How Earth Became Humanity's Home
1. Why Ask "Why"?
p13 An appropriate counterpoint to Sagan and the Copernican Principle
2. The Way the World Is
p17 Life at 3.47Gyr from fossils, 3.83 Gyr with the 13C/12C studies.
p18 High O2, low CO2 speaks of a vast time of photosynthesis. Points to exceedingly rapid recovery from extinction events. Great diversity with 8.7 million varieties of eukaryotes (6.5million on land, 2.2 million in the seas). Prokaryotes less well defined, 100,000 to 10 million.
p19 2.8 billion years of unicellular life, 1 billion multicellular of which the last 0.6 billion includes the animals. Comments on Darwin's gradualism in contrast to Eldridge & Gould's punctuated equilibrium, also comments on Simpson.
3. Essential Construction Materials
p24 Discussion of "Just Right Mass". The H-He step, critical density, dark energy and fine tuning.
p25 "Just Right Age", 9Gyr as an active preparation period.
p26 Diversity of heavy elements, required quantities, highlights 238U and 232Th as the long half-life elements which provided heat for plate tectonics and magnetic field. Fast radioisotopes blasted off excess atmosphere.
p27 Putting 9Gyr of elements to use.
4. The Right Neighborhood
p29 About galaxies - necessity of spiral galaxy for life, must be where it can consume dwarf galaxies to maintain spiral form.
p30 Main line is the defense of the need for spiral galaxy and the common circumstances that disrupt them.
p31 Box: "Why a Spiral Galaxy?" Only there is a long history of life possible. Argues the uniqueness of the local group of galaxies.
p32 There must be a star forming rate high enough to sustain the spiral structure.
p32 Why significantly larger or smaller galaxies won't do
p33-35 Comparison of MWG and Andromeda, which are of similar size. Discussion of location of solar system near the co-rotation axis of our galaxy.
p35 Initial site: as in a building site, solar system was volatile poor and refractory rich, a wealth of metals light and heavy including heavy radioisotopes
p36 Figure 4.2 The co-rotation axis. for MWG about 26000 light years from center. Related to solar systems proximity to co-rotation axis, fortuitous abundances of elements. Earth has < 1/1200 of carbon-based atmospheric gases and 1/500 of liquid water, <0.03% of total mass, so allows continents to form.
p37 Metal content suggests formation closer to galactic center. Fig 4.3 metallicity vs distance, minimum metallicity at co-rotation axis
p38 Discusses Al-26 - decay blew off volatiles. Interesting that Al comprises 8.1% of Earth's crust while it is <0.01% of universe's ordinary matter.
p40 Evidence that the solar system formed in a dangerous-to-life zone and then moved to the safest place, just inside the co-rotation axis.
p41 Staying in the plans +/- 228lyr compared to 1000 lyr thickness, so stays very near plane.
5. Site Preparations
p43 First 740 Myr called Hadean era
p44 Gas giant gaurdians
p45-48 Need to reread. The "Grand Tack" - modeling of Jupiter and Saturn migration.
p48 Moon-forming event
p49 Moon 50x larger than any other moon compared to its planet, and orbits more closely - too close to the Sun to have formed within the Sun's protoplanetary disk. "just right impactor struck Earth with just-right timing, angle and velocity to allow for the Moon's formation"
p51 Ward and Robin Canup, impact-generated disk. 50 to 100 million years after Earth coalesced. 2004 Canup study. 2008:Impactor 2x mass of Mars, 2012:zinc isotope study
p54 Canup 2013 "current theories on the formation of the Moon owe too much to cosmic coincidences" Diagram5.3 Lagrange points
p56 About 95 Myr after Earth formation
p56 List of 9 life-friendly implications of Moon-forming process
p58 Box The Moon's Marvelous Mass
p58-60 "Late veneer" or "late acretion". 6 features. Water and atmosphere, highly siderophile (iron-loving) elements, damped eccentricity, activated plate tectonics, increased mass of carbonaceous compounds
6. Not Quite Ready
p63 4.6Gyr age of Sun represents a minimum of flare activity. Diagram. 15-20% mass loss, 80% loss in luminosity, bombardment for 700Myr.
p64 Graph of Sun's luminosity
p65 Saturn and Jupiter dynamics, Trojan asteroids and Lagrange points L4 and L5 of Jupiter.
p65 Jupiter and Saturn went through 1:2 orbital resonance - caused Late Heavy Bombardment? 700 Myr.
p66 3.8-4.0 Gyr - impact melting on Moon vrom Apollo 15,16,17, 90% of Moon's craters about 3.9 Gyr
p66 1:2 orbit resonance of Jupiter & Saturn disturbed Uranus and Neptune and triggered hundreds of thousands of projectiles into the inner solar system. The main belt asteroids pitched in.
p66-67 1:2 orbit resonance of Jupiter & Saturn explains Kuiper Belt, 3-5 billion miles 100x more massive than asteroid belt.
p68-69 More discussion of the importance of the 1:2 orbit resonance of Jupiter & Saturn
p72 Five belts
p73 Terrestrial planets in the dry region of the protoplanetary disk, so water had to be delivered. Comets as delivery vessels. Also delivery of heavy elements since heavy elements on Earth sunk to core.
p75 Recap of Grand Tack, Moon forming, late veneer, LHB, fifth planet timing, jumping Jupiter.
7. Ready for the Foundation
p79 Biogenesis or abiogenesis
p79-80 Gliese 581g, 20 lyr from Earth, 3.1-4.3x Mass of Earth, dim red dwarf, half the orbit of Mercury radius, tidally locked - but maybe doesn't even exist.
p81 Starts cataloguing the multiple habitable zones
p93 Interesting reflection on abiogenesis. Cites David Spiegel and Edwin Turner. Because of the 4Gyr development of modern life, life had to begin as early as possible in the Sun's lifetime. "billions of years later, curious creatures noted this face [of origin] and considered its implications."
8. Construction Begins Below Ground
p94 Notes that he heard Carl Sagan proclaim a virtually guaranteed production of life from chemicals in ocean.
p95 Twisted stalk-like structures found in 1.9Gyr rock in Germany's Black Forest. But tectonic processes have removed evidence for older rock. Proposes that they may be found on the moon.
p96 Isotope signatures - life preferentially selects the lighter isotopes, so a departure from the expected natural ratio can be a signal of life. 12C/13C, 14N/15N, 32S/34S.
p96 All carbonaceous substances in Earth's oldest rocks show isotopic evidence of having come from once-living organisms. That negates the primordial soup model.
p96-97 Very good discussion of problems of abiogenesis.
p97 Niles Eldridge quote "One of the most arresting facts that I have ever learned is that life goes back as far in Earth history as we can possibly trace it ... In the very oldest rocks that stand a chance of showing signs of life, we find those signs."
p98 Section "The Dating Challenge" In the 1990s 3.86 +/-0.01Gyr zircon wit graphite content with the 12C/13C signature of life. Problem is that the zircon could be older than the graphite. UCLA mass spectrometer study of 12C/13C yielded 3.825Gyr.
p99 Oxidized water implying photosynthetic life before 3.7Gyr and such have >2000 gene products, so early life was complex.
p99 Biotic graphite in tubules whereas abiotic graphite forms as flakes.
p99 Black shales of biosignature 3.8-3.85Gyr, 32S/34S indicates sulfur-based anoxygenic photosynthesis.
p100 Suggests that granites owe abundance to early life's photosynthesis, and suggests that life influenced production of stable continents.
p100 The LHB Challenge: Moon rocks suggest that the Late Heavy Bombardment was intense until 3.85Gyr.
p101 Analysis of things that hit Earth in LHB. Discusses massive disruption of Kuiper Belt leading to LHB. High iridium content. LHB comets and water delivery.
p102 Suggests that LHB persisted until about 10 million years before life.
p102 Oleg Abramov and Stephen Mojzsis refuge theory for hyperthermophyle life.
p104 Extremophiles poor candidates for abiogenesis.
p104 This whole discussion extends the content of the Origins of Life book.
p106 Homochirality problem. Brief here. More thorough in Origins of Life
9. Up to Ground Level
p109-110 Photosynthetic bacteria are very diverse and geographically widespread.
p110 Banded iron formations 3.7-3.8Gyr show evidence of sulfur-based life.
p111 "Life needs plate tectonics to persist; and plate tectonics needs life to persist." This is a new idea to me and I still haven't gotten my head around it. He calls it a synergism. He also said it was first recognized in 2006.
p111 The interaction between photosynthetic life and plate tectonics. Photosynthetic life leads to a metabolic rate orders of magnitude greater than non-photosynthetic life. At present photosynthetic organisms contribute three times more energy to Earth's geochemical cycles than does interior heat.
p111 Interesting comments about granite. Rosing quote.
p111 Also life may have contributed to formation of lighter feldspars to produce continents.
p112 Moves to conclusion that life contributed to tectonic motions and that without it greenhouse gases would not have been removed. That would lead to runaway greenhouse effect and a sterile Earth.
p112 Craig O'Neill "window of opportunity for enduring plate tectonics is quite narrow" Usually closer planets are more dense, but Earth more dense than Mercury.
113 List of 10 factors critical to long term plate tectonics. One of the critical factors is the existence of life on the planet's surface.
113 Using Mg as reference, Earth has 610x more thorium and 340x more Uranium. Most of the heat flow driving plate tectonics for 4 Gyr contribute to uniqueness of Earth's plate tectonics.
116 Geodynamo 3.5Gyr, even 3.9Gyr suggested by Apollo 14 & 17 mission - ?? don't really understand that. OK, the finding of excess N and light noble gases in lunar samples from Apollo indicate that Earth lacked a strong dynamo at 3.9 Gyr because it would have prevented the transfer of these gases from the Earth to the Moon. Still don't understand it, but perhaps I'm ignorant at a higher level.
Some proposed chronology for plate tectonics. "Shortly after the origin of life, geodynamics and tectonics both began.." At 3Gyr plate tectonics became sustained, aggressive and global.
p117 "The maintenance of long-lasting plate tectonics requires abundant co-existing life, especially abundant photosynthetic life."
p119 "Earth's preparation for advanced life entailed appropriate oxygenation of the atmosphere."
p119-120 3.8-2.45Gyr =0.001 of O2 of present 21% as estimated from sulfur ratios, or <.0001% from biomarker studies.
p120 2.45-2.32Gyr O2 jumped to ~1% of current level in the Great Oxygenation Event (GOE) just after an explosive increase in continental crust volume. Analysis of S isotopes suggests that it never sank below 1% after that.
"photosynthetic life-forms were pumping prodigious amounts of oxygen into the atmosphere for at least a few hundred million years before the GOE."
p121 Atmospheric O2 and methane production in competition, cycling around a fairly constant level between 3.83 and 2.45Gyr. This gradually removed between 10% and 26% of water from Earth's oceans. This exposed more crust and there was a great crust increase just prior to 2.45Gyr. This tipped the balance of volcanos so that a larger number were above sea level. For reasons I didn't understand, underwater volcanoes consume more oxygen that above sea level. There was then a dramatic rise in atmospheric O2. A critical step which was new to me was the reduction in nickel in the oceans. Ni catalyzes the methane production, so there was a dramatic drop in methane production and a rapid O2 increase. "Between 2.45 and 2.32Gyr atmospheric oxygen increased from 0.00001 of the current atmospheric level to at least 0.01 and perhaps as much as 0.03 of the current level."
p122 The demise of surface methanogens removed methane greenhouse gas from the atmosphere, and after the GOE there were three major glaciation events.
p122 One glaciation event was extensive enough to be called a "slushball" event, meaning glaciation penetrated down close to the equator, but stopped short of being an "iceball" event where the entire Earth is covered with ice.
p122 After GOE there was a great diversification of minerals. There was a proliferation of eukaryotic species.
p123 The combination of the GOE, glaciation, and cyanobacterial blooms produced about 80% of Earth's manganese economic resource. This was essential for modern industrial society. He discusses the uses of manganese. It was a time of the greatest biological productivity in the time frame 2.2-2.056Gyr. The Lomagundi event involved the burying of a huge amount of biological material. Then the Shunga event at 2Gyr converted much of this to oil, kerogen, bitumin.
p124 Interesting discussion of proliferation of mineral species. From meteorites only ~60 mineral species are found. Early Earth influences increased that to ~250, then with the influence of early life ~1500. After the Cambrian explosion at about 543Myr the number increased to ~4300 distinct mineral species.
p125 The oxygen cycled up and down over time with large oxygenation events preceding the Avalon (575 Myr) and Cambrian (Myr) explosions.
p126-127 Recap of the 2.45-2Gyr oxygen history that I need to re-read.
11. Invisible Progress
p128 The period 2.0 - 0.8 or 0.58Gyr is dubbed the "boring billion" even though changes crucial to advanced life were made.
p129 There was a restoration of methanogen levels below the surface of the oceans. The oceans remained anoxic except for the surface.
p130 Remarkable story of the oxic-anoxic bacteria called euglena. Depending on their surroundings they could switch from oxic to anoxic metabolism. There were long term oscillations of photosynthetic and methanongenic organisms which acted to stablize the environment for the "boring billion" period.
p131 "Euglena species and others like them played a key role in keeping the boring billion boring enough for life to endure."
p131 Stromatolites. During the boring billion there was much higher UV, so the bacteria which constructed the stromatolites formed UV shields above them, then there was upward migration of the bacteria and the creation of another layer.
p132 Sulfate Reducing Bacteria (SRB). At this time soluble metals were so concentrated as to make food sources for advanced life lethally poisonous. But with the SRBs there would be reactions with soluble sulfates in, insoluble sulfites out.
p133 SRBs loaded Earth's crust with high-grade metal ores. Some of these metals are toxic to life but vital to life, so must be balanced.
p134 List of "vital poisons" Table 11.1
p135 The gift of dirt. During the boring billion the sun gradually brightened and erosion increased the sandstones and carbonates, driving down the CO2 and keeping the temperature stable. Diagram of portion of Earth's surface covered by continents Fig 11.2
p136 Proposed 5 supercontinents with Pangaea plus four. High human population not possible within 200 million years of a supercontinent.
p137 Puts Pangaea at 510Myr.
p138 Diagram of Himalayan mountain formation. Context is nutrient recycling by mountains
p139 Suggests that nutrient delivery to continental shelf contributed to the Avalon and Cambrian explosions.
p139 Enriching the dirt. BSC (biological soil crust) - gives list of components. Should have used the old Nietzche joke "get your own dirt!" Good description of dirt - its composition and the functions of its components.
p140 Describes functions of those components of BSC. Soil-darkened surface decreases albedo and decreasing need for greenhouse gases.
p141 2.0-0.6Gyr BSC expanded, helped oxygenate atmosphere
12. Heating and Ventilation
p144 The faint-sun paradox. Sagan-Mullen 1972 paper. 30% increase 3.8Gyr till now is within 2% of maximum tolerable - descriptions of models for coping.
p145 At 3.8Gyr 100 to 1000x the CO2 to compensate for the faint sun.
p145 Methane proposal of 03 and 04 - not enough methane to overcome 25-30 difference in Sun's brightness at origin of life.
p146 Pavlov & Kasting methanogen proposal, but turned out to be too cold.
p153 Proposal that mass loss by sun during first 800Myr puts the change in solar luminosity at 15% rather than the previously assumed 30%. Diagram of Suckmarin & Boothroyd.
p155 Guzek Mussack model
p157 Diagram of mass loss for the Sun.
p158 Box "Could Mars Have Been Warm and Wet?" Discusses carbonate catastrophe on Mars whereby CO2, water and other greenhouse gases were removed from the atmosphere into carbonates, reducing it to a dry, cold wasteland.
p158-159 Contributers for compensation as solution to faint sun paradox.
p159 Section "Thermostat Adjustments" discusses roles of mass extinction events in providing needed steps. Five ways that organisms compensate for the brightening Sun.
p160 1. Silicate erosion: From 0 to 29% continent coverage, silicates dominant, water + silicates + CO2 reacts to remove CO2 and helps compensate for brightening Sun. Importance of CO2 role. Burial of life tissues 20% and erosion of exposed silicates 80% of CO2 removal.
p162 2. Organic carbon burial. Burial keeps the CO2 out of the atmosphere. 20% of CO2 removed versus 80% for erosion of silicates.
p163 3. Atmospheric composition
4. Cloud cover variations
p164 5. Changes in Earth's albedo. Further discussion of timing of extinctions. Discusses extinctions preparing way for modern civilization.
13. The Structure Rises
p166 Earth has about all the species it can handle. Step by step process from "formless and void" . As conditions became inhospitable for some kinds of life, other forms arrived to replace them.
p166 Earth's atypical resources.
p166 For Earth's position from the Sun, it would be projected to have 1200x as much carbon dioxide and 250 times as much water. Table 13.1 p167. Might be interesting to include as a comparison of Earth and the galactic concentration.
p167 Table relative to magnesium. Magnesium used for comparison since its fractional abundance is about the same in the whole MWG. In addition to the table, it notes 1200x less carbon and 250x less water, both of which are essential conditions for life on Earth.
p168 250 natural minerals to 4300 largely due to life processes.
p169 Table of biodeposits.
p169 Mass extinction timing. About 27 Myr period of extinctions over 500Myr.
p170 Graph of percentage extinction
p170 Earth's impact craters have about 35Myr periodicity. Earth's passage through the galactic plane is one possibility.
p171 The "boring billion", then 300 million, then 500 million preceding humanity.
p171 At the end of the boring billion everything needed for small animal survival was in place except for oxygen. The cryogenian era 750-580Myr had three major glaciation events. They exposed basalt, and weathering basalt removes CO2 from the air. The greatest ice age was the Marinoan. Transition from CH4 dominated to CO2 dominated. Phosphorous to oceans, photosynthetic marine organisms gave the Neoproterozoic Oxygenation Event (NOE) immediately after the cryogenian era. Discusses the Sturtian, Marinoan and Gaskiers glaciation events with the Marinoan being the greatest known ice age.
p172 Warm interglacial episodes following each ice age enhanced transition from CH4 domination to CO2 domination. There was an increase of photosynthetic organisms. Oxygen sinks were now full. Stimulated by phosphorous and other nutrients to the oceans, the multiplication of marine photosynthetic organisms brings us to 580Myr.
p172 The First Avalon Explosion. Prokaryotes dominant at 575Myr.
p173 After the Gaskiers glaciation event the bottom of the ocean was transformed from anoxic to oxic. There was rapid development of complex organisms. The Avalon Explosion brought more symbiotic relationships.
p174 The Second Avalon Explosion. The First Avalon creatures were fixed to the sea floor, like sponges, with no evidence of mobility. Things changed at 560Mr. 550 Myr first reefs. 545 Myr first predators. But still no eyes, ears or digestive tracts.
p174 544-543 Myr major extinction of Ediacaran biota from the Avalon explosions.
p175 Cambrian Explosion 543-542 Myr. 50-80% of animal phyla known to exist appeared within no more than a few million years.
p175 Geologists "at Franklin and Marshall College showed that of the 182 animal skeleton designs theoretically permitted by the laws of physics, 146 appear in the Burgess Shale"
p176 Global changes in oceans - he associates it with the Great Unconformity - P, Mg and other changes in sea chemistry made skeletal formation possible.
p176 First optical devices during Cambrian explosion
p177 Cites Simon Conway Morris on no "reasonable delay" in development of predator-prey relationships.
14. Finishing Touches
p181 Geologic periods and eras. Atmospheric CO2 dropped from 7000ppm to 4500 ppm in Ordovician-Silurian transition and then to 280ppm in the preindustrial human era. Compare with my treatment of geologic periods.
p182 Mass extinction at Ordovician-Silurian ranks as second most devastating extinction. Wiped out 100 marine species, 49% of all animals, 85% of marine species. Major mass migrated to South Pole, freezing and lowering sea level, drying Ordovician shallow seas. Huge increase in volcanic activity. Then there was a movement back toward equator and recreation of the shallow seas.
p183 Lau Event and Devonian Explosion at 424Myr. Extinction of 2/3 of fish taxa. Then Devonian explosion 420-359Myr. Plant explosion, drop of CO2, trees near end of period, burial of forests. 4400-2200ppm CO2 end of Devonian. O2 up to 16%, wildfires, more carbon. Obligate symbiosis, fish multiplied.
p184 374Myr major extinction event 50% of genera. 359Myr Extinction of 44% of marine vertebrates. Net loss of 55-60% of Devonian species. Late Devonian gave petroleum.
p185 CO2 drop 2200ppm to 800ppm, cooled Earth out of the warm Devonian to the relatively cool Carboniferous and Permean. 359-305 Vast forests grew, trees bring O2. In Carboniferous the 8:1 bark to wood ratio and even up to 30% compared to 1:4 for present trees. Made the great coal beds.
p186 Permean 305Myr change from warm and humid to cold and dry. More elevation, more ice, lower sea level. Destruction of the carboniferous rainforest. O2 dropped to 23%, CO2 slightly up to 900ppm, lots of reptiles and insects.
p186 Permean-Triassic mass extinction 252.3Myr 90-96% of marine life, 70% of land species. Discusses possible causes.
p187 Triassic recovery 251-201Myr, dinosaurs and mammals
p187 Discusses O18-O16 ratios as proxies for ocean temperature. Major rise to 90F. Plate tectonics, Pangean split, temperature drop, new mass speciation event. Seed plants. Reptiles including dinosaurs, mammals, flying vertebrates - suddenly.
p188-189 Triassic-Jurassic Mass Extinction (TJEE) 201.564Myr quoted. Extinction of half of species. Eruption of CAMP central --4 huge eruptions that could cover Earth to nearly 20ft. Global extinction. Sulfur, SO2, global cooling, then bounce back with warming period, massive wildfires, 95% of terrestrial megaflora species plus the dependent animals.
p189 Jurassic recovery. Dated by magnetic reversals to give accurate time map. 10kyr large dinosaurs, 100kyrs full complement of dinos.
p190-191 Jurassic-Cretaceous Radiation and biodeposits. 201-66Myr. Breakup of Pangaea, dry to humid rainforest 61-64¡F temperature rise, conifers became dominant plants, dinosaurs the dominant animals. 201-146Myr Triassic birds , mammals, lizards, then a mysterious extinction followed by emergence of T-rex, triceratops. Flowering plants became dominant. 146-66 Cretacean birds, mammals, flowering plants.
p191 "life filled virtually every habitat on Earth"
p192 In the Jurassic and Cretaceous there was an enormous accumulation of biodeposits. He mentions the Deccan events in India.
p192 Cretaceous-Paleogene extinction. Chicxulub 66Myr. 3 billion times the combined Hiroshima and Nagasaki bombs. cits March 2010 science.
p193-194 Chicxulub summary. Includes comment about Deccan traps. 5m thick tsunami deposit on Dalmatian Island in Adriatic Sea has same isotopic signature as the Chicxulub impact material.
p194-195 Paleogene Recovery, quick and robust. Paleogene 66-23Myr. Big plate tectonic events, Antarctica, circumpolar current, retreat of North American shallow seas. Drop from 1700 to 500ppm CO2. Big role for ants. CaMg handling. Angiosperm appearance and great diversity, preparation for advanced life. "explosive appearance of diverse angiosperm species". Then explosive emergence of insects.
p196-197 Neogene Continental Alignment 23-2.59Myr. Producing current alignment. Puts N & S America connection near 2.6Myr. Decidious continued to replace conifers. Expansion of variety and extent of grasses. Ant impact is discussed again. CO2 down to 280. With Antarctica and cooling, move toward ice ages.
15. Ready for Occupancy
p198 The ice age cycle and how it ultimately enabled Earth to house a lot of humans. Quaternary period 2.6Myr to present.
p199 Ice ages history graphic- past much different from more recent cyclic ice ages
p200 Landmass to ocean reconfiguration
p201 2. Antarctica's move
3. Isthmus and Panama formation ~3Myr
p202 4. Greenland's uplift
p203 5. Rise of Tibetan plateau
p204 Milankovitch Cycles
p206 List of factors
p206 Shift from 41000 yr cycle to 100000yr cycle.
p207 Graph of Antarctic temperature variations. Mentions magnetic stratigraphy and tectonic sedimentology as time measurement methods.
p208 Major ice age 100000 years ago
p209 Benefits of ice ages. 12000 years ago, stabilization of mean temperature making possible widespread global agriculture.
p211-212 Table of ice age cycle benefits
p212 The long cool summer
p213 Fig 15.8 Last 150kyr temperatures. Global mean temperature steady for last 9000 years.
p214 Fig 15.9 Antarctic and Greenland ice cores. Optimum solar epoch. Neutrino studies using neutrino detection and fact that light to surface of sun is ~100000 years indicates extreme stability for 100kyr. Also mentions Sudbury study establishing pp fusion as 99% of sun's energy output.
p215 Optimum supernova moment, barely low enough for human beings to survive and sustain civilization.
p216 Deep floor sediments show an excess of 60Fe at 2 Myr corresponding with a marine extinction event - within 130 Lyr of Scorpius Cent giant stars -supernova. In 300000 years at least 23 supernovae within 980 Ly of Earth. Table 15.2 and 15.3 supernovae. None closer than 5000 Lyr in 12000 years.
p217 Optimum biological moment: grasses paleogene 66-23Myr, grains neogene, fruit trees, animals for cultivation- neogene quaternary, list of numbers of families of animals, cites Michael Denton
p218 Reflection - this won't last. Why now? reviews of forms of optimization for life now - unique moment
16. Why We're Here
p221 "The Bible tells us that the more we investigate the record of nature, the more evidence we will find for God's existence, for his handiwork in preparing the natural realm for our benefit, and for his purposeful involvement in our lives (Job 9,36:22-39:30, Ps 104).
p221-222 Good discussion in criticism of Krauss. Discussion in criticism of Kenneth Miller and Only a Theory, quotes a paragraph.
p222-223 Ps 104:27-30, then paragraph of perspective on multiple extinctions.
p223 Reflection on bountiful endowment, just right resources, includes rich deposits, regulation of CO2, plate tectonics, soil.
p224 Unique moment ice age cycle, 9000 yr stable temperature, nutrient rich plains
p225 Why we're here - summary of Biblical plan
Appendix A: Why Not Life on a Moon?
Responding to speculation that there might be life on a moon of a large gas giant in orbit about another star. Raises a host of improbabilities
Appendix B: Are We Alone in the Universe?
1900 extrasolar planets as of March 2015. Galaxy of several billion planets, list of unique features, "We humans are most likely the only sentient, self-aware physical beings", simple life for the joy of creating, angelic beings.
Bible Reference Material