Anyone who has ever been interested in astronomy will have reached the inevitable question: are humans alone in the Universe? There is no straightforward answer to that question. The Universe surrounding us appears to be completely void of any life. Simply observing the way things are, it might just be the case that we are the only highly intelligent form of life in existence. The Fermi paradox looks to answer this issue.
But things are not that simple. Various mathematicians and physicists have reached the conclusion that it’s impossible for us to be alone. The sheer high number of possibly habitable planets points to the conclusion that extra-terrestrial life exists. Our own planetary system is quite young in comparison to other planetary systems in the Universe. It makes sense that there could be another life form out there, way more advanced than us. But, yet again, there is no palpable evidence that is the case. Even with the possibility of interstellar travel, nothing seems to be happening or to have happened.
What is the Fermi paradox?
The Fermi paradox is the contradiction between the lack of evidence for any extra-terrestrial civilisation and the estimated high probability of the existence of various life forms. Enrico Fermi is the Italian-American physicist that famously raised this issue. Although unknown if completely true, Fermi had a casual conversation in 1950 with fellow physicists Edward Teller, Herbert York and Emil Konopinski. The conversation was about UFO sightings and faster-than-light travel. This led Fermi to wonder: “But where is everybody?”.
There are some hypothetical explanations for the paradox. While the paradox itself may convince many that there are truly no other intelligent life forms in the Universe, the issue might just be more complex. Here are some of the various available explanations:
Rare Earth hypothesis
This hypothesis argues that the conditions needed for complex life forms to emerge are incredibly difficult to come across in the Universe. As such, Earth is an isolated, rare example of a planet being able to host life for long enough that it evolves into highly intelligent creatures. Even if life were to emerge quite often on planets, random extinction events may wipe it all out. The extinction of non-avian dinosaurs on our planet is a very good example of that. What if life on Earth never recovered from such an event?
The nature of intelligent life is flawed
This is going into philosophical territory. Intelligent life may be inherently flawed and destined to auto-destruct. Competition for resources (which usually leads to war) is one powerful motivator for the emergence of new technology. Another one is the need for a better, easier life, as explained by astrophysicist Sebastian von Hoerner. The first motivator would lead a species to auto-destruction, while the second one would make it complacent and stop it from evolving further.
One could also argue that maybe intelligent life forms exist, but they actively avoid intelligent species that are still quite young. Very aggressive behaviour may characterise intelligent species in their early development. That would explain the apparent silence of the Universe.
Alien life may isolate itself from the outer world
What if alien life simply has reached a level of technology that allows it to continue living comfortably in isolation from the outer world? Why would they seek others if they are already content? They might be plugged in to virtual realities that are times better than the actual Universe. Their activities may be reserved to certain parts of their galaxy. Or perhaps their society is so different from ours that they might not even think about the existence of other intelligent beings. They might not think it’s relevant.
The great filter
The idea was first detailed by economist Robin Hanson in an online essay titled “The Great Filter – Are We Almost Past It?”. Simply put, it argues that one of the steps in the evolutionary process of intelligent life as we know it might be the filter that keeps life from evolving further and becoming intelligent. It might be something that we’ve already gone past (like simple single-cell life or sexual reproduction). It might also be something in the future that might bring us to extinction (trying to expand through the Universe – the tremendous amount of energy required might be impossible to sustain long-term).
As such, we have gone over the nature of the Fermi paradox and some of the possible explanations for it. The initial question comes up once more: are humans alone in the Universe? I’m sure everyone has different thoughts about it. But one thing is for sure: it’s a very fascinating thought exercise that intrigues many curious people. While it would be comforting to know we are not alone, it’s unlikely we’ll know the answer within our lifetimes.