An Unresolved Fermi Paradox
“The Hush of the Night Sky is the Silence of a Graveyard”
***Disclaimer: This post is quite different from my previous posts; it is a fun journey into the cosmic unknown. Hope you enjoy!***
Over the past few months, work and life have kept me pretty busy. But, whenever I have some spare time—especially at nights, I found myself staring at the night sky above us—that expansive dynamic painting filled with a multitude of dazzling stars. During these moments, one thought has often come up: are we truly alone in the universe?
This profound question has been on the mind of many scientists and astronomers. But so far, we have come up empty. However, given how vast the universe is, the possibility of us being the only intelligent life in this arena seems exceedingly small. But answering this question in the context of the universe as a whole seems impractical. If there is another foreign civilization living on a planet millions of lightyears from us, the chances of our first encounter with such a species happening anytime soon—even on a cosmic timescale—is very unlikely: the distance is far too great. In fact, if such a civilization exists but resides outside of our Hubble Sphere—our observable region of the universe—then even obtaining evidence of its existence is greatly diminished with that region of space moving away from us at a rate that is faster than the speed of light.
For these reasons, scientists have focused their search for extraterrestrial life to our own backyard: the Milky Way galaxy. So in this post, I will explore this topic by providing an overview to the Drake Equation as well as the Fermi Paradox. Then, I will introduce some of the leading explanations for why we have not seen evidence of an alien civilization. Finally, I will conclude with my thoughts on whether we are alone in our galaxy and why I believe it is a good thing that the paradox currently remains unresolved.
The Drake Equation
With Outer Space in a constant state of expansion after the Big Bang and its current size already incomprehensively large, the chances of humanity being alone in this vast cosmic playground is infinitesimally small. While there is no doubt that the human race is pretty unique, given the sheer number of galaxies in the universe, the chances of at least one planet in one star system in another galaxy also containing intelligent life is rather high. But, because of the time it takes to traverse the universe, this becomes more of a theoretical exercise as—unless a civilization has figured out how to travel much faster than light—we would likely never “receive” any evidence of this other species’ existence. This is essentially akin to the chances of a dolphin in the Pacific Ocean observing signs of a giraffe in the African Savanna.
Because of these circumstances, scientists and astronomers have focused their search for extraterrestrial life to our backyard: the Milky Way galaxy. It is a galaxy that is spiral in shape and is about 100,000 light-years across. While this is still a vast space, it is a much smaller sandbox in the grand scheme of the universe. It also makes sense for us to focus our search for extraterrestrial life to this environment because any life found here is close enough to present a more “immediate” risk (if they are a hostile species) and opportunity (if they are more like the Vulcans from first contact).
In aiding scientists’ search for intelligent life, in 1961, Dr. Frank Drake came up with an equation that attempts to proximate the number of “intelligent” civilizations that could exist in the Milky Way galaxy. Named the Drake Equation, it attempts to calculate the number of civilizations in the Milky Way that humanity might be able to communicate with via electromagnetic means such as radio waves. The equation is made up of seven components and is written simply as:
N = (R*)(fp)(ne)(fe)(fi)(fc)(L)
Where:
R* is the number of stars formed in the Milky Way on a yearly basis that would be suitable for the development of intelligent life;
fp is the fraction of those stars that would have planetary systems;
ne is the number of planets in such systems with environments suitable for life;
fe is the fraction of such planets on which life would appear;
fi is the fraction of such planets in which life would evolve into intelligent life;
fc is the fraction of these intelligent civilizations that would develop technologies that could broadcast signals of their existence; and
L is the length in years such civilizations would broadcast these signals
When these seven factors are multiplied together, you would arrive at N: the number of extraterrestrial civilizations in the Milky Way that humanity might be able to observe. An N-value much larger than 1 would suggest that we are not alone in our galaxy. But, if the N-value is much less than 1, it would indicate that the Milky Way is a lonely place for humanity. Given the number of factors involved and the lack of clear-cut scientific evidence to reduce many of these components to a tight range, estimates for the Drake Equation has been—no pun intended—all over the map. Some have calculated an N-value in the millions whereas others have found N to be extremely small.
However, recently, a consensus on each of these factors is emerging. According to Britannica, using the most commonly cited values for these factors, the Drake equation would simplify into N = L/10. If we assume that extraterrestrial civilizations have been broadcasting electromagnetic waves into Outer Space around the same amount of time as humanity has, then L would become 47—since we have been broadcasting into Outer Space since 1974. This would suggest that there is at least 4 other intelligent civilizations in the Milky Way.
The Fermi Paradox
Given the Milky Way’s sheer size, four other civilizations might not seem like that many. But, this number would make it possible that humanity would encounter signs of another civilization at some point. In addition, if such foreign civilization develops the capability to transmit electromagnetic signals, they will likely do it much longer than just 47 years—this also suggests that N must be much larger than four. And as these waves fan out in our galaxy, the chances of us picking up their signal become more and more likely. But, this creates a perplexing conundrum for many scientists and researchers. If there is a large body of evidence indicating that we are not alone in this galaxy, then why have we not encountered any signs of another intelligent civilization?
This exact question lies at the heart of the Fermi Paradox, which is named after the Italian scientist Enrico Fermi. According to the official lore, Fermi was walking with his colleagues to lunch when the topic of aliens came up. After some discussion on this matter, the conversation moved to other subjects. But, during lunch and out of the blue, Fermi randomly blurted out something to the effect of “But where is everyone?” While an apparent non-sequitur, everyone at the table knew exactly what he meant: with everything pointing to the existence of extraterrestrial intelligent life, then why have we not seen any evidence for such civilization? Thus, a paradox that has puzzled generations of scientists was born.
Common Explanations for the Fermi Paradox
Over the years, several explanations to the Fermi Paradox have been proposed. The four most popular ones are:
The Great Filter Hypothesis. Under this theory, all species will encounter a significant moment in its history that could lead to its extinction. It is extremely rare for any species to survive this “Great Filter” event. Hence, humanity is either (a) one of the rare species that made it past this evolutionary filter or (b) a species that has yet to, but will, experience this moment. If you are an optimist, you might prefer (a), but if you are a pessimist, you might believe more in (b). But, under either scenario, this is the reason why humanity have not encountered any evidence of extraterrestrial life. Intelligent life is scarce and rather ephemeral under the cosmic timeline. The existence of the Great Filter could mean that we are either genuinely alone or we would be long gone before the rise of another intelligent species.
The Zoo Hypothesis. With this hypothesis, scientists believe that there are other highly advanced foreign species that are aware of humanity’s existence. However, at this point of our development, they have chosen to observe us rather than try to communicate with us. To these civilizations, we are essentially cells in a petri dish. Hence, the only reason why we cannot detect signs of extraterrestrial life is because such evidence is actively being shielded from us. The reason for this could be one of many. Perhaps, it is because we are not truly an interstellar species yet and not ready to be a participant in the galactic village. Or perhaps, Earth just happens to be a part of a galactic museum, and our species is just another exhibit. Either way, we still have a long way to go before we are proven “worthy” of first contact.
The Dark Forest Theory. Popularized by Liu Cixin’s novel, the Dark Forest, this pessimistic explanation for the Fermi Paradox suggests that all species are in a struggle for survival in a resource-constrained galaxy. In such a universe, all civilizations are in a zero-sum game for survival. When one species encounters another species, it is inevitable a conflict will emerge between the two and one race will be eliminated with resources being scarce. Therefore, the reason why we have not detected signs of another intelligent civilization is because everyone is shielding themselves from being discovered. Much like a dark forest full of danger, nobody wants to be the first one to light up a fire and give away its position. In this sense, humanity is doing itself a disservice by broadcasting signs of its existence. The most optimal move for a species to make in such an environment is lay low and fully disguise any signs of its existence.
The Aestivation Hypothesis. Another explanation for the paradox takes into consideration the concept of dormancy. Backers of this theory argues that the reason why we have not found evidence of intelligent life is because such alien civilizations are currently conserving their resources in low energy states. Like a hermit kingdom, they are completely isolated from the rest of the galaxy and will remain so until certain threshold conditions are reached. Much like bears hibernating in the winter, they might be waiting out certain “dark ages” in the cosmic timeline. By isolating themselves, they can actively reduce their energy output and be better prepared for the moment when they decide to emerge back into the galactic spotlight. As a corollary, this theory also essentially suggests that humanity’s current state of development might be considered primitive because our technological advancements have not hit these other extraterrestrial civilizations’ threshold alert levels.
Small Boat Drifting in an Endless Ocean
In my opinion, the chances of us being the only intelligent civilization in the universe is extremely low. The universe is simply too big and too expansive for that possibility. However, the chances of us encountering aliens outside of our own galaxy is also very improbable. Given the distance, this first contact would require humanity to have had a significant technological breakthrough or discover wormholes capable of bridging across different regions of the spacetime continuum. Of course, this does not take into consideration the existence of an alien race with highly advanced faster-than-light transportation technology; such technology would empower this species to essentially defy the laws of physics as we currently understand them. If this were the case, it would cause an extreme paradigm shift and our knowledge of the universe would fundamentally be changed.
However, I think the more interesting question to consider is whether we are alone as the only intelligent species in the Milky Way. Just like a baby learning how to crawl before she can walk, our current and immediate Outer Space settlement goals are to take our first steps on another planet in our own system and then an exoplanet as part of a nearby star system. While it appears that we are on our way to landing humans on Mars, establishing a presence there will still take a few generations. After that, it will likely take many more generations before we come up with the technology and fortitude needed to travel to our closest foreign star system, Alpha Centauri, which is approximately 4.3 light-years from Earth. Hence, just exploring our immediate surrounding will likely already take us millenniums. Thus, the practicality of searching for life outside of our own galaxy is minimal. So, if we want to be more practical with our aim, we should indeed focus our search for extraterrestrial life to our own galaxy—where they would present the most immediate opportunity (or threat).
With the focus rightly honed in on our own galaxy, many are puzzled by the fact that we have not found signs of an alien civilization yet. But, I don’t find this so strange simply because we have not been looking for a very long time relative to the history of our galaxy. Under the cosmic timeline, the entire history of humanity is but a blip. The Milky Way is about 13.6 billion years old, and Earth has been in existence for about 4.5 billion years. However, humans—homo sapiens—first came into existence only about 300,000 years ago. That means humanity has only been roaming on Earth for the most recent 0.006% of Earth’s history and the most recent 0.0022% of Milky Way’s lifetime. Of the 300,000 years we have been in existence, we only started broadcasting out and listening for electromagnetic signals from our galaxy for the last 47 years, or 0.0156% of our own history. This is a very small sample of time. Also, let’s not forget that the Milky Way itself is still 100,000 light-years across, so it is very possible that signs of extraterrestrial life has either not reached us yet or travelled past our planet eons ago and have since stopped communicating this way.
So while we still have not found existence of other intelligent life in our galaxy, it doesn’t mean they aren’t out there. In fact, I think there is a high probability that we will eventually encounter another intelligent species in the Milky Way. But that thought also terrifies me because of what would happen if we were woefully unprepared for that moment of first contact. The chances of us encountering signs of a much more advanced alien civilization are much higher than the other way around—after all if we only ascertain their existence through our Earth-based detection methods, it means that they are at least as advanced as we are. One thing that the course of human history has taught us is that when a strong civilization encounters a weaker one, the outcome will almost certainly favor the strong and the consequences can be dire for the weak. Because of this fact, in a way, I am glad that we still have not detected signs of another intelligent species yet. I think humanity needs to be better prepared with more advanced technologies and scientific understanding of the universe before we are ready for that moment-lest we might get wiped out.
So when it comes to the Fermi Paradox, it’s my hope that it remains unsolved and unexplained for now. Well, at least until the day when we discover this other intelligent civilization not by detection on Earth but as a result of our race’s evolution into a peaceful interstellar species that can travel either close to or surpassing the speed of light with settlements fanning across the Milky Way.
