He was a small man with conspicuous shadows under his eyes. Years of calculation had saturated him deeply in the habit of counting and inference. Those years gave him a seeming magical gift: he could accurately estimate almost anything.
No matter how impossible or strange the idea, he could calculate something useful about it. The most complex things were broken down into a network of more tractable elements. Then, nearly instantaneously, he could put it all back together again into a coherent estimate.
He could measure what most could scarcely describe.
The summer of 1950 was particularly fateful for him and his gift for calculation.
Five years earlier marked the end of a conflict that had killed seventy five million people. That year, he would be instrumental in the creation of the most devastating weapon in human history. Less than five years later he would himself be dead.
1950 seemed to be the hinge of history. The world was still numb from the war and gradually convincing itself that it wasn't intensely traumatized. But how could it not have been?
The megadeath of the preceding years had searingly demonstrated the cost of planetary war. The advent of nuclear weapons had raised the stakes yet higher. The prospect that all future generations could be destroyed could make even the horrific loss of the war seem small.
The specter of recent mass tragedy and the risk of pending doom incubated profound cultural anxiety. The top grossing movie of 1950 was Cecil B. DeMille's Samson and Delilah. The trailer promised "the most spectacular scene of destruction ever filmed...shattering thrills, earth shaking excitement, savage drama!"
Indeed, audiences witnessed in stunning color as Sampson demolished the Temple of Dagon – pagan laughter giving way to apocalyptic panic:
The salience of the scene is not just its depiction of destruction and violence. The world has known plenty of tragedy and violence.
The film hinges instead on the surprise – at the moment when the crowd realizes that they misunderstood what was possible. After the first crack forms in the pillar, a low but eerie rumble resonates throughout the crowd. The destruction creates the drama, but it is shock that creates the horror.
Physical expectations about destructiveness had recently been upset. Certainly, no one was laughing in 1945 before the first atomic weapons were deployed. All the same, the catastrophe indicated a crack in the pillar of the world. An impossible thing had happened: one bomb murdered a city. What would happen next? Would the temple come down?
The small and clever man had played a decisive role in cracking the pillar. He had his reasons. He had fled his home country in 1938 when racial laws targeted his Jewish wife. In many respects, the world had already been sundered by the rise of vicious, virulent ethno-nationalism.
Creating a megaweapon has its psychological costs. Even if it is to end a war. Even if it is to protect your wife and your family. Even if you can hide behind the numbers. In some ways, especially when you are familiar with the math.
There is a peculiar relationship between trauma and mathematics. Both have a way of invading dreams. Both involve a repetitious effort of the conscious mind to penetrate a problem; sometimes finite and solvable, sometimes not. Calculation can be a way to hide, to be sure, but it is also a way to cope.
For instance: what does it really mean for seventy five million people to die? At first the number is too large. It is subtly substituted by a vague impression of a Number of Large Magnitude.
Fifty million might just as easily be called a huge number as seventy five million. Yet, it is half again more. And in the calculus of human life, everything you've ever felt and experienced would amount to the addition of just one more to that number.
If the clever and tired man had a dream that combined counting and trauma, it might have relied on his preternatural gift for converting sterile numbers into something visceral. A Number of Large Magnitude cannot stand in for human life.
Instead, imagine a dream of the most desolate place you know.
Running across this place, perhaps a forest or a meadow, is a chain of human shadows. They are holding hands. They proceed in a straight line towards the horizon, and recede behind you, as far as you can see.
If this line of shadows is seventy five million people long, the clever man would know in a flash that they could cross the continental United States eight times over in an unbroken chain.
In such an Asphodelian dream, the man would know that he had a measure of responsibility for at least two hundred thousand people. Not coincidentally, this number is an appreciable percentage of the population of two cities.
Tired and clever eyes had seen miracles and nightmares dance together; he had applied his incredible gifts to the creation of an entirely new epoch.
We'll pause here a little longer. The image of the chain of shadows gives some scale to the enormity of the loss, but it can't speak in the voice of the survivors. Fortunately, records exist of their voices. It is our responsibility to listen, and to be seared ourselves by the listening.
The truly excellent At The Brink podcast presented an interview with two survivors of the Hiroshima bombing. Here is an excerpt of their account, and you should listen to it:
One World or None
Within just a year of the first bombs, the scientific community could not entirely contain its disgust and its dread. A shattered planet made sense of what might come next, and the scientific community could see much, much further than most.
Here is a film some of them made in 1946, in which they declared that there must be a global awakening – a recognition of a stark choice:
There will be one world united, or there will be none.
Our clever man – most readers will recognize by now that he is Enrico Fermi – did not initially share their views.
Despite the concern voiced as early as 1946, the nuclear arms race continued, eventually giving rise to a debate about the construction of the hydrogen bomb, referred to at the time as the "super."
By October of 1949, just before his fateful summer, his views began to evolve. He co-wrote an opinion with physicist Isador Rabi urging against the development of the "super":
Necessarily such a weapon goes far beyond any military objective and enters the range of very great natural catastrophes. By its very nature it cannot be confined to a military objective but becomes a weapon which in practical effect is almost one of genocide.
The fact that no limits exist to the destructiveness of this weapon makes its very existence and the knowledge of its construction a danger to humanity as a whole. It is necessarily an evil thing considered in any light.
Despite their warnings, by January 1950 President Truman ordered an emergency program to rapidly develop the hydrogen bomb.
That same month, physicist Klaus Fuchs confessed to spying on behalf of the Soviet Union. It could only be inferred that the Soviets knew, in detail, American ideas about the "super." The weapon, the very idea of which constituted an existential danger to humanity, was exposed.
Then, in late June of 1950, North Korea launched a surprise attack on South Korea, igniting the Korean war. The world was emphatically not as one at the hinge of history. As scientists warned, would it soon be nothing at all?
Fermi knew he would play a role in the answer. Against his own advice, and knowing he was designing a "necessarily evil thing," he returned to Los Alamos that summer. This time it was to set his calculations towards the creation of a weapon to end all weapons and the possible extinction of the species.
The Menace of Things Once Seen Indifferently
Making a world-destroying weapon or not, everyone has to eat.
On the way to lunch one day, Fermi struck up a conversation with colleagues and eminent physicists in their own right, Edward Teller, Herbert York and Emil Konopinski. The conversation started with UFOs.
The subject had grown in popularity since 1947, apparently in tandem with apocalyptic preoccupations. Earlier in 1950, the small, nearby town of Farmington, New Mexico, had reported a mass sighting of bizarre objects flying over head. Though little remembered today, the incident was widely covered by the regional press. The event happened only some 120 miles from Los Alamos. The national press of had of course covered the larger "saucer craze" with some breathlessness.
With his gift – perhaps a compulsion – to estimate and to wager, Fermi asked Edward Teller what he thought the odds of detecting an object exceeding the speed of light in the next ten years. Teller claimed they were something like 10^-6 (i.e. tiny) – Fermi quibbled, saying they were more like 10%. Teller later recounted that this was a typical provocation from Fermi – colleagues knew 10% to be the measure of a "Fermi Miracle."
A rapid and lively exchange ensued, with numbers flying in the fray. At some point in the conversation, Konopinski mentioned a cartoon in the New Yorker poking fun at the topic.
Teller recalls that "flying saucers" as such were really only a stimulus to discuss superluminal flight. In Teller's estimation it was "obvious...that the flying saucers aren't real."
The context of the conversation was wisely captured from the participants by Dr. Eric M. Jones. Jones collected a series of letters from all of the participants that are well worth reading. You can find them at the bottom of this post in Appendix A.
Though the context for the discussion about flying saucers appears to have been lighthearted and perhaps even playful, contemporary intellectuals like Loren Eiseley detected a deeper anxiety about them in the cultural milieu:
Today, as never before, the sky is menacing. Things seen indifferently last century by the wandering lamp-lighter now trouble a generation that has grown up to the wail of air-raid sirens and the ominous expectation that the roof may fall at any moment. Even in daytime, reflected light on a floating dandelion seed, or a spider riding a wisp of gossamer in the sun's eye, can bring excited questions from the novice unused to estimating the distance or nature of aerial objects.
Since we now talk, write, and dream endlessly of space rockets, it is no surprise that this thinking yields the obverse of the coin: that the rocket or its equivalent may have come first to us from somewhere "outside." As a youth, I may as well confess, I waited expectantly for it to happen. So deep is the conviction that there must be life out there beyond the dark, one thinks that if they are more advanced than ourselves they may come across space at any moment, perhaps in our generation. Later, contemplating the infinity of time, one wonders if perchance their messages came long ago, hurtling into the swamp muck of the steaming coal forests, the bright projectile clambered over by hissing reptiles, and the delicate instruments running mindlessly down with no report. - Loren Eiseley, The Immense Journey, 1957
In these two short paragraphs Eiseley diagnoses vital shifts in the post-war period. The first was the experience of growing up "to the wail of air-raid sirens and the ominous expectation that the roof may fall." The sky was no longer exclusively the domain of pleasant daydreams; it could bring rapid death. The mere glint of a passing dandelion seed would be enough to provoke fear in the consciousness of the survivor of planetary war.
Further, he writes about the "obverse" of burgeoning space exploration: the idea that we might be visited ourselves. He goes on to write:
Sometimes when young, and fossil hunting in the western Badlands, I had thought it might yet be found, corroding and long dead, in the Tertiary sod that was once green under the rumbling feet of titanotheres. Surely, in the infinite wastes of time, in the lapse of suns and wane of systems, the passage, if it were possible, would have been achieved. But the bright projectile has not been found and now, in sobering middle age, I have long since ceased to look. Moreover, the present theory of the expanding universe has made time, as we know it, no longer infinite. If the entire universe was created in a single explosive instant a few billion years ago, there has not been a sufficient period for all things to occur even behind the star shoals of the outer galaxies. In the light of this fact it is now just conceivable that there may be nowhere in space a mind superior to our own. -Loren Eiseley, The Immense Journey, 1957
Here, we see Eiseley playing with titanic forces: the promise of "infinite wastes of time" contrasted with the recognition that time is not actually infinite – merely very long. It has not been long enough for all things to occur, and so Eiseley, in "sobering middle age" had ceased to wait expectantly for the visitor.
All of these themes would have been background of the Fermi conversation: the menace from the sky, an awareness of the expanses of time, and of course the possibility of the "obverse" rocket – the visitor from above.
According to the participants, the initial conversation ran its course and moved on to more banal topics. Considerable time passed. Fermi quietly mulled the measure of potential "miracles" – weighing in his unique way the "infinite wastes of time" and the likelihood of an obverse rocket.
Seemingly from nowhere, Fermi finished his calculations and pointedly asked "Where is everybody?"
Teller would later describe it as an uncanny moment. Despite the initial topic being abandoned, everyone at the table knew at once that Fermi had meant extraterrestrials.
He wasn't the first to ask the question, and he wasn't the first to do it in the context of oblivion.
The Sense of an End or the End of Sense?
Thinking about the potential extinction of humanity and the existence of intelligence in the cosmos has been intricately linked for centuries. Thomas Moynihan's brilliant X-Risk is an intellectual history of philosophical and scientific thinking about existential threats to the species.
Moynihan argues that humans have only recently been able to think systematically about extinction. Many of our earlier systems of thought were anchored in moral and theological notions that precluded the permanent destruction of sentience:
The belief that the cosmos is inherently moral in structure leads to the belief that it is inherently rational in structure, or that it accords with what we think of as reasonable and justified...[I]t projects onto independent nature our deeply intuitive belief that everything that exists is somehow, without any further qualification, in itself morally good, and has a reason to be as it is.
Though certainly Western societies conceived (and sometimes obsessed) about the Apocalypse, this is in stark distinction to a true conception of extinction.
Moynihan draws the distinction this way. An apocalypse is always fundamentally about a grand cosmic ending – it is the sense of an end of the story of creation. Instead, extinction is the end of sense and of meaning itself.
To be sure, ancients and pre-moderns did not struggle with the concept of disaster. However, they could not escape the notion that humanity, or at least sentience, would either be renewed or be continued elsewhere in the universe.
For example, in Timaeus Plato claimed that "the human race has often been destroyed in various ways - as it will be in the future, too." Further, he described "periodic destruction at long intervals of the surface of the earth by massive conflagrations." In turn, Aristotle described how “each art and science has often been developed as far as possible and has again perished...infinitely often."
In essence, humanity was like a phoenix – forever caught in a cycle of forgetting and remembering, making and unmaking. However transient any moment on the wheel of fate might be, the wheel itself endures unbroken and unbreakable. Exaltation and destruction alike were only temporary in a broader, infinite view of history.
The idea survived and evolved over centuries, in different modifications and guises. The French thinker Diderot imagined the extinction of humanity in the 18th century, followed by a lengthy replay of evolution back to human form:
At first, there will appear, I don't know what; and then another; and then, after several hundreds of million years of I-don't-know-whats, the biped animal who goes by the name of Man!
Monotheistic interpretations further layered moral expectations on the physical universe. Moynihan highlights the arguments of thinkers like Aquinas that the universe must be good because God is good:
Given the things which actually exist, the universe cannot be better, for the order which God has established in things, and in which the good of the universe consists, most befits things
Add to that Leibniz's cosmic rejoinder that "there is nothing fallow, nothing sterile, nothing dead in the universe," and one comes very close to a modern sentiment:
Fittingly, it is the character of Palmer Joss, a Christian philosopher, who comments that if there is no other intelligent life it would be "an awful waste of space."
This raises the question: who is "wasting" the space? Why should a human aesthetic or moral preference – the avoidance of waste – have anything to do with the physical order of the cosmos?
Moynihan points out that the idea is far older than Sagan speaking through Palmer Joss. In 1775, geologist Georges Buffon wrote:
Is it not more worthy to suppose that there everywhere exist [rational] beings, than to suppose the whole universe depopulated apart from the Earth, to despoil it of all beings and reduce it to a profound solitude, in which we should only find a desert of empty space, and frightful masses of inanimate matter?
Before him, Benoît de Maillet wrote in 1727:
Whatever may be the fate of this Earth and its inhabitants, there are reasons to believe that in the great multitude of globes contained in space there will always be other terrestrial globes besides ours which are inhabited by as many generations of men and animals.
In quotation after quotation, Moynihan demonstrates the recurrence of these twin ideas: God is too good and efficient for space to be empty, and human sentience (or something very much like it) will always return. Even if the human light goes out, someone somewhere else will endure. To think otherwise is simply too sad.
Empirical observation has nearly always served to complicate such simple moral narratives. The facts of existence are messy; they don't seem to care much for human sensibility.
Often, moral narrative has had a way of commingling with scientific or at least philosophical expectations. Before humanity had the capacity to meaningfully observe the cosmos, at least in European societies, there was an expectation that the universe is a well-ordered and tidy place. Such tidiness befits a careful, rational and ultimately good God. The Ptolemaic system is one prominent example of these ideas applied to cosmology:
However, a series of astronomical discoveries disrupted these certainties. Arguably, the discovery of sun spots was the first truly disquieting complication.
Although several others had observed sun spots, Galileo Galilei was among the first to widely publish the fact that the sun was not perfect – it had blemishes. The finding led him to remark on the possibility of a cosmic "corruption," as Moynihan recounts. Indeed, Leibniz would later admit that sunspots might eventually predict the darkening of our own sun, despite his conviction that nothing is "dead in the universe."
However, it is difficult to avoid the obvious implication. If the sun is subject to the same "corruption" – that is, fundamental impermanence – as everything else, then why should the Earth or humanity be eternal? If the sun is not immortal, how could the earth possibly be?
In the march of decades and centuries, the facts got messier.
Above, Plato and Aristotle described a never ending human cycle of civilization and knowledge. Others extended the idea to imagine that there would be countless layers of lost cities and technology underground (an idea that is not yet entirely dead, despite the evidence.) The idea was understandable from a medieval worldview, where the rediscovery of classic texts had involved finding sophisticated ideas in the ruins.
Simultaneously, others matched Leibniz's and Buffon's concept of the centrality of life in the cosmos. Indeed, Charles Darwin's grandfather, Erasmus Darwin, argued in 1791 that "it wasn't the planet that generates life, but life that generates the planet." He imagined that the Earth began as a clump of microscopic animals that over eons excreted rocks and eventually everything we know as the planet. Centuries before Lovelock's Gaia, Erasmus Darwin conceived of the planet as a mega-organism.
Beautiful and poignant as these ideas are – life creates the planets, and great knowledge awaits us in the depths – they were all dashed by advances of geoscience in the late 18th century. To be sure, there were intriguing archaeological ruins, but there was no record of cycles of high and low technology. For the most part, the earth just consisted of sterile rock.
The early 19th century raised even greater uncertainties. Heinrich Wilhelm Matthias Olbers hypothesized that the Mars-Jupiter asteroid belt was the shattered carcass of a destroyed planet he called Phaeton. He discovered Vesta, a massive asteroid, floating in the void.
Far from the pristine, geometric beauty of the dance of the spheres, humanity was discovering that the cradle of life was an outpost in a mass planetary graveyard. The poets, as they often tend to do, internalized the news quickly. Byron wrote of:
The burning wreck of a demolish'd world
A wandering hell in eternal space
In short order, the expectation for a tidy universe had collapsed. The sun would not live forever; the Earth was not infinitely old and is mostly just rock. The solar system was teeming with floating shrapnel of ancient catastrophes.
To depict the difference in cultural views, Moynihan contrasts a 1493 woodcut depicting the Ptolemaic Universe and Victor Hugo's 1854 Planète:
In one, we see a perfectly ordered and even crowded cosmos. In the other, an inky, lonely expanse.
The repeated upset of nature's fact to moral expectation was beginning to teach philosophers that anthropomorphic conceits were in fact naive. By 1843, German philosopher Freidrich Wilhelm Joseph von Schelling lingers on the problem of naivete:
[It was] naive for an earlier age of man to believe that the unite universe was constructed for the good and benefit of man, it is no less naive for our later time, to which a larger view of the cosmos is available, to go on presuming that humanoid beings are found everywhere and are the ultimate purpose
The key lessons had been to be cautious with notions of infinity and immortality. The Greeks thought in terms of an infinite Phoenix-like cycle. Theologians had pictured an infinitely good and powerful God. The combination of the infinity of space, time and benevolence meant that sentience could never die and could not be alone. But as the years progressed and the data came in, the facts spoke to something else: the precariousness and youth of the species.
From the Hermit Rocket Scientist to the 'Order of the Dolphin': Moral Answers to a Probabilistic Conundrum
So far we have seen that the question of extraterrestrial life has been intimately tied to other profound questions: the intrinsic moral structure of the universe and prospects for the fate of our species and of sentience itself, to name a few.
When Fermi asked "where is everybody" he was asking a new kind of question (although not entirely new, as we'll see shortly.) He was not asking from Palmer Joss's position that there ought to be life elsewhere to avoid an "awful waste of space." Instead, he was asking in probabilistic fashion how often life might emerge based on how vast and ancient the universe is.
Not coincidentally, his thinking comes from Dr. Arroway's part of the monologue above. The inflection of awe comes from just how big the cosmos is; not from a moral requirement for a rational or aesthetically pleasing universe.
It turns out that decades earlier, the pioneering Russian astronautics theorist and recluse Konstantin Tsiolkovsky had deeply meditated on the subject. Tsiolkovsky, a deaf hermit who spent most of his life in a log cabin, had already begun to describe the mathematical underpinnings of rocket propulsion in the late 19th century. Deeply concerned with the necessity for humanity to go beyond earth, Tsiolkovsky spent considerable time on philosophical and empirical questions related to astrobiology.
In a series of essays in the 1930s, Tsiolkovsky anticipated the Fermi question and wrestled with potential solutions. Reasoning from a position of a kind of Copernican monism, Tsiolkovsky calculated that there would be other planets around other suns. Following a similar probabilistic reasoning as Fermi, he concludes that intelligent life will have developed – though not necessarily contemporaneously with humanity.
Here, Tsiolkovsky's personal convictions (a subject for another blog post or eight) convinced him that intelligent life would inevitably travel to the stars and eventually to us:
Millions of millions of planets have existed for a long time, and therefore their animals have reached a maturity which we will reach in millions of years of our future life on earth. This maturity is manifest by perfect intelligence, by a deep understanding of nature, and by technical power which makes other heavenly bodies accessible to the inhabitants of the cosmos – 'Is There A God'
Tsiolkovsky then describes something like Fermi's question: if such beings exist, they would have visited the earth, and if they existed there would be some sign of them. But they haven't – how to explain the contrast in expectation and observation?
In attempting to solve the problem, Tsiolkovsky turns from temporal to moral arguments. He writes first about the aspect of time:
Probably they will visit us, but it is not yet time for that. Aboriginal Austrians and native Americans of past centuries were finally visited by Europeans, but many thousands of years passed before they appeared. Similarly, we will also be visited some time in the future. Probably the powerful inhabitants of other planets have been visiting one another for a long time.
Further, he doubts our ability to perceive "them," and if we were prepared to do so:
Our means are too weak to be able to perceive these signs. Our heavenly neighbors understand that with a certain degree of development of knowledge the people themselves will prove without a doubt that the other planets are populated. Besides, because of the low development of animals, and the majority of humans, there is no reason to inform them that the planets are populated. Would this knowledge even bring harm?
Finally, he writes on stark moral terms:
We are brothers, but we kill each other, start wars, and treat animals brutally. How would we treat absolute strangers? Wouldn't we consider them our rivals...and wouldn't we ruin ourselves in this unequal struggle? They cannot wish this struggle and destruction. Mankind, in its development, is as far from more perfect heavenly being as lower animals are from people...can we really have rational relationships with dogs and monkeys? In the same manner, higher beings are not able to communicate with us for the present.
In short, the time has not yet come – as a species, humanity is too unsophisticated to perceive or meaningfully interact with another species. Humanity has not yet "earned" entrance into the cosmic society in Tsiolkovsky's thinking.
Of course, Tsiolkovsky's solution is not the only one available.
As we saw above, Fermi's context – unlike Tsiolkovsky – was one of imminent self-genocide via nuclear weapons. Prominent among Fermi's potential reasons why we hadn't been visited, according to Herbert York's recollection, was the prospect that "technological civilization doesn't last that long."
What if civilizations simply don't last long once they reach a certain level of sophistication? Could it be that the galaxy and not just the solar system is a graveyard? Could the silent stars be proof that intelligence is ultimately suicidal?
Fermi's intellectual descendants in Francis Drake and Carl Sagan continued on in similar tradition. In 1961, a discreet gathering of scientists met at the Green Bank observatory in West Virginia. The conference attendees developed what would ultimately be known as the Drake Equation:
This toy model finally quantified the mathematical intuition underlying both Fermi and Tsiolkovsky's thinking. The model essentially multiplied a series of probabilities describing the steps on the path to technological civilization by the number of stars to estimate how many intelligent species might exist.
The famed researcher of dolphin intelligence John Lilly was among the attendees of the Green Bank meeting. Lilly's work raised new, provocative questions: what if intelligent life does not necessarily become tool-using? Moynihan writes:
The depressing implication of this line of thinking was that maybe extraterrestrial intelligences are all peaceful but unambitious dolphinoids – bright, capable, noble, but tragically uninterested in the twinkling stars above – and this because all the ambitious intelligences eventually snuff themselves out in nuclear orgies wrought by their own ingenuity.
Indeed, Lilly's research made a deep impression on the early SETI pioneers – they referred to themselves as "The Order of the Dolphin."
So far, we have seen three major streams of thought flowing from the same premises. The entry point to the argument is Tsiolkovsky and Fermi's intuitive understanding of the vastness of space and the monistic assumption that there are similar probabilities of life arising elsewhere. The challenge comes in explaining why we don't observe any evidence of such life:
- Tsiolkovsky explains that this a combination of temporal (perhaps the visit has not happened yet) and moral factors: humanity is simply not perceptive enough or worthy of a visit
- Fermi doesn't offer any strong solution (this was a lunchtime conversation!), but according to York wondered if the longevity and stability of civilization was the major factor.
- "The Order of the Dolphin" contemplated the teleological assumption that intelligence becomes tool using. Perhaps the ambitious and technological civilizations destroy themselves, leaving a universe of undetectable dolphinoid lotus-eaters. Not every intelligence is interested in tools or in building; the ones that are sometimes destroy themselves
But here is another thing to consider: what if the premises are wrong? What if Tsiolkovsky assumed too much? What if the small, clever man known for his ability to estimate made a mathematical misstep?
Dissolving the Paradox
Sandberg, et. al begin with the the observation that the estimates of the Drake equation are famously highly variable. They tend either to very large numbers, or to one. They quote Steven J. Dick on the scientific anxiety about such variance:
Perhaps never in the history of science has an equation been devised yielding values differing by eight orders of magnitude... each scientist seems to bring his own prejudices and assumptions to the problem.
Sandberg et. al ultimately diagnose the problem as stemming from the use of point estimates rather than probability distributions over the terms.
They begin with a toy model that is easy to conceptualize.
Imagine an equation with nine parameters giving the probability of extraterrestrial intelligence at each star. Assume that each parameter is between [0,0.2] with uniform uncertainty and each parameter is independent. A point estimate of .1 gives a probability of one in a billion. Given 100 billion stars in the galaxy, the the number of life bearing stars should naturally be about 100. Likewise, the probability of all 100 billion "chances" of life failing to produce one intelligence is tiny – something like 3.7x10^-44. This result accords with their survey of the literature on the Drake equation, which finds that 64% of studies find the number of expected civilizations greater than a hundred. The simple toy model reproduces the Fermi paradox: "a conflict between the prior extremely low probability of a galaxy devoid of ETI and our failure to detect any signs of it."
However, using a Monte Carlo simulation with the same parameters [0, 0.2] instead of the assumption of .1 gives vastly differently results:
The difference here is five lines or so of code in a crude toy model. At the level of point estimates nothing changes – the mean of the fermi_interval function above will be near 100. However, as often is the case, the mean is not the whole story. You get a lonely empty galaxy approximately 21% percent of the time – not exactly the overwhelming numbers required to produce a deep paradox.
As Jill Tarter famously said, "the Drake Equation is a wonderful way to organize our ignorance." Given our degree of ignorance, the point estimate approach is inadvertently misleading. Sandberg et. al demonstrate how practitioners have not fully accounted for this uncertainty in their models.
Sanberg et. al proceed to go beyond this toy example to more rigorously describe the uncertainty around each parameter and simulate the result. They then further incorporate information based on the Fermi observation – that is the, lack of any evidence of intelligent life from a multi-modal search thus far.
The result: "a substantial probability that we are alone in our galaxy, and perhaps even in our observable universe." They place the odds of being alone at 53%-99.6% for the galaxy, and 39%-85% for the observable universe. Sandberg, et. al answer Fermi's question of "Where are they" by saying "probably extremely far away, and quite possibly beyond the cosmological horizon and forever unreachable."
A Blank Canvas Is Not An Awful Waste of Space
The themes surrounding Fermi's provocative question have often been linked to moral reasoning. In ancient and pre-modern times, the expectation was that the universe is moral, rational and infinite. Speculation about other intelligent beings was common, driven largely by a presumption of the basic goodness of sentience, and sometimes as a kind of hedging of bets on the destiny of humanity.
By the 19th century, major thinkers had begun to shed the expectation that there must be other humanoid life in the cosmos as an anthropocentric conceit. Fermi and Tsiolkovsky had returned to the question from a mathematical perspective. They had calculated that while there was no logical necessity for other intelligent life, there ought to be based on the scale of the cosmos and our ordinariness in it.
Perhaps unsurprisingly, attempts to answer why we don't observe intelligent life when we ought to expect it led to another set of moral questions. Tsiolkovsky wondered if we were not (yet) worthy of extraterrestrial attention. Fermi considered if intelligent beings were able to keep their destructive tendencies in check long enough. The Order of the Dolphin and modern astrobiology continued on the work, and added new questions challenging teleological assumptions about intelligence.
Underneath the question however is a vast uncertainty. The degree of uncertainty in 2021 is great; it was much, much greater in Fermi or Tsiolkovsky's time. Their intuitive mathematical attempts to estimate were perhaps not quite up to the task. Sandberg et. al demonstrated that best on our cumulative best knowledge, there is not an overwhelming reason to expect intelligent life. There is not really a paradox.
The dissolution of the paradox renders moral hypotheses somewhat less applicable, but not less salient to our own precariousness. We can't safely conclude that intelligence is necessarily or usually suicidal because we can't safely assume that the universe is full of intelligent life. It remains up to us to determine if our collective path will be one of self-destruction or not.
Sometimes it can be tempting to turn to simplifications in contemplating such difficult questions. It is more comforting to think, like the Greeks and others, that if life is destroyed here it will return in some new form – as Diderot might say, in a sequence of "I--don't-know-whats." Or, to believe as Freeman Dyson once said "if our species is extinguished, others will be wiser or luckier." It is pleasant to look up and concur with Palmer Joss that the inky expanse ought to have wiser, luckier others in it. We can soothe ourselves and others by saying it would otherwise seem to be an "awful waste of space."
But this would be a bit like saying "everything happens for a reason" – comforting, perhaps, but also an abdication of responsibility. In truth, our aesthetic preferences have no power over the design of the universe. The vastness of space doesn't care what we think is wasteful or not. The odds on there being others are not zero, but neither are they overwhelmingly high, either. There is every possibility that we are stewards of all or nearly all consciousness.
In short, what we do matters too much to assume there are others because it is less scary than contemplating solitude.
Tsiolkovsky famously said "Планета есть колыбель разума, но нельзя вечно жить в колыбели" – "The planet is the cradle of intelligence, but it is impossible to live forever in the cradle." Contrary to those who interpret Fermi's question pessimistically, the choice is not many worlds or none. The silence may not be one of technological suicide. We may just be alone, or nearly alone.
"An awful waste of space" is the "Live, Laugh, Love" of astrobiology. It is a facile banality that obscures a daunting truth.
Heinrich Wilhelm Matthias Olbers told us what we need to know: the solar system is ringed with orbital flak, the possible remnants of once and would-be planets. Counter to Leibniz, the universe is overwhelmingly of the void and of sterility. We can assume no insurance policy for sentience, nor anyone to save us. Or to judge us ready. Our light can go out permanently.
This need not be a bleak realization, but rather a call to responsibility – to create our own wisdom and our own luck. If we do not take possession of ourselves, we will foreclose the fate of every possible future generation. And if we do see the silence as a challenge rather than a condemnation, we might appreciate that a blank canvas is not an awful waste of space. It is the only dare that matters.
Extra: Castle Bravo and 大怪獣の原点 ("Origin of the Great Monster")
This is already a very long post, but March 1st is an important anniversary in the history of nuclear weapons and fits with the larger theme above.
We'll return now to our small and clever man. After lunch, the physicists went back to their work. They were ultimately successful in creating "the super."
On March 1st, 1954, the United States detonated a 15 megaton blast in the Pacific in a test called Castle Bravo. It was the greatest radiological disaster in American history.
First, the yield was a full two and a half times greater than expected, and a thousand times greater than what fell on Nagasaki. Within less than ten minutes, a mushroom cloud expanded over sixty two miles. A dangerous radioactive cloud traveled immense distances:
A group of Japanese fishermen aboard the Lucky Dragon #5 (第五福龍丸) were seriously contaminated and burned by the fallout:
In the ever seemingly expanding aftermath, the Japanese fishing industry was dealt a massive blow. Nearly 900 vessels were deemed to have been exposed to radiation from the blast. Between March and November of 1954, over 75 tons of tuna were destroyed after they were found to be radiologically contaminated. The United States declared that there was a "negligible hazard" while simultaneously dramatically tightening its import standards on fish.
By September, one of the crew of the Lucky Dragon passed away. Nearly 400,000 attended his funeral. The growing anti-nuclear movement and outcry in Japan eventually found expression in November of 1954, in the first Godzilla film. The trailer proclaims "Mankind's final days are upon us! The hydrogen bomb has given birth to fear in the modern world!"
That same month Enrico Fermi would be dead from stomach cancer. Despite his warnings, the weapon he dreaded has been unleashed upon the world. Merely testing it had created a disaster, poisoning large swaths of the Pacific. The second nuclear trauma had forged the image of a new cultural symbol of disaster.
If Sampson breaking the Temple of Dagon had been a cultural echo the Hiroshima and Nagasaki bombings, Godzilla would be the embodiment of the hydrogen bomb: a colossus born of the primordial ocean and herald of mankind's final days.