VII. Pedia Sapiens: A Genesis Future on Earth and in the Heavens
C. An Earthropic Principle: Novel Evidence About a Special Planet
Sandberg, Anders, et al. Dissolving the Fermi Paradox. arXiv:1806.02404. Oxford University, Future of Humanity Institute scientist forecasters AS, Eric Drexler and Toby Ord contend that long after Frank Drake’s famous 1961 method to calculate anticipated cosmic civilizations, many new findings from genes to galaxies beg a whole scale revision. As the quotes say, and current works reach from other angles, even though the universe is filled with planetary objects, the answer to why no evidence has been found may well be that we Earthlings are the only sapiensphere species to have evolved this far.
The Fermi paradox is the conflict between a high probability of intelligent life elsewhere in the universe and the apparently absence we in fact observe. The expectation that the universe should be teeming with intelligent life is based on views that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should yield many observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty from highly uncertain parameters. We examine these parameters, incorporating models of chemical and genetic transitions on paths to the origin of life, and identify uncertainties that span multiple orders of magnitude. When the model is recast to represent realistic distributions of uncertainty, we find a substantial probability of there being no other intelligent life in our observable universe, and thus little surprise when we fail to detect any signs of it. (Abstract edits and excerpts)
Santos, Nuno, et al. Constraining Planet Structure and Composition from Stellar Chemistry. arXiv:1711.00777. An 11 member team from European observatories contribute to a growing sense that whole solar systems act altogether in a concerted way. The elemental makeup of the resident star is found to effect and determine what kind of orbital planets might be present. By this measure, different stellar populations can be evaluated for their relative propensity toward or away from a conducive habitability. See also Characterization of Exoplanet-Host Stars by this group at 1711.01112.
The chemical composition of stars that have orbiting planets provides important clues about the frequency, architecture, and composition of exoplanet systems. We compiled abundances for Fe, O, C, Mg, and Si in a large sample of solar neighbourhood stars that belong to different galactic populations. Assuming that overall the chemical composition of the planet building blocks will be reflected in the composition of the formed planets, we show that according to our model, discs around stars from different galactic populations, as well as around stars from different regions in the Galaxy, are expected to form rocky planets with significantly different iron-to-silicate mass fractions. Furthermore, the results may have impact on our understanding of the frequency of planets in the Galaxy, as well as on the existence of conditions for habitability. (Abstract)
Sardar, Ziauddin, ed. Rescuing All Our Futures. Westport, CT: Praeger, 1999. A theme of this website is the need for a global representation of all peoples in a peaceful, sustainable, much kinder abode. Within the palpable dominance of West and North over East and South, which augurs for a more of the same technological, consumptive future, these papers explore non-Western, indigenous, feminine options. Noted contributors include Susantha Goonatilake, Eleonara Masini, Sohail Inayatullah, Ivana Milojevic, Vinay Lal and Ashis Nandy. The traditional vision of the Maori peoples of New Zealand would make a suitable organic vision.
For the Maori, writes activist Ramana Williams, the appropriate term is the creation of a whanau. It means a vast universal family that connects the stars and the moon, the earth, and the sky and all life forms that reside therein, the world of animation and inanimation, the worlds of the living and the dead. (56)
Scharf, Caleb and Leroy Cronin. Quantifying the Origins of Life on a Planetary Scale. arXiv:1511.02549. The Columbia University astrobiologist and University of Glasgow biochemist scope out an advanced 2010s theoretical update of the 1960s Drake equation for better estimates of the likelihood of habitable abodes for organisms and peoples. See also A Probabilistic Framework for Quantifying Biological Complexity by Cronin, Stuart Marshall, and Alastair Murray at arXiv:1705.03460.
In this paper, we describe an equation to estimate the frequency of planetary “origin of life”-type events that is similar in intent to the Drake Equation but with some key advantages—specifically, our formulation makes an explicit connection between “global” rates for life arising and granular information about a planet. Our approach indicates scenarios where a shared chemical search space with more complex building blocks could be the critical difference between cosmic environments where life is potentially more or less abundant but, more importantly, points to constraints on the search. The possibility of chemical search-space amplification could be a major variance factor in planetary abiogenesis probabilities. (Significance)
Schwieterman, Edward, et al. A Limited Habitable Zone for Complex Life. arXiv:1902.04720. UC Riverside and NASA Astrobiology Institute scientists quantify another significant variable with regard to biospheric and atmospheric concentrations of carbon dioxide and carbon monoxide. While aerobic life from microbes to mammals requires a viable, stable CO2 range over time, CO levels are highly toxic for all organisms. Since numerous K and M-type dwarf stars are prone to CO, they are less habitable. Our G-type sun is a better place to be, if CO2 can be sustainably kept in a safe, conducive range.
The habitable zone (HZ) is defined as the range of distances from a host star within which liquid water may exist at a planet's surface. Substantially more CO2 than present in Earth's modern atmosphere is required to maintain clement temperatures. However, most complex aerobic life on Earth is precluded by CO2 levels of just a fraction of a bar. At the same time, most of the HZ volume resides in proximity to K and M dwarfs, which are more numerous than Sun-like G dwarfs but have greater abundances of atmospheric CO, a toxic gas for organisms. Here we show that the HZ for higher fauna is significantly limited relative to that for microbial life. These results cast new light on the likely distribution of complex life in the universe and the search for biosignatures and technosignatures. (Abstract excerpts)
Secco, Luigi, et al. Habitability of Local, Galactic and Cosmological Scales. arXiv:1912:01569. University of Padova astroscientists consider these near and far domains by way of the latest exoplanet and exosolar findings and again reach an auspicious conclusion. An “Earth peculiarity” appears due to features such as an optimum orbit around the sun, benign solar system, magnetic field strength, good nitrogen to oxygen ratio, ocean to land plate tectonics, an ideally placed large moon, obliquity tilt, and more. Akin to Planetary Astrobiology by Victoria Meadows, et al (2019, 2020 herein), as the second quotes alludes out of a concatenation of some 1020 candidate worlds, our emergent person/sapiensphere progeny could very well be its first, best, or last universal opportunity to observe, read, affirm self-select and begin a new creation.
The aim of this paper is to underline conditions necessary for the emergence and development of life. They are placed at a local planetary scale, a Galactic scale and within cosmic evolution. We will consider the circumstellar habitable zone (CHZ), a Galactic Habitable Zone (GHZ), and also a set of strong cosmological constraints to allow Anthropic life. Some requirements are specific to a single scale and their physical phenomena, while others are due to cumulative effects across scales. A surmise is that all the habitability conditions here so detailed must at least be met. Thus, some sixty years later a human-like presence may appear as "a monstrous sequence of accidents" as (Fred) Hoyle (1959) thought, or as a providential collaboration which can imply how finely tuned is the architecture within which precious Life is embedded. (Abstract edits)
Seppeur, Sonja. Impact of Gas Giant Instabilities on Habitable Planets. arXiv:1802.05736. A Goethe University, Frankfurt, astrophysicist posts an extensive study to date of the better or worse effect that gaseous worlds can have by their common presence and temporal movements upon solar system habitability zones. In regard, as Alessandro Morbidelli (search) and colleagues have found, our own hot Jupiter has been quite conducive by moving inward and then back so as to clear out the usual crunch of close-in rocky planets. The outward served a well-spaced orbit for Earth. One more feature amongst the cosmic contingencies is added to an especial significance for this home bioworld.
The detection of many extrasolar gas giants with high eccentricities indicates that dynamical instabilities in planetary systems are common. These instabilities can alter the orbits of gas giants as well as the orbits of terrestrial planets and therefore eject or move a habitable planet out of the habitable zone. In this work 423 simulations with 153 different hypothetical planetary systems with gas giants and terrestrial planets have been modelled to explore the orbital stability of habitable planets. Planetary systems consisting of two giant planets are fairly benign to terrestrial planets, whereas six giant planets very often lead to a complete clearing of the habitable zone. Observed gas giants with eccentricities higher than 0.4 and inclinations higher than 20 degrees have experienced strong planet-planet scatterings and are unlikely to have a habitable planet in its system. (Abstract excerpts)
Simpson, Fergus. An Anthropic Prediction for the Prevalence of Waterworlds. arXiv:1607.03095. As myriad orbital objects of every possible kind are being detected, the University of Barcelona, Institute for Cosmic Sciences, researcher notes that in contrast to a default state of wholly wet or dry surfaces, Earth’s mottled mantle of ocean and land is a rare anomaly. By way of a “planetary fecundity,” life has been able to evolve from primitive rudiments to human observers, thus an anthropic explanation. We include longish quotes to catch the gist, which appends another reason why this home Earth is so uniquely precious.
Should we expect most habitable planets to share the Earth's marbled appearance? Terrestrial planets within the habitable zone are thought to display a broad range of water compositions, due to the stochastic nature of water delivery. Such diversity, taken at face value, implies that the surfaces of most habitable planets will be heavily dominated by either water or land. Convergence towards the Earth's equitably partitioned surface may occur if a strong feedback mechanism acts to regulate the exposure of land. It is therefore feasible that the Earth's relatively balanced division of land and sea is highly atypical amongst habitable planets. We construct a simple model for the anthropic selection bias that may arise from an ensemble of surface conditions. Across a broad class of models we consistently find that (a) the Earth's ocean coverage of 71% can be readily accounted for by observational selection effects, and (b) due to our proximity to the waterworld limit, the maximum likelihood model is one where the majority of habitable planets are waterworlds. This 'Dry Earth' scenario is consistent with results from numerical simulations, and could help explain the apparently low-mass transition in the mass-radius relation. (Abstract)
Simpson, Fergus. The Longevity of Habitable Planets and the Development of Intelligent Life. International Journal of Astrobiology. 16/3, 2017. The University of Barcelona cosmologist applies mathematical finesse to figure how much duration is actually necessary for life to evolve and emerge from microbes of a collaborative sapience able to do this. As a result, another vital condition is added of an extended length of time it seems to require, some billion years in our Earthly case.
Why did the emergence of our species require a timescale similar to the entire habitable period of our planet? Our late appearance has previously been interpreted by Carter (2008) as evidence that observers typically require a very long development time, implying that intelligent life is a rare occurrence. Here we present an alternative explanation, which simply asserts that many planets possess brief periods of habitability. We also propose that the rate-limiting step for the formation of observers is the enlargement of species from an initially microbial state. In this scenario the development of intelligent life is a slow but almost inevitable process, greatly enhancing the prospects of future SETI experiments such as the Breakthrough Listen project. (Abstract)
Smith, Howard. Alone in the Universe. Zygon: Journal of Religion and Science. 51/2, 2016. In an Exoplanets and Astrotheology section, the Harvard-Smithsonian Center for Astrophysics scientist and philosopher updates his conclusion, as broached in American Scientist for July-August 2011, that based on a 2010s multitude of cosmological findings we human beings are most likely the only sapient personage. As this section along with Astrobiology, ExoEarths and elsewhere reports, such an epochal realization is in fact dawning upon us. A May 2016 Scientific American article Born of Chaos (Batygin), for example, describes our own solar systems as a uniquely ordered anomaly well suited for a long term habitable Earth. And from a Jewish perspective, the author notes that in his 2006 book Let There Be Light he evoked John A. Wheeler to say that we peoples might be the universe’s way of self-observation so as to bring into full creation.
We are probably alone in the universe—a conclusion based on observations of over 4,000 exoplanets and fundamental physical constraints. This article updates earlier arguments with the latest astrophysical results. Since the discovery of exoplanets, theologians have asked with renewed urgency what the presence of extraterrestrial intelligence (ETI) says about salvation and human purpose, but this is the wrong question. The more urgent question is what their absence says. The “Misanthropic Principle” is the observation that, in a universe fine-tuned for life (“Anthropic Principle”), the circumstances necessary for intelligence are rare. Rabbis for 2,000 years discussed the existence of ETI using scriptural passages. We examine the traditional Jewish approaches to ETI, including insights on how ETI affects our perception of God, self, free-will, and responsibility. We explore the implications of our probable solitude, and offer a Jewish response to the ethical lessons to be drawn from the absence of ETI. (Abstract)
Spalding, Christopher, et al. The Resilience of Kepler Systems to Stellar Obliquity. arXiv:1803.01182. Cal Tech planetary scientists CS, Noah Marx and Konstantin Batygin add still another highly variable feature of solar systems whence an axial tilt of its sunny star has a controlling impact on the number, orbital paths, and stability of any entrained worlds.
The Kepler mission and its successor K2 have brought forth a cascade of transiting planets. Many of these planetary systems exhibit multiple members, but a large fraction possess only a single transiting example. This overabundance of singles has lead to the suggestion that up to half of Kepler systems might possess significant mutual inclinations between orbits, reducing the transiting number. Here, we investigate the ubiquity of the stellar obliquity-driven instability within systems with a range of multiplicities. We find that most planetary systems analysed, including those possessing only 2 planets, underwent instability for stellar spin periods below ~3 days and stellar tilts of order 30 degrees. (Abstract excerpts)
Spohn, Tilman. Special Issue: Planetary Evolution and Life. Planetary and Space Science. 98/1, 2014. An introduction to this edition with six co-editors including Helmut Lammer and Frances Westall as we Earthlings began our near and far cosmic census of habitable ecobiospheres. With this home world as a measure, the 21st century project going forward involves quantifying an array of features such as core composition, geochemistry, outgasings, atmospheres, mantle hydration, and much more. See for example herein Plate Tectonics on Rocky Exoplanets, Earth-Like Habitats in Planetary Systems, and Biotic vs. Abiotic Earth. But an inkling seems to carry through the papers that this precious animate orb looks increasingly special and maybe unique.