It was a fine starry night, my friends and I were sitting outside for a cup of coffee when we saw a shiny object pierce through the sky. We were the only ones who caught a glimpse of this object which appeared for a fraction of a second. “A UFO!” my friend exclaimed, but you know the possibility of that happening is low to none. Or is it?
One of the most exciting topics for a conversation is: Do aliens exist? Are we alone in the Universe? or are there other species wandering about other parts of the Universe in search of other extraterrestrial life? It is generally backed by quite a several convincing and hilarious theories and conspiracies. But the real question is how much truth lies in these speculations. Surely, we must not be alone in this Universe. The Hubble site states that the Universe’s expansion rate to a precision of just over 1%. This shows that our Universe, which is unfathomably large, is also expanding.
So, every time you look up at the night sky, know that there are roughly an equal number of observable galaxies in our Universe as the number of stars in our Milky Way galaxy or, simply put, for every grain of sand on every beach on Earth, there are 10,000 stars out there. Now imagine a number of those stars have planets revolving around them. Statistics suggest that about 1% of those stars have an Earth-like planet revolving around them, a total of a whopping 100 billion Earth-like planets. Our Sun is relatively younger. There are older stars with planets older than Earth, having enough time to create life.
Many scientists have thought of the possibility of extraterrestrial life. One notable contribution is that of Frank Drake, who gave the Drake Equation, which helped find the number of intelligent civilizations according to its factors. The Drake equation tells us that by 2074 there should be about 10 civilizations in our galaxy alone. Furthermore, The Kardashev scale categorizes civilizations into 3 types; Type 1 civilization harnesses all energy of its planet (According to the renowned astronomer, Carl Sagan, we are a Type 0.7), Type 2 civilization harnesses the energy of its star while the Type 3 civilization harnesses the energy of the entire galaxy.
So, where is everybody? A scientist named Enrico Fermi is associated with this question. It gives rise to the paradox we must now highlight; “The Universe is about 14 billion years old. If there are other intelligent beings present, why haven’t we heard from them ” It is from this question, the Drake equation, and the Kardashev scale that The Fermi Paradox was born. Right now, we have no clear answer or evidence as to the best explanation for this paradox. We only have several possibilities and hypotheses explaining the absence of alien life. One of the most widely discussed are these possibilities:
THE GREAT FILTER
Statistics suggest that there must be at least a few with advanced civilizations for such a large number of probable earth-like planets present in the Universe. There are other stars and planets older than our Sun, which had enough time to create life on its planets. The math suggests that thousands of them must be there in our own galaxy. This shows us that there must be Type 2 and Type 3 civilizations present out there, but there are signs of none. This is an intriguing piece of the puzzle. Why are there no Type 2 and Type 3 civilizations? A possible explanation for this question is a theory called The Great Filter.
The Great Filter theory suggests that at some point of evolution from premature life to Type 3 civilization, there must come a time when further attempts to evolve cease completely. This is a stage that is impossible for life to cross. So the question is, when does The Great Filter arrive in our own timeline? It’s important to answer this question for our own survival.
There are three possibilities:
We have crossed it
This version suggests that somehow, miraculously, we have already survived The Great Filter. This shows that our kind of intelligent life is extremely rare and special. It explains how there are no other Type 2 or Type 3 civilizations, and ours could be the very few of the ones that actually make it. That must mean that we have passed the Great Filter somewhere in our evolutionary process. Was it at the beginning of life itself? Scientists have tried to create life in laboratories for quite a few years, but it was never successful. If the genesis of life was indeed The Great Filter, this could explain why there could be no life out there.
Or it could be when a prokaryotic cell turned into the eukaryotic one. When the prokaryotic cells came into it wasn’t until after two billion years that the first eukaryotic cell came into being. If this is The Great Filter, then the Universe might be full of prokaryotes. Hence, the reason we haven’t heard any signals from any of them.
So, the Great Filter is characterized by one-in-a-billion occurrence only.
We would be the first to experience it
If the first hypothesis is incorrect, we may move toward the Great Filter. It means that we are one of the primary civilizations, and it is still early in the Universe for intelligent life to develop. Other civilizations are either not born yet or even more primitive than us, and all of us are yet to become super-intelligent species.
We will experience it soon
This is undoubtedly the scariest of the three possibilities. Theorists that support this hypothesis claim that life normally evolves to the point where we are, but it is after it reaches this stage that it is eliminated by a mysterious phenomenon. And we won’t be an exception. We might even end up destroying ourselves once we reach a point in technological advancement that harms our survival. The more clues we find about the evidence of extraterrestrial life, the more insight we gain on which stage we lie on.
Another group of theorists believes that we are not as special as we think we are. We may just be a mediocre species living on a mediocre planet orbiting a mediocre star. And there are many like us that haven’t reached out to us due to one reason or the other. It must be noted that any search for alien life done by humans is limited in scope as we could only search 100 light years away from us.
Let’s explore the different theories supporting this claim:
- Some theorists believe that Earth has already been visited by aliens in the past, but it was before humans were here. Humans have only been here for 50,000 years. We would have no way of knowing if any contact happened before then. Even if it happened in the early times of human civilization, we have no proof of that.
- One of the most exciting theories is The Dark Forest theory. It states that predator civilizations are out there, and other civilizations are quiet and noiseless to keep themselves safe. There is no way for them to know if the predator civilizations are altruistic or would destroy them completely. Although, the safest option for any species is to destroy all others to ensure its protection. That is why we may not have received signals from the SETI(Search for Extraterrestrial Intelligence) satellites.
This phenomenon is best explained in this paragraph from the Novel ‘Dark Forest:
“The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound. Even breathing is done with care. The hunter has to be careful because everywhere in the forest are stealthy hunters like him. If he finds another life—another hunter, angel, or a demon, a delicate infant to a tottering old man, a fairy or demigod—there’s only one thing he can do: open fire and eliminate them.”
Astronomer Carl Sagan recommended that “the newest children in a strange and uncertain cosmos should listen quietly for a long time, patiently learning about the universe and comparing notes, before shouting into an unknown jungle that we do not understand.”
- If other much more advanced civilizations are already living out there, the Type 2 and Type 3 civilizations, then there is no need for them to visit us or contact us when they are utilizing all their resources from their own star or galaxies. Our system would be too underdeveloped for their needs.
- Our Sun is located in one of the Spiral arms of the Milky Way galaxy. If the colonization of the Milky Way has already occurred, then there was no reason for intelligent life to visit this rural area of the galaxy. It would just be impractical to travel such a long distance.
- Building on the Dark Forest theory, there might just be one Super civilization out there that does not let any other civilization grow and develop and eliminates it, so it does not threaten them.
- There may also be a possibility of an intelligent civilization out there, but we just don’t have the right equipment to catch the signals. Maybe the technology they use is too advanced or obsolete, so much so that it is impossible for us to detect it.
- Another exciting hypothesis is The Zoo Hypothesis which tells us that the more advanced civilizations know of our existence and are only just observing us from afar. There is a possibility that they are watching us with technology which does not let us determine that we are being watched.
- A theory suggests that we may be too irrelevant for high civilizations. So much so that they don’t even care to contact us. If that is the case, it also makes sense why we have not yet sensed them because, in the realm of physics, it would be difficult for us to perceive anything that is far too advanced than us
- Let me just add my favorite one out here in the end: Aliens have already contacted us, but the government is hiding it. This one is the most mind-bending one to me, for there is absolutely no way for contact to have already happened and it remains a mystery.
Looking at the night sky is a humbling experience. It either makes you wonder about what’s above and beyond, making you forget about all the frivolous problems of our daily lives, or it gives you something more to think about, like an existential crisis. To think that we are the only living civilization out there is a lonely experience but to think that there may be predator civilizations or The Great Filter waiting to happen is an even scarier possibility.
The Fermi Paradox gives us the most reasonable and sound theories regarding the existence of Alien life. It makes me sometimes wonder that we may be the highest-living predator civilization instead. It’s best to negate the fear of annihilation that way. We may even go on to develop a Dyson sphere and turn into a Type 2 civilization, or we may completely wipe ourselves out by over-consuming Earth’s resources. Whatever lies ahead of us is exciting as well as terrifying.
Tayyab Imam is a BS Computer Science student and an Astro-phile by nature. She’s an avid reader with areas of interest Astronomy, Astrophysics, Quantum physics and theoretical physics.