Brothers in Mind

British scientists have tried to find out how many intelligent civilizations can exist in the Milky Way galaxy. After making new estimates on the example of the Earth, they came to the conclusion that this number can be just over three dozen. This is reported by the newspaper “Gazeta” .
For centuries, scientists, peering into the depths of space, have wondered whether there are other civilizations in the universe, and if there are, how many of them. An important achievement in the estimation of the number of civilizations was the appearance in 1960 of the famous Drake equation.
The equation formulated by Dr. Frank Drake makes the number of intelligent civilizations in our galaxy dependent on seven different variables, including the number of stars born per year in our galaxy, the proportion of sun-like stars with planets, the probability of intelligent life forms on a planet that has life, and the lifetime of such a civilization.
From a practical point of view, the Drake formula is of little use — the uncertainty of most of the parameters used in it makes it useful only for reasoning about the number of intelligent civilizations in our galaxy.
The calculations used in the past gave completely different results-from zero to billions of civilizations in the Milky Way.
Scientists from the University of Nottingham (UK) conducted a new assessment, suggesting that different civilizations in different parts of the galaxy take about the same time to develop, and concluded that in our Milky Way galaxy there may be 36 of them.
It is believed that in the Milky Way galaxy, in which the Solar System is located, from 100 to 400 billion stars, while on average each star has at least one planet.
“There should be at least a few dozen active civilizations in our galaxy, assuming that it takes 5 billion years for intelligent life to form on other planets, as on Earth,” said study co — author Christopher Conselice. Scientists called the resulting estimate the Astrobiological limit of Copernicus.
At the same time, the scientists proposed to consider two scenarios. The first, “weak”, suggests that intelligent life on other planets is formed no earlier than 5 billion years later. The “strong” scenario provides for the emergence of intelligent life in the period of 4.5-5.5 billion years, which is more in line with the example of the Earth. For this criterion, the number of intelligent civilizations was equal to 36.
The study, published in The Astrophysical Journal, showed that the number of civilizations strictly depends on how long they are able to actively communicate — send radio signals from satellites, broadcast on television frequencies, etc.
The result is based on the assumption that other civilizations communicate for at least a hundred years, as well as human.
The Copernicus Astrobiological limit also takes into account a number of parameters that were little known half a century ago. Among them are the intensity of star formation, the proportion of stars with the metallicity of the Sun, and the proportion of stars with Earth-like planets in the habitable zone.
“The classical method of estimating the number of intelligent civilizations is based on guessing the values related to life, but opinions on this point differ very significantly,” explained Tom Westby, the author of the work. “Our new study simplifies these assumptions by using new data and giving solid estimates of the number of civilizations in our galaxy.”
At the same time, 36 is only the most plausible number, and the authors emphasize that the average distance to such civilizations is 17 thousand light years. “This makes detecting and communicating with them very difficult given the existing technologies,” they argue.