The astrobiological landscape, Milan M. Ćirković. Cambridge, UK: Cambridge University Press, 2012, ISBN:9780521197755, hardback, $110, 274 p.

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The connections between philosophy and astrobiology are many, ranging from the implications to our science and our sense of self that would come from finding extraterrestrial life (much less extraterrestrial intelligence), to the very question of why we humans are so particularly fascinated with this search. However, The astrobiological landscape is subtitled, “Philosophical foundations of the study of cosmic life” and it deliberately limits itself to discussing the philosophy underpinning the scope and methodology of the science of astrobiology.

The author, Milan M. Ćirković, is not a professional philosopher but an astronomer, a research professor at the Astronomical Observatory of Belgrade, Serbia, whose work covers not only astrobiology but also the evolution of galaxies. Thus, this book does not have the rigor of a philosophical treatise. Fortunately, this also means that, unlike a technical tome, it is written in a language and at a level that is accessible to other astronomers and astrobiologists, who are after all its primary audience.

Two insights of this work in particular stand out. First, the author draws a fascinating parallel between the state of astrobiology today compared with cosmology in the 1920s, at the time of Edwin Hubble's work. And later, he argues convincingly that understanding the philosophical issues of SETI is an essential element in properly designing a rigorous protocol for empirical SETI studies. In the process, he does an excellent job of defending even the most hypothetical aspects of the field of astrobiology, the specific search for life including intelligent life, against the scorners and skeptics who are not willing to accept it as a legitimate empirical science.

The parallels he sees between astrobiology and cosmology involve both the methodology and history of acceptance of these two fields, and the importance of the results of the one field on shaping the direction of the other. Noting that the historian of astronomy Stephen J. Dick, in The biological universe and elsewhere, first recognized that “the concept of extraterrestrial life is . . . a cosmological worldview” he writes that “as cosmology has had its many detractors, so has astrobiology . . . conservative criticisms, professing skepticism, emphasizing uncertainties, and deploring the ‘overly speculative’ nature of the endeavour . . . both fields have been denigrated as extravagant, frivolous, or remote from daily reality. Both tend to attract amateur and fringe ‘researchers,’ even if the outright quacks are fewer than is usually assumed.” But in spite of that, he notes that in the past 80 years, cosmology has finally passed into the realm of a respectable branch of astrophysics. “A pivot,” he notes, “which the discovery of the expansion of the universe provided to physical cosmology, is provided for astrobiology by the discovery of a large number of extrasolar planets; both showed that it makes sense to discuss dynamics in a wider, nontrivial sense” (pp. 52–53).

But the connection goes deeper. The limits on the size and age of the universe provided to us by modern cosmology provide constraints on the sort of life that might have had time to evolve, and the number of intelligent civilizations that one might reasonably expect to exist. Furthermore, the large number of different “anthropic” arguments applied to cosmology have their own ramifications within astrobiology . . . with similar workarounds. Within these limits, Ćirković outlines a “landscape,” an “archipelago of habitability,” which can be thought of as a phase space where one might expect to be able to find conditions compatible with life of one sort or another. As he points out, one can make reasonable and useful statements about the nature of such a landscape even absent any knowledge of the nature of that life.

When it comes to searching for extraterrestrial intelligence, Ćirković addresses what he calls the “big three” classical anti-SETI arguments: Fermi's paradox (if intelligence is a likely outcome of evolution, why don't we see traces of other civilizations?), biological contingency (if our own evolution was dependent on any number of unlikely contingent circumstances, then intelligence in general should be too rare to find), and the “anthropic argument” (it seems an unlikely coincidence that the timescale for the evolution of our planet so closely matches the evolution of intelligent life). He writes (on p. 150), “such working examples clearly show why philosophy is relevant to astrobiology. None of those arguments can be resolved by any conceptually simple empirical observation or experiment . . . there is no consensus about what kind of empirical research will lead to resolution . . .” He concludes, “it is no coincidence that we have encountered such deep conceptual issues in a young and immature field,” again drawing the parallel with the state of cosmology a century ago. And later (p. 197), he argues that the “lack of a universal ‘recognition protocol’ for strange forms of life and intelligence is perhaps the deepest problem where astrobiology and SETI do intersect with classical philosophical debates in ontology, epistemology and even aesthetics.”

Another topic addressed within this book is the historical development of the question of other inhabitants in the universe and its ties with the assumed teleology of those times. In the present context, he notes, astrobiology today can be regarded as the ultimate testing ground of Darwinism. His discussion also ranges over the nature of the questions asked by philosophers as opposed to scientists, as illustrated in the history of fantasy and science fiction stories about encounters with “the other.” And he discusses at some length the Ward and Brownlee “Rare Earth” hypothesis, which he praises for its clear and provocative exposition even as he argues against its conclusions.

I found plenty to disagree with in his discussions. For all that he attempts to not be tied to too many anthropocentric assumptions and 19th century “whiggisms” (expecting an inevitable forward progress in our understanding), his arguments often reveal his own Eastern European background. His arguments are colored by the assumptions of logical positivism (even as he correctly speaks against its limits) and a love of European science fiction such as the Polish writer Stanislaus Lem, whose works I always found rather heavy-handed and pedantic.

But even as I scrawled rude notes back at the author in the margin of my book, I realized I was thoroughly enjoying myself in this conversation. The author is clearly someone whose interests match mine, but whose point of view is sufficiently different as to challenge my own unspoken presuppositions.

Best of all, the book ends with twenty pages of notes and twenty-one pages of references. Just for this wonderfully comprehensive bibliography of the philosophy of astrobiology, this book deserves to be on the shelf of any astrobiologist's library.

Ancillary