in the Universe.
Duncan Forgan from the University of Edinburgh in Scotland developed a mathematical model and software that analyzed the probable number of inhabited worlds (not in the entire Universe, but only in the Milky Way) on the basis of three criteria: living organisms either occur with difficulty, but then develop well, or they have difficulty with turning into intelligent creatures, or life could be transferred from one planet to other one. As a result, three positive results were obtained. In the first case, the number of intelligent civilizations will be no less than 361, in the second – 31 513 and in the third – 37 964. William Borucki, the head of the group of researchers working with the «Kepler» space telescope, presented the data on potentially inhabited planets at the annual conference of the American Association for the Advancement of Science (AAAS). Statistical analysis of data gathered by means of the telescope showed that 44% of the stars in the galaxy have planetary systems. Since there are approximately 100 billion stars in the Galaxy, it turns out that they can have about 50 billion planets. Out of them, approximately 500 million may be in the so-called zone of life, i.e., at approximately the same distance from the star as Earth from the Sun.
Seth Shostak, a senior astronomer at the SETI Institute (Search for Extraterrestrial Intelligence Institute), while taking part in the NASA Innovative Advanced Concepts (NIAC) symposium held in 2014 at Stanford University, promised that the extraterrestrial intelligent life would be revealed in 2038. However, his optimism has subsequently diminished.
Nikolai Kardashev, the Russian astrophysicist, suggested evaluating civilizations by their energy consumption in order to classify them. According to this classification, Type I civilization uses planetary forms of energy, with the help of which it can adjust the weather, change the direction of hurricanes or build cities in the oceans. Sources of energy are mostly limited by their planet.
Type II civilization is the interplanetary one and uses the energy of the entire star, with which comets and meteors can be directed in the opposite direction, ice ages can be prevented, and climatic conditions can be changed. It is the thermonuclear energy which is used. Type II civilizations are actively moving through the Universe and populate (colonize) other planets.
Type III civilization is the interstellar one. Distant stars and new galaxies are reachable for colonization by it and captured and newly discovered stars become the new energy sources. It can travel through the galaxy freely. Such a civilization can use energy of 10 billion stars. Each type civilization increases the amount of energy used by the previous type by 10 billion times, i.e., the energy consumption of type III civilizations is 10 billion times higher than that of the type II civilizations’ one. Currently, humanity uses only about 0.16% of the total energy budget of the planet and approximately corresponds to the 0.72 level of technological development without reaching type I planetary civilization’s level.
It should be noted that the Kardashev scale is the hypothetical one and it is not possible to verify it at the moment. At the same time, it gives an idea of the possibilities for the civilizations development on a cosmic scale. In addition, these stages of the civilizations’ development are far from the distant future scientifically based scenarios. The Kardashev scale was supplemented by Carl Edward Sagan. However, these additions are not taken into account by astrophysicists but are considered by science fiction fans.
Sensitive new-generation telescopes allow astronomers to measure the level of background infrared radiation, which should be a type III civilization’s indicator according to the Kardashev scale. Professor Michael Garrett from the University of Leiden (the Netherlands) decided to verify this theory and studied about 50 galaxies from the list, not only in the infrared spectrum, but in other radio frequency bands as well. The analysis of the results showed that the type III developed civilizations do not exist in the observable Universe at all.
Numerous arguments supporting the idea of the existence of a significant number of technologically advanced civilizations in the Universe are not proved by observations. It has been established that there are more than 8.5 thousand stars and more than 3 thousand planets similar to Earth within a radius of 80 light years from Earth.
It is has been estimated that the diameter of our Galaxy is about 100 thousand light years. If at least one civilization capable of moving between stars at a speed 1000 times lesser than the speed of light existed in the Galaxy, it would spread throughout the Galaxy in 100 million years.
So far, it has not been possible to find a planet that would resemble Earth: with an oxygen atmosphere, water and a more or less acceptable climate. The airless Moon, the dead sands of Mars, the red-hot sulfuric atmosphere of Venus, the icy worlds of gas giant satellites cannot be an environment for the protein life’s development. No one has ever got the evidence of the aliens’ existence within the mankind’s existence. Therefore, the belief in the existence of intelligent beings on other planets is gradually dying away.
The direct contact with other civilizations is impossible at the modern changing level of scientific and technological development of human civilization due to the huge interstellar distances. Even Proximal Centauri, the closest star, after the Sun, is at a distance of about 40 trillion kilometers, and it would take the spacecraft about four Earth’s years to reach it, even at the speed of light. Therefore, the theoretical possibility of the direct contact may be assumed if other civilizations have the superluminal speeds’ methods of moving, which are difficult to imagine on the basis of modern physical knowledge of a human being.
Humanity has tried to establish contacts with the intelligent civilizations of our galaxy. Thus, the mathematician Carl Friedrich Gauss, a mathematician, put forward an idea to cut clearings in a dense forest and plant them with wheat or rye 200 years ago. The result would be in a contrasting geometric figure of gigantic dimensions, consisting of a triangle and three squares, known as the «Pythagorean pants». This figure, according to Gauss, could have been observed from the Moon and even from Mars. Soon after, Joseph Johann von Littrow, an Austrian astronomer, came up with a suggestion about digging wide channels and filling them with water with kerosene: «If one burns them at night, they will turn into geometric shapes – for example, into triangles – that Martians will not accept for a natural phenomenon, but for a sign of an intelligent life on our planet». All these ideas were based on the human analyzers’ ability to perceive the world around them. But the fact that other civilization can treat fire differently than a human being does it was absolutely not taken into account.
As for our time, there was an attempt to establish contact with the extraterrestrial civilization by means of a message transmitted by the Arecibo radio telescope on a distance of 21,000 light-years to the outskirts of the Milky Way, but again without a presupposed analysis of the other civilizations’ perception possibilities, only on the basis of human ideas and relatively modest knowledge in Physics. In addition, the message represented a series of digital images, 1679 bits of information in each of them. Today, these pictures resemble the very first video games due their primitivism.
Prior to this, the US space agency NASA launched the interplanetary probes Pioneer 10 and Pioneer 11. Each device had a metal plate fixed to the case with a set of characters and images of the naked men and women. However, it is likely that such drawings will turn out to be incomprehensible to aliens as well as the images on the Nazca plateau remain a mystery to us.
In other case, a gold plate was placed inside the «Voyager» apparatus, which was launched outside the Pluto orbit, for the playback of which a special player is needed and which is unlikely to exist in the other life form. Therefore, contacts organized on the basis of human ideas will not bring success without the other life forms properties’ comprehensive studying, as far as possible.
Sebastian Rudolf Karl von Hoerner, a German astrophysicist, in his article «The Search for Signals from Other Civilizations» explained the silence of the Universe by the fact that the tools of mankind are still very imperfect with the costs of the search being completely negligible. Perhaps people will never be able to visit other star systems, so it is possible to start looking for other
