Horizons of Spacefaring Civilizations
13 September 2015
In my recent presentation at Icarus Interstellar Starship Congress 2015, “What kind of civilizations build starships?” I recurred on several occasions to archaeology in the course of my exposition. More and more I have been drawing on concepts from archaeology, as it is in archaeology that we find an extant science that has come close to formulating a science of civilization. There are, at least, explicitly formulated theories of civilization in archaeology, which go much further than the unsystematic observations of historians about civilization.
In my talk I drew on archaeological definitions of civilization. Today I want to draw on another archaeological concept, the concept of an archaeological horizon, which is a concept employed pervasively throughout archaeology (as in “dark earth horizon,” for example), and, more specifically, I want to exapt the concept of an archaeological horizon for an exposition of the development of spacefaring civilization.
The term “horizon” is used pervasively in archaeology, though its usage is rarely explicitly defined. Here is an explicit definition from the Encyclopedic Dictionary of Archaeology:
horizon: Any artifact, art style, or other cultural trait that has extensive geographical distribution but a limited time span. The term, in anthropology, refers to the spread of certain levels of cultural development and, in geology, the layers of natural features in a region; in soil science, a horizon is a layer formed in a soil profile by soil-forming processes. The main meaning, however, refers to a phase, characterized by a particular artifact or artistic style that is introduced to a wide area and that may cross cultural boundaries. Provided that these “horizon markers” were diffused rapidly and remained in use for only a short time, the local regional cultures in which they occur will be roughly contemporary. The term is less commonly used now that chronometric dating techniques allow accurate local chronologies to be built. Examples of art styles that fulfill these conditions are called a horizon style-such as Tiahuanaco or Chavin. (syn. horizon style)
Barbara Ann Kipfer, Ph.D., Encyclopedic Dictionary of Archaeology, Springer, 2000.
And, much more briefly, here is another…
“A horizon, more like a popular fashion than a culture, can be defined by a single artifact type or cluster of artifact types that spreads suddenly over a very wide geographic area.”
David W. Anthony, The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World, Princeton University Press, 2007, p. 131.
More helpful is the discussion of horizons and traditions in Deetz’s Invitation to Archaeology. Deetz begins with a characterization of a horizon:
“The concept of an archaeological horizon is that of a set of traits which links a number of cultures over a broad area in a short time. In the Peruvian area a wide- spread art and architectural style, known as Chavin, appears at about 800 B.C. It is characterized by feline and condor motifs in the decoration of ceramics and architectural stone- work. Plotting the space-time distribution of sites containing Chavin type objects makes it clear that the spread of the ideas responsible for the style was rapid; the slope of the space-time line is quite shallow. This manifestation is known as the Chavin Horizon.”
James Deetz, Invitation to Archaeology, New York: The Natural History Press, 1967, p. 59
Contrasting horizon with tradition Deetz writes:
“…one might say that horizons are thin traditions of wide distribution, or that traditions are limited horizons of long duration. This may seem as ridiculous as the idea of the world’s largest midget, or smallest giant, but it makes and underscores the point that there should be no ﬁxed dimensions for either horizon or tradition. In fact, most space-time patterns formed by archaeological materials are neither in the true sense, since they are distributed in both dimensions to a considerable extent. The concepts of horizon and tradition are usually reserved for clear instances of extreme dimensions of time or space, usually if not always linking several cultures, and of use at the broadest level of archaeological integration.”
James Deetz, Invitation to Archaeology, New York: The Natural History Press, 1967, p. 61
As an aside, Deetz’s formulation of a tradition can be used to illuminate a definition of civilization found in the same Encyclopedic Dictionary of Archaeology quoted above:
civilization: Complex sociopolitical form defined by the institution of the state and the existence of a distinctive great tradition.
Barbara Ann Kipfer, Ph.D., Encyclopedic Dictionary of Archaeology, Springer, 2000, p. 119.
When I was preparing my talk on civilization I was searching for explicit definitions of civilizations, and this is one that I considered but didn’t use as it was not quite right for my purposes. But informed by Deetz’s spatiotemporal definition of a tradition, one might get close to a quantitative conception of civilization with the “great tradition” defined in spatiotemporal terms.
An archaeological horizon could be formulated in terms of the presence of a class of artifacts, or in terms of the absence of a class of artifacts “An archaeological horizon can be understood as a break in contexts formed in the Harris matrix, which denotes a change in epoch on a given site by delineation in time of finds found within contexts.” (Wikipedia) In other words, a horizon can be formulated as the beginning or the end of some class of artifacts. One might, then, define a horizon in the most general terms possible as a particular structure of material artifacts in time. While archaeologists work with artifacts of the past, often long out of use (perhaps so long out of use that their function is difficult to identify), there is no reason we cannot extrapolate horizons to artifacts in contemporary use, or even not yet in use.
With spacefaring civilization to date we are working with very little information, so much of the horizon structure of spacefaring civilization is conjectural. If, instead, we sought to explicate the horizon structure of scientific civilization, which has been in existence much longer than spacefaring civilization (which has not even yet fully attained its first horizon), there is much more empirical data at our command. The horizons of scientific civilization are marked by artifacts — scientific instruments — but more especially by epistemic horizons. When sciences or bodies of scientific knowledge became commonplace, we have an epistemic horizon. When Newton brought to maturity the astronomical, cosmological, and physics developments of the century or more preceding his work, an epistemic horizon we call The Enlightenment was the result. Such examples could be multiplied.
The useful aspect of the concept of a horizon is that it places less emphasis upon “firsts,” which can be outliers, and instead is concerned with when an artifact becomes common. In other contexts I have formulated this in terms of demographic significance, but since the term archaeological horizon is already established in its usage, it may be better to employ “horizon.” From this perspective, the celebrated firsts of what is sometimes deceptively called “the conquest of space,” are of little importance. What counts, from the perspective of a horizon, is, “…a single artifact type or cluster of artifact types that spreads suddenly over a very wide geographic area.” For the purposes of spacefaring civilization we can substitute “wide spatial distribution” for “wide geographic area.”
Our moonshots and even our multiple probes to other planets in our solar system were outliers. They do not define a horizon of space exploration. It is arguable that now, today, with inexpensive CubeSats becoming commonplace, that we are reaching a horizon for satellite technology. This is primarily a function of cost. A CubeSat is now within reach of even small budgets. When human spaceflight eventually reaches a cost at which space travel can be inexpensive and routine, then we may achieve a human spaceflight horizon, initially to low Earth orbit (LEO). Further horizons will follow as technology improve and costs diminish.
These further horizons can be defined in terms of the gravitational thresholds that technology allows us to overcome. Previously in The Moral Imperative of Human Spaceflight (as well as in other earlier posts) I formulated six stages of spacefaring civilization, as follows:
Stage O spacefaring civilizations, or a planet-bound civilizations, have no capacity for spaceflight. (Pre-Sputnik civilization)
Stage I spacefaring civilizations have the kind of minimal capacity that we now possess to loft satellites and human beings into orbit, and even to visit nearby heavenly bodies such as the moon. (Sputnik and after)
Stage II spacefaring civilizations might be defined as those that have established a permanent, self-sustaining presence off the surface of the world of a given civilization’s biological origin. This could also be defined in terms of practical, durable, and routine inter-planetary travel. This is the minimal level of civilization to assure long-term survivability.
Stage III spacefaring civilizations would have achieved practical, durable, and routine interstellar travel.
Stage IV spacefaring civilizations would be defined in terms of practical, durable, and routine inter-galactic travel.
Stage V spacefaring civilizations would be defined in terms of practical, durable, and routine travel in the multiverse, i.e., beyond the known universe defined by the consequences of the big bang.
While I formulated these stages of spacefaring civilizations in terms of practical, durable, and routine space travel, I see now that the way to approach these would be to identify each as a horizon of spacefaring civilization.
As noted above in relation to (relatively) cheap CubeSats, a spacefaring horizon may be achieved for automated probes before it is achieved for human beings; we are on the cusp of a satellite spacefaring horizon, when our artifacts achieve wide spatial distribution over a relatively short period of time. If this satellite spacefaring horizon is followed by a human LEO spacefaring horizon (Stage II above), cheap access to Earth orbit for human beings will open the possibility of the next wave, which would presumably be a planetary probe spacefaring horizon, followed by a human planetary spacefaring horizon (Stage III above). The expansion of terrestrial civilization into extraterrestrial space, then, may follow a pattern of an automated spacefaring horizon followed by a human spacefaring horizon.
I think it would also be useful to distinguish between initial horizons (when an artifact appears) and terminal horizons, when an artifact disappears. Perhaps archaeologists already do this, although I didn’t find any mention of such a distinction in any of the books I’ve recently skimmed, looking for discussions of horizons. Just as the emergence of a civilization would be attended by a sequence of initial horizons, the extinction of a civilization would be attended by a sequence of terminal horizons.
The extinction of a spacefaring civilization would involve the reverse sequence of terminal horizons (counting back from Stage V to Stage 0) as the spatial scope of a civilization diminished from spanning the multiverse to being represented only on a planet (not necessarily the planet on which such a civilization originated), or possibly several planets. This, in turn, suggests the interesting possibility of a multiplanetary civilization returned again to the severe limitations of planetary constraints, technically still a multiplanetary species, perhaps distributed across several star systems, but no longer an interstellar civilization in so far as they no longer interact over interstellar distances. This suggests a further distinction to be made between the interstellar presence of a species and the interstellar interaction of a species.
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