Let's keep this in mind: our galaxy, the Milky Way, is immense. Like all galaxies. It is estimated to contain about 300 million stars. Or what is the same, there are several hundred million sun-like stars in it, around which, on many occasions, a good number of planets also rotate - as is the case in the Solar System. Let's think about the entire cosmos now. As NASA published in 2016, it is estimated that there are at least two billion galaxies in the observable universe. That is, two million million places like the Milky Way. With its hundreds of millions of planets each. It is very difficult to think that we are alone. Most likely, apparently, there is intelligent life out there, in some corner of vastness.
In fact, other forms of intelligent life in the universe are as likely to exist as they do not exist at all . I explain myself: if it is so evident that, by pure probability, in that enormous ocean of planets there must be many other advanced civilizations, how is it that we have no evidence of the existence of any? How is it that nobody has contacted us, even through radio signals like the ones we send? Most likely, apparently, there is no intelligent life out there. As likely as it does exist, in view of the circumstances. And this is what is known as Fermi Paradox.
Enrico Fermi came up with this idea in 1950, chatting with his colleagues physicists Edward Teller, Herbert York and Emil Konopinski, but it wasn't until 1975 when astrophysicist Michael H. Hart developed it, also proposing a possible solution to the problem. Based on the Drake Equation , which estimates the amount of technological civilizations that could be in our galaxy, and the speed at which their ships could move through space, he deduced that an advanced extraterrestrial civilization would take about two million years to cross the galaxy And this period being so short - in cosmic time - if we have no evidence of the existence of these civilizations today, it is simply because they do not exist. A conclusion supported by US Senator William Proxmire to demand that NASA's funding be withdrawn from projects such as SETI, which sought to find signs of extraterrestrial intelligence.
On August 20, however, a study prepared by astrophysicist Jonathan Carroll-Nellenback and published by The Astronomical Journal proposed a different solution to the Fermi Paradox : having hundreds of millions of planets in the Milky Way, many of them more ancient than Earth, the existence of advanced extraterrestrial civilizations remains the most likely option; and if we have no record of them, it is because the exploration of the galaxy and the visit to Earth could have occurred hundreds of millions of years ago, when the human being did not even have the appearance of appearing on the face of the planet.
Carroll-Nellenback raises the possibility that these hypothetical technological civilizations, in their expedition and colonization work, travel through space taking advantage of the stellar movement. The planetary systems and their stars orbit around the center of the galaxy. The Solar System, for example, moves at 828,000 kilometers per hour in an orbit that completes a turn every 230 million years. What Carroll-Nellenback proposes is that perhaps an advanced extraterrestrial civilization does not move between planetary systems until his orbital trajectory brings him close enough to that of another in which there could also be intelligent life. The bottom line is that aliens may have already been here, but many millions of years ago . Or it could take many millions of years to come.
The theories that try to propose solutions to the Fermi Paradox are many. The Special Earth Hypothesis proposes that the circumstances of our planet are unique and, therefore, the conditions for harboring intelligent life are unrepeatable. There are those who suggest that, like us, other civilizations may not even know how to cross space. Others claim that they are us - Christopher Nolan based on this idea his film Interstellar -. Fermi argued that every civilization develops its technology with the potential to exterminate, as we humans do. But there have also been less categorical scientists, such as Carl Sagan , who boldly labeled Michael H. Hart's thesis - based on the speed of movement of ships -, since the processes of expansion and colonization are always much slower, as it demonstrates the colonization that men made centuries ago on Earth when they discovered the new world: it was not colonized at the speed at which the horses moved.
Actually, and taking as a reference how unpredictable human behavior is, the effort to conjecture why entire civilizations - if they exist - behave as they behave has something of an idealist, an illusion or a madman. Although, on the other hand, taking a look at what is happening on Earth, observing how humans treat each other and our own planet, it seems quite logical that any alien who is contemplating us does not feel like visiting us. Honestly, I would run to the opposite side.
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