Fermi's paradox: if there are aliens, why haven't they visited us?

When the human being looks up to the sky, he cannot help but be amazed. The universe is everything: a place where we live, nothingness, immensity, the incomprehensible and life.

The Milky Way, the galaxy where the solar system (and in turn the Earth) is located, has a mass from 10 to 12 suns, with billions of stars similar to the Sun itself that gives us the lifetime. If this seems inconceivable to you, imagine if we consider that the existence of two trillion galaxies in the entire universe is estimated.

However anthropocentric human thinking may be, (almost) we all agree that the probability that we are the only living and thinking form in the universe is very low, since this term encompasses the totality of all forms of matter, energy, space-time (what you see and conceive and what you don't). Faced with such a vast and unfathomable whole, statistically there must be some other living entity, right?

We no longer even speak of aliens with human forms, but an acellular microscopic entity, a concept, an ethereal "something" that can come to be classified as an open but self-regulating system (such as the cell is), although we are not capable of understand it. Based on these philosophical and biological premises, we expose you everything you need to know about

Fermi's paradox, since not all thinkers think the same regarding the existence of intelligent life beyond Earth.

• Related article: "Panspermia: What is it, and to what extent has it been proven?"

What is the Fermi paradox?

The premise of this paradox is very simple: If intelligent life existed beyond our planet, we would have already seen signs of it throughout our evolutionary history.

Based solely on scale and probability, there is no doubt that intelligent species or entities should exist outside of the Earth, but the fact that the interaction with external biological entities has been null indicates contrary. Any sign: a fragment of a building, parts of a space vehicle, a communicative signal, footprints, organic matter or biological evidence they would have been enough to throw the Fermi paradox to the ground.

Interestingly, as well-versed studies indicate, the Fermi paradox was neither coined by the physicist Enrico Fermi (creator of the first nuclear reactor) nor is it a paradox in itself. Fermi came to pose questions such as "Where is everyone?", But the first idea of ​​this thought came from the hand of Michael Hart, who posited that interstellar travel and planet colonization would have been inevitable at this point if intelligent life forms truly existed. In other words: "They are not here, and therefore, they do not exist."

This is a very clear apparent contradiction. Here is a series of data that puts thinking in perspective:

• There are billions of stars similar to the Sun in the Milky Way. In theory, by statistics and scale, there should be life in some of them.
• Many of these stars (and therefore their planets) are much older than the Sun. If we conceive of Earth as a typical planet, many others should have developed intelligent life long ago.
• Due to the age of many of these bodies, the intelligent life that inhabits them would have had more than enough time to develop interstellar travel.
• Despite the slow pace of studying Earth's interstellar travel, it is estimated that the entire Milky Way could be traversed in a few million years.
• Because many stars are billions of years old, by statistics, Earth should have already been visited.
• Despite these claims, our planet has not had any contact with extraterrestrial life. There is also no evidence of colonization on other observed planets.

Things get even more interesting if we know that, Although 99% of intelligent civilizations had self-annihilated, the absence of interaction with humans or the rest of the planets remains unexplained. The idea, again, is clear: they are not here, and therefore they do not exist.

• You may be interested in: "The 7 types of stars (and their characteristics)"

Drake's equation

The Drake equation, postulated by the American astronomer after whom it is named, tries to estimate the number of civilizations present in our galaxy through mathematical processes. The equation is as follows:

Simply put, this operation takes into account the rate of star formation, the number of stars that have planets orbiting their around, the fraction of planets that could have evolved life, the fraction of planets that might have evolved intelligent life, the percentage of these “communities” capable of emitting detectable signals in space and the time interval during which they could have been emitted these signs.

With all these parameters in mind, Drake postulates that there should be 10 detectable civilizations in the Milky Way, that we remember that it has a calculated mass of 10 raised to 12 suns. However, other professionals are not so “generous”, since other estimates using the same formula calculate 0.000000067 or less, depending on the parameters used.

Against the Drake equation, it can be argued that this formula does not take into account that fraction of planets with chemical elements conducive to life, such as water or carbon, as well as the presence of a stable and durable ecosphere in the weather. While it is true that all these parameters only apply to life present on our planet, we have no others, as this is the only concept of existence that we can imagine.

• You may be interested in: "Endosymbiotic theory: the origin of cell types"

Scientific explanations to the Fermi paradox

The Fermi paradox is based on the Drake equation to defend the non-existence of intelligent life in the universe. If mathematically there are a total of 10 civilizations emitting signals through the Milky Way, it is clear that we should have detected them. All this is further founded if we bear in mind that the Earth is a typical planet (principle of mediocrity). If life has arisen in a place where the initial characteristics were not far from the average, then it may have arisen in thousands more.

The biggest conceptual hole in all these postulations is that the Drake equation uses point estimates (Point estimates), or what is the same, the use of collected data to give rise to the most reliable conjecture around a value full. These estimates assume that we have absolute knowledge of parameters impossible to understand on a large scale, such as the probability of life appearing or the potential number of intelligent societies.

Let's be honest: even in the scientific community itself it is difficult to estimate what intelligence is as suchImagine the puzzle it must be to apply this ethereal concept to a living entity that may not even be governed by the same parameters as us. When we take into account the realistic uncertainty, replacing the point estimates by probability distributions that reflect current scientific knowledge, the observed picture is much more different.

The brilliant scientific publication Dissolving the Fermi Paradox (published in 2018 on the portal Researchgate) does the same, and presents us with data that directly collides with the paradox of Fermi. Taking into account the real scientific knowledge, it can be calculated that the probability that we are alone in the Milky Way ranges between 53 and 99.6%. We go further, because the probabilities that we are alone in the entire universe are placed at 39-85%.

Resume

While the Fermi paradox and the Drake equation are of great scientific and philosophical interest, we cannot do more than acknowledge that parameters that give rise to life, the concept of intelligence or even the registry of universal communication methods escape our hands. Perhaps intelligent life has been trying to communicate with us for centuries, but their methods may be imperceptible to human cognition or the machinery developed by our species.

It may also be that our planet is not as typical as we think, or that the conditions necessary for appearance of life are so extremely rare that they have not really been replicated in other planets At this point, we only have to look at the sky and, as we have always done, continue advancing in search of knowledge and hope that one day answers will arrive.