The formula for calculating extraterrestrial civilizations. Drake equation
The Drake formula was formulated by the American astronomer Frank Drake to estimate number of civilizations in the galaxy.
(Yes, this is not very relevant to the site. But still interesting.)
Appearing in 1960, the Drake formula was very fashionable in the era of "great cosmic hopes", but then, due to resentment that the hopes did not come true, it began to be criticized, and as a rule, not meaningful, but methodological. The main claim to the Drake formula is that it is, de, “about nothing”, you can count anything with this formula, the formula is not falsifiable, and therefore unscientific.
I will leave the assertion of non-falsifiability to the conscience of critics: they either do not understand the meaning of this concept themselves, or deliberately mislead the reader with a beautiful term. The emotional thesis "formula about nothing" is deciphered as follows: the problem area of the problem is so undefined that it seems pointless to derive any formula: we get false accuracy on too shaky ground.
So it is, but this is exactly how the task is set: to give a reasonable estimate of a certain quantity under extremely uncertain conditions that affect it. This situation is by no means unique. Very often in science, and in astronomy in particular, at the initial stage of research, one has to make assumptions under conditions of extreme uncertainty. Surprisingly, from general considerations, one can draw correct conclusions and obtain numerical estimates that do not differ much from the truth.
- How many hairs are on the head of the President of Venezuela?
- What is the weight of a female Porcula salvania?
- What is the viscosity in the solar photosphere?
On similar questions you can give an answer from general considerations and get a number that is not catastrophically very different from the correct one. In conditions of complete misunderstanding of the initial conditions, an error of a couple of orders of magnitude is already a worthy result!
It was in this situation that Drake was, offering his own, in general, banal formula. He reduced a completely incomprehensible task (to determine the number of extraterrestrial civilizations) to a set of subtasks that can be assessed. We can be wrong by several orders of magnitude, but in our situation, this is already good!
Here is Drake's formula in its original formulation:
N = R * f p n e f l f i f c L ,
- R* - star formation rate (stars per year)
- f p - fraction of stars with planetary systems
- n e - the average number of planets in the system that are ecologically habitable
- f l - the probability of the appearance of life on a similar planet
- f i - probability of evolution to reasonable
- f c - probability of civilization formation
- L - time of existence of civilization (years).
Some remarks should be made.
Firstly, Drake himself discussed the radio search for extraterrestrial civilizations and therefore meant technically advanced civilizations using radio communications, and estimated the parameter L for them. Without losing generality, one can define a civilization at one's own discretion and, accordingly, estimate its lifespan.
For example
… one can understand civilization in the most general view, as a socio-cultural structure, different from disparate tribes. In this case, earthly civilization begins with the Sumerians and today has about 5 millennia.
…following Jaspers, start counting from the axial time, when mankind formed the axiology in which we still exist (presumably, this is the necessary axiology of civilizational development). In this case, we have two and a half millennia.
... you can limit yourself to technical civilizations, whose age is only a couple of centuries.
Secondly, the dependence on the rate of star formation seems somewhat incomprehensible. At first glance, it is paradoxical that the number of extraterrestrial civilizations does not depend on the number of stars in the galaxy, but only on the frequency of star formation. In fact, the size of the galaxy is implicitly included in this parameter, because the larger the star system, the more new stars are born in it. However, in modifications of the formula, the number of stars in the Galaxy can also be used, but then one has to use the unintelligible parameter "the lifetime of the Galaxy." The original version of the form is more accurate.
I'll explain what I'm talking about.
It is clear that f = f p n e f l f i f c is the probability of a civilization appearing near an arbitrary random star. R* stars are born per year. After the required time has passed, n = R * f civilizations will appear on these stars. During the existence of a civilization (L years), its contemporaries will be n L other civilizations. This, in particular, means that R * is the rate of star formation not at the present time, but approximately at the time when the Sun was born. (Drake himself talked about the rate of star formation, averaged over the lifetime of the Galaxy, which is actually not true.) Within the limits of acceptable accuracy, this detail can be neglected.
There are serious factors that are usually not mentioned when talking about the Drake formula, which can seriously correlate the result. Some of them work to increase, others - to decrease the probability.
I'll start with bitter.
"Ecological habitability" depends primarily on the temperature at the surface, that is, on the temperature of the central star and the distance to it. It is important that the temperature regime should not go beyond acceptable limits during the entire period from the appearance of life to the death of civilization. In our example, it is worth talking about 4-5 billion years, which means discarding too hot stars, unstable stars and stars above the Hertzsprung-Russell Main Sequence (fortunately, there are not so many of them). In general, it would be worthwhile to redefine the parameter f p as "the fraction of stable stars with planetary systems", where the meaning of "stability" is explained above.
And here's a nice one.
The formula implies that civilization is a one-time phenomenon in the history of the planet. That is, the scenario is as follows: life appeared on the planet, evolved to a reasonable one, a civilization was formed, civilization died. And that's it.
And that's it? Why can't a new civilization arise on the basis of the same mind? Why can't a new mind arise (and create a civilization) if the old one is dead? Why can't there be new life, if the old was destroyed, say, as a result of a catastrophe, evolve to the mind, etc.? The "disposability" of civilization is a very strong and completely unreasonable limitation in Drake's formula. If civilization is a renewable thing, then in its present form the formula is essentially inaccurate: the parameter L must be multiplied by the number of reincarnations n r , and its growth will lead to nonlinearity when the total time L n r becomes comparable with the age of the star.
Of course, the question of the factor n r is highly speculative. In particular, it depends on the scenario of the death of civilization, and this is an area of pure futurism, and not at all a serious scientific forecast.
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Not so long ago, a material called "" was published on our resource "", which raised the question of the existence of alien intelligent civilizations in the Universe. But if there this possibility itself was called into question, then here we will consider a formula that often serves as a refutation of the above-named paradox. This formula is called the Drake equation.
Some general data
It’s worth starting with the fact that there is a special project under the general name “SETI” (an abbreviation for Search for Extraterrestrial Intelligence). It includes various projects and activities aimed at searching for extraterrestrial civilizations and making contact with them. The project has existed for several decades (since 1959), almost from the moment when the American astronomer Frank Drake conducted his first experiment. Searches for "SETI" are based on listening to radio waves that other civilizations can send from the depths of space. Drake himself already then considered this an indicator of a high-tech society, as well as the most acceptable and reasonable means for searching for extraterrestrial life forms.
The probability of detecting any signal at a distance of more than 500 light years is practically zero, i.e. 500 light years is the limit within the radius of which modern technologies can find any radio signal at all. It follows from this that the so-called "Great Silence", which is constantly detected by radio telescopes, does not yet mean that another life in the Universe is not possible. And a higher chance of asserting something with a less solid degree of certainty can only appear if the earth's "receivers" can increase the signal reception range by at least another 900 light years.
In the middle of the last century, mankind had even less data on this topic. However, already at the time when Soviet cosmonaut Yuri Gagarin became the first person to orbit the Earth (1961), Frank Drake developed his own equation that allows you to roughly estimate the number of possible alien civilizations in our galaxy, called the Milky Way. This equation is based on methods for detecting electromagnetic pulses.
Drake equation
The Drake equation is formulated as follows:
N = R * Fp * Ne * Fl * Fi * Fc * L, where:
N is the number of intelligent civilizations that are ready to make contact
R is the number of stars that appear during the year in the Milky Way galaxy
Fp is the percentage of stars that have planets in their orbits
Ne - the average number of planets and their satellites, the conditions of which are suitable for the origin of life
Fl is the probability of life appearing on a suitable planet
Fi is the probability of the appearance of intelligent life forms on planets where life is possible at all
Fc - the ratio of the number of planets on which intelligent life forms are capable of contact and are looking for it, to the number of planets on which there are intelligent life forms at all
L is the time that intelligent life exists, can make contact and wants to do so
Analysis of the Drake Equation
Considering the Drake equation, it becomes obvious that the value of N cannot be precisely determined. In addition, as you move through the equation from left to right, the estimates of all quantities become more and more abstract. However, this equation should not be evaluated only by numbers. Some researchers are convinced that this formula is only a way of some organization of human ignorance. And if we consider the hypothesis of the existence of extraterrestrial intelligence from a purely mathematical point of view, then the opportunity to get an answer to the question about the number of alien civilizations is significantly limited. The value of L is the most important in the whole equation. A person cannot know how long a technologically advanced civilization can last. And even if we assume that there is only one alien civilization, and has existed for billions of years or even eternity, then this will be enough to equate N and L in the equation.
But to search for extraterrestrial intelligence only by listening to radio waves would be erroneous. Thanks to the development of astrobiology and cosmology, human perception of the cosmos and the development of other life forms has changed dramatically. At the beginning of the existence of SETI, its specialists predicted the rapid development of terrestrial radio technologies and the growth of radio exchange, but the point-to-dash-to-point connection faded against the background of satellites sending their signals to the Earth, and the emphasis in telecommunications shifted from radio to fiber optics for the Internet. traffic and cable TV, which means that there will be no serious radio signals from Earth for at least another hundred years.
Other weak point formula is the number of planets on which intelligent life forms can develop. Presumably, their number should be within 10 thousand in our galaxy. But at present, there is no evidence that there is any underlying principle that could direct the primary substance on the path of development in Homo Sapiens. And this question will remain unanswered until confirmation of life is found on at least one planet in the solar system.
Among other things, the Drake equation does not take into account such indicators as the age of the galaxy itself and chemical-mechanical parameters, for example, the presence of certain elements necessary for the formation of planets and the origin of life. According to some experts, the Drake equation does not imply a universe that is constantly in dynamics, but a special cosmological constancy.
The formula contains an approximate number of Earth-like planets, but does not provide an estimate of when intelligent life forms appear on these planets. The enormous age of our galaxy and the likelihood that intelligent life on its planets could have been present both 2 and 4.5 billion years ago, but could have already died out, do not give practically any space for detecting radio waves.
To date, astronomers have found about 2,000 extrasolar planets. And the total number of stars like the Sun can be over 40%. But many planets are too big and are in orbits very close to "their" stars. These planets are called "Hot Jupiters". However, according to scientists' forecasts, if search methods are improved, it will be possible to find smaller planets and with more suitable orbital characteristics. Plus, over the past twenty years of research, it has been possible to find out that billions of planets can exist in the Milky Way, on which life is possible that can exist in extreme conditions, for example, with an increased content of carbon dioxide, at depths up to 10,000 meters and even in sulfuric acid.
But, despite the "flaws", Drake's equation greatly influenced people's thinking. Mainly, it served as the starting point for the emergence of astrobiological science. The eminent American astrophysicist Carl Sagan praised the fact that the equation showed a high percentage of detection of intelligent extraterrestrial life. And not so long ago, in 2010, the Italian astronomer Claudio Maccone published his version of the Drake equation - the statistical Drake equation, which is more complex, but also more reliable. With the help of the new formula, Maccone was able to determine that only within milky way there may be 4,590 extraterrestrial civilizations, which is more than 1,000 more than the number that was obtained in the classical version of the equation. In addition to this, the new formula showed that in addition to human civilization, there may be up to 15,785 others with high technology.
But even if the various galactic communities were at the same distance from each other, its average value would be 28,845 light years, which makes it impossible for any contact between these communities, even if it would be carried out with the help of electromagnetic radiation moving at the speed of light. And even if such a number of civilizations existed, interstellar communication between them would experience very serious technological problems.
In fact, the Drake equation is subject to scrupulous and detailed study, and without being an expert in the relevant field, it is quite difficult to really understand what's what. But our goal was by no means an exhaustive explanation of the equation, but only an indication that scientists around the world take the issue of the existence of extraterrestrial intelligence more than seriously and this has very good reasons.
The number of extraterrestrial civilizations wishing to make contact with ours is predictable.
Generally speaking, few large scientific discoveries strictly dated - not only by year, but also by month and date. However, at least one of them can be dated to the nearest minute. On the night of November 1-2, 1961, several scientists - participants of a conference held in Green Bank, Virginia, USA, sat up late in a bar discussing an article written by physicists Philip Morrison (Philip Morrison, b. 1915) and Giuseppe Cocconi (b. 1914). They argued whether earthly scientists, who had just begun building serious radio telescopes, could actually detect radio signals sent by extraterrestrial civilizations from deep space. If somewhere in the depths of the universe there really is at least one extraterrestrial civilization seeking to contact us, it is probably sending us radio signals, and we just need to catch them, they reasoned. At the same time, a task was formulated for the next day of the conference: to estimate the probable number of extraterrestrial civilizations ready to make contact with us.
The question was posed, and the next day the American radio astronomer Frank Drake proposed the answer to it. According to his formula, the number of extraterrestrial civilizations N is:
where R is the number of annually formed stars in the Universe; P is the probability that a star has a planetary system; N e - the probability that there is a planet among the planets earth type, on which the origin of life is possible; L is the probability of the real origin of life on the planet; C is the probability that intelligent life has taken a technological path of development, has developed means of communication and wants to make contact, and, finally, T is the average time during which a civilization that wants to make contact sends radio signals into space to contact us. The meaning of Drake's formula is, if you like, not to completely confuse everything, but to clearly show the full extent of human ignorance regarding the real state of affairs in the Universe and, at least approximately, split one purely guesswork estimate total number civilizations in it by several probabilistic estimates. At least in this form, everything begins to look less mysterious.
At the time of the Green Bank conference, the only more or less known number on the right side of the formula was the number of annually formed stars R. As for other numbers, the terrestrial planets (N e) even in our solar system could be assigned from one (only Earth) to five (Venus, Earth, Mars and one of the large satellites of Jupiter and Saturn) planetary-type space objects. With optimistic forecasts of this kind, it turned out that the Galaxy is literally teeming with millions of technologically advanced civilizations (N), and we are, in fact, juniors in this “galactic league”. This information immediately filled the funds mass media, and through them - both the mass consciousness and people simply ceased to doubt that the existence of extraterrestrial intelligence is an indisputable truth.
However, more than one decade has passed since 1961, and the further we go, the more we become convinced that it is necessary to moderate the optimism initially generated by the Drake formula in the mass consciousness of earthlings who yearned for brothers in mind. Today we know, for example, in contrast to the overly optimistic members of the Greenbanks group, that the existence of life within our solar system outside the Earth is extremely unlikely (unless it exists under a thick ice sheet in the ocean of Saturn's fourth largest moon, which, ironically, is called Europa ). And, although after 1961 we discovered many planetary systems around previously known stars, they all look a little like ours. solar system, since the planets there, for the most part, circulate in elongated elliptical orbits with a very significant eccentricity, which means that the annual temperature difference on them looks unacceptable from the point of view of the development of protein life. In fact, it turned out that the conditions conducive to the retention of water on the surface of a planetary body for billions of years without its evaporation and / or freezing are so severe that, apart from the Earth, no such planets have yet been found - and this is not surprising, since even a few percent changes in the radius of the earth's orbit will lead to the fact that our planet will become uninhabitable.
It so happened that in 1981 my astronomer colleague Robert Rood (Robert Rood, b. 1942) and I stumbled upon Drake's formula and decided to critically rethink it in the light of modern scientific knowledge. Substituting all the estimates we have on hand on the right side of the formula, we got the value of N, which is approximately equal to 0.003. That is, three out of a thousand (or about one out of three hundred) star systems have a technologically advanced civilization that wants to communicate with us. Or, if you like, this means that interstellar signals from extraterrestrial intelligence appeared in our Galaxy only in the last 1/300 of its existence. In any case, the rates for their discovery are extremely bad: 1:300. Naturally, over the past twenty extra years nothing has changed, and extraterrestrial civilizations have not given any signs of life. Their search has been going on for more than a decade, financed both at the state expense and by private funds. Alas... We still haven't found the notorious extraterrestrial brothers in mind, let alone try to make contact with them. Yes, okay. But we have accumulated a mass of absolutely reliable data regarding what is not there.\
Frank Donald DRAKE
Frank Donald Drake, b. 1930
American astronomer. Born in Chicago, studied in the electronics department at Cornell University. After listening to a course of lectures by the famous astronomer Otto Struve (1897-1963) on the formation of planetary systems, he became interested in extraterrestrial life and civilizations for life. After serving in the US Navy, he worked successively at the National Radio Astronomy Observatory (NRAO), Cornell University and the University of California (Santa Cruz). With the support of Struve, Drake organized the construction of a 28-meter radio telescope based on the NRAO (Project Ozma), the world's first measuring and recording instrument specifically designed to try to detect extraterrestrial life.
History
Drake formulated the equation in 1960 while preparing for the Green Bank teleconference. This conference marked the program
The equation is also often referred to as the Green Bank equation, as this is where it was first introduced. When Drake came up with this formula, he did not expect it to serve as an argument for supporters of Carl Sagan, a well-known supporter. A related argument is the Great Filter, which claims that the absence of observable civilizations provided huge amount observed stars is explained by the fact that there is a certain filter that prevents contacts.
Thus, the main meaning of the equation is the reduction of the big question about the number of intelligent civilizations to seven smaller problems.
Historical parameter estimates
There are many opinions on most parameters, here are the numbers used by Drake in 1961:
- R= 10/year (10 stars are formed per year)
- f p = 0.5 (half of the stars have planets)
- n e = 2 (on average, two planets in the system are habitable)
- f l = 1 (if life is possible, it will definitely occur)
- f i = 0.01 (1% chance that life will develop to a reasonable)
- f c = 0.01 (1% of civilizations can and wants to make contact)
- L= 10,000 years (technologically advanced civilization exists for 10,000 years)
The Drake equation gives N= 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 10000 = 10.
Value R determined from astronomical measurements, and is the least discussed quantity; f p is less defined, but also does not cause much discussion. Reliability n e was quite high, but after the discovery of numerous gas giants in orbits of small radius, unsuitable for life, doubts arose. In addition, many stars in our galaxy are red dwarfs that emit hard X-rays that, according to simulations, can even destroy the atmosphere. Also, the possibility of the existence of life on the satellites of giant planets, like Jovian Europa, or Saturnian Titan, has not been investigated).
Depending on the assumptions made N often turns out to be much larger than 1. It was precisely such estimates that served as the motivation for the movement
Some results for various assumptions:
R= 10/year, f p = 0.5, n e = 2, f l = 1, f i = 0.01, f c = 0.01, and L= 50,000 years N= 10 × 0.5 × 2 × 1 × 0.01 × 0.01 × 50,000 = 50 (at any given time there are about 50 civilizations capable of contact)Pessimistic assessments, however, argue that life rarely develops to a reasonable level, and advanced civilizations do not live long:
R= 10/year, f p = 0.5, n e = 2, f l = 1, f i = 0.001, f c = 0.01, and L= 500 years N= 10 × 0.5 × 2 × 1 × 0.001 × 0.01 × 500 = 0.05 (we are most likely lonely)Optimistic estimates claim that 10% can and want to make contact, and at the same time exist up to 100,000 years:
R= 20/year, f p = 0.1, n e = 0.5, f l = 1, f i = 0.5, f c = 0.1, and L= 100,000 years N= 20 x 0.1 x 0.5 x 1 x 0.5 x 0.1 x 100,000 = 5,000Contemporary estimates
This section provides the most reliable parameter values to date.
R = star formation rate
Rated by Drake as 10/year. The latest results from NASA and the European Space Agency give a value of 7 per year.
f p= proportion of stars with planetary systems
Rated by Drake as 0.5. According to latest research, at least 30% of solar-type stars have planets, and given that only large planets are found, this estimate can be considered underestimated. Infrared studies of dust disks around young stars suggest that 20-60% of solar-type stars can form Earth-like planets.
n e= Average number suitable planets or satellites in one system
Drake's score is a 2. Marcy notes that most of the discovered planets have highly eccentric orbits or pass too close to the star. However, systems are known that have a solar-type star and planets with favorable orbits (HD 70642, HD 154345, or Gliese 849). It is probable that they have terrestrial-type planets in a habitable region, which were not discovered due to their small size. It is also argued that a sun-like star or an Earth-like planet is not required for life to arise - Gliese 581d could also be habitable. Although about 200 planetary systems are known, this only gives n e> 0.005 . Even for a planet in the habitable zone, the emergence of life may be impossible due to the lack of some chemical elements. Also, there is the Unique Earth Hypothesis, which states that the combination of all the necessary factors is extremely unlikely, and perhaps the Earth is unique in this regard. Then n e is considered to be extremely small.
f l = Probability of life in the right conditions
Rated a 1 by Drake. In 2002, Charles Lineweaver and Tamara Davis rated f l as > 0.13 for planets with more than a billion years of history based on Earth statistics. Lineweaver also determined that about 10% of the stars in the galaxy are habitable in terms of having heavy elements, moving away from supernovae, and being reasonably stable in structure.
f i = The probability of development before the emergence of intelligence
Rated by Drake as 0.01.
f c= Percentage of civilizations that have the ability and desire to establish contact.
Rated by Drake as 0.01.
L = The life expectancy of a civilization during which it attempts to establish contact.
Drake's estimate is 10,000 years. In an article in Scientific American, Michael Schemmer rated L in 420 years, based on the example of sixty historical civilizations. Using statistics from "modern" civilizations, he got 304 years. However, the fall of civilizations has generally not been accompanied by a complete loss of technology, which would preclude them from being considered separate in the sense of the Drake Equation. At the same time, the lack of methods of interstellar communication also allows us to declare this period zero. Value L can be counted from the date of the creation of radio astronomy in 1938 to the present day. In 2008, therefore, L not less than 70 years old. Such an estimate, however, is meaningless - 70 years is the minimum, in the absence of any guesswork about the maximum. 10,000 years is still the most popular value. R= 7/year, f p = 0.5, n e = 2, f l = 0.33, f i = 0.01, f c = 0.01, and L= 10000 years
We get:
N= 7 × 0.5 × 2 × 0.33 × 0.01 × 0.01 × 10000 = 2.3Criticism
Since only one planet is known to date to support intelligent life, most of the parameters in the Drake equation are determined based on assumptions. However, the presence of life on Earth makes the hypothesis of the existence of extraterrestrial life at least possible, if not probable. In 2003, science fiction writer Michael Crichton stated in a lecture at Caltech: “To be precise, the Drake equation is absolutely meaningless and has nothing to do with science. I take the view that science can only create testable hypotheses. The Drake Equation cannot be tested and therefore I cannot attribute SETI to being like a religion, it cannot be refuted."
We also note that the experiments of light years from the Sun are a civilization that uses a certain section of the radio range for communication.”
One response to criticism of the Drake equation is that, even though it does not give exact numbers, the equation nevertheless provoked serious discussions of astrophysics, biology, geology and allowed significant funds to be allocated to the development of astronomy, focusing attention on practical aspects searches.
Alexander L. Zaitsev drew attention to the fact that being able to establish contact and establishing it are two different things. Mankind is able to pick up a radio signal from the nearest stars, but at the same time does not make regular targeted attempts to transmit its messages. Zaitsev proposed to introduce the METI factor (METI-coefficient), which determines the proportion of civilizations that purposefully send signals.
Drake equation in culture
- The Drake Equation is mentioned in episode 20 of season 2 of the American comedy series The Big Bang Theory by Howard Wolowitz to prove that their company has a chance to meet girls in a bar.
- There are mentions of him in the famous comic book http://www.xkcd.ru/384/
During the conference in the city of Green Bank, located in the state of Virginia, USA, which was held in 1961, a dispute arose between scientific participants, astronomers and astrophysicists on the topic of the report of physicists Philip Morrison (born in 1915) and Giuseppe Cocconi (born in 1914) . It discussed the possibility of scientists the globe, which have just begun to break through to a serious level of receiving and decoding radio signals, receive a message and contact civilizations of other worlds in the galaxy, through radio telescopes. There were also reflections on the fact that if such intelligent extraterrestrial civilizations exist, then most likely they are already sending signals and may be ready for contact with earthlings. It is only necessary to receive these signals and decipher them qualitatively. Moreover, during the conference a problem was posed: how can one calculate the number of such intelligent civilizations ready to contact us?
Literally the next day (namely, on the night of November 1-2), after this question was raised, the American radio astronomer Frank Drake recommended using the following formula to calculate the number of extraterrestrial civilizations (EC, aka N)
N = R?P?Ne?L?C?T?L, in which:
- R is the number of stars that are formed in the Universe every year;
- P is the chance that the star has a system of planets;
- Ne - the probability that between these planets there is one on which there will be a chance for the birth of life;
- L is the possibility that life can actually originate on such a planet;
- F is the probability of the emergence of intelligent life forms on the planet;
- C - the real probability that life that originated on the indicated planet has chosen a technogenically developing path, it has the means by which it can communicate through signals in space and is ready to contact other worlds;
- T is the standard average time during which a civilization that would like to contact other worlds constantly sends out radio signals in the hope of communicating with the EC.
N = N*?P?Ne?L?F?C?T/Tg, in which:
- N* is the number of all stellar objects in our galaxy;
- Tg is the lifetime of our galaxy.
- R is the number of stars equal to 10 that open each year;
- P - it is assumed that half of the stellar objects have planets;
- Ne - found that only two planetary objects can have life;
- L - equates to 1, if conditions allow, then life on the planet will definitely arise;
- F is only a hundredth of the probability that life on the planet will be intelligent;
- C - only 1% of intelligent worlds that are ready and express desires for contact with other worlds;
- T - an indicator of 10,000 years (a civilization that leads technological development lives for about 10,000 years).
However, during the passage of the above conference, only the number of stars that can form from year to year, that is, the variable R, could be known. Regarding other parameters in this formula, for example, Ne (the number of terrestrial planets), it is very ambiguous . If we take our solar system as a basis, then in it we can choose both the singular Ne (our Earth) and the plural (for example, the five planets of our system, such as Venus, Earth and Mars, and any one large satellite of the giant planets Jupiter or Saturn) objects of space with the properties and description of the planets.
If we take forecasts with an optimistic future, then our Galaxy is simply crammed with worlds that have sufficient technological development (N), and our civilization is just a young and inexperienced creature compared to them. Thanks to this, the news immediately became an accessible mass media, and then the idea was formed and settled in the minds of all people that the terrestrial civilization is not the only one in the Universe and extraterrestrial intelligence exists.
However, over time, the optimistic forecast that the Drake formula gave rise to becomes very distant. If we take the solar system as an example, then the possible origin of life on planets is very unlikely, and if it is possible, then only under a huge layer ocean ice on Saturn's moon Europa. Since 1961 (the year of the Green Bank Conference), terrestrial astronomers have discovered multiple planetary systems around stars that have long been known, but, alas, they very vaguely resembled our own, the Solar System. Since their planetary objects have orbits with the shape of highly elongated ellipses, with a very large eccentricity (the degree of deviation from the circle numerical characteristic canonical section). That is, the temperature indicators that occur on these planets during the year have a very large difference and are not suitable for the development of protein life on these planets.
It was also found that the necessary indicators that characterize the ability to retain water on its surface for a body, which is considered a planet, for a huge period of time (which is calculated in billions of years), without its evaporation and (or) freezing are quite large. And so far only our Earth corresponds to them, since no more such planetary objects have been found. This is explained by the fact that the radius of the body, if it does not correspond to certain parameters even by a few hundredths, then life on the planet will not arise or will be destroyed.
In 1981, astronomers rethought the Drake formula applicable to the then scientific research and discoveries. The value of N was calculated, equal in approximate calculations to 0.003. That is, 3 out of a thousand (or one out of three hundred) systems of star clusters should have a civilization that has a fairly developed technogenic base and expresses a desire to communicate. That is, following the calculations, the percentage of detection of such a civilization is 1:300.
Since then, no progress has been made to increase this figure. There is a lot of criticism about this formula, which cannot give an exact result, but its consideration has led to the development and allocation of funds (several million dollars) for the promotion of astronomy and many natural sciences (biology, geology, etc.), and also specifically VC search programs. Although, according to this formula, two variables can be exactly substituted:
- R - then, the number of stars formed per year in the Universe and which can be determined;
- P is the probability that the star has a system of planets.