The Fermi Paradox seeks to answer the question of where the aliens are. Italian physicist Enrico Fermi, known as the creator of first nuclear reaction, asked one day in 1950: Where are all the aliens? With this question, he postulated Fermi Paradox. It deals with the contradiction between high probability estimates for the existence of extraterrestrial civilizations and the lack of evidence. Almost 70 years we struggling with this paradox. Are we closer to the answer today?

Probability Vs Reality

We live in unimaginably vast Universe. The observable Universe is approximately 92 billion light years in diameter and it growing faster and faster. The universe contains at least one hundred billion galaxies. Each galaxy has at least one hundred to one thousand billion stars. The number of planets? Probably trillions. If we focus just on our Milki Way galaxy, there is 100–400 billion stars. A six-year search that surveyed millions of stars using the microlensing technique concluded that the average number of planets per star is greater than one. So, we are dealing with at least 100 billion planets in our own galaxy.

An artistic impression of Extrasolar Planetary Systems. Image Credit: NASA, ESA, and M. Kornmesser (ESO)

So, when we put on the table all these numbers, the question naturally arise: Are we alone? Same question asked himself an American astrophysicist, Frank Drake. In 1961 he wrote the equation, known as Drake equation. It represents probabilistically argument used to estimate the number of extraterrestrial civilizations in Milky Way galaxy. Regardless what value is set to the components of the equation, the result is always more or less same. Our galaxy is a full of life. Drake estimates there exist 10,000 communicative civilizations. But where are they? Why we can’t see them? Or at least to hear them? That is Fermi Paradox!

Possible Solutions

There are plenty ideas and solutions for Fermi’s Paradox. Some of them are pretty sci-fi, but some have solid ground. Let’s take a look at them.

  • Space is too vast – Space is, simply put, incredibly large. If we take into consideration and the fact that the Universe is in the fast expansion, there is no way for us to reach vast distance. Take an example of our closest star. If we beamed a transmission to the closest star, it would take 4 years just to reach the system. Even if the eventual response would send back to us, it might take decades. Basically, everything outside of our Local galactic group is unreachable.
  • We’re too primitive – In this scenario, alien civilizations are aware of our existence, but they don’t want to interfere with us. They just watch our development from afar to let us evolve. Also, they might use the technology that is unknown and undetectable for us. Maybe, one they when we reach high technology maturity, they will contact us.
  • The great filter – represent a presumption that there is some kind of absurdly difficult step in the evolution of life. The obstacle that precludes it from becoming interstellar. According to this idea, all high intelligent life after passing the filter is self-destructive. Probably we are still below that filter and the civilizations that passed it are already destroyed.
  • They are already here – this sci-fi idea suggests that aliens perhaps are already here, just we are unable to see them. Either they are too different so we can’t register them or they are too similar so we can’t distinguish them from us.
  • We are alone – Perhaps the simplest solution is the correct one. We haven’t encountered signs of life either because it doesn’t exist or it is extremely rare. On the other hand, we still don’t fully know how life began on this planet in the first place. Maybe when we figure out all the keys for complex life, we could better to search for extraterrestrial one.