Each ” . ” represents a million years.
In the beginning:
Space, time, matter, and energy exist for the first time ever.
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Light can travel long distances without hitting an atom, the birth of the Cosmic Microwave Background Radiation, which today is redshifted by an expanding universe into the 1.9mm wavelength, an expansion of 4,000 to 12,000 times its original wavelength.
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First stars form. Made entirely of hydrogen and helium, they are massive and very short-lived. Because scientists like to be deliberately confusing, they are known as population III stars because they were the first ones.
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The first galaxies form from cosmic hydrogen and helium. They are quite small, by which I mean millions of stars and tens of thousands of light years across. Tiny, really. These give rise to population II stars, many of which still exist today. Many of these are smaller, and thus longer-lived, but still very deficient of ‘metals’ — which in astronomy terms is anything other than Hydrogen and Helium.
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Large galaxies form. We know because we have pictures of them.
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The first quasar becomes active, and a massive black hole in the center of an early galaxy spews radiation into the void, becoming the most radiant type of object that has or will ever exist.
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The first confirmed measurement of dark matter by astronomers happened around this time. It was detected by gravitational lensing.
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The Andromeda Galaxy has formed and is falling into its characteristic shape.
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The Milky Way has achieved its spiral shape, and the stellar arms are clearly defined.
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Star formation peaks. It’s all downhill from here, and things will gradually get darker and colder forever.
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Alpha Centauri shines for the first time. It is a trinary system of two Sun-like stars and a red dwarf. No planets have been fully confirmed in this system, but there are tantalizing hints that they might exist. Today, this is the closest star system to Earth, but the Sun doesn’t exist yet.
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The oldest material ever recovered by scientists was created. Bits of stardust from within an ancient interstellar object were discovered inside a meteor that fell in Australia in 1969.
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Lots of things happened here, but nobody saw it. I think about that a lot.
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A large star in the Milky Way forms from a cloud of hydrogen, the massive gravity pulling the gas together into a roiling inferno of fusion and heat. The star is massive and is destined for a short life, ending in a massive supernova. Elements across the periodic table are formed in the massive compression and explosion that results in dispersing themselves into the vacuum of space.
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The remnants of the supernova begin to form streams and rivulets, mixing in with other clouds of interstellar gas, and in one tiny area, another star begins to form, a whirl of gas and dust forming dozens of planets, asteroids, comets, and a lovely yellow star in the middle that will eventually be called “The” Sun, as though there aren’t billions and billions of suns in the universe.
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Nine billion years have passed since, well, time began. There was no “before” the universe because time is a property of the universe, and until the universe existed, there was no “time.”
Earth forms as a conglomeration of dust and rock in orbit of a much cooler infant Sun. The entire planet is liquid, molten lava, and highly radioactive, with massive amounts of heavier elements like uranium still mixing about near the surface.
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A massive planet called Theia impacts the Earth, imparting considerable spin (although the Earth was already spinning before that) and restructuring the entire planet’s geology. Lighter elements fall into orbit around the Earth and eventually coalesce into the Moon, which is orbiting much closer to the planet than it does today. Days are about six hours long right now, and the Moon orbits every three or four days. Tidal forces are insane, and the molten crust of the young planet is massaged and kneaded by our sibling’s gravity. The collision tilted the Earth on its axis, giving us the seasons, which, in the early Earth, change between “the floor is lava” and “the floor is still lava, but now the air is burning too.”
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The crust begins to solidify, and initially, it is the elements with the highest melting point that solidify first, but they are quickly pulled down and replaced with lighter elements remaining on the cooling surface. Much of the surface is still molten, but lighter elements radiate heat more slowly into space. The atmosphere is very hostile to life, being caustic, acidic, and too damn hot.
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Water now exists on the surface of the Earth, and the pressure and temperature have changed to prevent it from boiling or evaporating too quickly. Puddles turn into lakes, lakes into seas, and seas into oceans.
Luca is born, the last universal common ancestor to all live on Earth. ‘Born’ isn’t the right word here — metastasizes, perhaps. Luca existed. She was single-celled, with a very simple cellular structure. She is little more than a lipid wall with DNA, RNA, and proteins floating inside. She is not to be confused with her older cousin, Fuca, the first universal common ancestor. Luca is the last link between Bacteria, Archaea, the Eukarya, the three great kingdoms of life. After her, they branch off into their own lineages. She is the last cell that all life on Earth today is descended from. All other lineages are extinct.
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Earth’s oceans begin to form, but they have very little salt in them. Volcanoes release water vapor into the atmosphere, which then falls as rain. The air is made of volcano emissions, consisting of hydrogen sulfide, methane, and two hundred times as much carbon dioxide as there is today. H2S is what gives rotten eggs their distinctive smell and can cause comas, convulsions, dizziness, headaches, and insomnia, depending on the dose. It is flammable, poisonous, and corrosive, as is the methane in the early air, but there is no oxygen yet to react with.
Water from comets and volcanic activity creates a layer of water that initially covers the entire planet.
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The Late Heavy Bombardment is ongoing, with many massive asteroids and comets falling onto Earth and all of the inner planets. Very little evidence of this remains on the planets, but the Moon has many craters that date to this era.
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During this period, the last of the iron band formations occurred, rather like the end of heavy metal music after the Black Album. Banded iron formations are over half of all iron deposits that humans mine.
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Earth’s magnetic field is forming as the core crystallizes into iron under immense pressure, with lighter elements making up the mantle. The Sun’s solar wind is a hundred times stronger than today, and it is precisely this magnetic field that protects the atmosphere from being stripped away as it was on Mars.
Greenstone belts are a geologic formation that tells us about this era, the remains of protocontinents. They are metamorphic rocks from volcanic island arcs and often contain silver and gold veins. Tiny amounts of oxygen are present in the atmosphere.
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Pongola glaciation, a partial glaciation event, and the first major appearance of ice on Earth. Hockey will not be invented for some time yet. Oxygen is present in some small, shallow sea beds.
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The rocks from this era hint at shallow seas, and continents are beginning to rise from the oceans. Stromatolites are forming, some of which are still around today, providing some early evidence of the complex, organized growth of life. The Earth is periodically covered in ice.
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The great oxidation event. Life has discovered how to use sunlight to split molecules, and massive amounts of free oxygen are released into the atmosphere. This event will last for five hundred million years. it was far short of today’s 18%, resting around 1–2% of the total atmosphere, but the changes were drastic. At first, the crust absorbed almost all of the oxygen as quickly as it was released by the cyanobacteria in the seas. Then, methane disappeared as it reacted with the oxygen, reducing the greenhouse effect drastically. The Earth is periodically covered in ice.
Oxygen changed the chemistry of every process on Earth, as it reacts with almost everything. Biochemistry is changing drastically as anaerobic organisms adapt to the corrosive and toxic oxygen. Protecting themselves from this new environment enhances cell membranes and endomembranes and leads to eubacteria adapting to life inside other cells, which later will evolve to become powerhouses — the mitochondria.
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Yarrabubba impact crater in modern Australia is formed. It is the oldest impact crater that we have found on Earth so far.
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The Earth has dozens of islands and tiny continents sticking out above the waves, but as yet no true continents have formed.
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The Bushveld Igneous Complex forms, containing some of the richest ore deposits on Earth in modern South Africa. It contains 75% of the world’s platinum.
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Sex is invented. Netflix is still a long way off, so what else are organisms supposed to do? This enhances the process of evolution and diversification, although we won’t see the results of it for a while yet. Now, instead of making clones of themselves, organisms mix and jumble their DNA together in a sticky and messy process that allows for more innovation and experimentation.
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Vredefort impact event. Vredefort crater is still clearly visible from overhead as an impact crater today and is probably the largest and most powerful impact event on Earth since the Hadean, considerably larger than the one that killed the dinosaurs.
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The islands on Earth’s great ocean are starting to move around. The Great Oxidation Event ends, and things settle down a bit.
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Sudbury impact basin in Canada forms the third largest impact even since the Hadean age. It is distorted due to plate tectonics but is now 62 by 30 km long and 15 km deep. The basin has been filled in over time.
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First multicellular life.
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First fungi.
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Hundreds of millions of years, and fungi are the best thing we’ve got going.
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Oh! There are some plants. Finally.
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The first animals evolve, but if you looked at them, you would think they were still plants.
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Cryogenian ice age. The entire Earth is covered in miles of ice, known as “Snowball Earth,” or perhaps there is a band of thaw near the equator, meaning it is more of a “Slushball Earth.” Scientists use those terms unironically. This is known as the Sturtian glaciation.
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Earth thaws. This period is very short, but also it lasts two million years. The climate is warm, and the oceans are anoxic (very little oxygen).
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Earth freezes again.
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Ediacaran biota was the beginning of the diversification of life. None of the lifeforms from this era have skeletons; thus, there are fewer fossils from this era.
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The Cambrian Explosion, or the Biological Big Bang. Everything just goes crazy in the biosphere, and from here on out, we see millions of species and massive diversification. There are massive deposits of life.
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Brachiopods evolve.
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Trilobites and exoskeletons evolve.
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Archaeocyatha extinction. These are sessile, reef-building marine sponges. The name means “ancient bowls” due to their shape.
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Burgess shale is laid down, one of the largest sites for the preservation of soft tissue fossils.
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Orsten fauna, evidence of the first tardigrades.
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The Cambrian-Ordovician extinction event. This event was caused by volcanic activity that greatly changed the chemistry in the oceans and atmosphere. It led to the near-total extinction of the trilobites, which had dominated Earth’s oceans for millions of years.
Ordovician period
Life is flourishing, and invertebrates such as mollusks and arthropods dominate the oceans. The first land plants evolve.
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The Ordovician meteor event. Several impact craters occur over a million-year period caused by the breakup of a large, Earth-orbit-crossing asteroid. The chaos in the climate caused by this may have led to the Great Ordovician Biodiversification event.
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Land plants discover spores.
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Andean-Saharan Glaciation. Nearly all of the land on Earth is in the Southern hemisphere, and all of it is covered in ice, which results in the Late Ordovician mass extinction.
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This is the second-largest mass extinction event in the history of Earth, where 85% of marine species disappeared. The ice melted, and the Earth warmed, creating climatic chaos. The recovery was quick, though, and within two million years (the blink of an eye, right?), life had found a way.
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A supercontinent has formed on the South Pole, including modern India, Africa, South America, and Australia.
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Early Devonian. Ammonoids dominate the biosphere, a mollusk characterized by their spiral shell pattern, related to the nautiloids that will come later.
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Shrubs and trees are common. Vertebrates exist, and are mostly fish.
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The oldest evidence of forests is from this time.
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This period is marked by a drop in oxygen levels below 13%, called the “charcoal gap,” because forest fires were impossible to sustain in the low oxygen content.
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Kellwasser event. The land is dominated by insects and plants, while massive reefs are built in the ocean by extant coral species. There is a major extinction event here that hit marine life, triggered by global cooling of an unknown cause.
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The Carboniferous Age. All of the coal that we burn today was laid down in this era, as massive forests sucked up the Sun’s energy and stored it away.
This is also the start of Romer’s gap, a twenty million gap in the fossil record of tetrapods (four-limbed vertebrates).
Land animal life is common during this period, and amphibians are the dominant form. They were much larger than today, taking advantage of the wet, warm climate.
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The end of Romer’s gap and tetrapod fossils become common again.
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Rainforests collapse, ending the age of amphibians, and the great continent of Pangea is still linked but exists now as pockets of diversification instead of single species being extant over the entire landmass. Oxygen levels are high, leading to very large insects and arthropods.
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Permian age. The world is divided — Pangea is most of the land mass, and there is only one ocean — Panthalassa. Vast regions in the interior of the land mass are deserts, and reptiles diversify to take advantage of the fading amphibians, who must lay their eggs in water to breed. Plants increase the durability of their seeds to compensate for the extremes of continental seasonal variations. Beetles appear.
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Permian-Triasic extinction event.
This is the largest extinction event ever and the only one to have affected insects to a great degree. Around 57% of biological families, 81% of marine species, and 70% of terrestrial vertebrates went extinct in only a few thousand years. It was caused by a massive release of carbon into the air that raised global temperatures by 5C, caused by volcanoes in Siberia which led to a cascade of effects and self-reinforcing cascades, which eventually raised CO2 levels to 2,500 ppm from a background rate of 400, which is what we are at today. Note that it was not the volcanos directly that caused most of the increase, but a succession of “triggers” or “tipping points” that followed that caused most of the increase.
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Trees have recovered
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Carbon-13 levels stabilize, putting the biosphere back in charge of the climate, but there is still a long way to go.
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Coral reefs have recovered.
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Sponges come back to the shallow seas.
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Vertebrates diversify and begin to fill many ecological niches. These include the earliest dinosaurs (including ancestors of modern birds), lepidosaurs (snakes and lizards), pterosaurs, and mammals.
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Triassic-Jurassic extinction is another extinction event caused by global warming and ocean acidification. This event wiped out much of the life left over from the earlier stages, and dinosaurs and mammals remained, allowing dinosaurs to dominate the world for the next 135 million years. The event lasted less than 10,000 years, and perhaps much less than that, but greater resolution is difficult when looking back that far.
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We are now in the Jurassic period, and the mega-continent is starting to break apart. Dinosaurs rule the land, along with pterosaurs, and reptiles and fish rule the oceans. Stegosaurs evolve.
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Sharks, rays, and crabs evolve.
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The world is much warmer than it is today, with CO2 levels around 1500–2000 ppm. Trees grow at the poles, and ice sheets are non-existent except in the high mountains.
Conifers are the dominant type of tree in many Jurassic forests, and cypress trees evolved, including the ancestors of today’s Sequoia.
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Stegosaurs are gone, replaced with brachiosaurs, cynodonts, and therapsids. Conifers continue to dominate the forests, with ginkgoes, cycads, and ferns also plentiful.
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The dinosaurs most of us know and love evolve, including T-Rex, Triceratops, Diplodocus, and many, many others.
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Pangea is breaking apart, and we might recognize the shapes of our modern continents.
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Three-quarters of plant and animal species are wiped out when a massive asteroid impacts near modern-day Mexico. When the dust settles, the dinosaurs are gone, only the avian branch surviving. Mammals come into their own. This happened on land and sea. Mammals start to get bigger.
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The end of the Paleocene is marked by the release of 2,500 gigatons of carbon into the atmosphere or about 75 years’ worth of what humans emit annually. Oceans became acidic, and surface water temperatures rose to 40C, which is what they were in Florida in 2023. This change, however, occurred over the course of 50,000 years, not 100. The Earth was very warm during this period.
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This era is marked by a gradual but complete climatic shift from the hot house model to the cold house. Glacial ice caps came into existence. Australia and Antarctica were still connected until this point, and when they broke apart, oceanic currents changed, and Antarctica froze over.
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Brain size in mammals begins to increase as food chains become more complex. Amber is forming in what will later be the Baltic region.
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Afro-Arabia collides with Eurasia, separating the Mediterranean from the Indian Ocean. The Mediterranean nearly evaporates, but then the Straight of Gibraltar collapses and refills the basin. Apes evolve. The Himalayas rise, creating the great deserts in China and the monsoons in India. Grass takes over huge ecosystems, wresting control back from trees.
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The species that will become humans are evolving. Glaciers extend to the 40th parallel and cover 30% of the Earth. Permafrost covers much of the rest of the land. Giant sloths, mammoths, mastodons, and the great cats roam the Earth. 300,000 years before the end of this period, Homo Sapiens evolve. We are mostly harmless for 290,000 years and do little of note except reproduce.
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The sixth great extinction begins, triggered by massive releases of carbon into the atmosphere and massive amounts of pollution in the form of long-chain polymers that don’t decompose, and are poisonous to most life forms.