The Search for our Cosmic Siblings (beyond the interplanetary ocean)

Almost 13.8 billion years after creation, on a remote corner of an average galaxy, a planet orbiting an average star presumably sew the first seeds of life. From a unicellular blob to semi-intelligent beings, life came a long way. But as the semi-intelligent beings called humans embraced the vastness, they started searching for their cosmic siblings. Extraterrestrials or more popularly ‘aliens’ became a popular topic among scientists, science fiction writers and general public. Even there is an entire department named SETI (Search for Extraterrestrial Intelligence) that monitors radio signals from space to find signs of extraterrestrial existence. But inspite of all the scientific excellence we have achieved, the presence of extraterrestrials still remains a question. However, “the absence of evidence is not the evidence of absence”.

Let us first try to understand really how staggeringly vast our universe is. The Hubble Ultra Deep Field image that was taken in 2014 can be used as an example. The Hubble Ultra Deep Field image is the image of a small region of sky , about the size of the opening of a soda straw in the southern constellation of Fornax. That small region of the sky contains as many as 10,000 galaxies! Now imagine the entire sky. So after embracing the vastness , one can definitely say that there has to be life elsewhere in the universe. Our own galaxy has about 300 million habitable planets. The term habitability however is not anthropocentric here.

A planet having the right conditions for a particular species can be termed as habitable. The same conditions might not be favourable for humans. All the habitable planets are however quarantined from eachother by an interstellar ocean of light years. This is the main reason behind why we have not yet heard anything from the aliens. The conflict between the lack of evidence of alien existence and high estimates of their existence is termed as the Fermi paradox. It was built on a casual chat between Enrico Fermi , a renowned physicist and his colleagues. They pondered about the existence of intelligent beings elsewhere in the universe and the reason behind the lack of contact.

Technology has equipped us with tools advanced enough to look for planets beyond our solar system and scientists have discovered a few potentially life-supporting planets in our galaxy like Kepler 442b which is considered habitable by all means. However , whether those planets still harbor life remains a question and finding an answer to this is increasingly difficult. Even if we are lucky enough to receive a radio transmission from an extraterrestrial , the hiatus between them sending a signal and us receiving it might have actually been long enough for an entire civilization of them to die out.

The universe might just be teeming with life and yet the chances of finding them might be close to impossible. Their existence might also be threatened by Great Filters , which as the name suggests is a cosmic interpretation of “survival of the fittest”. They can come as droughts , famines , pandemic , war , natural disasters from planetary scale , like geological disasters to astronomical scale , like asteroid impact , supernovae or gamma ray bursts rendering an entire planetary system sterile. Yet another outcome suggests that the technological gap might also be a reason behind the lack of communication as to them , the messages sent by us might just be too primitive to be detectable. Some scientists suggest that since the earth is a late comer in the cosmic drama , million other civilization might have lived before we even came into existence. About 1 to 2 billion years after big bang , when the universe became stable , a generation of habitable planets might have harboured the primitive lives in the cosmos and some of them might have attained the required technology to venture out into the interstellar void. However , the existence of such beings still remains an enigma. An alien civilization like that could be of a stellar type (Type 2) who can directly harness the energy of their star by building Dyson spheres (hypothetical mega structures) around it and colonize their entire planetary system or go beyond to become a galactic civilization (Type 3). This hypothetical classification of civilization based on their energy usage is called the Kardashev scale and we humans are at the grass root level of the Kardashev scale just about 30% away from becoming a type 1 civilization.

Habitability can also be of different forms. Not all organisms would require the ingredients that are vital for us. However , a planet orbiting its star’s goldilocks zone or circumstellar habitable zone (the zone around a star where liquid water can exist) might be able to sustain life and hence , astronomers always look for planet’s orbiting this particular zone around its host star. The complete radio-silence from extraterrestrials could be due to a plethora of reasons and thus we might never make contact with them. Due to the vastness of space and the non-uniformity of time , the Search for Extraterrestrial Intelligence will continue for a longer time. Also the lack of contact doesn’t indicate that we are alone as our galaxy is one in a trillion upon trillion with billions of habitable planets where a being might be looking up and wondering about the whereabouts of its cosmic siblings. As Sir Carl Sagan once said, “The universe is a pretty big place, so if it’s just us then it seems like an awful waste of space”.