Planet Formation and Panspermia. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

Автор: Группа авторов
Издательство: John Wiley & Sons Limited
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Жанр произведения: Физика
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isbn: 9781119640936
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which need to integrate understanding of natural processes from physical science with the human perspective which frames all our actions. It ranges from relatively innocuous lack of worry for the fate of Earth billions of years hence, when Sun enters the post-Main Sequence phase of its evolution, to much more malignant forms of ecological and climate neglect for problems facing our children and grandchildren in the context of climate change/ocean pollution/loss of biodiversity. In both cases, there is a contrast between clear predictions of physical science (“our Sun has finite Main Sequence lifetime, after which it will enter the red giant/asymptotic giant phases” or “the continuous pumping CO2 into the atmosphere leads to increased greenhouse effect, hence climate change”) and our explicit or implicit failure to observe any effects—or any obvious effects—at present. If we were not enthralled by chronocentrism, we would have immediately noticed that there is not a trace of doubt that anthropogenic climate change is real and incredibly threatening. The debate on the relevant timescales would lose much of its rhetorical strength if we accept that for humanity as such (and even terrestrial biosphere itself) it is hardly relevant whether drastic consequences will occur in 50, 75, or 150 years from now. Of course, it does matter from the standpoint of an individual lifetime—which also increases rather quickly in historical terms—but not from the standpoint of the species or the biosphere. Only the narcissistic underpinnings of chronocentrism make us discount things farther in the future than our own lifetime (and perhaps, for the equally selfish and narcissistic reasons, lifetimes of our biological children). The example of climate change is the most important and momentous, but there are other examples which demonstrate that chronocentrism is quite a dangerous belief.4

      Of course, one should not blithely accept chronocentrism’s opposite— what one can call temporal Copernicanism—either. It is almost a tautology that all epochs are not equally important, interesting, or relevant. The classical steady-state cosmological theory has tried to implement the idea of temporal Copernicanism most widely and literally, under the name of the “Perfect Cosmological Principle” ([3.10, 3.6]). The Perfect Cosmological Principle simply states that the universe is uniform in 4-D spacetime. The implication is, clearly, that all epochs are, on the average, the same. Although the steady-state theory has been a powerful alternative to the standard relativistic cosmology in the central formative period of the “Great Cosmological Controversy” (1948–1965), it was eventually refuted by empirical data [3.36]. There are other, much subtler modern versions of temporal Copernicanism which, as argued by Ćirković and Balbi [3.16], need to be resisted as well. These include reasoning in astrobiology and SETI studies which explicitly or implicitly assume that our epoch is typical for epochs containing living beings and intelligent observers (e.g., [3.50]). A partially confounding factor here is that we cannot take an agnostic position regarding cosmological pre-conditions for life and intelligence, since in the last quarter century or so we have learnt a great deal about those. So to what extent we take into account this, in philosophical parlance, admissible evidence, will influence our evaluation of the heuristics. Without entering this complex topic in epistemology, it is important to emphasize that the undermining of temporal Copernicanism as that of [3.16] does not mean any endorsement of chronocentrism. The truth has to be somewhere in the middle; we shall return to this point in the concluding section.

      While the continuity thesis suggests that the transition from non-life to life is easier than a priori thought, it does not really prescribe where and how the transition did actually occur. It is still possible that early life came to Earth from somewhere else, in particular from Mars, which had perhaps been more conductive to abiogenesis than our planet at that epoch (e.g., [3.18]). The scenario in which abiogenesis first occurred on Mars and some early life forms were subsequently transported to Earth (while, presumably, Martian life either became extinct or remained in very limited enclaves after the environmental conditions there deteriorated 3.5–4 Gyr ago; see [3.37]) is as perfectly in agreement with the continuity thesis as are any of the conventional abiogenesis scenarios on Earth. Mutatis mutandis, other forms of panspermia, are consistent with the continuity thesis and the epistemological “machinery” behind it.

      Now, there is an important consideration to take into account: while some panspermia could clearly occur naturally, and in an optimistic case, be effective very slowly over interstellar distances (see also the chapter by Balbi in this volume [3.7]), the constraints are much weaker in the case of its technogenic version, directed panspermia. The latter has been suggested by two titans of biochemistry, Francis Crick and Leslie Orgel, as a halfserious solution for multiple problems facing origin of life research: maybe our planet has been seeded, intentionally or not, with early life forms by an advanced technological civilization [3.17]. Directed panspermia is often made to sound like science fiction—which should not be taken pejoratively in the first place—although it is a scientifically legitimate hypothesis or a class of hypotheses. Critics have charged that it is untestable, although it is at least doubtful whether it is indeed so, or we should emancipate from the common myopia inherent in human short-term timescales in epistemology as well.

Schematic illustration of the feedback created by directed panspermia.