Experts do not exclude the possibility that the other worlds’ representatives of live somewhere in the depths of the vast universe. Physicists of Stanford University have been able to establish a hypothetical number of universes formed as a result of the Big Bang. Moreover, it is possible that they can be included into each other and inside our Earth as well. Perhaps there is a hidden Earth-2. They also estimated the amount of information that such a number of the parallel worlds’ existence carries, and came to the conclusion that a person is not able to observe all the universes, since the structural features of his brain are not able to perceive more than ten raised to the sixteenth power bits of information during his lifespan.
Frank Donald Drake, a professor of astronomy and astrophysics at the University of California, has developed a formula that, in his opinion, determines the number of extraterrestrial civilizations. The formula named after him consists of seven constituent elements: the number of stars formed during the year; fraction of stars representing planets; the number of planets or their satellites with livable conditions; the probability of the life’s occurrence, the probability of turning it into an intelligent one; fraction of planets with highly developed creatures; lifetime of a civilization that lives on the planet. Depending on the choice of parameters, the Drake formula gives grounds to believe that there are from 10 to 100 extraterrestrial civilizations in the galaxy at each separate moment.
However, repeatedly performed calculations with the Drake’s formula being used gave a different number: from their complete absence up to 5 thousand. Such a dispersion arose due to the fact that the researchers evaluated the values of the parameters included in the formula in different ways. Critics note that the Drake’s formula does not take into account the time variation of the parameters included in the formula. At the current level of the scientific development, only two coefficients for this formula can be relatively accurately determined, while others cannot be determined at all.
Brian Lacki, an astrophysicist at the Institute for Advanced Study showed that depending on the combination of parameters necessary for the intelligent life’s occurrence, the probability of its existence in the world ranges from 1.4 up to 48%. He mentioned the type and mass of the planet, the distance between it and the star, as well as the variety of genetic material for the various life forms’ occurrence among the factors determining the appearance of civilization.
Adam Frank, a professor of Physics and Astronomy from the University of Rochester and his colleagues from the University of Washington’s astronomy and astrobiology department, by means of the Drake’s formula, calculated not the estimated number of intelligent civilizations, but rather the probability that human civilization is the only one intelligent in the Universe. It turned out that this probability is less than one divided by 10 raised to the 22nd power. Their further calculations showed that there are approximately 10 billion intelligent civilizations in the Universe. There are several thousands of them only in our galaxy, in the Milky Way. Many of them died, but it is possible that several hundreds of high-level civilizations still survive in our galaxy. In their view, the intelligent life is a common phenomenon 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