How big a role space travel will play in our future is a question with implications for our civilization’s intellectual, economic and philosophical growth. It may even be the hinge upon which swings the survival of the planet. But as Centauri Dreams regular Nick Nielsen points out in the essay below, enthusiasts for spacefaring can overlook historical analogies that show us the many ways humans can shape their culture. Numerous scenarios swing into view. An interstellar future may not be in the cards, depending on the choices we make, which is why seeing space travel in perspective is crucial for shaping the exploratory outcome many of us hope to see.
By J. N. Nielsen
The Role of Spacefaring in Spacefaring Civilizations
What is, and what will be, the role of spacefaring in spacefaring civilizations? If we count the present human spacefaring capability as constituting a contemporary spacefaring civilization, the question can be partly addressed by assessing the role of spacefaring in contemporary civilization. There are several different ways in which we might measure the impact of our spacefaring capability on civilization as a whole, some of them easily quantifiable and some of them not so easy to quantify.
It would be relatively easy to quantify the economic impact of the space industry on the planetary economy. Economists do this sort of thing all the time. A little more difficult would be to estimate the impact on our civilization of technologies made possible by a spacefaring capability, such as the existence of GPS and Earth observation satellites. More difficult yet would be to estimate the impact of our spacefaring capability not as an industry or a technology, but as a cultural and social influence. The influence of, say, the “Blue Marble” photograph was profound, but how can we measure the impact? Are there ways to quantify the overview effect? Should we even attempt to quantify such things? Are qualitative changes in the nature of civilization resulting from qualitatively new experiences intrinsically unquantifiable?
Some of these measures would make our contemporary spacefaring capability quite important to human civilization, and some less so, but I don’t think that any of these contemporary measures would point to our spacefaring capability as being the central project of our civilization. However, when I think about spacefaring in relation to the future of civilization, I often implicitly assume that spacefaring would be either the central project of a civilization, or would play a crucial role in the central project. This now appears to me as an unwarranted assumption, and perhaps even a marginal condition for a civilization to adopt. As we will see, the analogue provided by our own civilization suggests that spacefaring will be a socially and demographically marginal effort, necessary to the economic infrastructure, but not likely to be pursued as an end in itself, at least not on a demographically significant scale.
While I see our spacefaring capability as being interesting primarily for what it portends for the future, how it will shape human life and thought, it is entirely possible that our spacefaring capacity will continue to grow and to develop into a robust and influential industry that shapes the economic and technological future of our civilization, without at the same time dominating our civilization culturally or socially.  I will call civilizations that conform to this latter profile indifferently spacefaring civilizations. We can express the idea concisely in this way: an indifferently spacefaring civilization is a civilization with a mature spacefaring capacity, but for which spacefaring is not the central project of that civilization, nor is spacefaring integral to the central project.
Permutations of Indifference
In the model of civilization that I have been developing—according to which civilization is an economic infrastructure joined to an intellectual superstructure by a central project —a spacefaring capability could be consistent with the primary role of spacefaring residing in either the economic infrastructure or the intellectual superstructure of a given civilization with indifference to spacefaring in the other, and with spacefaring absent from the central project. If, however, spacefaring is the central project of a civilization, neither the economic infrastructure nor the intellectual superstructure can be indifferent to it, though there may be subordinate institutions and groups within these structures that are indifferent to the central project and are pursing some other aim as an end in itself.
Spacefaring might also be integral with the central project without being identical to the central project. For example, a civilization that took the expansion of scientific knowledge as its central project, i.e., a properly scientific civilization, would rely heavily on a spacefaring capacity in so far as the scientific study of the universe beyond the confines of Earth would be a great epistemic challenge to a scientific civilization, and this challenge could only be pursued through spacefaring. Nevertheless, the focus would be the growth of scientific knowledge and not on the further development of spacefaring. Further development of spacefaring would come about indirectly as a result of pursuing further scientific research, or as a consequence of building larger scientific instruments than could be built on the surface of a planet.
If a civilization is in possession of a mature spacefaring capacity but does not have spacefaring as an integral part of its central project, we would expect that this mature spacefaring capacity would be integrated either into the economic infrastructure, the intellectual superstructure, or both. For example, spacefaring may be important in the economy of a mature civilization, but no more central to the project of that civilization than our contemporary communication and transportation networks are to our civilization. If you took away all our communication and transportation networks, our civilization would cease to function, so that our civilization is existentially dependent upon this economic infrastructure, but the same infrastructure does not define the core of our civilization. On the other hand, a civilization with an intellectual interest in questions that can only be addressed by spacefaring would involve spacefaring in its intellectual infrastructure, and, again, if you took away the spacefaring capacity, the intellectual inquiry predicated upon that capacity would cease to function, which could deeply comprise an advanced civilization; nevertheless, the central project is not defined in terms of the spacefaring capacity integral with intellectual inquiry. 
Indifferently spacefaring civilizations in which spacefaring is integral only to the conceptual framework could be said to be economically indifferent to spacefaring, while indifferently spacefaring civilizations in which spacefaring is integral only to the economic infrastructure could be said to be conceptually indifferent to spacefaring (or intellectually indifferent to spacefaring). In the case of spacefaring being integral to both economic infrastructure and intellectual superstructure yet absent in the central project, such civilizations could be said to be morally indifferent to spacefaring. We will consider each of these permutations of indifferently spacefaring civilizations in turn.
Economically Indifferent Spacefaring Civilizations
A civilization might be economically indifferent to spacefaring even while incorporating spacefaring as an integral part of its intellectual superstructure. Spacefaring could be significant for science, for art, for poetry and literature, and still be economically irrelevant if that civilization does not exploit its spacefaring capacity for economic growth and the development of economic institutions.  However, past human civilizations that have been economically indifferent to transportation have also been largely intellectually indifferent to transportation, so that it is difficult to produce an historical analogy for this permutation. This could be expressed such that economic indifference to spacefaring may entail intellectual indifference. For this there are obvious historical analogies.
A civilization economically indifferent to transportation would of necessity be a civilization of limited geographical (i.e., spatial) scope. Let us take, as an example, the civilization of early medieval Europe, after the collapse of Roman political and military power in western Europe, and before the crusades (we can adopt the approximate dates of 476-1096 AD, so this a civilization of about 600 years’ duration). Early medieval Europe was largely indifferent to transportation, and even indifferent to a degree to cities. Roads were poor, and virtually impassable in the rainy seasons, spring and fall. What modes of transit there were consisted of walking, horseback riding, oxcart, and shipping. There were no great port cities in western Europe during this period of time, so even shipping traffic was minimal.
Life in early medieval Europe was intensely local. There were rare travelers (merchants, soldiers, itinerant musicians and preachers, etc.), but most individuals never traveled beyond a few miles from the village where they were born. Life was focused on the rural manorial estate, which was a self-contained and self-sufficient community in which all needs were met (if they could be met) locally, and the local feudal lord was a law unto himself. This was an economic (and cultural) system born of risk aversion and the inherent food security of subsistence agriculture.
Trade was minimal, usually a mere trickle of luxury goods, which dovetailed with the social structure of the society: only the feudal lords had disposable income and so were the sole consumers of imported luxuries, which were employed to enhance the image and status of the local court. The institutionalized restrictions on social mobility embodied in the feudal system (or even the mere appearance of social mobility, which was controlled by sumptuary laws), mirrored the absence of geographical mobility: there was a place for everything, and everything was expected to remain in its place.
The lack of transportation and communication networks meant that idea diffusion was slow. Risk averse subsistence agricultural communities were conservative in the extreme when it came to the adoption of new technologies, not to mention the adoption of new ideas. Because food production was local, a failed local agricultural experiment resulted in starvation. Better to stick to old, known ways of farming than to risk a famine; life was hard enough without courting disaster.
A civilization of this kind, then, is possible, i.e., a civilization economically indifferent to transportation, but it is a civilization that is self-limiting, not only in transportation choices, but also self-limiting culturally, intellectually, socially, and economically. This is transparently obvious from the role that transportation and communication networks play in idea diffusion. Moreover, a regional civilization that remained economically indifferent to transportation would remain a regional civilization and would not grow to become a planetary civilization. Civilizations that build planetary scale transportation networks will eventually encircle exclusively regional civilizations, which latter will become assimilated to the former, which surround and absorb them.
However, it is possible to imagine a civilization in which the economy is so large that the buildout of a spacefaring capability for scientific research represents a marginal economic activity so that the economic infrastructure of that civilization could remain largely indifferent to its spacefaring capacity. This would be implicitly a conception of civilization in which some non-spacefaring economic infrastructure played a large role, or, at the opposite end of the spectrum, a civilization that voluntarily divests itself of its large-scale industrial infrastructure and retains only what is minimally necessary in order to maintain a spacefaring capability for scientific purposes. If a civilization achieved a sufficiently high level of technology, it might live with a light footprint on its homeworld and not require great industrial resources for spacefaring. However, this level of technological achievement would likely only come about as the result of an earlier industrial capacity build out as a necessary stage of development, which was then later dismantled.
Intellectually Indifferent Spacefaring Civilizations
A civilization might be intellectually indifferent to spacefaring even while incorporating spacefaring as an integral part of its economic superstructure. Space could be used for transportation, for economic development, for population expansion, even for entertainment, adventure, and excitement, and still be intellectually irrelevant if that civilization does not exploit its spacefaring capacity for intellectual stimulation, i.e., for scientific, philosophical, and aesthetic growth and the further development of its conceptual framework.
Here we have several historical analogies that we can invoke. It is at least arguable that seafaring was at the heart Viking civilization and Venetian civilization, and was no less central to Iberian civilization during the Age of Discovery, when both Spain and Portugal explored at a planetary scale. By contrast, Mediterranean seafaring was extremely important to Roman and later Ottoman trade, but one would not say that Roman civilization or Ottoman civilization had seafaring as a central project. Our own civilization today is a case in point in this respect: since the invention of the shipping container, international seafaring trade has been central to the global economy, but I don’t think many would be willing to identify seafaring as the central project of contemporary planetary civilization.
The International Chamber of Shipping notes, “The worldwide population of seafarers serving on internationally trading merchant ships is estimated at 1,647,500 seafarers, of which 774,000 are officers and 873,500 are ratings.” In other words, all the seafarers in the world today represent too small of a population to appear in any planetary employment statistics. Even if we were to add port, longshore and warehouse employees we would still not be up to one percent of global population. This is less than the portion of global population presently employed in the agricultural industries of industrialized societies. If we expand the scope to include all workers in the global transportation industry—shipping, air freight, rail, and trucking—this would probably be a respectable figure, but even this respectable figure would not represent a powerful force shaping contemporary society.
Employment numbers, however, do not tell the whole story. The software industry today is far more powerful than transportation (or, for that matter, agriculture) in terms of setting the political and social agenda, despite the fact that employment in the software industry is not large on a global scale. In a 2014 study, The Economist Intelligence Unit estimated direct global employment in the software industry at 2.5 million, with a total of 9.8 million employment if indirect measures are included. This is probably significantly less than global employment in the transportation sector, but, at the present juncture of history, it is far more influential.
Transportation sector employment and influence is almost invisible; software industry employment and influence is highly visible, frequently the focus of political conflict, and influences a mass audience through ubiquitous personal electronic devices. We hear about transportation when an airplane crashes or a train wreck occurs; otherwise, it is part of the economic infrastructure that we take for granted, much as we take it for granted in the industrial world that, when we turn on a light switch, the light will come on because the electrical grid is functioning.
Spacefaring conceived after the manner of the transportation sector of an interplanetary or interstellar economy largely conceptually indifferent to spacefaring, in no way ensures that spacefaring as an end it itself will play any constitutive role in the central project of a civilization with a spacefaring capacity.
Morally Indifferent Spacefaring Civilizations
Indifference to transportation (i.e., spacefaring in a spacefaring civilization) need not be only an economic or conceptual indifference. A civilization might be morally indifferent to spacefaring even while incorporating spacefaring as an integral part of its economic institutions and conceptual framework, and we can express this as a spacefaring civilization in which spacefaring is not the central project of that civilization, nor is it closely integrated with the central project.
An example of civilization morally indifferent to spacefaring is one of the most familiar conceptions of the potential future state of civilization. Indeed, indifference to spacefaring dovetails with what I have called the SETI paradigm (i.e., that technologically advanced civilizations will communicate rather than travel over interstellar distances), as a robust spacefaring engagement would be expected to drive forward spacefaring technology so that it would be unrealistic to postulate a civilization that focused on spacefaring for hundreds or thousands of years and yet still remained incapable of interstellar travel, which is a central tenet of the SETI paradigm. 
Dyson’s one-page paper “Search for Artificial Stellar Sources of Infrared Radiation”  was published in 1960 and Kardashev’s paper “Transmission of Information by Extraterrestrial Civilizations”  was published in 1964. The two papers have become entwined in collective memory, largely because Dyson’s Dyson sphere provides a perfect model for Kardashev’s Type II civilization; it is almost as though the authors had coordinated their efforts and were jointly involved in the exposition of one and the same cosmological extrapolation of civilization. This is a vision of a possible future state of civilization that is expansive to the point of grandiosity, but it is not a vision in which spacefaring plays a role as a central project.
Dyson’s conception of a civilization so advanced that it could build a Dyson sphere, but so uninterested in other civilizations that the only way it could be detected would be by its distinctive IR signature, contrasts sharply with Kardashev’s conception of a civilization radiating information to the universe as powerfully as a quasar, but both were approaching the idea of cosmologically significant civilizations  from the perspective of SETI, i.e., from the perspective of the technosignatures of a very old and very advanced civilization, which might, with luck and skill, be detected by younger and less advanced civilizations.
Dyson focused on thermodynamically inevitable waste heat that even a civilization indifferent to the wider cosmos must leave as a technosignature, while Kardashev focused on civilizations so demonstrative to the wider cosmos that they would radiate as brightly as a quasar; these are antithetical orientations toward a civilization’s relationship to its cosmological complement (i.e., everything outside itself), but neither Dyson nor Kardashev had much to say about spacefaring in this context.
In Dyson’s later paper, “The Search for Extraterrestrial Technology”  he discusses the disassembly of planets in order to build megastructures, which would require robust spacefaring technologies, at least within a civilization’s home system, but this discussion is almost entirely utilitarian and instrumental. In other words, disassembling entire planets in order to build megastructures as Dyson describes in this paper is a matter of the economic infrastructure of a civilization seeking to maximize its Lebensraum within its home system.
Dyson wrote another paper, “Interstellar Transport,”  which is much more focused on actual spacefaring, but, again, the emphasis is upon spacefaring as a transportation solution to economic problems posed by spacefaring civilization; there is no discussion of spacefaring as an end in itself. The final paragraph of this paper gives more of the context within which Dyson was developing his thoughts on interstellar transport, though Dyson prefaces these reflections with the assertion, “I am only concerned with the engineering aspects of the enterprise.” While there has been little discussion of Dyson’s social vision of a spacefaring future, there has been a great deal of discussion about Dyson spheres,  as well as the engineering problems of megastructures that would face any Kardashevian supercivilization. I will not here attempt to address Dyson’s conception of the social consequences of spacefaring, which he does address in several articles ; I only wish to note in this context that spacefaring is a necessary condition of megastructure construction, but not necessarily the focus of a civilization engaged in megastructure construction.
Kardashev is similarly spare in his discussion of actual spacefaring. In his 1964 paper he mentions only, “…we may anticipate that space rockets will clear up the question of whether or not life exists on other planets in the solar system in the years to come.”  This is entirely of a piece with Dyson’s exposition, though Dyson’s civilizations are indifferent even to communication with the outside world, whereas Kardashev’s civilizations are engaged in a central project of transmitting a cosmological legacy to the universe at large.
What would civilizations of this scope and scale, nevertheless morally indifferent to spacefaring, do with the time and resources available to them? This is a question that I have explored several times, for example in Stagnant Supercivilizations and Another Formulation of Stagnant Supercivilizations and What Do Stagnant Supercivilizations Do During Their Million Year Lifespans? and Supercivilizations and their Cosmological-Scale Dark Ages, inter alia. The question could be turned around, and we could ask instead, What would a supercivilization not do, given the resources available to it? Our parochial imagination, acculturated during the early stages of the development of civilization, limits our ability to answer this question.
As futurism scenarios today increasingly focus on the technologies that have experienced exponential growth over the past few decades, an obvious response to a question like this would be an answer that emphasized computers, robotics, and artificial intelligence. Michael Lampton has called a scenario like this the possibility of an “information-driven society,” asserting that the development of, “…increasingly powerful tools for observation, modelling and data processing,” may drive social change resulting in a re-direction of development: “On the multimegayear time scale of species evolution or interstellar travel, this change is rapid enough to be regarded as a step-function transition to an information-driven society.” 
For Lampton, a human information-driven society would still be interested in the wider universe, but this is not necessarily the end point of this developmental trajectory. Rather than turning outward, and employing spacefaring technologies to project itself into the cosmos, an advanced civilization may turn inward and explore a virtual cosmos. John Smart has called a later development of this trend the Transcension Hypothesis, in which, “…a universal process of evolutionary development guides all sufficiently advanced civilizations into what may be called ‘inner space,’ a computationally optimal domain of increasingly dense, productive, miniaturized, and efficient scales of space, time, energy, and matter, and eventually, to a black-hole-like destination.”
We could construct a developmental trajectory encompassing Lampton, Dyson, and Smart in this way: the development of computational technologies converges upon an information-driven society, still oriented toward the outside world, but increasingly focused on information acquisition and processing. To optimize this development, solar insolation harvesting increases until the harvesting of the sun’s energy converges upon a Dyson sphere, supporting a computational infrastructure by means of a spacefaring technology optimized to produce platforms for the harvesting of solar insolation, rather than for space travel and exploration for its own sake. During the period of convergence upon Dysonian totality, the motivational structure of the civilization shifts away from information acquisition and processing that involves the universe beyond (perhaps exhausted by this time), turning inward to virtual worlds and thus the new focus of civilizational optimization converges on a scenario like that of Smart’s transcension hypothesis.
Image: Curtiss “Beachey Special,” piloted by Lincoln Beachey, in banking flight over mile racing track, Davenport, Iowa, September 1914 (https://airandspace.si.edu/collection-objects/beachey-lincoln-oldfield-berna-eli-barney-exhibition-flight-barnstorming).
The Barnstorming Era in Spaceflight
Over the longue durée, spacefaring might pass into and out of the central project of an advanced technological civilization that had the power to act upon spacefaring initiatives if it chose to do so, but this was not always or continuously the social consensus. One could easily imagine a civilization coming into advanced spacefaring technologies, and there being a period of great excitement during a phase of expansion, only to be followed by indifference once spacefaring became routine.
It is to be expected that in the early stages of spacefaring there will be a “barnstorming” era, in which spacefaring will be a challenge and a sport, and, at the farthest reaches of technological capabilities of spacefaring, it will remain a dangerous (and therefore thrilling) sport for some time to come. We are almost a hundred years’ past the barnstorming era for atmospheric flight, and still today there are wealthy sportsmen who indulge themselves by setting new records. The potential scope for spacefaring is far more extensive than that of flight (both in terms of technology and in terms of the spatial extent opened up to sporting opportunity), so that spacefaring as sport, as adventure, and as a romantic engagement with the world, could endure for hundreds if not thousands of years. Nevertheless, this sort of spacefaring is likely to be demographically marginal, of interest primarily to enthusiasts, and largely invisible to the general public.
Say, then, that the barnstorming era in spacefaring endures for a thousand years, after which time a technologically advanced civilization in possession of spacefaring technologies settles into a routine in which spacefaring is a pedestrian activity incorporated into the economic infrastructure of this civilization. After a period of lethargy and apathy, perhaps even a prolonged period of stagnation in which little or nothing is done to improve spacefaring technologies (which period could endure for thousands of years), a civilization might rouse itself once again and project itself outward into the cosmos, with renewed vigor and to a greater extent.
Because the scale of time at which civilization as we know it develops is so short in comparison to the scale of time of cosmology, a cosmologically significant civilization might pass through several multi-thousand year cycles of spacefaring as a central project of a civilization, followed by multi-thousand year periods of civilization in which spacefaring plays no role whatsoever in the central project of the civilization in question.
Image: La tache noire (“The Black Stain”), by Albert Bettannier, in which Alsace-Lorraine is depicted as a black spot on the map of France.
Central Projects, Selective Indifference, and the Development of Civilizations
In the above, spacefaring has served as a lens through which we can view the structure of civilization. What has been investigated here in terms of spacefaring could be applied to other technological capabilities or sociopolitical institutions, present or potential. For example, a similar study could be made of transhumanism, or, rather, in proper generality (i.e., in a non-anthropocentric formulation), the technological augmentation of an intelligent biological progenitor (or progenitors) of civilization. A civilization might take non-anthropocentrically defined transhumanism (perhaps trans-speciesism) as the central project of its civilization, or transhumanism could be economically, conceptually, or morally indifferent even if the technology for these developments is available, as follows:
- Properly trans-biological civilization: conceptual, economic, and moral trans-speciesism
- Indifferently trans-biological civilization: conceptual indifference to trans-speciesism
- Indifferently trans-biological civilization: economic indifference to trans-speciesism
- Indifferently trans-biological civilization: moral indifference to trans-speciecism
Each of these permutations could be given an exposition as I have given above in relationship to spacefaring. Perhaps just as importantly, indifference is a matter of degree, so that a survey of many different civilizations would be likely to result in examples of indifference from the mild to the total, and indifference itself is a mid-point between enthusiastic embrace on the one hand and aversion and avoidance on the other.
We would do well to distinguish between total indifference, in which an idea or activity simply plays no part whatsoever in the lives of a given population, and active aversion, in which an idea or activity is pervasively present through its avoidance.  Superficially these conditions look similar, and the two may be conflated in a low resolution survey of a field, but each points to a fundamental and distinctive difference in the structure of human motivation that will be manifest in other ways in other aspects of life.
This kind of motivational phenomenon is crucial for understanding the central project of a civilization. If we mistake aversion for indifference, we may suppose that some topic might be innocently broached, only to find that we have committed the worst possible faux pas. If we mistake indifference for aversion, we may fail to introduce some crucial but thoughtlessly elided matter, thereby dooming an otherwise hopeful enterprise. In either case, we will fail to understand what is transpiring before our eyes even as we believe ourselves to grasp the essence of the situation, and this is a recipe for disaster.
All central projects incorporate matters of both indifference and aversion alongside matters of engagement and propagation. In order to understand what is going on in a civilization at the largest scale of its development, we must mind these distinctions carefully, as the past leading up to the present structures we observe, and the future developments that will follow from these present structures, would be different in the cases of different motivational structures (and the evolution of these motivational structures). History, then, manifests the development of an idea in time. If we identify the wrong idea as being central to a civilization, or if we fail to appreciate, for example, the difference between indifference and aversion, we will fail to understand the nature of the civilization in question.
For example, how and why did the assassination of Archduke Franz Ferdinand expand to engulf the world in a war of planetary scale, rather than resulting in just another Balkan war (such as were fought, without the planetary scale of loss of life or property, in 1912 and 1913)? Europe before the First World War was a continent riddled with silences and unspoken animosities, given concrete expression in secret treaties and alliances, and, at the same time, the great powers of Europe were engaged in enterprises throughout the world. Balance of power politics after the example of Bismarck had not only constructed a system of alliances, but also a system of aversions no less carefully cultivated, but shrouded in obscurity. If we consider the motivational structure of Europe in 1914 as the central project of European civilization understood only in terms of publicly avowed engagements, without reference to the underlying indifference, aversions, and animosities, we would be as surprised as anyone at the time at the outbreak of a planetary-scale war.
Limitations of Historical Analogies
Since its inception in the latter half of the twentieth century, what has been the role of spacefaring in the central project of civilization? One could argue that the Cold War Space Race was primarily an ideological undertaking, so that space travel during the Space Race was part of the intellectual superstructure at that stage in the development of our civilization, and that it did not inform the central project of civilization at that time. One could also argue, alternatively, that the Cold War Space Race was a temporary manifestation of the central project of planetary civilization at the time, serving to align the interests of individuals and political entities globally, as a prelude to a later, more robust central project of planetary civilization (yet to come).
Why did the Cold War not spill over into a planetary-scale war, as with the escalation that preceded the First World War, or why did the Cold War not become the first war in space? It would be folly to assign a single cause to any course of events as complex as those of the twentieth century; many forces were in play, not least the palpable fear that a war would result in a nuclear exchange that would have meant the end of human civilization. But the Cold War Space Race itself fizzled after the moon landing (perceived as the US winning the Space Race). Other possibilities might have played out under other conditions. If the Space Race had become the primary outlet of superpower competition, the Space Age might have developed differently, perhaps along the lines of Spanish/Portuguese rivalry during the Age of Discovery, without having to sacrifice Earth to a thermonuclear exchange.  But that didn’t happen either; instead, the Space Age moved from initial enthusiasm to widespread indifference.
It could be argued that too great a reliance upon historical analogies is a weakness in attempting to understand the nature and structure of future civilization, but in this present context I find the analogies explored here to be quite telling. While individuals like myself still find spaceflight to be as exciting as when it was new, for many the excitement now has a tinge of nostalgia for the Space Race. Even I find space boring when I hear people banging on about the size of the global satellite industry; this is where the money is, but this is a pedestrian aspect of spaceflight with none of the adventure and none of the excitement. This is space according to the economic infrastructure, and shorn of its significance for the intellectual superstructure and the central project of a civilization.
However, I recognize that my own attitude probably represents a small minority, and to cast the future in the light of the interest of a small minority is almost certainly to get it wrong. What the above analogies make clear to us is that, if I have misrepresented the spacefaring future, it is because I have gotten the emphasis wrong, and not that the future will be without a spacefaring component. A fully spacefaring future for humanity might have spacefaring as simply the transportation infrastructure of a large and thriving civilization, with little or no importance for the central project of this civilization, and therefore only a marginal concern — Do the spacecraft run on time?—for the majority of individuals who are (or would be) a part of this civilization.
 For those who see spacefaring as the future of our civilization, the cultural and social impacts of spacefaring are ultimately much more important than the economic or technological impacts; for those signing the checks for the next satellite launch, the economic and technological side of spacefaring will always be the most prominent factor. However, in what follows I will be discussing civilizations with a mature spacefaring capability, which would make the relationships between individuals embedded in different sectors of society different from the way we regard spacefaring today in terms of its potential.
 For more on this model of civilization cf. “Martian Civilization” (note 2 and its context) and my talk “The Place of Lunar Civilization in Interstellar Buildout.” I discussed my use of “intellectual superstructure” and “economic infrastructure” (terms I have adopted from Marx, though other terms will work equally well) in my earlier talk, “What kind of civilizations build starships?” but I hadn’t yet at that time integrated the idea of a central project into this model.
 For example, a civilization that chose to remain tightly-coupled to its homeworld but nevertheless continued to maintain an active interest in scientific questions that could only be studied through spacefaring, might build scientific instruments dependent upon spacefaring, though this capacity would likely be marginal in comparison to the total size of the economy. A civilization like this would be a scaled up version of contemporary terrestrial civilization, which is not at present settling other worlds within our solar system, but which has studied the other worlds of our solar system though robotic spacecraft.
 Throughout this essay I am using “economic” in its widest possible significance, in the sense in which Alfred Marshall wrote of economics as, “…a study of mankind in the ordinary business of life; it examines that part of individual and social action which is most closely connected with the attainment and with the use of the material requisites of wellbeing.” (Principles of Economics, Book I, Chapter I, Introduction. § 1)
 I give an exposition of the SETI paradigm in “Stagnant Supercivilizations and Interstellar Travel.”
 Freeman Dyson, “Search for artificial stellar sources of infrared radiation,” Science, 131(1341):1667–1668, 1960.
 N. S. Kardashev, “Transmission of Information by Extraterrestrial Civilizations,” Soviet Astronomy, Vol. 8, No. 2, Sept.-Oct. 1964, 217-221.
 What is a “cosmologically significant civilization” and how does it differ from a cosmologically insignificant civilization? I cannot answer this question now, but it is a problem on which I am working. I am counting on the reader’s sympathetic intuitive reading of the term, and if it should prove, upon investigation, to be overly problematic, it can be dispensed with in this formulation without loss. A minimal way to define a “cosmologically significant civilization” would be as a civilization that produces a technosignature that can be detected over interstellar distances. A higher threshold would be the production of technosignatures visible over inter-galactic distances. A different approach might be in terms of scale (like the Kardashev typology) or in terms of age.
 This paper is included in Selected Papers of Freeman Dyson with Commentary, with a Foreword by Elliot H. Lieb, Providence and Cambridge: American Mathematical Society, 1996, pp. 557-570 (though the original journal pagination of 641-654 is also retained in this edition). With the exception of Dyson’s original Dyson sphere paper, “Search for Artificial Stellar Sources of Infrared Radiation,” the other papers by Dyson cited in this essay are not included among these Selected Papers.
 Physics Today, Volume 21, Issue 10, October 1968, doi 10.1063/1.3034534
 Papers on Dyson spheres appear regularly. For example, at least two new Dyson sphere papers appeared on Arxiv in April 2018, “On the possibility of the Dyson spheres observable beyond the infrared spectrum,” by Z. Osmanov and V. I. Berezhiani (Submitted on 11 Apr 2018), and “SETI with Gaia: The observational signatures of nearly complete Dyson spheres” by Erik Zackrisson, Andreas J. Korn, Ansgar Wehrhahn, and Johannes Reiter (Submitted on 23 Apr 2018).
 For example, “Human Consequences of the Exploration of Space” in Bulletin of the Atomic Scientists, Sept. 1969, Vol. XXV, No. 7, pp. 8-13, and “Pilgrim Fathers, Mormon Pioneers, and Space Colonists: An Economic Comparison,” in Proceedings of the American Philosophical Society, Vol. 122, No. 2 (Apr. 24, 1978), pp. 63-68.
 Kardashev, ibid., p. 221.
 Michael Lampton, “Information-driven societies and Fermi’s paradox,” International Journal of Astrobiology 12 (4): 312–313 (2013).
 For a concrete example of being pervasively present through avoidance, after the Franco-Prussian War, when the Germans annexed Alsace-Lorraine (which they called Reichsland Elsaß-Lothringen), of this territorial loss it was said in France, “Think of it always; speak of it never.”
 An extended Cold War Space Race has been imagined in the counterfactual history of Mac Rebisz’s Space That Never Was, who writes of his artistic vision, “Imagine a world where Space Race has not ended. Where space agencies were funded a lot better than military. Where private space companies emerged and accelerated development of space industry. Where people never stopped dreaming big and aiming high.”