Nov 16, 2022 I Brent Swancer

Are We Alone in the Universe?: The Great Filter and the Death of Alien Intelligences

The human race has been fascinated with the vast sea of space for as long as our first flickers of awareness that it even existed began to form. Specifically, one very profound question that has gestated within our collective consciousness is simply: are we alone? We have long pondered whether there might be someone else out there amongst that uncharted ocean of stars, and this has become the focus of science fiction stories, personal reflection, philosophical dilemma, and scientific debate from the time we were able to comprehend that there were even other planets out there. In recent years our ever advancing technology has allowed us to peer into the deep black of space and locate many other planets orbiting stars just as our own, with quite a few even displaying signs that they may even be similar to ours and be habitable, and for decades we have carefully listened in to hear if there is any message flying about in the void. But is there anyone there at all? Why has no one answered us or made themselves known? Are we truly alone, hurtling through a cold, uncaring universe on this rock of ours? According to some experts, perhaps the answer to these questions is even grimmer than we could have ever imagined. 

In 1950, the influential and notable physicist Enrico Fermi was working for Los Alamos National Laboratory, and one day while having lunch with colleagues Emil Konopinski, Edward Teller and Herbert York, the conversation came around to UFOs and alien life. The group began discussing the possibility of other alien civilizations out there scattered across the galaxy, and that was when Fermi simply and bluntly asked “Where are they?” This generated a bit of laughter around the table, but he was perfectly serious. When the others asked exactly what he had meant, Fermi explained that if there was another civilization or civilizations that had developed out there with the technological ability to traverse space, then eventually they should have already spread out all over the galaxy, and we should have had some brush with them by now in some form.

Fermi reasoned that there had been plenty of time for them to do so, and utilized complicated equations to illustrate that over millions and millions of years, just a drop in the bucket compared to the age of the universe, these hypothetical alien civilizations should have at least found us by now. Fermi explained that with so many stars and potential planets in the observable universe, then if even a fraction of those had produced intelligent, spacefaring life then they would have exponentially broken their barriers and moved out into the galaxy, colonizing new worlds, and we would have surely known about them by now. By Fermi’s various calculations, the probability for intelligent life somewhere in the universe was high considering the sheer scale of it all, and if such advanced societies had developed, then after so much time aliens should be everywhere by now, or at the very least given us some sort of sign of their existence, even if such societies are rare. Yet there is no one, no evidence of such a thing, not a single sign that there is anyone else out there at all. Essentially, like Fermi asked, where is everybody?

This is the main gist of what has gone on to become known as the “Fermi Paradox,” and although it has been criticized by many as being perhaps too simplistic and making too many assumptions based on our own ideas of life, it has nevertheless gone on to become a major cornerstone for debate on the topic of intelligent life elsewhere in the universe, and has inevitably hung over most discussions on the matter. This offhand lunchtime remark has propelled the imagination and driven the efforts of organizations like SETI. No matter what one thinks of the veracity of Fermi’s question, it is a compelling one to say the least, and there have been many numerous and varied theories that have come forth to try and explain just why we have not found anyone else out there in this cold universe of ours.

Although it all started as just sort of a fun thought experiment, there was no real way at the time for us to really test out or solve Fermi’s Paradox, but over the decades things have changed. Technology has advanced in leaps and bounds, allowing us to peer into our universe to a degree never seen before, and as we have made these advances the search for other intelligent life has become more embraced by science, taking it out of the realms of thought experiments and science fiction stories and into real discourse. We now have sophisticated, cutting edge observatories and telescopes, and dramatic developments in rocketry, radio astronomy and computational power have driven us into new frontiers in this field, in the process uncovering thousands of exoplanets, attesting to the ubiquitous nature of planetary systems, with some even thought to be habitable, and we have even used specialized equipment to analyze them for bio-signatures. We have bombarded the vastness of space with transmissions announcing our existence and listened in on any possible response. Surely with the unfathomable number of stars and planets in our galaxy there should have been something by now, yet we are met with silence. We have found nothing, and the answer to Fermi’s original question of “where are they?” has become an increasingly urgent and oft-discussed conundrum. Associate professor of economics at George Mason University and a research associate at the Future of Humanity Institute of Oxford University Robin Hanson has said of it:

Our planet and solar system, however, don't look substantially colonized by advanced competitive life from the stars, and neither does anything else we see. To the contrary, we have had great success at explaining the behavior of our planet and solar system, nearby stars, our galaxy, and even other galaxies, via simple "dead" physical processes, rather than the complex purposeful processes of advanced life. Life is expected to expand to fill all available niches. With technology such as self-replicating spacecraft, these niches would include neighboring star systems and even, on longer time scales which are still small compared to the age of the universe, other galaxies. If such advanced life had substantially colonized our planet, we would know it by now.

There have been numerous theories and ideas on why we have not heard from alien civilizations, at least as far as we know, but one of the most sobering of these is an idea usually referred to as “The Great Filter.” Originally proposed by Hanson, the basic idea is that at some point along the line of a civilization’s development from the earliest stages of abiogenesis, that is the emerging of life from inanimate matter and inert chemicals, all the way up to a technologically advanced spacefaring race something happens that prevents that budding civilization from progressing any further and perhaps even wiping it out, some sort of barrier to further development that makes detectable extraterrestrial life exceedingly rare or even nonexistant. In essence, there are a series of hurdles that any would-be spacefaring civilization would have to overcome to make it to that next level, and one of them is tripping them up, some critical step they cannot get past. The idea is that if there is such a barrier, then the reason we are not hearing from anyone is that there is no one out there to hear, and that despite the possibility that there have been many extraterrestrial civilizations they have just never reached a sufficient stage to make contact and perhaps we truly are alone, ourselves hurtling towards the imenetrable wall that is The Great Filter. 

But what is the Great Filter? What sort of barrier could it possibly be that stops a civilization dead in its tracks? It is perhaps best to first look at the stages of development of a spacefaring race and where we sit on it, and this can be see with what is called the Kardashev scale, which seeks to create a functional definition of civilization based on the immutability of physical laws and using the human civilization as a model of extrapolation, as well as to make a classification system for the levels of technologically advanced civilizations. To put it in the most basic of terms, the first step is obviously that a planet capable of harboring life must form in a star’s habitable zone and it must develop life through abiogenesis. After this, those lifeforms must be able to reproduce, using such molecules as DNA and RNA and simple cells (prokaryotes) must evolve into more complex cells (eukaryotes). Multicellular organisms must then develop and be capable of sexual reproduction, which greatly increases genetic diversity, and then complex organisms capable of using tools must evolve. Those tool-using organisms must then create the advanced technology needed for space colonization, and then this spacefaring species must go on to colonize other worlds and star systems, all while avoiding the pitfalls of destroying itself. If all of these steps are cleared, then the species can roam the sea of stars, and if anyone has done it we should have expected to have seen or heard something by now. So where are they, and if the Great Filter theory is true what is the step that is keeping us alone, that threshold that needs to be passed? With no solid evidence of intelligent life in places other than on Earth, it appears that the process of starting with a star and ending with "advanced explosive lasting life" must be unlikely and that something on this scale is holding it back, but what could that be? 

Looking through the steps, we know that we have made it through most of them. We know that abiogenesis can happen, multicellular life, tool use and intelligence have all developed on our planet so we know it is possible and there is no real reason to think that it could not happen anywhere else. Indeed, humanity has cleared almost all of these steps except that of colonization of other worlds, so it is often thought that this must be the step that no one can pass. If they had, then it could be assumed that, given the vast age of the universe, there should be at least a few interplanetary species colonizing the entire galaxy by now, but we have no reliable evidence of this. Why should this be? There have been several ideas on just where this invisible barrier lies. One is that the barrier occurs very early on, and while planetary systems and even conditions for life seem to be relatively common in the cosmos, perhaps abiogenesis is a rare process, or even one completely unique to Earth. After all, the interaction of chemicals and conditions that gave rise to life required an extremely balanced and precise series of effects and parameters that seem almost mind-bogglingly unlikely. Everything had to be just so for life to evolve from nothing, and so perhaps it was just a fluke, a pure one in a trillion chance, and life on Earth was just an anomalous glitch. If this were the case, then life would be extremely rare in the universe, or even nonexistent outside of our planet. The paper Avoiding the “Great Filter”: Extraterrestrial Life and Humanity’s Future in the Universe, by Jonathan H. Jiang, Philip E. Rosen, Kelly Lu, Kristen A. Fahy, and Piotr Obacz of NASA's Jet Propulsion Laboratory says of this possibility:

Life, in as much as has been determined from extensive sampling of only a single world, poses a dilemma. In a universe whose normal matter is almost entirely hydrogen – with just a single proton, the simplest of the elements - humanity finds within itself and its environment a wealth of chemical complexity which seems to defy logic. The solution to this riddle of higher development is found, oddly enough, in grand scale destruction. In their explosive demise, stellar furnaces fuse together heavy nuclei which, upon combining with electrons, enable exponentially branching combinatorial chemistry including the formation of large molecules. In this realm hydrogen is rendered merely a bit player, ubiquitous but no longer occupying center stage. Rather, the sixproton nucleus of carbon, with its particular arrangement of electrons given over to orbital hybridization, seizes the central role in biochemistry. But, if “life as we know it is merely an afterthought in the global scheme of the cosmos”, we may well be led to conclude the Earth’s bounty is of truly extraordinary – perhaps even unique – nature. Are humans, just one among the millions of species sharing this remarkably hospitable but fragile oasis in the cosmos, a kind of multiply improbable instance of fused ash first assembling to primitive life then, much later, tumbling into self-awareness followed by spacefaring technological prowess? One school of thought posits this ‘Rare Earth’ hypothesis: given a Universe stretching approximately 92 billion light-years and existing for nearly 14 billion years, intelligent life can be both inevitable but still exceedingly rare. Hence, present era Earth is merely the particular time and place such extraordinarily long odds, in effect, paid off and we are the lucky beneficiaries. While such a notion may come as comfort to some as they (philosophically speaking) claim universal ownership, this scenario would also leave us profoundly isolated and stunted.

Or perhaps life has indeed emerged countless times, but maybe the overwhelming majority of life never progresses beyond simple single-cell organisms, giving us a universe full of planets with nothing but bacteria and germs that never progress beyond that. Still another twist on this is that perhaps intelligence and self-awareness are also rare; flukes and glitches that occur very rarely or only in us. It is all a sobering thought, but the good news in that if this is the case then we have already cleared the Great Filter. A more sinister common take on the Great Filter is that we have not yet reached it yet and that it lies somewhere in our future. In this scenario, technologically advanced civilizations reach a point where they self-destruct before they are able to truly reach the stars, either through climate change, war, exhaustion of resources, overpopulation, malevolent artificial intelligence, nanotechnology running amok, a doomsday machine, or some other self-induced catastrophe. The idea here is that such extinction events are virtually inevitable throughout the cosmos, and that intelligent species are predestined to reach a point where they ultimately destroy themselves somehow before they ever really spread out into the cosmos. Perhaps there are many civilizations out there at our level of development or below that will just inevitable sputter out before they reach the stars, and we are in for the same ultimate fate. A mere glimpse at the news and a look at what is going on in the world today is enough to convince that this scenario is perhaps not so entirely far-fetched. 

If the Great Filter lies ahead, then there is a good chance that we are doomed, but there is still some possible good news. One is that if our Great Filter is lying in the past, then it means that we have already passed the bottleneck and are able to survive our journey into the future. Another is that even if we have not reached that Great Filter yet, there is hope that we as a species could somehow avert it, despite our self-destructive tendencies. The same paper from NASA's Jet Propulsion Laboratory says of the dangers facing our civilization and the possible way to avoid them:

Human civilization over the past 5000+ years, and in particular since 1945, has revealed much of what would surlily impede, if not outright arrest, our aspirations to colonize other worlds in the Solar System and beyond. It seems as though nearly every great discovery or invention, while pushing back the borders of our technological ignorance, is all too quickly and easily turned to destructive ends. Examples such as splitting the atom, biomedical innovations and resource extraction and consumption come to mind with disconcerting swiftness. If life arisen on Earth is ever to know of life elsewhere, assuming such exists, we as the Earth’s sole technological species must first come fully to terms with ourselves and our environment. The struggle for survival, security and dominance - all rooted in human passions - drives creativity and with it, civilization and invention. As history has shown time and again, however, this cleverness comes at great cost. The key to humanity successfully traversing such a universal filter is found in understanding what characteristics the barrier will constrain, identifying those attributes in ourselves and neutralizing them in advance.

Of course there are other ideas on the Great Filter that would be out of our control, such as an asteroid impact, and there has even been the idea that a more advanced civilization watches from the shadows and destroys any new ones that develop and pose a threat. Perhaps some dark alien presence is intentionally avoiding us and ready to wipe us and anyone else out if we ever get close to the stage of interstellar travel. Then again, maybe there is no filter at all, and that there are other reasons for why we have not yet met or detected alien civilizations. Maybe they are hiding, or lack the will or resources to colonize the galaxy, or maybe they are just simply ignoring us. Maybe Earth is just in a galactic backwater, or that other races aren’t interested in going so far out past their own solar systems. There is also the possibility that civilization does not necessarily go for bigger is better, and that these races have focused on their own worlds rather than branching out into the greater universe, or that their technology is just so advanced that we can’t detect it no matter how much we scan exoplanets for signs of technology. Astronomer Seth Shostak of the SETI Institute has said of some of this:

This is, of course, a variant on the Fermi paradox: We don't see clues to widespread, large-scale engineering, and consequently we must conclude that we're alone. But the possibly flawed assumption here is when we say that highly visible construction projects are an inevitable outcome of intelligence. It could be that it's the engineering of the small, rather than the large, that is inevitable. This follows from the laws of inertia (smaller machines are faster, and require less energy to function) as well as the speed of light (small computers have faster internal communication). It may be—and this is, of course, speculation—that advanced societies are building small technology and have little incentive or need to rearrange the stars in their neighborhoods, for instance. They may prefer to build nanobots instead. It should also be kept in mind that, as Arthur C. Clarke said, truly advanced engineering would look like magic to us—or be unrecognizable altogether.

In the end we are just as in the dark now as we were when our ancestors first learned of other worlds and looked out into that sea of stars to wonder if there were others looking back. For all of our advances in technology and science we still know nothing more than we did centuries ago in this regard. We keep looking, we keep sending messages, and we keep getting no reply. Why should this be? Is there some reason for it, and these civilizations are actually out there but somehow undetected? Or is this truly a cold universe, the intelligent races that once lived here long gone or having never existed at all? Is it perhaps possible that the galaxy was once populated by such civilizations but they were wiped out by some impenetrable barrier and we are next in line? It remains unknown, the universe remains silent, and as far as we know we are the only ones even searching for other life in the galaxy. 

Brent Swancer

Brent Swancer is an author and crypto expert living in Japan. Biology, nature, and cryptozoology still remain Brent Swancer’s first intellectual loves. He's written articles for MU and Daily Grail and has been a guest on Coast to Coast AM and Binnal of America.

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