I shall not discuss in detail other (less interesting) possibilities, for example, connected with the invention of an artificial mind and self-producing machines (this is often told by the western futurologists ). They bring nothing new to the problem under consideration as they encounter the same Fermi's paradox. On the contrary, I want to show that in reality the Fermi's paradox is only a pale shadow of that actual problem which stands before the modern natural science. As a matter of fact, it stands already for several centuries.
Let us return to our formula. What has it from the modern science? First, an exponent. Second, an observable rate of development of our civilization and, third, the age of the Universe. Imagine now you were living in the last century and trying to write a formula of such kind. What would change? An exponential development had been already observed. The characteristic time, t, of civilization development, was known already. In those days it was somewhat longer than nowadays but in our calculations it was taken as from the last century. As concerns the age of the Universe, the matters were quite different. In the last century, I had to substitute in the formula . Indeed, the expansion of the Universe was not yet discovered, and, the Universe was believed to be eternal! And it would be no matter for me how quick were the development of a civilization: in a thousand, million or billion years. Everything is equal in comparison to eternity.
Then, in the answer we would obtain not an anomaly great number but an infinite one. This is not only a paradox, this is a real ``deadlock''. It is astonishing, how could the best minds of the last century pass by such an obvious fact? The nature having a possibility to give birth to a life during an infinitely long time sooner or later had to give rise to SUPERINTELLIGENCE. Even in our century A. Enstein, and F. Hoyle after him, tried to argue for eternally living Universe. They didn't know what they created, did they?
For a long time I have tried to find a physicist or a philosopher who discussed, though in passing, this fact appealing for comprehension. And such a man has been found, although not in the last but in our century. As a matter of fact, he reasoned as a representative of the last century because he didn't suspect about the expansion of the Universe, or didn't believed in that (the matter is that the first estimates of the age of the Universe were extremely low and contradicted to the geological data). It was K.E. Tsiolkovskii, technician of genius, dreamer and evident philosopher. Unfortunately, his most consecutive ideas were stated orally when he was speaking to Chizhevskii and the latter wrote down their talk later . But the results of reflections were published from time to time. Yes, Tsiolkovsky understood, from his pure materialistic point of view, that infinite development of the nature sooner or later (it is an expression almost out of place) must come to complete expansion of intelligence. And so he derived the idea of ``an intelligent atom'', ``perfect creatures'', and Intelligent Universe. These ideas, of course, may be conceived by a modern natural scientist with an irony, nevertheless a reason of their appearance is quite natural for a scientific method. If the Universe has lived for an infinitely long time then the Tsiolkovskii's paradox can be solved only with this key, the key of ``Superintelligence''.
You may say, thank God, there was the astronomer Hubble who discovered expansion if the Universe, and we understood that our Universe had not been eternal. This ``only'' being something about ten billion years, we can safely close the eyes to this ``ten'' with 43 million of ``0''s, and refer to the uniqueness, ``deadlock branch'' or ``an eastern variant''.
First of all, as we saw, this is not so simple at all because of the remoteness of years ``lived out'' by the nature. And besides, is not indeed this world eternal, is it?
The current state of matters in cosmology has been formed in the beginning of 80ths when the inflation idea saw the light .
In reality, as A.D. Linde and A.A. Starobinskii show in their models of stochastic birth, our Universe is only a part in some quasistationary process of permanent arising and fanning universes. In other words, the old dream of humanity about other universes is now considered from a quite scientific point of view although in semi-qualitative manner, in limits (more precisely, at frontiers) of the Grand Unification Theory which is not yet constructed. There are two important items here: 1) our Universe is not alone, 2) there exists a ``pre-Planck's'' life time for every such universe when, generally speaking, the classical conception of time loses its sense (due to, for example, purely quantum indeterminacy of causal-consequent cohesions). Briefly speaking, in spite of the rescue discovery of E. Hubble a question about the time infinity of our Universe has floated once more, as in the 19th century. And we are to consider once again the stationary variant by Einstein or that proposed subsequently by Bondi and Hoyle. Of course, now we deal with quite different concept of time. The significant point is that the nature has had an infinite number of possibilities to create the worlds of our type, consequently, for the life appearance. And so, we must solve the Tsiolkovskii's paradox once more.