Fermi ‘s paradox concerns a question made by the Italian physicist Enrico Fermi (1901-1954) while debating at the table with colleagues, in the year 1950. The paradox deals with the discrepancy between the great probability of life on other planets (due to of the enormous number of planets in the Universe) and the fact that we have never been able to detect any sign of life outside Earth .
Understand what the Fermi paradox is
Fermi’s paradox arose when Enrico Fermi and other scientists were debating at the table the possibility of life beyond Earth, so Fermi asked: where is everyone? If we take into account that, in our galaxy alone, there are billions of other suns and that, in the Universe, there are billions of galaxies , the possibility that there is life on other planets is statistically high.
Fermi, still, went a little beyond the reasoning that involved the large number of stars in the Universe. He also suggested that if some alien civilization were able to travel with their spacecraft at 1% the speed of light , our galaxy, which is about 100,000 light-years across, could already have been colonized at least a thousand times. So why do we never hear of alien civilizations?
Over the years after the Fermi paradox, many scientists debated the possibility of life beyond Earth. Among them, the physicist Frank Drake stood out . Drake created an equation whose purpose was to estimate the number of alien civilizations existing in our galaxy. To do so, he used a series of conditions and astronomical data, however, it is known that the equation had problems, such as arbitrariness in some of its factors as well as the assumption of information that we do not know.
Possible solutions to the Fermi paradox
There are several attempts to solve the Fermi paradox, that is, answers as to why we were never able to communicate with any alien civilization or even identify signs of life on other planets. Let’s check one of them:
the great filter
Some scientists use the theory of the great filter to try to explain why we have never made contact with other living beings outside Earth. This theory makes mention of all the obstacles that make abiogenesis unlikely or even impossible.
Abiogenesis is the line of thought that indicates that life arose from non-living matter, in the form of simple organic compounds . However, for life, in its simplest stage, to reach the level necessary to establish contact with other civilizations, a series of highly unlikely things must occur, such as:
- Abiogenesis must occur in the right planetary system, that is, on potentially habitable planets.
- Specific molecules must emerge, as is the case with RNA .
- Single-celled lives must arise.
- More complex single-celled lives must emerge.
- Sexual reproduction needs to happen.
- Intelligent animals must emerge and be able to use tools.
- A civilization must advance to the point of exploring space.
- The colonization of space needs to happen in order to establish contact with other forms of life.
As you can see, according to the theory of the great filter, Fermi’s paradox is explained by the fact that the chances of a life form appearing in the Universe are extremely low , so we were not able to establish contact. However, critics of this idea point out that life could evolve in different ways than we are familiar with.
Some hypotheses that seek to explain Fermi’s paradox take into account the fact that, although the chances of life occurring in the Universe are high, most habitable planets, which have characteristics similar to those of Earth, have not yet been formed , or that is, when new civilizations arise, we may not even exist.
Other hypotheses suggest that there is not even a paradox: only we exist. In addition to them, there are those who claim that other civilizations may have visited us, but millions of years ago. Considering that our period as an intelligent civilization is extremely short and that space travel is extremely long, we may be visited again in tens of millions of years, so that our existence will not even be noticed.