III. Ecosmos: A Revolutionary Fertile, Habitable, Solar-Bioplanet, Incubator Lifescape
I. Our EarthMost Distinction: A Rarest Planetary Confluence of Life in Person Favorable Conditions
We have reached an especial Natural Genesis section which can report and documentan increasing apparent but unknown 21st century radical realization. It has long been thought that due to the vast multitudes of galaxies, stars and now orbital planets ought to contain myriad life-bearing worlds. But as Earthumanity learns on her/his own, by 2022 it is found that a biosphere to noosphere evolution process need pass through many check points (see below) to reach this moment. In novel regard, our home Earth might well be the fittest, optimum candidate.
For a title citation, we propose to expand “Anthropic principle” about cosmic parameters that have precise values so to allow life and people to exist (Chap. III. G). An “Earthropic principle” could denote the unexpected discovery that amongst an infinity of stochastic bioworlds our special planet merits a rarest temporal and spatial significance. We continue on with some October 2022 musings (cutting it much to close).
Super Earth Nova Some 13.8 billion years on, our collective, aware observance and accumulated knowledge repository, so it may seem, could be what life’s evolutionary developmental gestation in a solar incubator needs to retrospectfully affirm both our “geonate” success, and possibly the whole ecosmic procreation. A vital point may then be that an informed realization requires our own (autocatalytic) personal and planetary initiative. We broach such glimpses so to wonder what awesome vistas might be in our midst so to reveal a peaceable future.
Here is broad sample of recent findings across the 140 section entries. It is followed by a long tabulation of just how problematic it has been
Ambrifi, Alessandro, et al. The Impact of AGN Outflows on the Surface Habitability of Terrestrial Planets in the Milky Way. arXiv:2203.00929.
Anand, Rajagopal. Orbital Properties and Implications for the Initiation of Plate Tectonics and Planetary Habitability. arXiv:2202.10719.
Ballmer, Maxim and Lena Noack. The Diversity of Exoplanets: From Interior Dynamics to Surface Expressions. arXiv:2108.08385.
Canup, Robin, et al. Origin of the Moon. arXiv:2103.02015.
Chopra, Aditya and Charles Lineweaver. The Case for a Gaian Bottleneck: The Biology of Habitability. International Journal of Astrobiology. 16/1, 2016.
Erdmann, Weronika, et al. How the Geomagnetic Field Influences Life on Earth. Origins of Life and Evolution of Biospheres. 51/231, 2021.
Foley, Bradford and Peter Driscoli. Whole Planet Coupling Between Climate, Mantle, and Core. arXiv: 1711.06801.
Frank, Adam. Light of the Stars: Alien Worlds and the Fate of the Earth. New York: Norton, 2019.
Hall, Shannon. Summer Solstice Mystery: Does the Earth’s Tilt Hold the Secret to Life? New York Times. June 21, 2018.
Haqq-Misra, Jacob. Does the Evolution of Complex Life Depend on the Stellar Spectral Energy Distribution? arXiv:1905.07343.
Horner, Jonathan, et al. The Influence of Jupiter, Mars and Venus on Earth’s Orbital Evolution. arXiv:1708.03448.
Kopparapu,, Ravi, et al. Characterizing Exoplanet Habitability. Meadows, Victoria, et al, eds. Planetary Astrobiology. Tempe: University of Arizona Press, 2020.
Lingam, Manasvi. Implications of Abiotic Oxygen Buildup for Earth-like Complex Life. arXiv:2002.03248.
Martin, Rebecca and Mario Livio. Asteroids and Life: How Special is the Solar System?. arXiv:2202.01352.
McIntyre, Sarah, et al. Planetary Magnetism as a Parameter in Exoplanet Habitability. arXiv:1903.03123.
O'Callaghan, Jonathan. A Solution to the Faint-Sun Paradox Reveals a Narrow Window for Life. Quanta Magazine. January 27, 2022.
Olson, Stephanie, et al. The Effect of Ocean Salinity on Climate and its Implications for Earth’s Habitability. arXiv:2205.06785.
Provenzale, Murante, et al. Climate Bistability of Earth-like Planets. arXiv:1912.05392.
Raymond, Sean, et al. Solar System Formation in the Context of Extrasolar Planets. Meadows, Victoria, et al, eds. Planetary Astrobiology. Tempe: University of Arizona Press, 2020.
Schwieterman, Edward, et al. A Limited Habitable Zone for Complex Life. arXiv:1902.04720.
Secco, Luigi, et al. Habitability of Local, Galactic and Cosmological Scales. arXiv:1912:01569.
Smith, Howard A. The End of Copernican Mediocrity. Zoe Imfeld and Andreas Losch, eds. Our Common Cosmos. London: Bloomsbury, 2018.
Synder-Beattie, Andrew, et al. The Timing of Evolutionary Transitions Suggests Intelligent Life is Rare. Astrobiology. November, 2020.
Wade, Jon, et al. Temporal Variation of Planetary Iron as a Driver of Evolution. Proceedings of the National Academy of Sciences. 118/51, 2021.
Way, M. J.. et al. Large-scale Volcanism and the Heat Death of Terrestrial Worlds. arXiv:2204.12475.
Webb, Stephen. If the Universe is Teeming with Aliens-- Where is Everybody? New York: Springer, 2015.
Benign G-Type Star Our sun has been on relatively good behavior for billions of years. While M red dwarfs make up some 80% of galactic stars, this preferred solar type and temperature range is more conducive for life and evolution.
Multiple Suns are Common A majority of stellar objects are found to occur in vicarious double pairings or triple combinations. Binary star regimes in constant motion are considered to be hostile, highly variable environs.
Stellar Clusters in Galaxies Another usual condition is a tendency for stars to cluster together in fluid galactic groupings, which makes suns with orbital planets harder to form and maintain. Our star is not in a crowded area.
Stable Solar System Our own warm sun with an array of eight distinct worlds has experienced a rare long-term stability. A ninth outer planet or more is seen as disruptive. Most exosolar arrays found so far exhibit all manner of chaotic instabilities.
Unique Orbital Geometries For another anomaly, our familiar orrery of worlds all lie in the same plane, with mostly well spaced, circular orbits. A Bohr atom type swarm of planets every which way, often close in, is more prevalent.
Solar Habitable Zone Precious Earth resides in a relatively benign middle location from the sun between fried too near and frozen far out. So situated, its daily rotation and 365 day annual orbit are very conducive.
Galactic Habitable Zone The solar system is located half way from a prohibitive center and too far outer bands. By virtue, beneficial metallicities can occur in the sun and for planetary accretions.
Jupiter’s Journeys This orderly milieu is due to past movements of the gas giant Jupiter in toward the sun and back again. This is known as a “grand tack,” which served to remove a usual inner crush of rocky worlds, leaving only Mercury.
Rare Ratio of Land and Water Among thousands of exoworlds found so far, Earth has a unique 30 – 70 % division of dry land and ocean over a long time. A more usual state, e.g. Mars and Venus, and through the galaxy, is a default to all arid, wet/icy, or gaseous.
Plate Tectonics Still another rarity is the past movement and contact of continental land masses over many millions of years. Their geological and climatic dynamics are seen to foster evolutionary development, which a stationary mantle would not do.
A Timely Oxygenated Atmosphere Earth life’s embryonic biosphere was able to achieve at an early age (Gaian bottleneck) a stable optimum of a 21% oxygen and 78% nitrogen balance. Below 15% or above 25% oxygen would starve or burn environments and organisms.
Asteroid Impact Rates By many paleo-studies, it has been found that Earth sustained a tolerable degree of asteroid hits, while the more usual rain of many more collisions which would be catastrophic to life and intelligence able to learn all this.
An Ideal Moon However it happened, Earth has had a largish moon in just the right place for a long duration. Its presence then causes moderate tidal flows and basins to foster stromatolites and cyanobacteria at life’s origins, go onto mediate weather, light up a dark night for hominins, and more favors.
A Good Axial Tilt for Seasons Earth’s polar axis goes through a 23.5 degree swing each year, aka obliquity, which causes vital seasonal variations. While a 10 to 50 degree range may harbor life, a spring, summer, autumn, winter cycle seems well suited.
A Geomagnetic Field 2021 findings imply that a relatively steady, stable strength is a vital necessity from life’s origin and throughout its developmental emergence.
Arboreal Tree Height As evident on Earth, life’s evolution was fostered by the right amount of ground water so that fertile forests could grow to an optimal size.
Planetary Magnetism Earth has maintained liquid surface water and an airy atmosphere over eons aided by a strong magnetic dipole moment. Other planets such as Venus and Mars do not have this vital feature.
Stellar Spectral Energy Radiance As a sun shines, it must do so at an appropriate rate over a long time span so that life on a habitable, orbital world can evolve from simple to complex entities like us.
Active Galactic Nuclei Their energetic emission in the Milky Way is another factor which can influence living, evolutionary systems
Volcanic Activity A vicarious degree of eruptions from molten global interiors can life’s chances to appear, survive and evolve. (May 2022)
Ocean Salinity It appears that the salt levels of watery expanses are beneficial, while higher, lower or changing amounts can inhibit. (May 2022)
Variable Flows of Cometary Chemicals It is newly found that while comets can bath the planet with biomaterials, their timings and amounts can occur on a stochastic basis. (September 2023)
Paleoclimate Effects from Passing Stars Interstellar movements may brush close enough to have an atmospheric influence. (February 2024)
2020: With regard to this incredible significance, we propose an EarthMost identity so to properly name and represent our possibly fittest, optimum home. As a Pedia progeny now may embark on her/his open frontier of evolitionary continuance, we are aware of how rudimentary our current understandings must be. But in this geonatal moment, when a decisive self-selection between end or begin, kinder or cinder, must be made, this august finding could bring a vital incentive. For an example so far, we suggest works by Marina Alberti and David Wallace-Wells.
2020 - 2023 References:
Boyle, Rebecca. Astronomers Reimagine the Making of the Planets. Quanta. June 6, 2022.
Burkhardt, Christoph. Planetary Genealogy. arXiv:2203.02203.
Canup, Robin and Philip Christensen, Co-Chairs. Origins, Worlds and Life: A Decadal Strategy for Planetary Science and Astrobiology. Washington, DC: National Academy of Sciences, 2022.
Drazkowska, Joanna, et al. Planet Formation in the Era of ALMA and Kepler: From Peebles to Exoplanets. arXiv:2203.09759.
Cirkovic, Milan. The Great Silence: Science and Philosophy of Fermi’s Paradox. Oxford: Oxford University Press, 2018.
Frank, Adam, et al. Earth as a Hybrid Planet: The Anthropocene in an Evolutionary Astrobiological Context. Anthropocene. August, 2017.
Gilbert, Gregory and Daniel Fabrycky. An Information Theoretic Framework for Exoplanetary System Architectures. arXiv:2003.11098.
Madhusudan, Nikku, ed. ExoFrontiers: Big Questions in Exoplanetary Science. Online:IOP Science Books, 2022.
Mishra, Lokesh, et al. A Framework for the Architecture of Exoplanetary Systems. arXiv:2301.02374.
Secco, Luigi, et al. Habitability of Local, Galactic and Cosmological Scales. arXiv:1912:01569.
Smith, Howard A. The End of Copernican Mediocrity. Zoe Imfeld and Andreas Losch, eds. Our Common Cosmos. London: Bloomsbury, 2018.
Raymond, Sean and Alessandro Morbidelli. Planet Formation: Key Mechanisms and Global Models. arXiv:2002.05756.
Sandford, Emily, et al. On Planetary Systems as Ordered Sequences. arXiv:2105.09966.
As an October 2023 presentation, this five part Nova program draws on the latest scientific findings to vividly illustrate the long past eons from fiery origins all the precarious way to such a worldwide reconstruction. As the episodes proceed, a series of volcanic, gaseous, thermal conditions and awesome cataclysms are shown, any of which could have ended it all. Yet as if from an essential, innate fertility, living flora and fauna rise Pheonix-like again each time.
As a further observation, while a standard view is that since myriad galaxies and planets are now known to exist, there must be many other Earth-like habitable worlds. But as these graphic displays evince, as the closing words aver (Humans), and this section documents, life’s evolutionary development is constantly fraught with serial capricious perils. Our own Earthhuman persona, 4.5 billion years on, had to pass through many narrow check points. Please see the new 2024 edition for much more on these issues.
Witness the dramatic history of Earth from its birth to the emergence of humanity. How did a hellscape of molten lava transform into a lush, green, watery planet filled with life? With realistic animation based onthe latest research, each of five episodes reveal long-lost, imperiled eras that ultimately led to the present biosphere. (Introduction)
Birth of the Sky: 4.5 billion years ago, Earth was a very different place: a hellscape of molten lava and barren rock under bombardment from meteors, and with no atmosphere. How did our familiar blue sky come to be? A chorus of science experts reveal how the primordial inferno gave rise to a cauldron of toxic gasses that would be deadly to us today.
Frozen: 700 million years ago, Earth was a giant snowball cloaked in ice from pole to pole. How did life manage to hold on in this forbidding world? Leading scientists investigate how this catastrophe may have become a catalyst for life to evolve in creative new ways as it bounced back from the brink.
Life Rising: For billions of years, life teemed in the oceans of planet Earth while the land was desolate and inhospitable. Here we explore how the earliest life emerged and invaded a barren, rocky landscape, eventually transforming it into a verdant, green world. See how the first plants made landfall and partnered with fungi to create soil that would sustain them.
Inferno: 252 million years ago, the most devastating mass extinction abruptly wiped out around 90% of all species on Earth. The culprits were the biggest volcanic eruptions the world has ever seen, emitting some 700 thousand cubic miles of magma and rock. The event – now called “The Great Dying” – came close to wiping out life on the planet. Follow scientists as they gather geologic evidence from the deep past to discover how life made it through.
Humans: The story of Earth can only be told because a technological and self-aware animal species now roams its surface and studies the planet that gave rise to it. This segment shows the cataclysmic asteroid strike that wiped out the dinosaurs, changing climates that allowed primates to appear and led to the evolution of a bipedal being. It closes with the power and paradox of humanity’s profound impact on our planet, and ponder how peoples may shape its future.
Humans Narrative Opening: From a fiery hellscape to a thriving oasis. What an extraordinary series of events gave rises to us. Closing; The planet we have transformed now supports eight billion people. A remarkable milestone for a species that was unlikely to have evolved at all. The chances that any and all of us existing are so small, it must make us realize how lucky we are.
Ambrifi, Alessandro, et al.
The Impact of AGN Outflows on the Surface Habitability of Terrestrial Planets in the Milky Way.
Into 2022 Vergata University of Rome and Florida Institute of Technology exophysicists including Arnedeo Balbi and Manasvi Lingam can quantify and report how such energetic emissions across the parsecs could be another factor which can influence living, evolutionary systems.
Active galactic nuclei (AGN) are accompanied by winds and emission which may reach 10 percent the speed of light. Here, we describe how AGN winds can heat atmospheres and drive their escape, which forms nitrogen oxides which cause ozone depletion. Our models estimate the maximal distance to which these deleterious effects are rendered significant for Earth-like planets, and show that this value may extend to ≲1 kpc. In the case of quasars hosting larger supermassive black holes, such effects could actually influence the AGN host galaxy as a whole. (Abstract excerpt)
Orbital Properties and Implications for the Initiation of Plate Tectonics and Planetary Habitability.
new findings pour in, an Indian Institute of Technology astrogeologist can look more deeply into our Earth life occasion and realize the vital role played by mobile plate tectonics. Thus another key factor is added to an extent that the paper closes with an Earth, the Unique Planet title.
The existence of plate tectonics on the Earth is directly dependent on the internal viscosity contrast, mass of the planet, availability of liquid water and an internal heat source. However, the initial and long term optimum conditions of rotational velocity and periodicity of the Earth’s orbit around the Sun must also have been significant for the inception of plate tectonics. Such an optimal condition for the rotational and revolutionary periodicities could be essential for the development of plate tectonics on the Earth. (Abstract excerpt)
In either case, these two events (moon formation and core segregation) have major implications for the initiation of plate tectonics and the emergence of life. Plate tectonics provided the essential ingredients in the form of a uniquely evolving atmosphere, hydrosphere and active geomorphology. The latter in turn provided sources and sinks for sedimentation processes that could circulate nutrients for organic evolution and contribute to the ultimate emergence of life forms as diverse as it is on the Earth. (2)
The Earth’s Shell has Cracked, and We’re Drifting on the Pieces.
New York Times.
The popular science writer draws upon a Royal Society meeting about plate tectonics and Philosophical Transactions A issue from it (see Robert Stern herein for more) about how our home planet has been distinguished and enlivened by mobile continental forms over a billion years, while Venus and many other worlds have not. It is noted that this ancient surface balance of land and sea is vitally crucial for a planet to become habitable for life and evolution. She consulted with R. Stern (UT Dallas), Jun Korenaga (Yale), Aubrey Zerkle (St. Andrews, Scotland)), and others as this rare Earth crustal and oceanic interplay grows in significance.
This volume brings together contributions from the Royal Society Discussion Meeting on ‘Earth dynamics and the development of Plate Tectonics’ held in March 2018. Plate tectonics is not seen on other planets, so why does it occur on Earth, and when did it start? The nature of tectonics depends on initial conditions, mantle thermal states, and an ability to weaken the lithosphere to allow plate boundaries to form. Geodynamic models, rock deformation experiments, models for growth of the continental crust, and evidence from the rock record are consistent with the development of plate tectonics from a single-lid state. Major changes occurred in the geological record near the end of the Archaean, suggesting that plate tectonics had become the dominant gobal regime by the Proterozoic. Modern plate tectonics and the generation of stable continents were key events in the evolution of the biosphere on Earth, and similar tectonic processes could be crucial for the development of habitability of exoplanets. (Synopsis)
Armstrong, Stuart and Anders Sandberg.
Eternity in Six Hours: Intergalactic Spreading of Intelligent Life and Sharpening the Fermi Paradox.
The physicist Enrico Fermi famously asked in the 1950s that for a universe then thought to be rife with advanced civilizations, so “Where is everybody?” This question has been much debated since, a Wikipedia entry under its name provides a good survey. Here Oxford University, Future of Humanity Institute, philosophers contend that galactic travel and celestial reengineering are really not prohibitive, so once a world which did not destroy itself got unified and going, they should have formed evident reconstructions. But nothing like a “Dyson sphere” built by a civilization around its star has been seen. Even though Kepler satellite discoveries forecast some quintillions of earth-like bioplanets across galactic spacescape, the authors go on to allude that there may not be anyone else out there.
The Fermi paradox is the discrepancy between the strong likelihood of alien intelligent life emerging (under a wide variety of assumptions) and the absence of any visible evidence for such emergence. In this paper, we extend the Fermi paradox to not only life in this galaxy, but to other galaxies as well. We do this by demonstrating that travelling between galaxies – indeed even launching a colonisation project for the entire reachable universe – is a relatively simple task for a star-spanning civilisation, requiring modest amounts of energy and resources. We start by demonstrating that humanity itself could likely accomplish such a colonisation project in the foreseeable future, should we want to. Given certain technological assumptions, such as improved automation, the task of constructing Dyson spheres, designing replicating probes, and launching them at distant galaxies, become quite feasible. We extensively analyse the dynamics of such a project, including issues of deceleration and collision with particles in space. Using similar methods, there are millions of galaxies that could have reached us by now. This results in a considerable sharpening of the Fermi paradox. (Abstract)
The “we are the first/only civilization” explanation is also weakened from the expanded potential origin space: the likelihood of intelligent life must be reduced by many orders of magnitude compared to previous arguments. If this explanation is the true answer, the future is also far bigger than commonly thought; (post)humanity can expand over very vast distances and achieve very large populations in an otherwise empty and value-less universe. We may hence be obliged to safeguard the potential value of this vast future from risk to a far greater degree than is normally recognized. (12)
Astrobiology, Sustainability and Ethical Perspectives.
In this online journal which has become a home for authoritative writings about saving the planet, a CNES French Space Agency philosopher contends that an expansive panorama that views earth and human in the context of a conducive, life friendly cosmos could be of much utility and incentive.
Astrobiology, a new field of research associating the prospects and constraints of prebiotic chemistry, mineralogy, geochemistry, astrophysics, theoretical physics, microbial ecology, etc., is assessed in terms of sustainability through the scientific and social functions it fulfils, and the limits it encounters or strives to overcome. In the same way as sustainable development, astrobiology must also take into account the temporal dimension specific to its field of investigation and examine its underlying conception of Nature. (Abstract)
Bach-Muller, Nanna and Uffe Jorgensen.
Orbital Eccentricity: Multiplicity Correlation for Planetary Systems and Comparison to the Solar System.
As exoplanet findings grow in number and variety, Niels Bohr Institute, University of Copenhagen astroscientists can perceive another unusual aspect of our home orrery. With regard to most other systems with a few worlds, our 8 or 9 member planets as well as their relatively round orbit and even spacings is a quite rare confluence. As we post in late 2020 with our precious, precarious Earth beset by so many perils, this awesome significance grows in validity. See also Solid Tidal Friction in Multi-layer Planets by Emeline Bolmont, et al at 2010.04587.
The orbit eccentricities of the Solar System planets are unusually low compared to the average of known exoplanetary systems. A power law correlation has been found between the multiplicity of a planetary system and the orbital eccentricities of its components for systems above two worlds. In this study we investigate the correlation for an expanded data sample by way of planetary systems as units (unlike studies of individual planets). Our full survey contains 1171 exoplanets in 895 systems whence the correlation between eccentricity and multiplicity follows a clear power law. We find that Solar System orbits fit the general trend and suggest that the Solar System might not show uncommonly low eccentricities but rather more planets compared to a "standard" planetary system. Based on the power law correlation, we estimate that the probability of a system having 8 planets or more is of the order of 1%. (Abstract excerpt)
Balbi, Amedeo and Adam Frank.
The Oxygen Bottleneck for Technospheres.
After some 15 years of habitable exoworld studies across solar system and galactic zones, University of Rome and University of Rochester astrophysicists (search each) realize that the narrow O2 window between enough for fauna to breathe but not for flora to combust is a prime parameter with regard to possible intelligent civilizations. At this juncture, one more
strident value now delimits the presence of optimum Earth-like occasions. So still another winnowing factor might well distinguish our fittest anthropocene to astropocene opportunity.
On Earth, the development of technology required easy access to open air combustion, which is only possible when oxygen partial pressure, P(O2), is above 18\%. This suggests that only planets with significant atmospheric oxygen concentrations will be capable of developing advanced technospheres.
Fig. 1: Planets capable of supporting high O2 concentrations and, hence, technological
civilizations. This figure shows the likely composition of atmospheres based on mass
and equilibrium temperature. For planets whose temperature and mass would lead to
CO2/N2/H2O atmospheres, high oxygen levels require a biological origin, i.e. photosynthesis.
Fig. 2: Earth’s atmospheric O2 concentration over time. Top: O2 concentration at 4 Gyr ago. Bottom: O2 concentrations 600 Myr ago, around the development of multicellular life. The horizontal lines represent the current P(O2) level, the threshold for global wildfire and the minimum requirement for combustion. In both figures we label important events in the evolution of life.
Balbi, Amedeo and Francesco Tombesi.
The Habitability of the Milky Way during the Active Phase of its Central Supermassive Black Hole.
Nature Scientific Reports.
Vergata University of Rome astrophysicists add still another deleterious impediment due to excessive galactic radiations from the main galactic black hole which prohibit the long multi-million year span necessary for organisms to form, evolve and complexify.
During the peak of their accretion phase, supermassive black holes in galactic cores are known to emit very high levels of ionizing radiation, becoming visible over intergalactic distances as quasars or active galactic nuclei (AGN). Here, we quantify the extent to which the supermassive black hole at the center of the Milky Way may have affected the habitability of Earth-like planets. We focus on the amount of atmospheric loss and biological damage suffered by planets exposed to X-ray and extreme ultraviolet radiation. We find that terrestrial planets could lose a total atmospheric mass comparable to that of present day Earth even at large distances from the galactic center. (Abstract excerpt)
Ballmer, Maxim and Lena Noack.
The Diversity of Exoplanets: From Interior Dynamics to Surface Expressions.
The paper also appears in a special issue Geoscience Beyond the Solar System issue of Elements magazine (17/4, 2021). University College London and Free University of Berlin astroscientists extend exoworld studies so as to factor in effects of variable internal compositions upon relative habitability. Indeed it is found that over eons and eras their core to crust fluctuations could play a major role. See also Starting Life and Searching for Life on Rocky Planets by Paul Rimmer, et al (2108.04.08388) in the same edition.
The coupled interior-atmosphere system of terrestrial exoplanets remains poorly understood. Exoplanets show a wide variety of sizes, densities, surface temperatures, and interior structures, which all effect this coupled system. Many exoplanets could have a "stagnant lid" at the surface, with a rigid stationary crust, sluggish mantle convection, and minor volcanism. However, if exoplanets have Earth-like plate tectonics and tectono-magmatic activity, then these features may be critical for planetary habitability and have implications for the development (and evolution) of life in the galaxy. (Abstract)
Testing the Multiverse: Bayes, Fine-Tuning and Typicality.
Reviewed more in Anthropic Principle, the University of Sydney astronomer (search) posts his presentation at a 2014 London Philosophy of Cosmology conference. As a coauthor with Geraint Lewis of A Fortunate Universe (2016), this entry discusses anthropic themes along with Bayesian “theory testing” methods for better iterations of “relative certainties or credences.” For this Greatest Earth section, it is wondrous that inquisitive, globally cognizant peoples can imagine whole cosmoses at all. With 400th anniversary events underway for Galileo, what can these expansive vistas from our moon to a multiverse ever portend? As latest currents seem to presage, human beings ought to have a significant purpose in the actual scheme of things.
Tidal Locking of Habitable Exoplanets.
Celestial Mechanics and Dynamical Astronomy.
A University of Washington astronomer quantifies one more crucial condition as to whether a candidate orbital world could harbor living, evolving systems, or be prohibitively hostile to it. Since this Earth has been benign long enough to reach our global observation, its tidal regime, in accord with the moon and sun, must have been fortuitous. See also Niche Amplitude, Tidal Locking and Fermi’s Paradox and Evolutionary Exobiology II by David Stevenson in the International Journal of Astrobiology (Each online July 2018).
Potentially habitable planets can orbit close enough to their host star that the differential gravity across their diameters can fix the rotation rate at a specific frequency, a process called tidal locking. Tidally locked planets on circular orbits will rotate synchronously, but those on eccentric orbits will either librate or rotate super-synchronously. Lower mass stellar hosts will induce stronger tidal effects on potentially habitable planets, and tidal locking is possible for most planets in the habitable zones of GKM dwarf stars. These results suggest that the process of tidal locking is a major factor in the evolution of most of the potentially habitable exoplanets to be discovered in the near future. (Abstract excerpt)
Tidal locking is the name given to the situation when an object’s orbital period matches its rotational period. A great example of this is our own Moon. The moon takes 28 days to go around the Earth and 28 days to rotate once around it’s axis. This results in the same face of the Moon always facing the Earth. We see other examples of this in our solar system and universe. An extreme example is the case of Pluto and Charon. Charon is such a large satellite compared to Pluto that they are tidally locked together. (spaceanswers.com)