Thinking about a great filter through which a civilization must pass before its survival is assured usually leads to catastrophic scenarios, such as planetary suicide by nuclear war, or climate holocaust (assuming the filter lies ahead of us and not behind). But filters may be more subtle and tied in with epistemology. How does intelligence view its place in the universe and thereby engage with other beings? In today’s essay, Ian Brownlie looks at the matter from the standpoint of how knowledge is acquired and transmitted. Based in New Zealand (near Hawke’s Bay on the North Island), Ian is an Electrical Engineer who works with commissioning high voltage complex power systems. The survival and evolution of technology may be a harder step than we think.
by Ian Brownlie, BE(E&E)
Intelligence has appeared on Earth in many forms. Science-like inquiry has appeared more than once. But sustained, cumulative science appears to be different. It survives across generations, sharpens its own methods, and turns curiosity first into instruments, then into machines capable of leaving the world. So far as we know, that has happened only once. That asymmetry may matter. The night sky has always been there—indifferent and immense —but only one lineage seems to have kept turning that view into telescopes, rockets, and radiodishes. The outward gaze did not merely happen; it had to be sustained. And that fragile fact may tell us something unsettling about why the rest of the galaxy seems so quiet.
The Fermi paradox begins with a straightforward expectation: if life arises easily, and intelligence follows often enough, then the Milky Way should be full of civilizations that have spread, signalled, or at least left detectable traces. Yet we see nothing. The Great Filter hypothesis—a phrase the economist Robin Hanson coined in the 1990s—tries to explain this silence by proposing that somewhere along the path from chemistry to starships lies a step so improbable that almost nothing passes it.
Most discussions place that step either very early (life is rare) or very late (civilizations destroy themselves). But there is a transition hiding in plain sight—one usually folded into the broad category we call “intelligence.” It is not intelligence itself. It is not tool use, language, or even culture. Nor is it the first appearance of science-like inquiry. It is something stranger and more fragile: the sustained decision to look outward, to ask questions about things that may offer no immediate survival advantage, and to keep asking them long enough for the answers to accumulate into a durable scientific tradition.
This essay proposes that the successful preservation of outward-directed inquiry across generations—a self-sustaining relay that accumulates observations, models, instruments, and knowledge faster than they are lost —may be one of the rarest steps in the entire cosmic sequence.
The difference between intelligence and curiosity
Earth is full of cleverness. Corvids solve puzzles. Octopuses manipulate objects with eerie precision. Dolphins invent games. Intelligence, in the broad sense, has evolved repeatedly. But cumulative outward-directed inquiry—the kind that leads a species to build durable models of realities beyond its immediate niche—appears much rarer.
A raven can plan several steps ahead, but we have no evidence that it wonders what stars are. A dolphin can understand symbols, but it does not build instruments to examine worlds beyond its own. Intelligence, even sophisticated intelligence, is not enough.
The outward turn is a different kind of trait. It is the moment a lineage stops using the sky as a tool—for navigation, calendars, and omens—and begins interrogating it. It is the moment curiosity turns toward the remote and the abstract: costly, impractical, and directed at things that cannot feed you, shelter you, or help you survive.
Galileo’s telescope did not cause this shift. It revealed it. Grinding a lens to ask whether Jupiter has moons is not a survival behaviour. It is a declaration of intent: we want to know what is out there, even if knowing does nothing for us.
That kind of curiosity is not something natural selection can easily target directly. Evolution is myopic. It rewards traits that help organisms survive and reproduce in particular environments. Curiosity about distant objects with no obvious payoff is more likely to arise as a by-product of cognitive machinery built for mapping danger, opportunity, social life, and time. Such by-products need not be unique. But they are unreliable. They can appear without becoming central to a culture; they can flare without compounding.
A sample of one—and a pattern inside it
We have only one biosphere to study, and that makes every inference precarious. Still, within that single record, the pattern is suggestive. Across billions of species and several independent origins of complex cognition, we have evidence for many kinds of cleverness and for more than one human culture that practised early scientific or astronomical traditions. What appears singular is not inquiry itself, but an unbroken lineage of inquiry that became cumulative, instrument-building, self-correcting, and ultimately capable of leaving its planet.
That does not prove it is improbable. It might simply be suppressed: the first lineage to achieve it monopolizes the niche, preventing others from following. Or perhaps Earth has not had enough time for a second instance.
However, the cultural record tells a more nuanced story—one that shifts the argument from biology to history.
The spark that keeps failing to catch
Humanity did not look outward once. We looked outward many times—and each attempt depended on something more delicate than insight.
Long before formal science, people built temples aligned to the sky. Later, Babylonian astronomers tracked the heavens with astonishing precision. Greek thinkers built geometric models of the cosmos. Chinese imperial astronomers kept continuous records of comets and novae for centuries—though largely in service of the calendar and the court, with the sky read as an instrument of statecraft rather than interrogated for its own sake. Medieval Islamic scholars constructed observatories, critiqued inherited models, and developed mathematical tools that later reappeared in Europe.
These were not minor sparks. They were bright, sustained attempts to understand the sky. Nor were they sealed off from one another: knowledge moved through translation, trade, conquest, correspondence, and inheritance. The story of astronomy is not a set of isolated awakenings, but a long and uneven transmission.
That is the point. The outward turn is not a single step. It is a relay—a chain of observation, mathematics, instrument-making, patronage, teaching, criticism, and memory passed from one generation to the next. A chain can strengthen. It can also break.
Institutions collapse. Dogma intrudes. Political priorities shift. Economic margins shrink. Languages of scholarship are lost or become inaccessible. Instruments decay. A culture may look outward for a century and then turn inward again, leaving its questions unanswered, or answered only in forms that later generations cannot use.
The European scientific tradition of the 17th century was not the first outward turn. It was the one that became self-amplifying: mathematically precise, institutionally protected, technologically useful, and increasingly public. It ran long enough, and continuously enough, to accumulate the observational and technological scaffolding required to leave the planet.
This is where the argument touches decades of work on cumulative cultural evolution—the ratchet effect, a term the psychologist Michael Tomasello coined for the way human culture locks in improvements without slipping backward. Humans, unlike even our closest relatives, do not merely invent; we preserve, copy, correct, recombine, and lock in improvements so that each generation starts from the accumulated position of the last rather than from scratch. No other species on earth ratchets this way, which is why a raven’s cleverness never compounds and a physicist’s does—the capacity the anthropologist Joseph Henrich calls the secret of our success. Science is an extreme, formalized instance of that process: it requires not only minds capable of wonder, but also social systems capable of keeping wonder alive and passing it forward intact.
If this pattern is general, then the rarity may lie less in the spark than in the sustaining. Many worlds may produce sky-watchers. Some may even produce science. Fewer may produce scientific traditions that survive long enough to become physics, engineering, and eventually spaceflight.
The ladder that burns
If the outward turn is a relay rather than a single step, then the relay must survive not only ignorance, dogma, and institutional decay, but success itself. A sustained scientific tradition eventually produces technologies powerful enough to threaten the conditions that allowed that tradition to continue.
This is the ladder that burns. The ladder is not only fuel; it is the whole chain of conditions that lets curiosity become spaceflight—preserved knowledge, industrial capacity, and usable access to orbit, each of which must be sustained in turn. These are not separate filters, but successive tests of the same fragile achievement.
The first test is whether knowledge can survive long enough to become industry. Industrial civilization may require a burst of dense, easily exploited energy to extract materials before it has the wisdom to manage the consequences. On Earth, fossil carbon formed one rung of that ladder: a one-time inheritance accumulated over hundreds of millions of years. It is at least a live hypothesis that industrialization requires access to unusually concentrated energy resources before a civilization possesses the technology needed to exploit more durable alternatives. On Earth, that energy windfall opened a narrow window in which humanity bootstrapped itself from pre-industrial life to radio astronomy, rockets, and planetary-scale measurement.
But an energy rung can be consumed as it is climbed. The same energy source that accelerates industrial capacity can destabilize the climate, exhaust cheap reserves, intensify competition, or weaken the institutions that make cumulative science possible. The danger is that a civilization may acquire planetary power before it has built the habits of restraint, coordination, and long-range reasoning needed to preserve the relay that produced that power in the first place.
The second test is whether industry can survive long enough to support spaceflight. Practical early spaceflight requires concentrated energy: engines, propellants, exhaust, heat, discarded stages, and machines operating near failure. Each launch may leave artefacts behind. Satellites die. Upper stages fragment. Collisions create debris, and that debris raises the chance of still more collisions—the runaway cascade that Donald Kessler and Burton Cour-Palais modelled for NASA in 1978, now known as Kessler syndrome. A world can begin climbing toward space and, through the accumulated residue of its own first attempts, make access to orbit progressively more dangerous.
The third test is whether access to space can be sustained once it becomes possible. It is not enough to invent rockets; a species must preserve the relay long enough to improve them, the industry long enough to build them, and the orbital environment long enough to launch them at all. Each depends on the same cumulative capacities as before: memory, measurement, correction, restraint, and cooperation across generations. If low orbit becomes a minefield before a civilization learns those habits at planetary scale, the path outward may narrow just when it is first opening, as the energy window disappears.
In that sense, the outward turn may be essential not only for discovering the sky, but for surviving the consequences of having discovered it. The same habits that make astronomy possible—modelling unseen systems, trusting abstract evidence, coordinating across generations, and caring about consequences beyond the immediate horizon—are also the habits needed to survive industrial acceleration and keep space usable.
Humanity is inside this window now. We must keep the chain intact at all three levels: knowledge, industry, and orbit. The question is whether the outward gaze can become durable enough—not merely in imagination, but in institutions, energy systems, launch practices, and habits of care—to survive the phase in which space becomes a real destination.
What the silence might mean
The usual readings of the Fermi paradox are grim. Either life is rare, or intelligence destroys itself. But there is a third possibility—speculative, but consistent with the pattern we can actually inspect.
It might be objected — with David Brin’s Principle of Non-Exclusiveness, or what Jason Wright calls the monocultural fallacy — that a filter most civilizations fail explains nothing, since a single exception could colonize the galaxy alone. The objection is decisive against filters of choice, which assume every species settles on the same fate forever; uniform behaviour is not even universal among humans. But two things blunt it here. First, we have no demonstrated case of the turn being made and held — ourselves included, since we are still inside that test rather than through it — so the exception the objection requires may simply not yet exist. And second, more decisively, the window for spaceflight opened late: only after billions of years of stellar enrichment laid down the metals a technological species needs. Even a genuine exception would have to have arisen early enough in that window to have already crossed to us — and we may be not alone so much as early. The early always look out on a silent sky.
The Galaxy may be full of life. Full of intelligence. Full of brief outward glances, and perhaps even repeated beginnings of science. And quiet—because those beginnings almost never become durable civilizations of inquiry.
Civilizations may look outward for a while—a century, a millennium—and then turn inward again, or collapse, or lose the institutional continuity required to sustain the relay. Their astronomies may be bright but brief. Their questions may be asked but not accumulated. Their telescopes may be built but not improved.
From a distance, such civilizations would appear as little more than flickers: a thin smear of radio leakage, a brief industrial glow, and then silence. On that reading, we are not necessarily the one species that looked when others did not. We are simply the one spark, so far as we can see, that may be allowed to continue.
And the work of continuing it—of passing the question to the next mind before we go—may be the rarest and most fragile part of the entire cosmic sequence.
A closing thought
If the outward turn is a relay, not a step, then our task is not merely to keep looking. It is to keep the chain unbroken: the institutions that preserve knowledge, the habits that reward difficult questions, the energy transition that buys time, and the long view that makes any of it matter.
The spark may be common. The chain is not.
And right now, we may be running the stretch where the chain most often breaks.
A note on prior work
The argument of this essay draws on several established bodies of work, named here so that its debts are explicit and its own contribution is clear. The framing of the Great Silence in terms of a Great Filter is Robin Hanson’s (1998). The claim that human culture is distinguished by a cumulative “ratchet” that locks in improvements across generations, rather than slipping back, is Michael Tomasello’s; the broader case that this cumulative cultural transmission, and not raw individual intelligence, is the true source of human capability is Joseph Henrich’s. The runaway orbital-debris cascade invoked in the discussion of sustaining access to space is the syndrome modelled by Donald Kessler and Burton Cour-Palais for NASA in 1978.
What this essay adds to these is the proposal that the sustaining of outward-directed inquiry across generations — the unbroken relay, rather than the first spark — may itself be one of the rarest and most fragile steps in the cosmic sequence, and that the same habits which keep that relay intact are the ones a civilisation needs to survive the industrial and orbital hazards its own success creates.
References
Hanson, R. (1998). The Great Filter — Are We Almost Past It? Working paper, George Mason University.
Henrich, J. (2015). The Secret of Our Success: How Culture Is Driving Human Evolution, Domesticating Our Species, and Making Us Smarter. Princeton University Press.
Kessler, D. J. & Cour-Palais, B. G. (1978). Collision Frequency of Artificial Satellites: The Creation of a Debris Belt. Journal of Geophysical Research 83(A6), 2637–2646.
Tomasello, M. (1999). The Cultural Origins of Human Cognition. Harvard University Press.
In Larry Niven’s Known Space stories, an ongoing plotline is the galactic core going up in a supernova chain reaction, which will eventually sterilize all known planets. The explosion is only discovered because an alien race with a super-hyperdrive was looking for a publicity stunt to show it off. At one point, the human they got to fly to the Core and back argues that curiosity – the seeking of knowledge for its own sake – IS ACTUALLY a survival characteristic, that it leads both to useful discoveries you didn’t know to look for, and learning about existential threats you didn’t know were there. Intelligent species without it either never got off their world of origin, or had some other advantage that compensated.
(He also tied it in to most sapient species being omnivores like humans – Niven was big on biological determinism.)
The “relay” concept is interesting. The early stages were less a relay than a flowering and dying, with teh seeds later picked up for the next leg. The Islamic “science” period lasted over 450 years, about the same length of time our “Scientific Revolution” and modern scientific periods have lasted.
The end of Islamic science seems coincident with the pushing out of Europe of Islamic rule on the Iberian Peninsula, and the failure of Christianity to pick up the reins of science. This was not unlike the demise of Greek “science” with teh ascent of Rome.
Our global civilization may be better able to pass on the science developed by European culture as the nations in the East – Japan and China, have pushed science forward now that science and technology are accepted as drivers of continuing economic growth.
The ability to “look outward” is being threatened by that very growth. You mention the Kess;er Syndrome, which looks like it is getting closer every day. Musk’s SpaceX is intent to increase their satellite assets tenfold to one million. Add competing satellite swarms and space may quickly become inaccessible; even looking through the fragments may make ground-based observations impossible.
Our global failure to deal with global heating may impoverish the global economy and add to the loss of science funding, already being gutted in the USA, which seems intent on exiting the “science relay race”.
However, as you note, we cannot assume a monoculture of all civilizations taking the same path that fails to avert this Great Filter. Furthermore, even if our current civilization fails and there is a long scienceless interregnum, what would stop a future civilization from acquiring the curiosity to pick up all the science we have created, relearn our technologies, and manage to look outward again?
Should the future civilization be post-biological, building a civilization independent of surface conditions and a biosphere, it may be able to breach the debris filling space around Earth and resume space exploration, both observational and with exploration machines. Shouldn’t even one of the other civilizations, if they exist, take a path to avoid the post-industrial Great Filter problems we have created through our own foolishness?
While I hope that there is not a Great Filter ahead of us, I think that the simplest explanation is still the most probable: that we are the first, i.e., early. Life may be ubiquitous, but other advanced technological civilizations either do not exist or are so rare in space and time that we cannot detect them. Let’s try not to bring on a Great Filter upon our heads.
The increase in Elons sats to 1 million is only around a 5km by 5km blocking area, hardly blotting out the sky. But the streaks will be there, not sure if they are darkened or not. Might reduce global warming a little ;-) and maybe reduce fossil fuel consumption over their lifetime.
This article in Science suggests that satellite swarms are unsustainable.Planned satellite megaconstellations could generate runaway space debris
Starlink satellites have a limited bandwidth and are far more expensive than surface technologies. They have a niche role to play, but not a general internet and communication role.
The V3 satellites will have an order of magnitude greater capability according to Musk. Direct to cell service is on the horizon so starlink will likely be much more than a niche role. I do find it hard to believe they will launch over a million. Time will tell
Thank you for the thoughtful comment and for reading so closely.
I think the question turns on what the relay actually is. In the essay I am not arguing that a civilization gets only one chance at science. History suggests the opposite. The relay has already survived multiple breaks. The transmission from Babylonian, Greek and Islamic traditions was neither smooth nor continuous, but neither was it a series of complete restarts.
The harder question is whether the chain can remain intact long enough to carry a civilization all the way to having a durable presence beyond Earth. That is the sense in which I use “relay.” The danger is not that knowledge disappears forever. It is that the process repeatedly breaks before it gets there whether that is a narrow window created by industrialization and access to space or institutional decay.
A future civilization, biological or post-biological, might indeed pick up where we left off. If enough knowledge transferred, it could climb much faster than we did. But that possibility does not eliminate the filter. It merely means the filter may have to be faced more than once with less easy to find resources to bootstrap the transition.
That is also why I think your final point is important. We should be cautious about assuming every civilization follows the same trajectory. My argument is not that failure is inevitable, only that sustaining the outward turn across generations may be rarer than we usually assume.
And, as you say, we may simply be early. If so, the task remains the same: not to become the civilization that drops the baton during the stretch where it matters most.
Sir Martin Rees wrote Our Final Hour: A Scientist’s Warning: How Terror, Error, and Environmental Disaster Threaten Humankind’s Future In This Century—On Earth and Beyond. in which he outlines the possible existential threats to humanity. Whether his suggestions to counter those threats would work, I am doubtful.
It is possible that our global civilization is creating its own potential existential threats as Rees outlines, and because it would be a global end to civilization, it may not be recoverable. There has been a lot of discussion about how far could we fall back with technology and recover. I have read that around 1950-level technology might be possible. Others have suggested that it could be as far back as the 18th century after a collapse.
Whether we could bootstrap our civilization[s] with the stored knowledge we have depends on what happens. A long period of scrabbling might end the desire to recover, as well as the decay of records, both physical and digital. We also know that it takes expertise to successfully manage some technologies, whether it’s how to make certain fabrics or the frontier of microchip manufacture.
However, how we look outward may be restricted by what we know about our biology. Science fiction stories assumed we could freely explore and colonize space. We now know that we are intimately connected to the Earth’s biosphere. This may make ideas of humans settling the solar system untenable. Even space habitats are not fully self-sustaining and require imports from Earth. I can see our technology exploring space, even reaching the nearer stars, but perhaps not sufficiently so that another civilization could recognize that activity.
Is our path inevitable for all civilizations? It seems unlikely to me. Thus the monoculture argument seems valid. Of course, any number of other explanations of the Fermi Paradox could work too. As @John Rumm makes reference to Clarke’s “Childhood’s End”, civilizations may generally become transcendent in some way. But again, would they all go this way, or would there be species like Karellan’s that don’t or can’t?
If we prefer to have a long-lasting run as a species, rather than a James Dean “Live fast and die young” one, would it be so terrible if we managed our presence to be sustainable? It would feel stultifying to us, but not to a population that was steeped in such a culture. Jared Diamond’s “Collapse” indicates that Japan made that transition until disturbed by the arrival of the West’s trading ships. H.G.Wells made his choice clear in “Things to Come”, but is this the choice we should make, or was Japan’s a better long-term, stable model?
Of course, if we discover alien artifacts in our explorations, we will know that at least one other civilization got past the posited Great Filter, at least as far as these artifacts indicate.
Your detection of our current window is accurate, but limited. If our curiosity has already enabled the spread of pandemics, habitat destruction, ozone depletion, nuclear weapons, global warming, the perfection of mass persuasion toward sociopathy, and soon, automated warfare, the Kessler syndrome, and the AI singularity, it seems that the ratchet effect applies to the threat level created by our curiosity as well as the technology level. Who is to say the technology solutions to the next threat we create will arrive in time? It’s still an open question whether the energy transition has done so. The trend at this time is that the threats are outpacing solutions.
This brings back memories of a discussion I had with a guy at Alcor (cryonics) in the late 80’s who said essentially the same thing. He said stagnant bureaucracy was likely the explanation for Fermi’s paradox, then cited India as an example. Humans always have a propensity to create and sustain stagnant bureaucracies.
As is my wont, I’ll offer a discordant note to Ian Brownlie’s essay, which I’ve reread several times, each time coming away dispirited rather than inspired. Perhaps it’s because the irony hasn’t escaped me that it was published on the anniversary of the atomic bombing of Hiroshima 81 years ago, followed only days later by the bombing of Nagasaki. As a historian, it leads me to paraphrase the question Paul asked in introducing Ian’s essay, “Knowing its own history (and proclivities), how should an intelligent species view its place in the universe and thereby engage with other beings?”
Brownlie’s key point is that it isn’t ‘intelligence’ that separates us from other species; instead, he asserts, it’s “the outward turn,” which he defines as “the sustained decision to look outward, to ask questions about things that may offer no immediate survival advantage, and to keep asking them long enough for the answers to accumulate into a durable scientific tradition.” And, although the word itself doesn’t appear in his essay, it’s about progress, the fuel which impels the continuation of what he terms “[the] relay—a chain of observation, mathematics, instrument-making, patronage, teaching, criticism, and memory passed from one generation to the next.”
What interrupts the relay’s functioning? According to Brownlie, it is the antithesis of “the outward turn”: the “inward look”—the things which threaten it, such as “ignorance, dogma, and institutional decay.” Presumably, such an inward look includes entire areas of human intelligence, knowledge and human creativity, ones which Brownlie discounts, or barely mentions, such as art, literature, or philosophy. Perhaps this is because he sees them as offering nothing that contributes to the survivability of the human species; they’re not “the habits needed to survive industrial acceleration and keep space usable.” Only by preserving knowledge, accelerating industrial capacity, and maintaining an “orbital environment,” Brownlie insists, will “the ladder that burns” be sustained. “[T]he same habits which keep that relay intact,” he writes in the closing line of his essay, “are the ones a civilization needs to survive the industrial and orbital hazards its own success creates.”
My take on all this is different. It envisions a spectrum that runs between two words that begin with the same two letters as “human,” namely, “hubris” and “humility.” The one leads to unrestrained confidence, even cockiness and arrogance; the other leads to empathy, compassion, and wisdom.
Two thoughts ran through my mind as I was rereading this essay. One was a moment from our own history, not that long ago—back in the early 1970s. We’d won the Space Race, beating the Soviet Union to the Moon with the Apollo Program. Flushed with that success, Tom Paine and others at NASA began making the case for moving forward quickly with what they viewed as the next step: landing a crew of humans on Mars. Just about everyone expected that President Richard M. Nixon, who’d made a “historic long-distance phone call” to Neil Armstrong and Buzz Aldrin as they stood on the surface of the Moon on July 20-21, 1969, would enthusiastically embrace the idea. Yet Nixon demurred—mindful of the mounting costs, both economic and human, of the Vietnam War, but also heeding a felt need among a large part of the American body politic that greater attention should be paid to addressing a host of social issues: racial unrest, poverty, pollution chief among them. And so, he pulled the plug on the Mars plans. I’m no admirer of Nixon, but I do applaud how, in this instance, it was an “inward look,” at least in part, which prevailed.
The other thought that struck me was the moment in Arthur C. Clarke’s Childhood’s End in which Karellen, leader of the Overlords, holds a press conference to announce the discovery that a human, Jan Rupert, had stowed himself away on one of their starships. Karellen shares a holographic view of a swirling field of stars—our own Milky Way—and asks, rhetorically, whether humans truly believe themselves capable of confronting such a prospect. “It is a bitter thought, but you must face it,” he says. “The planets you may one day possess. But the stars are not for Man.”
Born at the dawn of the Space Age, I’m incredibly grateful to have lived through the decades that followed the late 1950s, in which the Moon and the planets and their satellites and the asteroids became known to us, and in which unimagined vistas of the farthest reaches of the cosmos were opened to us, through astonishing feats of science and engineering and science. And yes, by all means, we should continue furthering our efforts to explore the solar system and the wider universe beyond it. But I hope that the outward look which impels us to do this will be tempered with an inward look that wonders, not only what’s out there, but whether we’re truly prepared to impose ourselves upon it.
In one of his many poems, e.e. cummings famously asked (and I won’t attempt to preserve the line breaks): “everybody happy? WE-WE-WE & to hell with the chappy who doesn’t agree. (if you cant dentham comma bentham; or 1 law for the lions & oxen is science). Q:how numb can an unworld get? A:number.”
Unless coupled with an inward look that privileges humility, I fear a hubristic, unrestrained outward look will lead to that numbing sense of “unworldliness.” And in the end, perhaps it’s that fear—a fear gleaned from an inward look—which constitutes the “Great Filter” for other intelligent life forms that may be out there.
A magnificent comment John. Thank you and thanks to the other contributors for their remarks.
Thank you for reading the essay. This is exactly the tension worth pressing. You’re right that arriving at powerful knowledge before we understand its uses is the danger, and that it is the humanities, broadly, the frontiers of knowledge and craft beyond the engineering, that must grow alongside the science to answer the bigger questions: why are we going, and who are we when we get there? Will we simply become an optimizer, or an outright consumer, on a larger frontier? It also doesn’t absolve us of our duty to care for our own planet and species first.
Expansion of the science domain creates opportunity. This can be used for good or ill, or carry consequences unforeseen even by those who made the discovery in good faith. The same nuclear science gave us Hiroshima and Nagasaki, and gave us energy, medicine, and the instruments that measure our effect on the world. The knowledge was never the danger; the use of it was.
Your example of Nixon is a legitimate inward turn, and it highlights the choices a civilization must make as it juggles its priorities at home. Those come first. But every such turn also adds to the relay’s fragility — and the danger is never the pause itself, only a civilization that loses the ability to resume.
If it turns out that sustaining the Giant Leap, as Armstrong put it, is a cost too great for a civilization to endure, then we can expect a quiet neighbourhood.
Ian, I appreciate your thoughtful reply. I’m in agreement with you on “the bigger questions” that should be asked, and answered—where we’re heading, why we’re heading there, and who we’ll be when we arrive (all of which assumes, of course, that there’s a consensus around what the destination is and how we’ll know it when we’ve reached it).
Yet left lurking in the background of these questions, as you frame them using your analogy of the relay—or that ‘Giant Leap’ of Armstrong’s—is what is perhaps the key pivot point on which everything turns: ‘Who’ asks and answers these questions?
Great leaps can go very well—but they can also end very badly, the most famous example being Chairman Mao’s “Great Leap Forward,” which brought China to the brink of ruin, caused huge famines and profound social dislocations, and led to the deaths of untold millions of people. It was an abject case of what happens when decisions are made under authoritarian regimes with brash expressions of optimism and almost total disregard for consequences.
Decades later, ‘we’—meaning the greater mass of humanity—are largely being kept out of decision-making surrounding another Great Leap, the rush to embrace AI. Opposition to things like the rapid spread of data centers is being dismissed by proponents of AI as anti-progress at its worst. Which means that ‘we’ who may not be so eager to embrace AI face the risk of being run amok, like it or not.
You write, “the danger is never the pause itself, only a civilization that loses the ability to resume.” Or, to borrow from your analogy, once the baton is dropped, the relay race is over for your team. But the fallacy with that line of reasoning, as I see it, is that the outcomes of relay races aren’t subject to, or determined by, votes. ‘Society,’ or ‘the body politic,’ to use my term, doesn’t get the opportunity to weigh in.
You and I can both agree that answering the big questions “doesn’t absolve of our duty to care for our own planet and species first.” But that duty isn’t a relay—it’s a responsibility. And it’s one that very definitely can, and should, be dealt with in the political arena, with courses of action and decisions about policy-making and resource allocation being at stake.
That should hold true, also, for the fraught question of whether ‘we,’ as a planet, can or should move forward and strive for the stars, or turn our efforts instead to preserving the very future of life on this planet we call home. Especially if, as it may turn out, we’re the only sentient, intelligent life forms around at this moment of time in the universe, or among a very few. It would seem, at least to me, to behoove ourselves of the opportunity to pause, no matter how long, to get our house in order, lest we disappear and contribute nothing into the bargain.
Human history alone provides abundant examples of Ian Brownlie’s argument. An old friend of mine liked to say, contrary to the argument that humans are an intelligent species, that we are actually a species of termites with a few intelligent individuals who are disrespected most of the time.
Though this and other articles are inspiring and thought provoking, the responses are as well difficult acts to follow.
In the essay, of course, our own biological, mental and political history are considered and compared with a hypothetical alien intelligence, akin to the “unknown god” depicted in a square in Athens of the Roman Empire era, remarked on by Paul in Acts, citing earlier Greek writers, Epimenides and Aratus. I should stress this is an analog since we are in a position much akin to the Athenians, suspecting the nature of things we cannot as yet see, yet hope to understand anyway.
Here on Earth but engaged in studying the dark night sky, and pre-occupied with the physical and cerebral adventures of homo sapiens as well, one could reflect now and then on the pioneering work of other species, conscious or otherwise. It was millions of years back, but several mammalian species returned to the oceans from the bogs; cetaceans, for example. And it appears to me that they obtained a wider domain. Not one bog, but several oceans through which they have migrated with seasons ploughing the depths for millions of years. Adapted as well. Admittedly they are unlikely to contemplate travel to Mars or the stars, but I think they have larger domains here on “Earth” than most of us. And yet their perspective on things is difficult for us to delve, other than that they want to survive.
We have identified and characterized both solar system worlds and exoplanets, but I would contend that for some hypothetical species that can reason, throwing them a clip board full of interplanetary and interstellar objectives is unreasonable from their likely perspective. It is quite possible that many of the worlds of mass between ours and Neptune’s are oceanic too; and the window to observe the stellar source of energy is more diffuse and less relevant to regular or frontier life. Assuming life is sentient in a spherical depth segment of a Hycean world, the stellar source of heat might be treated like a benevolent light bulb and the real frontier to many “sentients” would be the planetary volume thousands of times larger than the one obtained here; not by us, but by whales.
This is not meant to be entirely frivolous. But rather to better balance the equation invoked when it is asked, “Where is everybody?” Red dwarf suns are much more numerous than suns like our own, so that could cause increased dispersal for aliens grown and adapted more along our expected environmental lines. And the prospects for retaining an atmosphere over eons are better if a planet is more massive than Earth – which has certain pitfalls. E.g., getting out and racing to the moon or another planet.
It could be considered foolish to begin with “because it’s hard’ and less rewarding for the effort.
It has been argued that advanced civilizations could be detected by their adherence to the criteria of the Kardeshev scale, but this also assumes that the LGMs have a compulsion to build the Ford River Rouge Plant on a star system or galactic scale to be rewarded an official Roman numeral. Do we really want to leave a business card at a place like that?
The farther one goes, the number of stars and planets increases to the third power. The distances we ourselves can’t overcome in the near future or maybe even ever, but nonetheless, the odds increase that somebody out there can with some sort of bypass. And we might not be the most interesting place that they can/could visit. Which gives us a breather for the time being to get our affairs in order. Though monitoring radio news that ET might intercept, collectively we could be getting dumber by the day. Should they be optimistic about the outcome of contacting or meeting us?
Plasma gun
https://phys.org/news/2026-08-plasma-gun-technology-space-laundry.html
https://phys.org/news/2026-08-flying-focus-laser-key-limitation.html
Perhaps good for propulsion
https://phys.org/news/2026-08-technology-star.html
This is a comment more for Paul, I suppose. I found the post here difficult to enjoy because it is so riddled by markers of AI-generated prose. Having been exposed to a certain amount of AI prose by now, I find the substitution of the AI’s voice for the author’s–and I presume Ian Brownlie has a more distinct voice than this when he writes his own material–to be too tiresome to allow me to relax and learn what the article has to offer. I see other commenters have enjoyed the article, and I wouldn’t presume to say that my own reaction should be considered more valid than theirs. But I at least wanted to post my disappointment so there is a data point against AI-crafted contributions, if Paul ever wants to consider a policy of asking authors to compose their own prose.
For the record, I started perceiving the AI-isms early on; by halfway through I was sure and couldn’t keep going, and before posting this comment I pasted the article into Pangram, which I generally trust well enough, and it returned a verdict of 100% AI-written.
I hope this comment isn’t perceived as rude. But if no one says anything, everyone will continue to think it’s fine to substitute AI prose for their own voice, and I would regret that happening.
Thank you for this – I found the distinction between intelligence and sustained outward-directed curiosity genuinely interesting.
So, let me see if I understand where this takes us.
First, WE decided what intelligence is.
Then WE decided what an advanced intelligence should do.
And finally WE are astonished that those intelligence do not seem to exist…because they do not behave as WE decided they should.
As you said, we have just one biosphere to study. I would add that we also have just one reference point from which to define what intelligence should like: our own.
I guess the anthtopocentric assumption begins even before we decide what an intelligence should do. It begins when we decide how intelligence should look like.
But, what if a civilization were vastly more advanced than ours?
Why do we assume that it would have any particular interest in contacting us?
Are we searching for intelligence in the universe…or just for a reflection of ourselves?
@Delia
Probably. Also, we search with the tools we have, which naturally rely on certain assumptions about who we are and aspire to.
We once assumed Martians might be very like us, with cities and structures we would make. Because we communicate by radio, we argued that this was teh most effective way to communicate between systems, so we set up radio SETI. When Kardashev levels of civilization were proposed, we looked for Dyson Shells…because that was assumed to be what our mega-engineering projects would want to build. Because we think beamed sails are the best way to manage interstellar travel, we propose looking for beam leakage. Now that we have tools to scan for artificial objects, we start looking for crashed artifacts and lurkers/Bracewell/von Neumann probes.
We don’t bother to look for evidence that civilizations might inevitably become transcendent, because we have no way to search for that. If the most long-lived intelligent species either stay pre-technological or low-tech, they would be invisible to us.
Cetacean-level intelligence has been around a long time. Arguably, recognizably modern whales (toothed and baleen) are at least 10 million years old, and certainly over a 1 mone years, yet would be undetectable on an exoplanet. Humans are nowhere near that old, and city construction and agriculture are probably no more than 15 millennia old. If we self-destruct, our civilized period will be measured in millennia, and our communication period (Drake equation term L) measured in centuries. A mere cosmic “flash in the pan.”
SETI assumes that intelligence, progressing to technology, and then communication, is almost inevitable. Even if true, it may be that this invites a Great Filter to cut its development shortly after some technology level. Only intelligent species that avoid technology development last a long time, but remain invisible. This even avoids the Dark Forest hypothesis. Either species are technological and become briefly visible, or they aren’t and stay invisible. Even if there were aliens wanting to “uplift” intelligent species, they would not bother with the limitations of whales. Each uplift they attempt may be an “experiment” that almost certainly leads to failure and extinction. This would seem to be immoral, and a “Prime Directive” would be in effect to prevent its use.
Alex, perhaps old vocabulary is useful to keep us stuck in old ontologies.
First science and physics is based on necessity. Someone invents a technology that works better or more efficiently or a new invention makes life more easier which does not work without “sparks” or flashes of insight and ideas. All of today’s technology is based on the physics we learned in the past. Curiosity is intelligence and observations are limited to the knowledge of the observer which is why we know much more about the physical world and cosmos today than five hundred years ago. I like the idea of filters and contingencies and we know there are a lot of them that must be met if we use our planet as a model. The great filter idea has a too pessimistic view of the evolution of humanity and intelligent life because it lacks a knowledge of genetics and biology. It assumes that the complexity of our DNA is too improbable and therefore it is the same with all other worlds. I disagree with the great filter idea on this basis. I think it is the exact opposite. Once we have all the contingencies met, I think the probability of DNA based life evolving is one hundred percent not improbable as the great filter idea assumes. The same is true about intelligent life when the conditions are met. Our DNA has a complexity that at one point in life’s evolution where it does not need any transmission since it already has variation and selection and mutation built into it so it’s nature with nurture and not one without the other. Our DNA is designed to adapt to all environments within the range limits of survival of the DNA chemistry which is known physics. The one hundred percent probability that DNA based life will evolve if Earth’s environmental conditions are met is an axiom which will become fact if we find any life on planets in our solar system like Mars because it is harder for life to evolve there.
I also don’t agree with the idea that space travel is too hard so ET’s can only visit another solar system once it it’s lifetime. This is only true about our civilization which is limited to sub light interstellar travel, but not FTL. It is a viewpoint at best limited to the technology we have today and the past. I agree with the idea of the ET invisibility but for different reasons: ET’s with an FTL Alcubierre warp drive with interstellar travel which are much more advanced than us can’t be seen approaching or leaving during FTL and even just in orbit around the Earth. They could hide anywhere out of site in Earth’s shadow and stay there for a long time and we never know or between the Earth and the Moon. Just because we don’t hear any radio signals does not mean there is not anything out there. Intelligent ET’s don’t have to send us any radio signals, but just watch us which is more benign. I’d like to to see some money invested searching with infra red telescope and infra red lasers or even LIDAR. We might just think that we are the greatest power in the universe, so any such search is considered a waste of time because there could not possibly be anything out there more advanced than us. Since such a search would be expensive, money might be better invested telescopes, interplanetary probes, etc.
I think Delia got it right.
It is a lot easier to develop technologies that are potentially capable of getting out of control than it is to develop the wisdom to manage our technologies so we (and the rest of the biosphere) are not threatened by that same knowledge. I think we have stumbled onto the Great Filter. Perhaps Dr Fermi realized this too, after all, look at what he was working on when he proposed his Paradox. Remember Forbidden Planet? Perhaps WE are the Krell.
I initially wrote a much longer comment with essentially the same message, but the system hiccupped and it was erased before I could submit it. My apologies if it appears later.
I’m in line with what Delia, Alex and Henry have expressed, but I’d add that we don’t simply “reflect” ourselves—we project our aspirations and allow them to become operative. Along the lines of Abraham Maslow’s famous adage about the only tool in your box being a hammer, we’re predisposed to think as humans, and so we envision futuristic technologies to indicate how *we* would solve a given problem—such as imagining using Dyson spheres to capture a star’s energy output . . . . Which is fine, so far as the concept goes, but then we persuade ourselves that this *must be* how other intelligent life forms have learned to solve such problems, and begin looking for technosignatures to prove the concept.
Is it possible for us to really free ourselves of our human biases and truly envision the cosmos through utterly alien senses? Perhaps, but only with great difficulty. In a famous essay, ecologist Aldo Leopold urged “thinking like a mountain,” meaning freeing oneself of human-centered perspectives and adopting a holistic one that, with humility, views everything as interconnected and operating without us. It’s yet another expression of that “inner look.” Yet unless and until we’re able to “think like an alien,” the very alien-ness of their intelligence, the nature of their technologies, and their view of *their* place in the cosmos will elude us.
I wonder if beavers would look for intelligence by observing whether lakes on exoplanets were formed by rivers being dammed with lodges? Would alien “beavers” marvel at the Grand Coulee or Hoover dams as being advanced technology (using materials superior in strength to tree wood) and obviously built by intelligent, terrestrial beavers, but be puzzled by the lack of obvious living quarters in the structures?
Would a long-lived alien civilization wonder why we keep growing our presence, as this is clearly unsustainable? Even modest economic growth would make us a Kardashev II civilization within a few millennia. The speed of light would restrict the growth to a much lower level to reach a K-III level. Perhaps they might infer that our increasingly destructive wars are necessary to destroy people and stuff to allow growth to continue from a reduced starting point, a cyclical method to sustain the high [1-5%] growth model with frequent resets?
It is interesting that mass extinctions are required to shake up the terrestrial ecosystems to facilitate the emergence of new forms of life. Each mass die-off removes established forms, often those that have attained very large sizes, allowing other species with different phenotypes to radiate into a new species to occupy the niches that were “abandoned”. Mass extinctions seem to allow rapid radiation of forms again, which were suppressed by the previous forms. So we see biodiversity take on cyclical patterns, each time changing the mix of forms that are the base that radiate to provide the rapid growth of biodiversity. Thus, biodiversity growth rate averages are higher than if no mass extinctions occurred. On a smaller scale. geographic changes also create species radiation opportunities, such as island formation, continent breakup via plate tectonics, etc. We are causing the 6th mass extinction. What might the Earth’s biosphere look like in a million years? If we were able to build enormous space habitats on the O’Neill model, what might rapid species evolution occur in response to the limited species brought to the habitats and the exacerbating effects of higher radiation exposure from solar and cosmic ray particles, especially if humans disappear for some reason? Rather than try to recreate species that go extinct due to our destructive natures, what might we do with advanced genetic tinkering or engineering? Our baseline dominant species are those we have developed by artificial selection over millennia. They would surely evolve new species over time. However, our direct genetic manipulation might jump-start and accelerate that evolution into new forms. An artificial, rather than natural, growth rate of biodiversity.
Thank you for raising this. You have defined the observer problem. This is related to a phenomenon well known in control systems which is my field. The devices added to measure the control system add an effect to the system itself. To truly stand outside any framework you need to be outside of the known Universe, which then gives no sensible means of measurement. No one can be an unbiased observer and operate inside the system being observed. Control systems with feedback loops are essentially a parallel to behaviors of complex systems that govern biology, the environment and even social systems like economics and negotiating. Which may be your answer. With no vantage outside ourselves, we cannot help but search, in part, for our own reflection.
We are a space faring intelligence. Our existence insists on the category “space faring intelligence”. This relationship is no different than that between us and the category “mammal”. When predicting where we sit within the category of either SFI or mammal we have three main choices
1. The distribution is shaped exactly like us.
2. The distribution is larger than us and we are an outlier. We are a platypus.
3. The distribution is larger than us and we are an average example. We are hairy, give live birth, produce milk.
The prediction that we are representative of the average mammal or SFI is the most humble and most scientifically and statistically rigorous. Unfortunately, exploring choice 3 looks like hubris because it looks like we are growing the distribution from us.
Migratory birds raised in captivity need to be taught how to migrate. Orca ecotypes are maintained by relaying hunting strategies and have lasted for at least 100,00 years. Relays, as a category, are not unique to humans. Curiosity is everywhere in nature and everyone uses it the same way; without knowing if the result of curiosity is harmful, benign, or helpful. The fact that humans are curious without knowledge of value doesn’t make them special. That’s just the only way to use curiosity. It was impossible to know that GLP-1 drugs would result from being curious about gila monsters.
Obviously our relay bandwidth and the effectiveness of our curiosity dwarfs that of other species. My point is that we don’t need a new category of trait to explain the potential rarity for space faring intelligence. Requiring a collection of traits all past a high threshold for productivity and each with a deep evolutionary history, is conceptually stronger than requiring a highly productive trait without an evolutionary history.
A K3 galaxy, Kipping’s 100 quadrillion systems devoured by runaway self-replication, Hanson’s Grabbies, etc are all monocultures. Have we ever seen a model use non-exclusivity to defend the concept of space faring intelligence that doesn’t then use the absence of a monoculture to demonstrate the improbability of other SFI besides us. Hopefully, the following analogy makes my point clear.
Let’s play a variation of poker. The ranking of hands remains the same but the mechanisms for dealing hands will vary. There are any number of players playing for the same pot with the winning hand taking the pot. To accommodate any number of players, every player has a full deck. Card type maps to traits for body plan and mode of living.
Scenario 1. Players only know how to shuffle and deal, they are not SFI.
Players shuffle their deck and deal themselves five cards. This produces variation directly proportional to the number of players. The probability that the winning hand is a royal, straight flush is also directly proportional to the number of players.
Scenario 2. Players understand the rules of poker and can deal themselves any hand, they are SFI
If SFI possess rational self interest, we will see a monoculture of royal straight flushes. The ability to understand the game’s mechanics and choose the best option creates the monoculture.
All of our supposedly influential models assume that conceptualizing a hand warrants the prediction that we will see unlimited demand for the hand. This is absurd. They don’t force us to choose option one or two.
This is an impressive and important piece, with several impressive comments. I’m glad it’s opened C-D to discussion of things like our present ruling foolishness and the harm that a break in more or less sensible behavior, especially at the wrong time, can do to our prospects.
We need a lot more people to think well and vote well. Then we need lots of people to be willing to bear the hard, expensive work of getting us back on track. I wish us luck.
I would agree this has been a valuable discussion to ponder. I would only add that we should consider the shifts between outward and inward looking as cyclical over millennia. Nature prefers spirals over straight lines. It may be that outward expansion reverses itself based on this frequency of oscillation, with the outward bound set by the frequency and the applicable natural constraints (‘c’ or other cosmological limits).
Ian Brownlie has written a thoughtful post that I can’t get out of my mind. But relaxing in Vermont’s Northeast Kingdom for two weeks allowed it to ferment properly like a good Heady Topper beer!
First, I was surprised that no one’s comments mentioned Asimov’s Foundation series. Is it not the ultimate “ratcheting” storyline? Aldrin’s “Encounter with Tiber” approaches the thought within a museum of sorts. I’m sure CD’s sci-fi cognoscenti have other titles to suggest.
Anyway, I think Intelligence and curiosity differ less than Ian posited and that the combination actually results in play, or if you will, experimentation. Furthermore, I argue that the missing ingredient is the ability for a creature to recognize that an event or result it observes or partakes in while “playing around,” is part of a larger puzzle.
Thus, I propose to add a third necessary characteristic, that of PATTERN RECOGNITION. Biology and technology, thus civilizations, run on patterns: the tides, the days and seasons, cosmic cycles, a clock ticking.
Humans, seemingly alone on Earth, put the patterns to work, and on finding them useful, figured out a way to record, enhance, and perpetuate their utility. Regardless of a creature’s sensorium or type of consciousness, recognition of patterns is fundamental to their survival.
How does the three-legged stool of Intelligence, Curiosity, and Pattern Recognition relate to the so-called Great Silence? One has to agree that the “outward look” Ian posits still needs to be ACTED ON. But there may be circumstances on a majority of planets or moons that make action, especially space flight, difficult.
For instance a civilization on a rocky planet of 10 Earth masses has a gravity 2 to 2.5 times Earth’s gravity which is near the edge of viable chemically-based rocket launches according to Wikipedia. Or an iced-over water world would likely inhibit metallurgy for machines and things like radio telescopes. Or a planet with no plate tectonics would have fewer resources readily available for industry to develop.
However, these may be negative anthropological biases on my part; that is to say, other creatures may be clever enough to overcome any limitation we can think of.
In conclusion, if the proposed universality of pattern recognition across conscious species is acted on, it seems to be either a rare, or cryptic behavior.
It doesn’t take a filter if no one is, or has, played the game at the same time as we are capable of being dealt in.
Thanks for this post. A couple of things I’ll point out:
– Competition, driven by fossil fuels or any other cause, isn’t a barrier to spaceflight. On the contrary, the Space Race literally began as a competition between two different superpowers.
– Kessler syndrome is a potential problem, but also one that can be counteracted (https://www.sciencedirect.com/science/article/pii/S2666188825004149), and unlikely to be a permanent barrier to spaceflight
Nice design criteria for station design
https://hecia.space/
I’m going to side with David Jernigan here. The past decade or two tempts me to define technology as “that which gives those who have it power over those who do not”. As technology grows ever more advanced, the amount of power in the hands of one fallible person increases, to the point of nerve agents, nuclear war, engineered smallpox and beyond. And those hands, far from being the best of us, are chosen most often from the very worst – Putins and Kims – because those are the best at seizing such power.
We can explore a similar idea that can be evaluated as numerical gradation rather than probability: pollution. In a long session with Google AI (which failed to make a share link for some reason), the AI was citing figures in terms of 1.3 years of the Earth’s total electrical power production to clean up a few classes of pollutants – but far more if CO2 is considered. This is based on empirically observed inefficiency, but fundamentally on the thermodynamic consideration that a varied mixture of chemicals has a lower free energy (higher entropy) than the natural distribution. I don’t claim that it or I have done close to a decent analysis of the point, but I think the machine was right when it suggested that without a source of limitless clean energy, the cleanup simply can’t be done. (This is despite the amount of money going into “Direct Air Capture” of CO2, which is worse than useless, the physical answer to the question of what would happen if the Devil made a tree)
I’m thinking that until we can more clearly recognize why the self-destruction of intelligent life on Earth is inevitable at the philosophical level, we won’t even have an idea how to slow it down.
This reply is a week late, but I doubt that pollution cleanup is actually impossible. Did that analysis take into account removal of pollutants by nature? Obviously, photosynthesising organisms remove CO2, but other pollutants can be removed as well, such as particulate matter by plants: https://www.sciencedirect.com/science/article/pii/S0048969721023810
@Fish on Land
We don’t know which pollutants can and cannot be handled by nature, nor how long it would take. For example, the vast majority of plastics cannot be digested by bacteria…yet. Of the few that can, it is a very slow process that cannot keep up with production. If it could scale up to meet production, those digestible plastics would become useless.
CO2 can be handled by nature, but we produce more than can be fixed, so it goes into storage in the oceans, acidifying them. Eventually, nature will correct the imbalance after we stop overloading the biosphere, but that takes a very long time and will happen after we have changed ecosystems, just as happened after major extinction events. For example, the Paleocene–Eocene Thermal Maximum (PETM), 56 mya, lasted 200k years.
The time scales are so long that humans 1.0 may go extinct in the meantime, hardly the situation we want. (H. sapiens sapiens (after the cultural explosion) have been around for less than 100K years. Will we still be around as we are in another 100K years?)
“the vast majority of plastics cannot be digested by bacteria” This part is untrue, as shown by the results obtained by searching “organisms that digest X”, with X being polyethylene, polypropylene, PVC, PET or other types of common plastics. The part about them being slow is true, admittedly.
And something which I hadn’t mentioned in my previous comment, but which is also a counterargument to what Mike said, is that artificial methods of dealing with pollutants needn’t always consume energy. Using the example of plastics again, these are routinely incinerated in countries like Japan, thus generating energy instead of consuming it.
Humans 1.0 not being around in timescales of hundreds of thousands of years is inevitable, rather than something to worry about.
The essay is compelling and to me, formalizes a line of reasoning regarding how durable, communicative intelligence and technology scaffolding carries an organic species into becoming a space faring organic species. But in my mind I don’t see tests 2 & 3 as being germane to the concept of communicating with ETI. Since the start of radio and tv, we have been broadcasting into space and it’s possible that ETI in the appx 100 light year radius of earth have heard us. The questions are — have they heard us, do they plan on responding and lastly will we have the technology to detect an incoming message? These questions and our ability to recognize and comprehend messages directed to earth by ETI are not dependent upon us becoming a space faring species.