We always gazed up into the sky since the birth of civilization. We admired the stars, planets, and galaxies above us. We always wonder if other intelligent lifeforms exist other than us humans. Outer space is a vast expanse from which we still have a lot to learn, which is why it's impossible to dismiss the possibility of other intelligent lifeforms. Extraterrestrial life is a concept that never ceases to inspire and amaze, influencing a variety of films, books, and stories. We live in an age when technological advances have enabled us to search for signs of life in other parts of the universe. So, do alien beings exist? We still don't have enough evidence yet to prove they exist.
The Milky Way is a massive galaxy with a diameter of 100,000 light-years and an age of 13.5 billion years. We believed that it is one of the first galaxies to form within our universe. There are over 200 billion galaxies in the universe, each with billions of star systems, implying that we may be just another civilization in a vast universe. The Fermi Paradox, named after Italian physicist Enrico Fermi, explored the contradiction between high probability estimates of extraterrestrial life's existence and its apparent absence. He tries to answer the question: "Are humans alone in the universe?" and remains one of science's most debated mysteries that we looked forward to for answers.
There are billions of stars in our galaxy, and there's a decent possibility that some of them have Earth-like planets orbiting them. Based on a recent report published in Proceedings of the National Academy of Sciences of the United States of America (PNAS), 22% of Earth-like planets orbit sun-like stars in their habitable zones, the closest one being just 12 light-years away. If even an ample proportion of these planets develop intelligent life and interstellar travel is possible, colonizing the cosmos will take just a few million years – a relatively short period on both geological and astronomical scales. On this basis, we should have discovered another life form by now, but we still haven't.
Several scientists suggested few theories in response to this question. The existence of what is known as "The Great Filter" is perhaps the most well-known. The Great Filter is a hypothetical barrier that life will find incredibly difficult to overcome concerning The Fermi Paradox. If we discover aliens and life is abundant in the galaxy, The Great Filter is much more certainly ahead of us. As a result, we are likely to experience it in the future, implying a bleak future for humanity, as life will find it difficult to surpass it. On the other hand, if we are alone and fail to discover life, we should assume that we have gone through The Great Filter. How the Great Filter has manifested or may manifest itself is unknown.
Abiogenesis, according to others, was the origin of The Great Filter. The evolution of life from inorganic substances is known as abiogenesis. The gradual evolution of life on our planet from single-celled organisms to complex, multicellular organisms began more than 3.5 billion years ago. It eventually followed by biogenesis, the theory that life develops from life. Others say we are carrying the seeds of our destruction, which may be due to climate change or nuclear war. Whatever the case may be, humanity knows that no evidence of alien existence is a good sign, implying that The Great Filter is behind us.
The Great Filter is not the only possible explanation for The Fermi Paradox, despite its popularity. The simulation argument, which proposes that an alien species developed a simulation to make the universe appear lifeless, is another common explanation. Nick Bostrom, a philosopher at the University of Oxford, proposed the simulation argument. The simulation argument considers that if another form of species at our current level of development will be able to avoid extinction and is interested in running computer simulations of minds similar to our own, we are almost certainly living in a simulation. He added that we should not change our way of life if we are living in a simulation. Instead, we should use an extrapolation of past trends and scientific modeling to predict what will happen next in our simulation.
The Rare-Earth hypothesis is another explanation for The Fermi Paradox. It claims that the conditions that enable life to survive on Earth are far too rare. The Earth has the necessary conditions for life to exist: it is in the habitable zone of the Sun, has a required magnetic field, the correct atmospheric composition, and oceans and plate tectonics. According to the Rare-Earth hypothesis, this mixture of factors seldomly occurs on other planets as they do on Earth for life to develop.
Another plausible theory is that aliens already visited before. Perhaps aliens visited Earth thousands of years ago, but we were unable to detect them. Or, even, they might be here right now, undetected. Some scientists believe intelligent life exists elsewhere in the universe but is in a primitive state. Extraterrestrial species can remain in a primitive state if abiogenesis is the Great Filter, which they lack the technology needed for space travel. Others conclude that civilizations are too far from one another. Since the universe is constantly expanding, it is possible that even if intelligent life exists in another galaxy, it is difficult to contact them.
We are fascinated by the idea of life beyond our planet, staring back at us with the same awe and curiosity. We have difficulty in not believing that we are the only inhabitants given the age and size of the universe. Technology has only helped us to explore the universe in the last few hundred years. Despite the above advancements, humanity may still have a long way to go.
If aliens exist and we contact them first, we might be the advanced species, and the aliens are probably more like productive pond scum, which may explain why we fantasize about such encounters less than visits to Earth. And when the aliens are the explorers, we are in the pond scum. What was once considered science fiction is now widely accepted, encouraging those who gaze up at the night sky to keep looking.
Note: The cover image is created by the author using Canva.
