Famed science fiction writer Arthur Clarke once said: “There are two possibilities: either we are alone in the universe, or we are not. Both are equally awful. Humanity is fascinated by the idea that life can exist outside the Earth. For more than fifty years, the specialists of the search for extraterrestrial intelligence SETI have been scanning the galaxy to no avail. It would seem that the answer is obvious, but the succession and prospects of exoplanet discoveries over and over again give us hope that someday the search will be crowned with success.
Do aliens exist and where are they?
Ever since one of the "fathers" of the atomic bomb and Nobel Prize winner in physics Enrico Fermi formulated the famous question "Where is everyone?" decades have passed. There is still no answer, but there is a paradox named after the scientist.
The paradox can be formulated as follows: the universe is more than 14 billion years old, which means that other creatures have had plenty of time to contact us. So where is everyone?
Of course, a series of the greatest space achievements lies ahead - imagine what awaits us after the first interplanetary flights and the launch of interstellar probes to Alpha Centauri. After all, the first manned flight into space took place only 58 years ago - childhood time on the scale of the universe.
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Drake's equation
However, in order to confidently state that we are alone in the universe, we need proof. And they are, to put it mildly, not enough. Not to say that it does not exist at all. In addition, not everyone is satisfied with the talk that the laws of physics do not allow spaceships to reach speeds above a certain one.
Drake's equation.
In 1961, scientist Francis Drake wrote an equation to evaluate the technologically advanced and message-carrying civilizations in the Milky Way galaxy. Drake's idea turned out to be brilliant due to the fact that he wrote down many parameters that can be estimated and then multiplied.
According to the equation, the number of civilizations (N) in our galaxy with which we could establish contact can be determined by the following formula:
N = R * x fp x ne x fl x fi x fc x L, where:
- R * is the average rate of star formation in our galaxy
- fp is the fraction of stars that have planets
- ne is the number of planets on which life is possible
- fl is the number of planets on which life can develop
- fi is the number of planets on which intelligent life can develop
- fc - the number of civilizations that will develop data transmission technologies
- L is the length of time during which these civilizations must transmit their signals into space
Many astrophysicists have tried for a long time to calculate each value, but today there is no final solution. In addition, Drake's equation only refers to technologically advanced civilizations. But while all the parameters in the equation cannot be specified with absolute precision, the more we learn, the more accurate the equation will become. As they say, enthusiasts, do not lose heart!
Kardashev scale
When discussing the solution to the Fermi paradox, it is impossible not to mention the Soviet astrophysicist Nikolai Kardashev. He proposed a classification of civilizations according to the amount of useful energy that they can use. The scale divides civilizations as follows:
- Type 1. A civilization capable of harnessing all the energy available on its planet
- Type 2. A civilization capable of harnessing all the energy emitted by its star
- Type 3. A civilization capable of harnessing the energy of the entire galaxy
Representatives of a civilization of the second or third type should be able to move around the Galaxy at a speed close to the speed of light. They are unlikely to succeed faster, since for this they will have to violate the existing laws of physics.
According to modern calculations, within a few thousand years we will be able to become a civilization of the second type, but before the third we will still grow and grow - this process can take humanity from 100 thousand to a million years. Astronomer and popularizer of science Carl Sagan believed that we are somewhere on the 70% path to the civilization of the first type, but we can only reach this level in a couple of centuries.
Possible solutions to the Fermi paradox
There are no aliens and never existed. This is exactly what one of the possible solutions to the Fermi paradox sounds like. Last year, physicist Alexander Berezin published a paper in which he proposed the darkest scenario. According to Berezin, the first technologically advanced civilization that mastered interstellar travel will destroy all the rest. Having absorbed all possible resources for the sake of its own existence, it will begin to drain the worlds in which there is already life, thereby destroying other civilizations on its way. The scientist is convinced that humanity is the only intelligent civilization in the Universe that has gone so far in its development.
There is life. But she is unreasonable. The discovery of water on Mars last year promises previously unseen discoveries, such as the identification of the simplest alien microorganisms, such as algae or microbes. Most likely, in 10-20 years, humanity will know for sure that life outside the Earth exists. Today, many scientists suggest that a variety of life forms can inhabit icy worlds, such as Saturn's moon Enceladus and other recently discovered exoplanets. It remains only to look for answers to eternal questions - what makes unreasonable forms of life intelligent?
Zoo hypothesis
In 1973, American astronomer John Ball suggested that other civilizations are well aware of our existence, and numerous attempts to contact us were unsuccessful. Imagine that you meet a chimpanzee in the forest. Will you talk to him and, if so, will your conversation take place? The answer is obvious, and according to Ball, we are simply not worried, preferring to watch like animals in a zoo. It sounds pretty offensive, especially since no one can refute this hypothesis.
To date, the question "are we alone in the universe" has no answer. Nevertheless, biology on Earth has a lot to say about the likelihood of life and the conditions that lead to the development of intelligence. After all, the absence of observable intelligence does not mean that advanced civilizations exist for a short time or do not exist at all.
Lyubov Sokovikova