“Where are the aliens?” That’s the question that Enrico Fermi asked along with some other collaborators. He wondered…, considering how vast the universe is, shouldn’t it be the case that we would already have evidence of the existence of life forms outside Earth?
Enrico Fermi, Italian nuclear scientist, naturalized American, is considered “the architect of the nuclear age”, as he was the first to achieve and maintain a controlled nuclear reaction; or in other words, was the first to fabricate a nuclear reactor. Fermi won the Physics Novel prize in 1938 for his experiments in induced radioactivity, a theory he later put into practice by creating this experimental nuclear reactor under the University of Chicago stadium at the end of 1942.
Fermi is considered one of the last scientists who dominated both the theoretical and the practical or experimental part of his scientific field, physics; having contributions in the development of quantum theory and particle physics.
Fermi paradox origin
This paradox’s origin dates back to the summer of 1950, when Fermi was part of Los Alamos National Laboratory. While he was commenting with his teammates (Konopaske, Teller and York), an article that the New Yorker magazine published regarding the mysterious disappearance of trashcans in New York City; and particularly, a theory that considered that this was related to aliens who were stealing them, Fermi then presented them with the following question … Where all they are? Referring to the aliens.
Question that was followed by a series of calculations that Fermi did to have an estimate of the number of planets similar to Earth, where life and a technological civilization could have developed, with capacity to make contact. Concluding that even with very conservative estimates, humans should have already been contacted multiple times. But then … why wasn’t this the case?
Fermi was not the only one to ask himself this question, Konstantin Tsiolkovsky, Soviet Aerospace Scientist also presented this paradox in an unpublished paper from 1933.
Similarly, in 1961, Dr. Frank Drake formalized this with his equation to estimate the probable quantity of possible extraterrestrial civilizations with communication capabilities; this in order to interest the scientific community in his program aimed at extraterrestrial intelligence searching (SETI).
This equation establishes a series of factors and is as follows:
N= R∗ x fp x ne x fl x fi x fc x L
Where these factors are…
N = The number of civilizations in the galaxy having communication capabilities.
R∗ = The average number of stars that form in the galaxy.
fp = The fraction of stars that have planets.
ne = The average number of planets that can support life (in our criteria, if the planet is in the habitable zone of a star, where there may be liquid water, as in the case of Proxima-b).
fl = The fraction of planets in which life eventually develops.
fi = The fraction of planets where life evolves until it host an intelligent life. (or civilizations)
fc = The fraction of civilizations that develop technology that can reveal their existence in space.
L = The time that these civilizations release detectable signals in space. Very important factor as it is the time interval where this civilization is “detectable”.
Considering these factors, and even with initial pessimistic estimates, and accounting for the latest exo-planets exploration results, (existing planets in distant stars), it is highly likely that what happened here on earth, has occurred at least ten billion times in the whole history of the cosmos.
But, if we limit this only to the events occurring simultaneously to our technological era and within our galaxy, then the number is much smaller, yet still not zero, but about on the order of hundreds of civilizations. But bear in mind that even with simultaneity, the distances of the galaxy complicate a possible contact, taking into account the time in which a signal travels; as these travel at the speed of light.
Why is there no one?
The fact is that, so far, there is no scientific evidence of the existence of alien life. And it is understandable that with sensationalism and voragine of information about extraterrestrial contacts, this sounds unlikely. But being strict, if we consider only evidence that’s scientific, repeatable and documented, then this amount of identified civilizations is zero!
The great filter.
There are many theories as to why such signals haven’t been detected or haven’t had contact with intelligent life. In probabilistic terms it is very difficult to determine how common life is, or to have life types similar to ours; Even when it is possible to artificially create complex organic molecules, getting from those molecules to a living unicellular life is a big stretch; and from such life form to highly complex organisms is even more complex (see ScienceKindle – Life!).
One of the theories of why we do not detect signs of extraterrestrial life is the so-called great filter. Theory stating that life has to advance in predetermined steps. The great filter considers that there is an event in the evolutionary process where the obstacle to continuing with this evolution is simply impossible to overcome, and for this reason, the way of life is doomed for its annihilation. This hypothesis considers two possible scenarios:
The first scenario is that we have already passed the large filter and we are the first technological species (at least in the near space); This great filter can be the transition from single-cell to multi-cellular life (prokariote to eukariote), or evolution to a kind of life that we consider intelligent.
The second scenario is that we haven’t reached this great filter; and our evolutionary history has faced only filters that can be crossed. Global scale events such as the Chicxulub impact; a truly devastating event, but that didn’t ended the life on earth (as a matter of fact allowed our evolutionary ancestors, mammals, to have a better evolutionary development).
Perhaps the great filter is related to problems that arise in species with technological capabilities that allow somehow to fully control the host planet’s resources, technology which in certain situations get out of control; cases like the mismanagement of nuclear energy (nuclear conflict), or annihilation due to errors in genetic manipulation or artificial intelligence; or irreversible damage to ecosystems that have a runaway effect that alters the planet in such a way that inexorably leads this species to its extinction (climate change, anyone?).
It may also be that the great filter is something that we still do not know and therefore we have not faced yet, something that is obvious to discover at certain point for technological species and therefore all species discover it; but in the same time, also leads that civilization to an inexorable extinction.
Perhaps this great filter does not arise with civilizations like ours, but with much more advanced civilizations. To distinguish this advance there’s also a scale.
The Kardashev scale
The Astronomer Nikolai Kardashev defined a method to distinguish a civilization’s technological advancement on a three-level scale, based on the ability to harness energy. The Kardashev scale.
- Civilization type I – Planetary: Use or store the energy of their own planet.
- Type II Civilization – Stellar: Use and control the energy of your solar system (speculated in the case of Tabby’s Star, KIC 8462852).
- Civilization type III – Galactic: You can use and control your own galaxy’s energy.
So then, it is possible that we may be at the verge of the type I of this scale; and the problems we face, although they are major and can seriously affect life, are not such that they represent an extermination condition.
So are we alone?
It may be that the large filter is in type II or Type III civilizations and therefore we have not yet identified other civilizations. But there may be multiple explanations for this condition, some may be:
- Advanced civilizations simply do not want to be identified.
- Our means are still so primitive that they don’t allow us to identify such civilizations. Trying to contact them would be like us trying to establish communication with an insect.
- There is only one super-civilization that’s expecting us to reach certain level to a) contact us, b) take ownership of us or c) exterminate us.
- We are the alien species; which has been established on this planet to develop our own means. Maybe we are like a “showcase anthill,” where a more advanced species entertains itself by watching us.
- Advanced civilizations are hard to detect as they don’t stay in planets, given that they need to be close to a more abundant source of energy, maybe closer to neutron stars or black holes?
A more radical possibility?
- We are part of a simulation, and the restrictions imposed in this simulation only allow us to have only one place where what we call life is developed.
- We have already been contacted, but governments are hiding this. Very unlikely, because something that governments have are difficult to keep such things secret.
Fermi’s paradox is certainly a scientific exercise that allows the imagination to go wild, and yet the question still persists; having so many planets where life can proliferate, it is highly unlikely that we will be the only ones, and therefore, the exception regarding advanced civilizations.
As the great Carl Sagan said in his novel Contact said, “The universe is a pretty big place. If it’s just us, seems like an awful waste of space”.