American astrophysicist Brian Luckey highly appreciated the chances that advanced extraterrestrial civilizations could inhabit the foreseeable part of the Universe.
Every fifth star warms aliens
Brian Lacki, an astrophysicist at the Institute for Advanced Study (Institute for Advanced Study), calculated that the probability that advanced extraterrestrial civilizations are "found" in the part of the universe that is accessible to observation is 18 percent. In general, if you change the initial parameters within reasonable limits - combine data on the type of star, distance to it, data on the mass of the planet and its size, take into account the diversity of genetic material, then the chances of "bumping" somewhere on aliens can vary from 48 percent to one and a half. That is, to be both very high and low, but not zero.
To his calculations arxiv.org/abs/1609.05931 Lucky adds the so-called Bayesian inference - a scientific method that takes into account the received data, playing both in favor and against a certain hypothesis. The scientist believes that the evidence already accumulated is enough to believe in the existence of aliens. 18 percent is the average probability of such, so to speak, reality.
There are at least 10 billion intelligent civilizations scattered throughout the universe
Lucky was far from the first to take up the consideration of brothers in mind. In 1960, Professor of Astronomy and Astrophysics at the University of California, Frank Donald Drake, derived a formula that, in his opinion, could determine the number of extraterrestrial civilizations. In the formula named after the scientist, there are seven members: the number of stars formed per year, the proportion of stars with planets, the number of planets or their satellites with conditions suitable for life, the likelihood of the emergence of any life, the probability of its transformation into a reasonable one, the proportion of planets with highly developed creatures, the lifetime of a civilization that lives on the planet.
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Calculations, carried out many times according to Drake's formula, gave a different number of brothers in mind: from their complete absence - to 5 thousand. The spread arose from the fact that scientists differently estimated the values of the parameters included in the equation. They were based, naturally, on the ideas of their time.
Drake's equation allows you to estimate the number of brothers in mind
Much has now become clearer - especially thanks to the observations that were carried out using the Kepler space telescope. It turned out that there are more stars in the Universe than previously imagined, as well as planets suitable for life.
The latest data on the universe was armed by Adam Frank, professor of physics and astronomy at the University of Rochester, with colleagues from the Department of Astronomy and Astrobiology at the University of Washington. Scientists have turned to Drake's formula again. But to begin with, they did not calculate the estimated number of intelligent civilizations, but, on the contrary, the probability that we are alone in the Universe. And it turned out that such a probability is vanishingly small - less than one divided by 10 to the 22nd power.
And since the probability that we are alone is so small, then, most likely, we are not alone, the researchers decided. Their further calculations showed that there are about 10 billion intelligent civilizations in the Universe. Nothing less. Only in our galaxy - the Milky Way - there are several thousand.
In the Milky Way, the galaxy we live in, there are billions of stars with habitable planets.
Frank believes that most civilizations appeared long before ours. And have already disappeared. So archaeologists - astroarchaeologists will have to look for them. But at the same time, it is possible that several hundred high-level civilizations in our galaxy have survived.
Scientists are upset: if the speed of movement in space is really limited by the speed of light and there are actually no "holes" connecting distant regions of the galaxy in a short way, then we are unlikely to ever come into contact with brothers in mind. They are too far away - on average, according to Frank, at least 20 thousand light years.
There are at least 361 intelligent civilizations in our galaxy
Duncan Forgan from the University of Edinburgh in Scotland in his own way estimated the number of inhabited worlds, but not in the entire Universe, but only in the Milky Way. And he determined that there were no less than 361 of them.
Duncan created a mathematical model of our galaxy, in which, as you know, intelligent life appeared - we are evidence of this. He set a program, the parameters of which he correlated with the current knowledge of the ability of stars to acquire planets of suitable size and located in a zone favorable for the emergence of life. And launched into work on three scenarios.
The first scenario assumed that living organisms appear with difficulty, but then develop well. In the second, they experience difficulties in transforming into intelligent beings. According to the third scenario, life could be transferred from one planet to another, as follows from the very popular hypothesis of its origin on Earth.
As a result, despite all the difficulties, the scientist received three positive results. Namely, 361 intelligent civilizations for the first - the most difficult - case, 31,513 - for the second. And as much as 37,964 - for the third.
BTW
We'll hunt them down soon
FAST (Five-hundred-meter Aperture Spherical Telescope), one of the largest radio telescopes in the world, has been commissioned in China. Almost 2/3 of the entire sky will fall into his field of vision. FAST is not only very large, but also very sensitive. Astronomers who will work on it do not hide the fact that they will also search for signals from extraterrestrial intelligence. Most likely, the Chinese telescope will get part of the $ 100 million that Russian Internet entrepreneur Yuri Milner is going to spend on searching for signals from aliens. As part of a project called Breakthrough Listen (literally - Breakthrough in listening), he is just about to rent the largest radio telescopes.
Chinese new telescope
Seth Shostak Senior Astronomer at the Search for Extraterrestrial Intelligence Institute at NASA's 2014 NASA Innovative Advanced Concepts (NIAC) symposium, which was held in 2014 at Stanford University, promised that intelligent life on other planets will be found in 24 years. That is, in 2038. After all, according to him, radio astronomers will "comb" not thousands of stellar systems, as before, but millions, trying to detect the electromagnetic signal of an extraterrestrial civilization. And they will definitely spot.
Today Shostak has not diminished his optimism. On the contrary. Indeed, according to the latest data obtained with the help of NASA's Kepler space telescope, every fifth planet in our galaxy - the Milky Way - is in the so-called habitat zone. That is, it can support life. This fits well with the probability calculated by Brian Luckey: 20 and 18 percent are almost the same.
Either we find them, or they us
Vladimir LAGOVSKY