The Fermi Paradox: Cosmic Silence Explained
Now, let's consider planets. Most stars have planets orbiting them. It is said that there are trillions of planets in the universe where life can exist. In our Milky Way galaxy alone, there are millions of planets with the potential to sustain life. If the universe is 13.8 billion years old, in such a vast universe and over such a long period, isn't there a possibility for other beings like humans—or even beings technologically superior to humans—to exist?
If a society has achieved the technology to travel through the universe, where are their spacecraft or robotic probes? Or at the very least, why haven't we received even their radio signals? It is as if humans, an insignificant species living on this small planet Earth, are blindfolded. Are there powerful other beings in the universe evading our searches? Even if not ready for massive cosmic voyages, we humans have at least acquired the techniques to observe the universe deeply. Why, despite the possibilities, do we not hear the voice of any other being in this vast universe? This silence is called the Fermi Paradox. In the 1950s, the scientist Enrico Fermi put forward a question: "Where is everybody?" While the calculations regarding Earth-like planets and the potential for life on them keep increasing, actual observations do not match this at all. This contradiction remains an unanswered question in the scientific world today. We are going to talk about the Fermi Paradox.
Let me tell you how big our universe is. What you see in the picture is our own galaxy, the Milky Way. When we simply look up at the sky at night, all the stars we see are located in this small part of the Milky Way galaxy—the stars inside that red circle. Our Milky Way galaxy contains approximately 400 billion stars. That means 40,000 crore stars. Among these stars, about 20 billion are said to be similar to our Sun in size and energy. At least one-fifth of these stars have Earth-like planets within their habitable zones. Even if life exists on only approximately 0.1% of these planets, their number would be a minimum of 1 million.
But there is a small twist, too. The Milky Way galaxy is about 13 billion years old. Even if conditions were not suitable for life in its early stages, the first habitable planets likely formed after one or two billion years. Our Earth is only 4.5 billion years old, so there would have been trillions of chances for life to emerge and evolve on other planets in the past. If at least one of them had developed into a space-traveling super-civilization, we would have met them by now.
If such a civilization—or a community of beings—exists in the universe, we can classify them into three categories according to a system put forward by the scientist Nikolai Kardashev. A Type 1 Civilization is a society capable of harnessing all the energy available on its own planet. Are we humans a Type 1 Civilization? No. Humans have still not been able to fully utilize all the energy sources on Earth; based on our current status, we stand only at a level of about 0.73. A Type 2 Civilization would be a community capable of harnessing the entire energy of their host star. Suppose we were to become a Type 2 Civilization; we would be able to collect all the energy emitting from our Sun and use it for our needs. For this, those beings would construct structures like a Dyson Sphere. Finally, those who have grown to the next stage—a Type 3 Civilization—would control their entire galaxy and utilize its energy. If the concept of 'Gods' actually existed, we could consider them a Type 3 Civilization. A Type 3 Civilization would have the ability to rule over all other civilizations in that galaxy.
Hearing all this, you might have a doubt whether this is actually possible. When we calculate the speed of human technological growth, if we could build spacecraft capable of sustaining a population for a thousand years, we could establish numerous human colonies across the Milky Way within about two million years. While two million years might sound like a long period, it is a very negligible amount of time when compared to the age of other objects in the universe. Let us think about this point: if any other society of beings in our galaxy had gotten this much time—or even more—what would they be doing now?
So far, we have only spoken about living in this universe. However, now let us talk about death and the obstacles the universe places before us. We are talking about barriers that are very difficult for life to overcome. More primary than survival is the process of life originating. The formation of complex life is more difficult than we think. Life forms and grows only if thousands of factors come together in unison. At a stage where a civilization is growing, a crisis might arise among them, causing them to perish. This condition is what is often referred to as a "Great Filter." To give a hypothetical situation: our technology might develop so much that the technology itself destroys us and our Earth completely. It could be a nuclear bomb, or it could be a deadly virus. Another possibility is an interstellar object coming from another corner of the universe. It could be a piece of rock traveling at high speed, or a comet we have not yet encountered. The filter we have to face might be ahead of us. Life may have existed in many places in the universe, but when it reaches a certain stage, it perishes. The reasons for destruction could be anything.
Life has existed on Earth for 3.6 billion years, but intelligent humans have existed for only about 250,000 years. Furthermore, we have possessed the technology to communicate over great distances for only a mere century. It is the technological knowledge of the subsequent century that has made us who we are today. Alien empires may have existed millions of years ago, and we may have simply missed them. If we take a count of the species that have gone extinct on Earth, it amounts to about 99% of all life that has ever existed. The process of intelligent life forms emerging, spreading to a few places, and then perishing might be repeating. Civilizations arising in the galaxy might never meet each other; at different points in time, they are born, they live, and they perish. As Enrico Fermi asked, "Where is everybody?" Looking at the stars and wondering this might be a common experience for all life forms in the universe.
Even if there are civilizations living at the same time, the communication method we use might not be the one others are using. Perhaps our communication methods—for example, radio waves—might be outdated. If others are using a more efficient, faster, advanced, and new technology, then they cannot hear what we are saying. Even if they hear, we might not be able to recognize the messages they send in reply. This communication gap between two civilizations has the potential to isolate us.
Now, let us assume we do establish contact with another civilization. We might not be able to hold a meaningful conversation with them; at the very least, it would be a very difficult challenge for us. Imagine calling the smartest squirrel and lecturing it for hours about our life and needs—you cannot make it understand. A squirrel has its own specific requirements, and if those needs are met, the squirrel is satisfied. But what about humans? We encroach upon our territory and the squirrel's territory. We become a threat to the squirrel's peaceful life. If a Type 3 Civilization were to meet us, the same thing might happen, just in a different way. To take what they need, they might start exploiting our resources. They might drain our oceans and mine the minerals beneath the earth. To them, we are just an insignificant species of monkeys.
However, if a culture that desires to 'destroy' other life forms is the one meeting us in this manner, that encounter will not end in mere exploitation. Those arriving with advanced weapons would wipe out the last remnants of life on this small sphere. For their own survival, they might conquer other living planets and destroy the living communities there. They might separate the resources of that planet into various components and turn them into fuel for their own cosmic travels. To ensure no challenge arises against them from another corner of their own galaxy, the goal of such civilizations might be to wipe out all other possibilities of life. Although hearing this might feel like a scene from a science fiction movie, it is one of the many possibilities behind the mysterious truth of the silence the universe keeps hiding.
All such answers to the Fermi Paradox have a problem: we do not know where the boundaries of technology lie. Perhaps we are close to those boundaries, or perhaps we have reached nowhere near them. A super-technology that makes us like Gods might be waiting for us in the future. If we take the entire period of human evolution, for 90% of it, we lived by hunting and gathering food. Just 500 years ago, we thought we were the center of the universe. 75 years ago, the world was standing in two camps and fighting wars. When looking at the timeline of the universe, we are merely embryos—the rulers of the universe who are yet to be born.
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