The Transplanetary Perspective
5 January 2013
Though I’ve already written a longish post on the relationships among earth sciences, planetary sciences, and space sciences, and I feel that a definitive formulation of this relationship continues to elude me, so I continue to write about it and think about it, in the hope that this exercise in self-clarification will eventually culminate in a more-or-less satisfying account. Or maybe not. But I will continue to think about it nonetheless, and I take a keen interest in the steady stream of new findings in planetary sciences, such as in Newborn Star Study Reveals Never-Before-Seen Stage Of Planet Birth and The Primordial Star at the Edge of the Milky Way that Shouldn’t Exist Challenges Theories of Star Formation.
Part of the difficulty is that the earth sciences, planetary sciences, and space sciences, while all having roots that go back to the very beginnings of human scientific inquiry, are relatively recent in their current incarnations, and any distinctions among them are similarly recent. Also, all sciences begin on the earth (what I will below call “earth-originating”), and all natural sciences begin, in a sense, as earth sciences, because human civilization and the science it produces originates on the earth, so that there is an inherent ambiguity once these earth-originating sciences are extrapolated beyond the earth to other celestial bodies (moons, planetesimals, etc.), other planets in our solar systems, other solar systems around other stars, other star systems in other galaxies, and so on.
There is a quote from Foucault that I have cited on several occasions that is (partially) relevant here:
Each of my works is a part of my own biography. For one or another reason I had the occasion to feel and live those things. To take a simple example, I used to work in a psychiatric hospital in the 1950s. After having studied philosophy, I wanted to see what madness was: I had been mad enough to study reason; I was reasonable enough to study madness. I was free to move from the patients to the attendants, for I had no precise role. It was the time of the blooming of neurosurgery, the beginning of psychopharmacology, the reign of the traditional institution. At first I accepted things as necessary, but then after three months (I am slow-minded!), I asked, “What is the necessity of these things?” After three years I left the job and went to Sweden in great personal discomfort and started to write a history of these practices. Madness and Civilization was intended to be a first volume. I like to write first volumes, and I hate to write second ones. It was perceived as a psychiatricide, but it was a description from history. You know the difference between a real science and a pseudoscience? A real science recognizes and accepts its own history without feeling attacked. When you tell a psychiatrist his mental institution came from the lazar house, he becomes infuriated.
Truth, Power, Self: An Interview with Michel Foucault — October 25th, 1982, Martin, L. H. et al (1988) Technologies of the Self: A Seminar with Michel Foucault, London: Tavistock. pp.9-15
The portion of the above most often quoted out of context is this:
You know the difference between a real science and a pseudoscience? A real science recognizes and accepts its own history without feeling attacked.
Far from the earth sciences, planetary sciences, and space sciences (or, rather, their predecessors) constituting pseudo-sciences, they are the very standard by which we ought to judge “hard” natural sciences, but as earth-originating sciences are extrapolated beyond the earth there may be an intellectual tension (hopefully, a creative tension) between the earth-specific forms of earth-originating sciences, and the generalized forms that these sciences take when earth-originating sciences are applied to other planets. I don’t think that planetary sciences and space sciences will feel “attacked” by their earth-originating predecessors, but the tendency to specialization in the most advanced natural sciences may well lead to territoriality among disciplines. This would be regrettable.
The generalization of earth-originating sciences into non-earth-specific planetary sciences and space science will be a necessary prerequisite to the long term growth of human civilization. A future interstellar civilization will be intensely interested in where in the galaxy valuable resources are to be found, in the same way that our planetary-based (and, currently, planetary-bound) civilization is intensely interested in the distribution of mineral resources under the surface of the earth. Much of the contemporary relationship between science and industry stems from this need for resources to fuel the fires of industry. (In this connection I urge the reader to consult the excellent book by Simon Winchester, The Map That Changed the World: William Smith and the Birth of Modern Geology, which traces the development of the first geophysical map of England to the search for coal seams.)
What coal and oil have been to planetary civilization, titanium and fissionables (inter alia) will be to interplanetary and interstellar civilization; and the role that coal and petroleum geology have played in the exploitation of coal and oil for planetary civilization will have their parallel in the role that planetary sciences and space sciences will have in the exploitation of resources necessary to interplanetary and interstellar civilization. To grow as a civilization, therefore, we need to adopt a transplanetary perspective in our sciences. This is already occurring.
Planetary formation must ultimately be understood in the context of stellar formation, since stars and planets ultimately coalesce from the same disc of gas and dust, and stellar formation must ultimately be understood in the context of galactic formation, since stars coalesce from the matter that swirls together as galaxies, and galactic formation must ultimately be understood in the context of the formation of galactic clouds, clusters, and superclusters, etc. In short, the entire structure of the universe is implicated in the formation of planets, and how we are to distinguish kinds of planets or generations of planets.
Astronomers distinguish between population I stars, population II stars, and population III stars (from youngest to oldest, respectively), based on their generation of enrichment with heavier elements (called the metallicity, or Z, of a star, i.e., its composition in terms of chemical elements other than hydrogen and helium) as a result of the nucleosynthesis of earlier generations of stars. To date, population III stars, hypothetically extremely metal-poor stars from the earliest ages of the universe (coincident with the advent of the stelliferous age and the universe “lighting up” with star light), have been postulated but not observed. However, some recently reported observations (The First Stars of the Universe — Major Discovery Announced by MIT) may be of a population III star.
It is to be expected that each of these populations of stars will have planetary systems typical of for these particular stellar populations (if they have planetary systems at all). If, then, we can refine the astrophysics and cosmology of stellar and planetary formation, breaking down population I stars into a more finely-grained account, perhaps even tracing back individual stars to individual stellar nurseries, it may be possible to determine the likely composition of solar systems (and therefore their resources available for commercial and industrial exploitation) derived from a given stellar nursery. Stars and their planetary systems, where these planetary systems exist, formed from one and the same concentration of gas and dust, so that there is a systematic correlation between the chemical composition of stars and their planetary systems, both in the case of our own solar system and in other solar and planetary systems that science has only recently begun to study. While stars and planets may form at different times and from different portions of a proto-planetary disc, the whole process of stellar and planetary formation constitutes a single natural history of a solar system.
As I noted above, this kind of research is already underway. Robert McGown has directed by attention to the paper Enhanced lithium depletion in Sun-like stars with orbiting planets published in Nature, which the authors conclude with this paragraph:
“It is known that solar-type stars with high metallicity have a high probability of hosting planets. Those solar analogues with low Li content (which is extremely easy to detect with simple spectroscopy) have an even higher probability of hosting exoplanets. Understanding the long-lasting mystery of the low Li abundance in the Sun appears to require proper modelling of the impact of planetary systems on the early evolution of solar analogue stars.”
“Enhanced lithium depletion in Sun-like stars with orbiting planets,” Garik Israelian, Elisa Delgado Mena1, Nuno Santos, Sergio Sousa, Michel Mayor, Stephane Udry, Carolina Domínguez Cerdeña1, Rafael Rebolo1, & Sofia Randich, Nature 462, 189-191 (12 November 2009)
The lithium-planetary system correlation suggests a range of research questions, such as the following: Is the sun especially rich or poor in any other element that might point to the existence or composition of a proto-planetary disc during stellar or planetary formation? Does the chemical composition of the planets of our solar system stand in any systemic or predictive relationship to the chemical composition of our sun as revealed by its spectrum? Does the spectrum of a star predict not only the presence or absence of a planetary system, but also the chemical composition of any planets? Does the chemical composition of planets predict the chemical composition of the stars they orbit?
The lithium-planetary system correlation also suggests research questions bearing upon stars that have no planetary system associated with them. While the technology does not yet exist to study in detail stars without planetary systems, improved telescopy and imaging techniques may provide data for such questions in the not distant future. The most obvious hypotheses to account for stars without associated planetary systems would include isolated stars formed from a proto-stellar mass with nothing left over for planets to form, and solar systems with asteroid belts as large as an entire solar system, such the the matter for planetary formation was available but no planets formed despite the existence of a proto-planetary disc. It is an especially interesting question whether lithium had any role to play in the planetary formation or the lack thereof in either of these cases.
However, lithium-planetary system correlation relies on our very sketchy knowledge of exoplanet systems at present. All of this knowledge is strongly skewed toward large planets that tug their stars around. Astronomers have been able to figure out the planetary system around Alpha Centauri because it is close enough to detect the smaller wiggles that would betray smaller planets, but even here we don’t have any information about what surrounds the star other than a few planets. Stars without any large planets at all might have many smaller planets, or they might have a solar system sized asteroid belt. There are probably also a few stars in which all the precursor materials managed to get into the star with very little left over for planets or asteroids.
Perhaps it could be said that lithium deficiency correlates with the absence of large planets, because we have no idea what may be surrounding stars with no detectable large planets — not until we have a very large telescope in orbit or on the moon. This too suggests interesting questions. How might the formation of large planets be correlated with lithium deficiency in a star? Also, it has been theorized that large planets clear debris out of a solar system, thereby making it possible for smallish, rocky planets to exist in a more stable planetary environment, and a more stable planetary environment likely correlates with the emergence of life and eventually industrial-technological civilization. Thus lithium-planetary system correlation could extend all the way to being a predictor of industrial-technological civilizations.
It might be fruitful to compare the lithium spectra from double (and triple) star systems with known systems including hot Jupiter exoplanets (some of which are just short of being companion stars) and stars that show no evidence of large planet formation. Also, it is worth considering whether double stars or hot Jupiters play a role in the formation of other planets, e.g., such a large gravitational mass might upset the proto planetary disc just enough that the disc congeals into (large) planets, whereas the absence of such a gravitational “trigger” might result in greater uniformity in the proto-planetary disc and therefore its failure to congeal into discrete planets.
Such inquiries are now only in their infancy, and we can both expect and look forward to a flowering of knowledge in the fields of planetary science and space science as the technology to image distant stars and planetary systems rapidly improves, and as access to earth orbit becomes routine, allowing for a robust multiplicity of telescopes in earth orbit outside the atmosphere.
Not only will science on the whole be stimulated by this research, but, as I have often argued, it is the intrinsic nature of industrial-technological civilization to be spurred on by scientific innovations that result in new technologies, and new technologies are engineered into new industries that go on to create new scientific instruments that increase and improve scientific knowledge. Thus the cycle that defines and drives industrial-technological civilization escalates. This cycle is nowhere even close to being exhausted; as I have just pointed out above, instead of a handful of telescopes in orbit, the next decades may see hundreds if not thousands of telescopes in orbit, as there are now thousands of telescopes on the surface of the earth.
Civilization itself will be the beneficiary of these developments, as it continues its spiral of technological progress with its unexpected and unpredicted advantages for human life and commercial opportunity. There is also the sheer joy of better understanding the world in which we live. All of these factors will continue to fuel the growth and diversification of civilization in the future, thus at least partially mitigating against the existential risk of permanent stagnation.
The transplanetary perspective resulting from the extrapolation and generalization of earth sciences into planetary science and space sciences is to be welcomed for these far-reaching benefits both practical and intellectual.
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