Perhaps this insatiable thirst for cognition of cosmic connections … is inherent in us by the fact that we ourselves are composed of cosmic matter?
In every era, people in their dreams solved the problem of contacts with aliens based on the technology of their time. Until the 18th century, people did not have any heat engines like steam or internal combustion.
They used only the energy of the wind, which inflated the sails of ships and twisting the wings of windmills, and the energy of water, which turned the wheels of water mills. And of course, the energy of muscles, our own and pets. And therefore, even fantasizing, the only thing that people could then offer for a flight "to them" was just a crew harnessed … to a flock of birds! After all, it was necessary to fly up to the sky. Our distant ancestors did not know that the air on this way would end as soon as you “fly away from home”. Nor did they imagine the huge distances separating us from the Moon and the planets, not to mention the distances to the stars.
Then, having measured these distances and having learned that the celestial bodies are separated by an almost empty, airless space, they began to dream at least of mutual signaling.
In the 19th century, just a hundred years ago, almost everyone believed in the existence of the Martians. And then, quite seriously, scientists put forward assumptions about optical communication with them. Now it is difficult to remember this without a smile.
The mathematician Karl Friedrich Gauss suggested, for example, cutting a many kilometers long clearing in the form of a triangle in Siberian forests and sowing it with wheat. The Martians will see through their telescopes a neat light triangle against the background of dark green forests and understand that the wild blind nature could not have done this. This means that intelligent beings live on this planet. Many people liked Gauss's idea, but in order to show the Martians that earthlings are highly educated, they suggested making squares on the sides of the triangle to make a drawing of the Pythagorean theorem.
The Gauss project still had noticeable flaws. The "Pythagorean Theorem" located in Siberia will often be covered by clouds, covered with snow and may remain unnoticed by the Martians for a long time. And most importantly, even in good weather, it will be visible only during the day. The daytime side of the Earth is visible from Mars when the Earth is far from it. At the moments of the closest approach to Mars, the Earth faces it at night.
Therefore, the project of the Viennese astronomer Josef Johann von Litrow seemed more correct. He suggested in the Sahara Desert, where it is always cloudless, to dig channels in the form of regular geometric shapes. The Pythagorean theorem is also possible. The sides of the triangle must be at least thirty kilometers long. Fill the channels with water. And at night, pour kerosene over the water and set it on fire. Fiery stripes will trace a bright, glowing geometric pattern on the night side of the planet. The Martians cannot fail to notice him right away.
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Of course, a picture of canals blazing with flames in the desert would be very effective. But this "signal" must have been too expensive. And the Frenchman Charles Cros suggested a much cheaper way of communication. He advised his government to build a huge battery of mirrors to reflect the sun's rays as a "bunny" towards Mars. The bunny, of course, would be dazzlingly bright. But … it could only be sent from the daytime side of the Earth and, therefore, again from a very long distance. But Charles Cros's project had a huge advantage. The mirrors could be moved, and then, when viewed from Mars, a dazzling bright point on Earth would wink. And this will prove that it is not water or ice that glitters, but something artificial. And most importantly, a telegram could be sent to the Martians by blinking. Whether Charles Cros was referring to Morse code or something else, we do not know.
Naive! But all this happened quite recently, during the life of our great-grandfathers.
Meanwhile, science and technology developed. The successes of the artillery gave rise to the science fiction writer Jules Verne to write his novel "From the Cannon to the Moon". With the help of huge cannons, the Martians of the English writer Wells also flew from Mars to Earth in his book The Struggle of the Worlds.
But now it’s funny to remember about cannons. Tsiolkovsky was the first to reasonably prove that interplanetary flights can only be carried out using rocket technology. And in the book by Alexei Tolstoy "Aelita" engineer Elk with his faithful companion, the soldier Gusev, fly to Mars in a rocket.
The successes of rocketry in the postwar years, and most importantly, the launch in our country in 1957 of the world's first artificial earth satellite gave a powerful impetus to the old dreams of mankind about interplanetary travel. A whole avalanche of a wide variety of sci-fi works poured in, in which the nearest planets of the solar system were inhabited and earthlings visited them without much difficulty in their small, but very comfortable rockets. For example, having flown to Venus and Mars, the heroes of the books began to easily fly to the stars, surfing the vast expanses of the Galaxy on huge interstellar ships. Think of the "Magellanic Cloud" by Stanislav Lem or "The Andromeda Nebula" by our writer Ivan Efremov.
But the reader went literate. After reading the book, he picks up a fountain pen and tries to figure out with a simple calculation what is possible and what is impossible in reality. After all, everyone is now more or less familiar with the structure of the solar system, and with the scale of space, and with celestial mechanics, and with the capabilities of rocket technology. And here again, for the umpteenth time, a rigorous analysis cruelly cooled the dreamers.
Our modern chemically fueled rockets are only good for "local flights" within the solar system. And even then not all.
Judge for yourself. Engineers have squeezed out almost everything they can give from rocket engines. Of the designs of the missiles themselves, too. They are made multistage, without which it is generally impossible to go even into low-earth orbit. Docking in orbits near the Earth and near other celestial bodies has been mastered, which makes it possible to manage with smaller rockets. Everything is used that can make a rocket and a spacecraft lighter - the lightest and most durable materials, the most portable equipment. For long-distance flights, systems have been developed that allow you to purify and reuse water and air, and grow food on the way. Solar batteries are widely used - a source of "free" electricity on the way. In a word, everything that science and technology of today is able to give has been applied. Scientists and engineers have worked so hardthat in the near future it is somehow difficult to expect very rapid progress in these areas.
And yet, despite such perfection of rocketry, the ultimate in our dreams is just a flight to Mars or a flight to Venus.
The fact is that chemical fuels weigh too much and are consumed too quickly. And so a modern rocket looks like a can with thin walls. Empty, it weighs ten times less than filled. Nine-tenths of its weight when launched from Earth is fuel. And it only suffices for the most necessary: to accelerate to the second cosmic speed - eleven and a little kilometers per second - to overcome gravity and go into orbit to another planet, for the necessary maneuvers at the target and then to break away
away from the planet and go back to Earth. The Earth has no fuel left for braking. You have to "cheat" - to crash into the atmosphere "obliquely" and, gradually deepening into it, slow down by air resistance.
A human flight to Mars, which at best will be carried out by the end of the 20th century, will require colossal costs. But it's not only that. It will go on for a very long time. It is known that our machines, which have already flown to Mars, spent six months on the road one way. You can fly a little faster, but fuel consumption will increase greatly, it makes no sense.
We must also take into account that flights to other planets are not possible at any time. A certain relative position of the planets is required. For Mars, this happens, for example, only once every two years. The same goes for the return flight. Therefore, on Mars you need to wait for the opportunity to start to the earth. As a result, the journey to the planet can last one and a half or even two years.
The travels on the land of our brave navigators of the past, who made long voyages around the world, to Antarctica, along the Northern Sea Route, took two years or more. So the duration of the flight to Mars, in the end, is not terrible. But if in the future we want to fly to Jupiter and back, then we will need a period of ten years. This is already a bit too much.
And yet flights within the solar system are real. But here we have no hope of meeting intelligent beings. There are chances to find them only in other planetary systems, near other stars.
On a modern rocket powered by chemical fuel, it is possible to develop the third space speed - about seventeen kilometers per second. At this speed, the rocket will be able to overcome the gravity of the Sun and go to the stars. Its speed, however, will gradually decrease. At the cost of additional fuel consumption, we will be able to maintain the speed so that we can “walk” all the way at seventeen kilometers per second. But even with such a "crazy" speed, our flight even to the nearest star - Alpha Centauri - will last you know how many years? No, the duration of this flight is simply difficult to pronounce. We'll have to fly for eighty thousand years!
As they say, thanks, don't!
Thus, it makes no sense to talk about flying to the stars on modern rockets. But why not dream about flying on some special rockets of the future?
Let's try. We will only agree that it is necessary to dream within the framework of some immutable laws of physics.
Apparently, rockets with thermonuclear and ion engines will be made in the future. They will make it possible to accelerate the rocket up to a speed of thousands and even tens of thousands of kilometers per second. This will reduce the flight time to the star Alpha Centauri to several hundred, at best, several decades. If we learn to put the astronauts into hibernation during the flight, into a kind of "suspended animation", this is perhaps tolerable.
But Alpha Centauri is the closest star to Earth. It is only four and three tenths of light years away, or forty thousand billion kilometers. But the whole galaxy is ninety thousand light-years across, twenty thousand times more! You don't have to encroach on the entire Galaxy, but you have to fly for tens of light years! However, even here the flight will last hundreds and thousands of years only in one direction! Many generations of cosmonauts will change on the rocket until the lucky ones are finally born and grow up who will be able to achieve their goal. And what will be the return to Earth, where by that time everything had changed beyond recognition. Where there are strangers around, another life and the results of the flight no longer interest anyone.
The highest speed that is generally possible in nature is the speed of light - three hundred thousand kilometers per second. Can't you fly at this speed of light? Or at least at a speed close to light, so to speak, near-light, or, scientifically, sub-light?
In principle, you can. It is necessary to create a photonic rocket, in which, instead of a fiery jet of incandescent gases, a jet of light or some other radiation will hit from the nozzles of the engine. But the jet is so dense, the beam is so powerful that, escaping backward, it will, like a jet of gases from an ordinary rocket, forcefully push the photonic rocket forward. This is basically. And practically no one yet knows how to approach this task.
In a photonic rocket, matter and antimatter must serve as fuel. For example, hydrogen and antihydrogen. In other words, hydrogen with a core charged with positive electricity, and hydrogen with a core charged with negative electricity. In the first, an electron revolves around the nucleus - a particle charged with negative electricity. The second has a positron, a particle charged with positive electricity. The entire world around us consists of matter. But physicists assume that there must also be a world consisting of antimatter. When in contact with each other, matter and antimatter should instantly disappear, turning into a huge amount of energy. Therefore, such a reaction should be the most beneficial for us, since we must take many times less fuel with us on the flight than even ordinary nuclear fuel. But … no one yet knows how to make antimatter in our environment, where there is an ordinary substance all around, with which it has no right to come into contact for the time being, nor how to store it, in what containers. It is impossible to make them from a substance, because contact of the "dishes" with the contents is inadmissible. It is impossible to make of antimatter, because the contact of "dishes" with the outside world is inadmissible.
Nobody knows yet how the "engine" should look like, in which matter and antimatter should meet. After all, they must meet gradually, in small doses, so that the deafening explosion does not scatter the entire spacecraft into dust. But theoretically, if it was possible to make antimatter, learn how to store it and invent an appropriate engine, then, in contact with each other, matter and antimatter would instantly disappear - and in their place would arise radiation of monstrous power. Not only light, but mostly gamma rays. Of course, they will fly in all directions, and we still need to learn how to collect them and direct them in one direction.
Just like in a spotlight, light is collected and directed by a narrow beam in one direction. And if all this could be done, it would be possible to build a photonic rocket. Although, along the way, we would have to solve many engineering problems, which we still do not know how to solve either. After all, the rocket must be of colossal size, unusually strong, heat-resistant in some parts, and impermeable to deadly radiation in others. And with all this, it is so light that you can take fuel with you, that is, substances and antimatter, hundreds of times more than an empty rocket weighs.
But since we have already decided that it is possible to dream about anyone, as long as "it" does not contradict the laws of physics, then it is possible to dream of a photonic rocket.
Let's assume we have it. Can I fly it to the stars? Can. But we must take into account some of the subtleties of flying at such high speeds. From the experience of today's space flights, we know that the acceleration of a rocket is accompanied by overloading of astronauts. Their weight increases.
During a flight in orbit at a constant speed, by inertia, the astronaut experiences weightlessness. But when after that the rocket starts to accelerate, weight appears. It does not depend on the speed itself, but on how quickly it increases. This weight can be equal to the usual, earthly weight of an astronaut, and he will feel "at home." But if the speed build-up goes faster, the weight will increase. It can double - a person will feel that instead of, say, seventy kilograms, he began to weigh one hundred and forty. This will be a double overload.
Weight can triple - triple overload. Within a few seconds, a person can even withstand a tenfold overload - while he will weigh almost three quarters of a ton, as if he were cast in bronze! In order not to risk the lives of astronauts, the rockets are accelerated and slowed down gently, gradually, avoiding overloads exceeding two or three times. And then if they last no more than a few minutes.
The photonic rocket will have to accelerate not minutes, not hours, not even days or weeks, but months and more. Therefore, forcing astronauts to live with overloads for months is unthinkable. It is necessary to accelerate the rocket at such a pace that the astronauts, instead of weightlessness, only feel their normal earthly weight. But at the same time, it will take … a whole year to accelerate a photonic rocket to sublight speed! During this time, the rocket will travel one-tenth of the way to the nearest star.
Then you can fly for three years calmly, by inertia, at a constant speed, "resting" in a state of weightlessness. And a year before "landing" start braking again in order to approach the goal slowly. Thus, the rocket will travel to the nearest star, the distance to which is only four and three tenths of light years, in five years. Almost a year longer than the light goes, because it rushes all the way at light speed, and the rocket is forced to first accelerate and then decelerate.
Some things could be improved. You can make a rocket automatic, and somehow learn how to freeze people during the flight so that they are not afraid of large overloads. Of course, in this case, the rocket also needs to be made more durable so that it does not flatten or break under heavy overloads. Then you can accelerate much faster. And slow down more sharply. And the total flight time will be reduced from five years to four and a half. The difference is small, but still something like this is worth using.
Now the main question: does the photonic rocket completely solve the problem of interstellar travel?
Not. Doesn't decide. For the simple reason that reaching the nearest star is one thing, but flying in the Galaxy, to more distant stars, is another. On the planetary systems closest to us, there is little hope of meeting intelligent life. We must count on flights to more distant stars. Remote from us at least hundreds, and better - thousands of light years. You yourself understand that flights to them on the best photonic rockets will take hundreds and thousands of years at best.
But a person lives only for several decades! This means that descendants will fly to the goal again!
Here, however, there is one subtlety that can soften the chagrin a little. On a rocket traveling at sublight speed, time flows much more slowly than usual. If, say, of two twin brothers, one went on a flight, and the second remained on Earth, then upon returning from the flight, the first brother, the cosmonaut, will still be a young man, while the second, who remained on Earth, will already be a very old man.
During distant flights, over distances of thousands of light years, an astronaut on a rocket will live only a couple of decades, while thousands of years will pass on Earth during this time. This is convenient in the sense that in a rocket flying at sublight speeds, interstellar travel fits into one human life. He flew himself, flew himself, returned himself. But this does not change anything in the sense that, upon returning, the cosmonaut still finds on earth not only strangers, but generally a completely new, alien, incomprehensible civilization, for which he became a "fossil dinosaur." It will be difficult for him to report on the flight, and it is difficult for them to understand him. The expediency of such flights is questionable.
Add to this that many prominent physicists generally believe that photonic rockets will never be built. The difficulties of their creation are too great, and perhaps insurmountable.
Thus, subluminal photonic rockets are only suitable for science fiction writers. And then on condition that the readers are not picky about the plausibility of the written.
There is another option for interstellar travel. It does not require a very high speed, which means that a photonic rocket is not required. With him, there is no sad prospect of ending up as a "dinosaur fossil". This option is to fly … without returning!
A huge ship is being built - a small copy of our planet, since its own circulation of matter has been created on it, providing passengers with an arbitrarily long existence. People settle on the ship forever. It flies for centuries, for millennia. Generations of cosmonauts are changing. The worlds that come across on the way are studied, if possible, populated by landing troops. Civilizations will meet - contacts will be established with them.
Such a flying independent "little world" can, in principle, go as far as you like. But first, it is hardly easier to build than a photonic rocket. Secondly, the connection of the ship with the Earth gradually loses its meaning due to the range. He is a cut off hunk. He is no longer a particle of earthly civilization, not a scout of earthly science, not a messenger of friendship. So, a "seed of reason" thrown into the wind, in the hope that it will fall on fertile soil and give rise to the "earthly rock". Is it just "earthly"? For thousands of years of flight, the "seed" will degenerate into some kind of ugliness, which will only discredit you and me.
In a word, "it is possible, but not necessary."
It is not without reason that physicist F. Dyson, who draws us amazingly bold and large-scale prospects for the dispersal of mankind in the solar system, at the same time says that the problem of interstellar travel is a problem of motives that drive society, and not a problem of physics and technology. Of all that, in principle, mankind could do technically, it realizes only what is necessary for it, for one reason or another. The Tsiolkovsky-Dyson sphere will be needed simply for survival. If you want to live, build! But flights to visit aliens in all variants will give nothing to people left on earth. Unless they are needed for prestige, to satisfy their vanity as a spectacular, generous gesture for the good of unknown brothers in mind and their distant descendants.
Of course, theoretically speaking about the very distant future, one can assume that a moment will come when people will feel cramped even on the Tsiolkovsky-Dyson sphere. Will need resettlement to other stars. But that's another topic. Returning to the topic of contacts, we can say: there is complete confidence that interstellar flights will eventually be technically possible. But they are highly unlikely to be used for direct, personal contact with aliens.
Nevertheless, the situation is not at all hopeless. Contacts of other types are quite real.
American scientist Bracewell was the first to express the idea of the possibility of contacts with the help of "probes". Its essence is as follows. The inhabitants of any planet, having reached the appropriate level of development, make automata stuffed with complex cybernetic devices that can completely replace a person. Such an automaton, not afraid of huge overloads, is launched into space by a powerful, perhaps a photonic rocket, accelerates to sublight speed and is directed either by automatic devices and embedded programs to a certain star, or is launched into free flight, but is supplied with sensors and analyzers, allowing him to detect some inhabited planet by one or another radiation and "turn" to it.
Such a probe can fly for centuries, millennia, without requiring either heating or power, without boredom, without aging, without losing efficiency. Having reached the goal and becoming a satellite of the planet, "showing signs of life", he begins its detailed study.
The probe records the received data, analyzes them. Intercepts, "eavesdrops" on radio and television broadcasts. He studies the language of the inhabitants of the planet, their writing. And, if he finds it necessary, he is "smart", and communicates with the inhabitants of the planet by radio. Such an automaton, without landing on the planet, can transmit to its inhabitants all the necessary information about the civilization that sent it. He can find out and write down everything that interests him about this planet. Send this information on the radio "home".
Contact with the probe can take the form of a dialogue, a conversation in the form of questions and answers, in the form of a conversation. At the same time, a mutual show of television programs is possible, in which works of art, films, documentary and fictional ones, showing the life of both planets, will be shown.
Naturally, the automaton probe can only tell about its planet what was there then, long ago, at the time of its departure, a hundred, thousand years ago. What happened after
this, he does not know. Information about us, which he will pass on to "his", will reach them, too, only after a hundred, thousand years. They will also be of great, but purely historical interest to them. Draw the "old days" of the planet Earth. And we will go far ahead by that time.
It will be a conversation between two civilizations separated by time. Does he lose his value from this? Not much. We parted in time with Homer, with Avicenna, with Pushkin. But don't we have contact with them? Reading books written one hundred, five hundred, even thousands of years ago, we plunge into that era and, while we read, we live with the heroes of the book, we rejoice and weep with them, we learn from them nobility, courage, and hard work. And the fact that neither the author of the book, nor the people around him, from whom he “copied” his characters, has long been dead, is not so important.
Probes are thought of as a kind of libraries, museums, generally repositories of the most varied information in all possible forms: textual, visual, sound, - disinterestedly sent by civilizations to all ends of the Galaxy. With the hope that all centers of mind will logically come to this method of contact.
The probe can also be a “guest from the future”. How? It's very simple.
Imagine that he flew from a planet on which a civilization similar in type to ours went ahead, say, three thousand years. "Guest" flew to us for a thousand years. This means that the civilization that he represents and which he will tell us about is still two thousand years "older" than ours. The era that he will draw for us is, to some extent, our future. He is our "elder brother". And we have a lot to learn from him.
To Bracewell's thought about the possibility of contacts with the help of probes, it should be added that today many major cybernetics of the world talk about the possibility in the future of creating a cybernetic "brain" that is not inferior in its mental abilities to a human.
Maybe even in some way and superior to him.
And now, from the area of assumptions, let us return to the area of the real, the reliable.
From the very first stages of their development, living beings began to develop means of communication at a distance. Without touching each other. Some, like insects, have learned to communicate chemically - smells. But this method allows you to transfer very little information, and also rather slowly. Most of the animals, especially the higher ones, have come to a much more perfect way - to shake the environment in which they are immersed. If they live in water, shake the water, if in the air, shake the air. In other words, make sounds. In this way, a wide variety of information can be transmitted, and it reaches the addressee almost instantly.
Nature did not give us a "throat" so that we could scream through the interstellar void. But science and technology were given. Today these are electromagnetic waves, in particular radio. With its help, we “shake the world ether” into which we are immersed together with our planet. We "shout" to the moon, and there we are heard by the astronauts working on its rocky expanses. We "shout" into orbits, and the cosmonauts in spaceships answer us. We "shout" even to Venus and Mars, and there, tens of millions of kilometers away, the submachine guns obediently carry out our commands.
Today we have the ability to “shout from island to island” in the vast ocean of the universe using radio. We ourselves have the opportunity to hear a similar "cry" from distant cosmic distances. Radio is a powerful and highly sophisticated vehicle for interstellar communication.
Of course, it is possible that in the future a person will master other ranges of electromagnetic waves for communication purposes. Some scientists believe that soon optical communication using a laser beam will surpass radio in its capabilities. But these are assumptions. In reality, for now - radio. And we need to get to know him better.
G. Naan, academician