving matter in our time? This can only be explained by the fact that previously existing life will not provide the opportunity for a new birth of life. Microorganisms and viruses will literally eat the first sprouts of new life. The possibility that life on Earth arose by chance cannot be completely ruled out.

There is one more circumstance that may be worth paying attention to. It is well known that all “living” proteins consist of 22 amino acids, while over 100 amino acids are known in total. It is not entirely clear how these acids differ from the rest of their “brothers”. Is there some deep connection between the origin of life and this amazing phenomenon?

If life on Earth arose by chance, it means that life in the Universe is a rare (although, of course, by no means an isolated) phenomenon. For a given planet (such as our Earth), the emergence of a special form of highly organized matter, which we call “life,” is an accident. But in the vast expanses of the Universe, life arising in this way should be a natural phenomenon.

It should be noted once again that the central problem of the emergence of life on Earth - the explanation of the qualitative leap from “non-living” to “living” - is still far from clear. It is not without reason that one of the founders of modern molecular biology, Professor Crick, said at the Byurakan Symposium on the problem of extraterrestrial civilizations in September 1971: “We do not see a path from the primordial soup to natural selection. One may come to the conclusion that the origin of life is a miracle, but this only testifies to our ignorance.”

The exciting question of life on other planets has occupied the minds of astronomers for several centuries. The possibility of the very existence of planetary systems around other stars is only now becoming the subject of scientific research. Previously, the question of life on other planets was an area of purely speculative conclusions. Meanwhile, Mars, Venus and other planets of the solar system have long been known as non-self-luminous solid celestial bodies surrounded by atmospheres. It has long become clear that in general terms they resemble the Earth, and if so, why shouldn’t there be life on them, even highly organized, and, who knows, intelligent?

It is quite natural to believe that the physical conditions that prevailed on the terrestrial planets (Mercury, Venus, Earth, Mars) that had just formed from a gas-dust environment were very similar, in particular, their initial atmospheres were the same.

The main atoms that make up the molecular complexes from which living matter is formed are hydrogen, oxygen, nitrogen and carbon. The role of the latter is especially important. Carbon is a tetravalent element. Therefore, only carbon compounds lead to the formation of long molecular chains with rich and variable side branches. Various protein molecules belong to this type. Silicon is often called a carbon substitute. Silicon is quite abundant in space. In the atmospheres of stars, its content is only 5-6 times less than carbon, that is, it is quite high. It is unlikely, however, that silicon can play the role of a “cornerstone” of life. For some reason, its compounds cannot provide as much variety of side branches in complex molecular chains as carbon compounds. Meanwhile, the richness and complexity of such side branches is precisely what provides a huge variety of properties of protein compounds, as well as the exceptional “information content” of DNA, which is absolutely necessary for the emergence and development of life.

The most important condition for the origin of life on the planet is the presence of a sufficiently large amount of liquid Medium on its surface. In such an environment, organic compounds are in a dissolved state and favorable conditions can be created for the synthesis of complex molecular complexes based on them. In addition, a liquid environment is necessary for newly emerged living organisms to protect them from the harmful effects of ultraviolet radiation, which at the initial stage of the planet’s evolution can freely penetrate to its surface.

It can be expected that such a liquid shell can only be water and liquid ammonia, many compounds of which, by the way, are similar in structure to organic compounds, due to which the possibility of the emergence of life on an ammonia basis is currently being considered. The formation of liquid ammonia requires a relatively low temperature of the planet's surface. In general, the temperature of the original planet is very important for the emergence of life on it. If the temperature is high enough, for example above 100°C, and the atmospheric pressure is not very high, a water shell cannot form on its surface, not to mention ammonia. Under such conditions, there is no need to talk about the possibility of the emergence of life on the planet.

Based on the above, we can expect that the conditions for the emergence of life on Mars and Venus in the distant past could, generally speaking, be favorable. The liquid shell could only be water, and not ammonia, as follows from an analysis of the physical conditions on these planets during the era of their formation. Currently, these planets are quite well studied, and nothing indicates the presence of even the simplest forms of life on any of the planets of the solar system, not to mention intelligent life. However, it is very difficult to obtain clear indications of the presence of life on a particular planet through astronomical observations, especially if we are talking about a planet in another star system. Even with the most powerful telescopes, under the most favorable observation conditions, the size of the features still visible on the surface of Mars is 100 km.

Before this, we only determined the most general conditions under which life can (not necessarily must) arise in the Universe. Such a complex form of matter as life depends on a large number of completely unrelated phenomena. But all these arguments concern only the simplest forms of life. When we move on to the possibility of certain manifestations of intelligent life in the Universe, we are faced with very great difficulties.

Life on any planet must undergo a huge evolution before becoming intelligent. The driving force behind this evolution is the ability of organisms to mutate and natural selection. In the process of such evolution, organisms become more and more complex, and their parts become specialized. Complications occur in both qualitative and quantitative directions. For example, a worm has only about 1000 nerve cells, while humans have about ten billion. The development of the nervous system significantly increases the ability of organisms to adapt and their plasticity. These properties of highly developed organisms are necessary, but, of course, not sufficient for the emergence of intelligence. The latter can be defined as the adaptation of organisms for their complex social behavior. The emergence of intelligence must be closely connected with a radical improvement and improvement in the ways of exchanging information between individuals. Therefore, for the history of the emergence of intelligent life on Earth, the emergence of language was of decisive importance. Can we, however, consider such a process universal for the evolution of life in all corners of the Universe? Most likely no! Indeed, in principle, under completely different conditions, the means of information exchange between individuals could not be longitudinal vibrations of the atmosphere (or hydrosphere) in which these individuals live, but something completely different. Why not imagine a way to exchange information based not on acoustic effects, but, say, on optical or magnetic ones? And in general, is it really necessary for life on some planet to become intelligent in the process of its evolution?

Meanwhile, this topic has worried humanity since time immemorial. When talking about life in the Universe, we always meant, first of all, intelligent life. Are we alone in the boundless expanses of space? Philosophers and scientists since ancient times have always been convinced that there are many worlds where intelligent life exists. No scientifically based arguments were given in favor of this statement. The reasoning, essentially, was carried out according to the following scheme: if there is life on Earth, one of the planets in the solar system, then why shouldn’t it be on other planets? This method of reasoning, if logically developed, is not so bad. And in general, it’s scary to imagine that out of 1020 - 1022 planetary systems in the Universe, in an area with a radius of tens of billions of light years, intelligence exists only on our tiny planet... But perhaps intelligent life is an extremely rare phenomenon. It may be, for example, that our planet, as the abode of intelligent life, is the only one in the Galaxy, and not all galaxies have intelligent life. Is it even possible to consider works on intelligent life in the Universe to be scientific? Probably, after all, with the current level of technological development, it is possible and necessary to deal with this problem now, especially since it may suddenly turn out to be extremely important for the development of civilization...

The discovery of any life, especially intelligent life, could be of great importance. Therefore, attempts have been made for a long time to discover and establish contact with other civilizations. In 1974, the automatic interplanetary station Pioneer 10 was launched in the United States. Several years later, she left the solar system, completing various scientific tasks. There is a negligible probability that someday, many billions of years from now, highly civilized alien beings unknown to us will discover Pioneer 10 and greet him as a messenger from an alien world unknown to us. For this case, there is a steel plate inside the station with a pattern and symbols engraved on it, which provide minimal information about our earthly civilization. This image is composed in such a way that intelligent beings who find it will be able to determine the position of the solar system in our Galaxy and guess our appearance and, possibly, our intentions. But of course, an extraterrestrial civilization has a much better chance of finding us on Earth than finding Pioneer 10.

The question of the possibility of communication with other worlds was first analyzed by Cocconi and Morris in 1959. They came to the conclusion that the most natural and practically feasible communication channel between any civilizations separated by interstellar distances could be established using electromagnetic waves. The obvious advantage of this type of communication is the propagation of the signal at the maximum speed possible in nature, equal to the speed of propagation of electromagnetic waves, and the concentration of energy within relatively small solid angles without any significant scattering. The main disadvantages of this method are the low power of the received signal and strong interference arising from vast distances and cosmic radiation. Nature itself tells us that transmissions should occur at a wavelength of 21 centimeters (the wavelength of free hydrogen radiation), while the loss of signal energy will be minimal, and the probability of receiving a signal by an extraterrestrial civilization is much greater than at a randomly chosen wavelength. Most likely, we should expect signals from space on the same wavelength.

But let's say that we detected some strange signal. Now we must move on to the next, rather important issue. How to recognize the artificial nature of a signal? Most likely, it should be modulated, that is, its power should change regularly over time. At first, it should apparently be quite simple. After the signal is received (if, of course, this happens), two-way radio communication will be established between civilizations, and then more complex information can begin to be exchanged. Of course, we should not forget that answers may not be obtained earlier than in several tens or even hundreds of years. However, the exceptional importance and value of such negotiations should certainly compensate for their slowness.

Radio observations of several nearby stars have already been carried out several times as part of the large OMZA project in 1960 and using the telescope of the US National Radio Astronomy Laboratory in 1971. A large number of expensive projects for establishing contacts with other civilizations have been developed, but they are not funded, and very few actual observations have been made so far.

Despite the obvious advantages of space radio communications, we should not lose sight of other types of communications, since it is impossible to say in advance what signals we may be dealing with. Firstly, this is optical communication, the main disadvantage of which is the very weak signal level, because, despite the fact that the divergence angle of the light beam was brought to 10 -8 rad, its width at a distance of several light years will be enormous. Communication can also be carried out using automatic probes. For obvious reasons, this type of communication is not yet available to earthlings, and will not become available even with the beginning of the use of controlled thermonuclear reactions. When launching such a probe, we would be faced with a huge number of problems, even if we consider the time of its flight to the target to be acceptable. In addition, there are already more than 50,000 stars less than 100 light years from the solar system. Which one should I send the probe to?

Thus, establishing direct contact with extraterrestrial civilization on our part is still impossible. But maybe we should just wait? Here we cannot fail to mention the very pressing problem of UFOs on Earth. There are so many different cases of “observations” of aliens and their activities that have already been noticed that in no case can one unequivocally refute all this data. We can only say that many of them, as it turned out over time, were inventions or the result of an error. But this is a topic for other research.

If some form of life or civilization is discovered somewhere in space, then we absolutely, even approximately, cannot imagine what its representatives will look like and how they will react to contact with us. What if this reaction is, from our point of view, negative. Then it’s good if the level of development of extraterrestrial beings is lower than ours. But it may turn out to be immeasurably higher. Such contact, given a normal attitude towards us from another civilization, is of the greatest interest. But one can only guess about the level of development of aliens, and nothing at all can be said about their structure.

Many scientists are of the opinion that civilization cannot develop beyond a certain limit, and then it either dies or no longer develops. For example, the German astronomer von Horner named six reasons, in his opinion, that could limit the duration of the existence of a technically advanced civilization:

1) complete destruction of all life on the planet;
2) destruction of only highly organized beings;
3) physical or spiritual degeneration and extinction;
4) loss of interest in science and technology;
5) lack of energy for the development of a very highly developed civilization;
6) the lifetime is unlimited;

Von Horner considers this last possibility completely incredible. Further, he believes that in the second and third cases, another civilization can develop on the same planet on the basis (or on the ruins) of the old one, and the time of such “resumption” is relatively short.

From September 5 to 11, 1971, the first international conference on the problem of extraterrestrial civilizations and communications with them was held at the Byurakan Astrophysical Observatory in Armenia. The conference was attended by competent scientists working in various fields related to the complex problem under consideration - astronomers, physicists, radiophysicists, cybernetics, biologists, chemists, archaeologists, linguists, anthropologists, historians, sociologists. The conference was organized jointly by the USSR Academy of Sciences and the US National Academy of Sciences with the participation of scientists from other countries. At the conference, many aspects of the problem of extraterrestrial civilizations were discussed in detail. The questions of the multiplicity of planetary systems in the Universe, the origin of life on Earth and the possibility of the emergence of life on other space objects, the emergence and evolution of intelligent life, the emergence and development of technological civilization, the problems of searching for signals from extraterrestrial civilizations and traces of their activities, the problems of establishing communications with them, as well as the possible consequences of establishing contacts.

Modern technologies are bringing humanity closer to solving this question. But only a little. Today, with the help of SETI - the Search for Extra Terrestrial Intelligence (search for extraterrestrial intelligence), as well as using radio telescopes, signals from extraterrestrial civilizations are being searched. The system, however, is characterized by passivity, when researchers have to sit with their hands folded and wait by the sea for weather. And so far this method has led to nothing.

But there is another method, more effective. SETI will use a collection of telescopes, including the famous 305-meter Arecibo telescope, to search for nearby stars to send electronic signals that could reveal whether there is intelligent life in those systems. And if a civilization living somewhere out there uses the same methods to work with exoplanets, then the SETI team will be able to detect the signals.

By and large, a project is being launched that is somewhat different from SETI, called METI. Messaging Extra Terrestrial Intelligence or Sending messages to extraterrestrial intelligence is actively sending messages to certain places in space, which can serve as a kind of greeting to potentially alien astronomers living somewhere.

But some scientists consider the project quite dangerous. For example, the famous physics theorist Stephen Hawking said that by informing aliens that we exist, we could bring disaster to us and our planet. A story similar to the voyage of Columbus and his landing in America may happen. Another mind may perceive humanity as an underdeveloped part of life. And this will lead to the same thing that happened to the Indians after the Old World learned of their existence.

Another researcher, Douglas Vakoch, assures that all the concerns are too far-fetched. The fact is that if there are such aliens who can travel throughout cosmic space, then they already have the ability to catch our TV, radio and other signals. So, if someone wanted to attack us, they would have done it a long time ago.

The question then arises: why keep sending signals? Yes, for the sake of science. After all, perhaps somewhere there live the same developed forms of life as we do. And it's nice to know that they are not alone. In other words, as Douglas Vakoch says, the zoo theory can be tested. According to this scheme, it turns out that the presence of intelligent life is more widespread in the Universe than we can even imagine. Why then, for example, is there no signal from nearby star systems? Perhaps they are simply waiting for someone else to take the initiative.

Moreover, Douglas Vakoch believes that signals do not need to be sent very far. When it can take up to five thousand years to receive a signal. We need to explore the nearest stars, in case we have neighbors.