The Fermi Paradox. Where are the aliens?

The human mind is inquisitive and it wants to answer every single question that troubles it. It is not recent that humans have started contemplating the sky. We have been using the position of stars to navigate ships and vehicles. It is more recent that we started depending on GPS for navigation. When we look at the sky after the sun is set, we see a huge number of stars and few galaxies (Andromeda or The Magellanic Clouds). Whatever you may think, but the stars visible to our naked eyes are just a small bunch located locally, near to our solar system. In fact, the stars you see at night are not even 99 % of our galaxy.  Our Milky Way is about 150,000 light-years big on an average and the brightest star Sirius A is just eight light-years away, which lead us to think about the vastness of our galaxy. To put more pressure on our thought process, there are more than 100 billion galaxies in the visible universe and still, we are nowhere near to get a complete picture of the entire universe. 

The Milky Way Galaxy

Let us leave other galaxies aside and focus on our own galaxy - The Milky Way. With the Milky Way harbouring about 200 thousand millions of stars and each star system having several planets, it is highly likely that life may have flourished somewhere else in the universe, apart from the Earth. If not billions, there will be millions of planets having an Earth-like environment, which can sustain life or at least generate it. Let us assume that the probability of finding Earth-like planet is very less, say 0.0001%; even at then we are left with at least a million Earth-like planet. 

Our solar system and the Earth are about 4-5 billion years old, which in the scale of the universe (13.4 billion years old) is quite less. Which means that there are several star systems, which are older than our solar system, and they all got more time for life to evolve and flourish. 

             Timeline comparison between Humans and a hypothetical civilization 

Now, if life were evolved in one of the star system, which formed billions of years before the solar system, then there is a chance that it comprises life more advanced than we are. Let us take our own example. For nearly three thousand years of history, the earth was thought to be the centre of the universe and, it was only in the fifteenth century, a mathematician named Nicolaus Copernicus postulated that the Sun rather than the Earth is the centre of the universe. Even though the Sun is not the centre of the universe, it was a huge step in understanding the structure of the universe. Slowly after the industrial revolution, it took only two hundred years to reach the moon, colonize space (International Space Station) and now we are even planning to colonize Mars (SpaceX). With this pace, if a civilization evolved on a planet millions of years older than earth, some of these civilizations should have developed means of interstellar transport and in another million years, they should have colonized the entire Milky Way.

                                  SETI: Search for Extraterrestrial Intelligence

According to this argument, either we should have found extra-terrestrial life or they should have visited us. Yet, we see no clue for such civilization. Search for Extra-terrestrial Intelligence (SETI) is collaborative project involved in discovering the presence of intelligent life form on other planets. They constantly gather and interpret electromagnetic signals received from outer space. As of now, we are unable to perceive any intelligent signals receiving from the space. Most of the data we collect is either weak or noise. So, where are the aliens? Are we unaccompanied? Where did we come from? Where are we heading?

This apparent contradiction between the dearth of evidence for extra-terrestrial life and high probability of such civilization evolving is The Fermi paradox argued by physicist Enrico Fermi.

To categorize the possible types of civilization that may evolve, there is something called as Kardashev Index, introduced by a Russian astronomer Nikolai Kardashev. It is a measure of a particulars civilization’s level of advancement based on the source of energy it is utilizing.

Type I civilization:

It is able to utilize all the energy resources available on the planet. Currently, we are at 0.7 on Kardashev scale. It will take another 20-50 years for us to become a full type I civilization.

Type II civilization:

This type of civilization is implicated to harness the total energy of its star using its technological advances. It brings about the idea of Dyson sphere, which can encompass the whole start and transmit the energy to the planet.

Type III civilization:

They are able to capture and use the energy of the whole galaxy. This is the most advanced civilization and if present, it will be extremely rare.

At present, the possibility of finding higher civilization is rare and it can be explained by the Great Filter hypothesis. It can be thought of as a checkpoint in the timeline of evolution. Most other species will extinct at this checkpoint while the worthy ones will pass. This is the similar case, which happened with many species on earth. We do not see any dinosaurs, trilobites, sabretooth roaming around. Had they been around, there would not have been the slightest possibility for humans to evolve and head toward type I civilization.

There are three possibilities for the occurrence of the Great Filter:

          Enjoy! We have left it behind us long back.

There is a chance that the great filter happened long back and we are the lucky civilization, which survived. The transition from single to multicellular organism, the evolution of mammals, and increase in human cranial capacity etc. can all be an example of the great filter. However, if we have crossed all of them, we will be the first one to pass this filter on the Earth.

               Beware! We are getting filtered at this moment.

There are more than 7 billion humans on earth and the number is expected to increase further. We are crossing the limit our earth can tolerate. All our natural recourses are depleting and climate change is on the path to destruction. With the doomsday clock showing 2 minutes to midnight, we are near to our end. If it is the Great Filter then this is where our journey ends and we are not the ones who are destined to head towards type II or III civilization.

We are doomed! The Great Filter is somewhere in future.

All our efforts and advancement will go down the drain if the Great Filter is somewhere in future. Let us hope we cross it safely.

Even though the chances of crossing the Great Barrier for a civilization are slim, if we consider the vastness of our Milky Way, there is still one in a million chance that somewhere in our galaxy there is a Type III civilization. The beauty of type III civilization is that, to harness the energy of the whole galaxy, it will spread across it colonizing the entire galaxy. For us, it just took 70 years of space exploration to planning a colony on Mars and we are not even a type I civilization. At this pace, the entire galaxy can be colonized in 2-3 million years. 

“Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.” 
― Arthur C. Clarke

So if there is a higher civilization out there, why have we not seen them? Where are they?

There are several possible explanations.

                 1. They visited us in past

It is possible that they arrived millions of years back, found dinosaurs and thinking them unworthy, they never came back. Is it possible that the concept of God started when they visited us in the past? Let us hope so because if it is true then the concept of religion was wrong and there would not have been apartheid and false interpretation of religious scriptures.  

                 2. The rare earth hypothesis

Evolution of life was very rare phenomenon involving millions of components falling in place at the right moment and at the right time.

                  3. Intelligent species are reluctant to develop advanced technologies

Probably they have understood the dangers of too much advancement and decided to dismantle whatever technologies they have developed.

                  4. The Zoo hypothesis

Intelligent life is present in our galaxy, aliens are observing us, and allowing us to evolve on our own.

                  5. We are left alone deliberately

Maybe they know our presence and left us alone because we are like a village area in the vast galaxy of ours. There is nothing, which they can harness from our solar system.

                  6. We are not able to communicate with them

Our technology is not advanced enough to capture their signals. They may be sending signals in different codes than what we use and so we are not able to interpret them.

                  7. They are secretive about themselves

Maybe they are too shy to communicate. They may be listening to us but they are not transmitting anything.

                  8. The Simulation theory

As suggested by Elon Musk, we may be living in a simulation created and managed by type III civilization.

These are some of the possible explanations, given by theorist around the world. It may be possible one of these are true or someday we will be able to contact them.

It is for us to decide if it is a wise idea to contact alien species. It is a common tendency of all the species on earth to survive and replicate. In order to replicate, it will either destroy other species or it can help it survive (symbiosis). If ever aliens visit us, they can destroy us like we generally see in most of the Hollywood movies, or we will capture them for our own use just like that in the movie Avatar. Whatever the result will be, let us hope it will for the best of both of us.

“I'm sure the universe is full of intelligent life. It's just been too intelligent to come here.” ― Arthur C. Clarke

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