Astronomers have given a new estimate of the number of civilizations in our Galaxy.
Until we get unambiguous evidence of the existence of advanced extraterrestrial civilizations — for example, their radio signals — the question of whether they exist and in what quantity remains very speculative. As a rule, such estimates are based on the well-known Drake equation, which takes into account such factors as the probability of a star having a suitable planet for life and the development of life on it.
So far, we know the only example of life and civilization — here on Earth-so many of the parameters of the equation have to be borrowed exclusively from our own experience. The probability of the emergence of intelligent life forms, the duration of the existence of civilization-for them, a variety of figures are offered. It is not surprising that, according to some calculations, the cosmos seems to be overflowing with intelligence, and according to others, we are completely alone.
However, some parameters of the Drake equation — for example, the proportion of stars with planets, and among them-the proportion of planets with suitable conditions for life-can be found out using astronomical observations. And as our knowledge of space improves, these values become more precise. Based on this up-to-date information, Tom Westby and Christopher Conselice of the University of Nottingham have made a new calculation of the number of civilizations that can be contacted, based on a refined formula. According to their data, there should be about 36 of them in the Milky Way. The scientists write about this in an article published in The Astrophysical Journal .
The authors relied on modern ideas about the number of Earth-like planets within the “habitable zone” of their stars, as well as the rate of evolution of life on Earth. Based on different estimates, they obtained results ranging from four to 211 highly advanced civilizations in our Galaxy, with the most likely value being about 36.
The existence of several dozen “mind brothers” who can make contact may seem very inspiring. However, Westby and Conselis note that if you remember the really huge size of the Milky Way, the enthusiasm should decrease. If we imagine that all 36 civilizations are scattered evenly across the Galaxy, then the average distance between them should be 17 thousand light-years. It is not known when and how it will be possible to overcome such distances — and whether it will be possible in principle. Even radio conversations will take 34 thousand years to exchange just a couple of phrases.
In some of the more favorable scenarios considered by scientists, a suitable civilization for communication can exist much closer, just 1,000 light-years away. But even then, we will receive the first response message only in 2000 years, when (and if) the first radio signals of humanity reach it — and the response messages will be sent. Will our own civilization survive for this amount of time, or will it perish without passing the “Great Filter”? “The lifetime of civilizations is the biggest unknown in all these calculations,” the authors conclude.