In 1985 Shklovskii formulated the problem of Extraterrestrial Intelligence. He was engaged in this problem almost all his life. But most surprising is the fact that having passed the way from the early romanticism of 60's (the artificial creation of Fobos and Deimos) through the more realistic concept of the uniqueness of life in the Universe (an absence of space miracles ), which engages the west scientists up to now , he came to the conclusion which could be obtained still before the space age and the programs of searches of extraterrestrial life!
As a matter of fact, the problem is reduced to the so called Fermi's paradox which in modern language looks as follows (Lipunov,1987):
there are two observational or, if you like, experimental facts: 1) the age of the Universe is year, 2) a specific time t of exponential development for our civilization is of the order of some tens of years. For the sake of simplicity it san be adopted years which is obviously an overestimation. A gigantic dimensionless number characterizes the growth of a technological civilization over the time of existence of the Universe:
It is enough to say that the theoretical physics never dealed with so great dimensionless numbers. For example, the full number of elementary particles in the Universe looks ridiculously small -- . Fermi himself exclaimed: ``If there were anywhere space civilizations, their spaceships would have been in the solar system long since'' (I don't guarantee the exactness of the quotation). Naturally, this number is so gigantic that any unknown intermediate factors are unimportant. Really, it can be confirmed that probability of absence of ``space miracles'' in our Universe is , i.e. is equal to zero! Nevertheless, nobody has discovered them even after 20 years of searches. On the contrary, a Giant Silence of the Universe has been revealed. The world without miracles is incredible but it exists -- that is the paradox.