path: root/src/CosmicCalendarEvents.hs

{-# OPTIONS_GHC -Wall #-}
{-# language NoImplicitPrelude #-}
{-# language OverloadedStrings #-}
{-# language QuasiQuotes #-}

module CosmicCalendarEvents where

import Rebase.Prelude
import NeatInterpolation

import CosmicCalendar

theYear, yearsBeforeCommonEra :: Integer -> NominalDiffTime
theYear = yearsAgo . toRational . (currentYear -)
yearsBeforeCommonEra = yearsAgo . toRational . ((+) (currentYear - 1))

theCalendar :: Map NominalDiffTime CalendarEntry
theCalendar = buildCalendar $
  [
    CalendarEntry 0
    Nothing
    "The Big Bang"
    "The universe begins"
    ""
    "",

    CalendarEntry (370 & thousandYears & afterBigBang)
    Nothing
    "Recombination"
    "The universe becomes transparent"
    [text|
    At about 370,000 years,[3][4][5][6] neutral hydrogen atoms finish forming
    ("recombination"), and as a result the universe also became transparent for
    the first time. The newly formed atoms—mainly hydrogen and helium with
    traces of lithium—quickly reach their lowest energy state (ground state) by
    releasing photons ("photon decoupling"), and these photons can still be
    detected today as the cosmic microwave background (CMB). This is the oldest
    direct observation we currently have of the universe.
    |]
    [text|
    https://en.wikipedia.org/wiki/Chronology_of_the_universe#The_very_early_universe

    3. Tanabashi, M. 2018, p. 358, chpt. 21.4.1: "Big-Bang Cosmology" (Revised
    September 2017) by Keith A. Olive and John A. Peacock.

    4. Notes: Edward L. Wright's Javascript Cosmology Calculator (last modified
    23 July 2018). With a default H 0 {\displaystyle H_{0}} H_{0} = 69.6 (based
    on WMAP9+SPT+ACT+6dFGS+BOSS/DR11+H0/Riess) parameters, the calculated age of
    the universe with a redshift of z = 1100 is in agreement with Olive and
    Peacock (about 370,000 years).

    5. Hinshaw, Weiland & Hill 2009. See PDF: page 45, Table 7, Age at
    decoupling, last column. Based on WMAP+BAO+SN parameters, the age of
    decoupling occurred 376971+3162−3167 years after the Big Bang.

    6. Ryden 2006, pp. 194–195. "Without going into the details of the
    non-equilibrium physics, let's content ourselves by saying, in round
    numbers, zdec ≈ 1100, corresponding to a temperature Tdec ≈ 3000 K, when the
    age of the universe was tdec ≈ 350,000 yr in the Benchmark Model. (...) The
    relevant times of various events around the time of recombination are shown
    in Table 9.1. (...) Note that all these times are approximate, and are
    dependent on the cosmological model you choose. (I have chosen the Benchmark
    Model in calculating these numbers.)"

    https://en.wikipedia.org/wiki/Recombination_(cosmology)#cite_note-2
    |],

    CalendarEntry (13.4 & billionYearsAgo) Nothing
    "The first observed star"
    ""
    "First Light Viewed Through the Rich Cluster Abell 2218"
    "https://sites.astro.caltech.edu/~rse/firstlight/",

    CalendarEntry (4.6 & billionYearsAgo) Nothing
    "Formation of the Sun"
    "The formation of the solar system begins"
    [text|
    The formation of the Solar System began about 4.6 billion years ago with the
    gravitational collapse of a small part of a giant molecular cloud.[1] Most
    of the collapsing mass collected in the center, forming the Sun, while the
    rest flattened into a protoplanetary disk out of which the planets, moons,
    asteroids, and other small Solar System bodies formed.
    |]
    "https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System",

    CalendarEntry (4.54 & billionYearsAgo) Nothing
    "Formation of Earth"
    ""
    [text|
    The standard model for the formation of the Solar System (including the
    Earth) is the solar nebula hypothesis.[23] In this model, the Solar System
    formed from a large, rotating cloud of interstellar dust and gas called the
    solar nebula. It was composed of hydrogen and helium created shortly after
    the Big Bang 13.8 Ga (billion years ago) and heavier elements ejected by
    supernovae. About 4.5 Ga, the nebula began a contraction that may have been
    triggered by the shock wave from a nearby supernova.[24] A shock wave would
    have also made the nebula rotate. As the cloud began to accelerate, its
    angular momentum, gravity, and inertia flattened it into a protoplanetary
    disk perpendicular to its axis of rotation. Small perturbations due to
    collisions and the angular momentum of other large debris created the means
    by which kilometer-sized protoplanets began to form, orbiting the nebular
    center.[25]

    The center of the nebula, not having much angular momentum, collapsed
    rapidly, the compression heating it until nuclear fusion of hydrogen into
    helium began. After more contraction, a T Tauri star ignited and evolved
    into the Sun. Meanwhile, in the outer part of the nebula gravity caused
    matter to condense around density perturbations and dust particles, and the
    rest of the protoplanetary disk began separating into rings. In a process
    known as runaway accretion, successively larger fragments of dust and debris
    clumped together to form planets.[25] Earth formed in this manner about 4.54
    billion years ago (with an uncertainty of 1%)[26][27][4] and was largely
    completed within 10–20 million years.[28] The solar wind of the newly formed
    T Tauri star cleared out most of the material in the disk that had not
    already condensed into larger bodies. The same process is expected to
    produce accretion disks around virtually all newly forming stars in the
    universe, some of which yield planets.[29]
    |]
    "https://en.wikipedia.org/wiki/History_of_Earth#Solar_System_formation",

    CalendarEntry (8.8 & billionYearsAgo) Nothing
    "Thin disk of the Milky Way Galaxy"
    "Our galaxy begins to form"
    [text|
    The age of stars in the galactic thin disk has also been estimated using
    nucleocosmochronology. Measurements of thin disk stars yield an estimate
    that the thin disk formed 8.8 ± 1.7 billion years ago. These measurements
    suggest there was a hiatus of almost 5 billion years between the formation
    of the galactic halo and the thin disk.[253] Recent analysis of the chemical
    signatures of thousands of stars suggests that stellar formation might have
    dropped by an order of magnitude at the time of disk formation, 10 to 8
    billion years ago, when interstellar gas was too hot to form new stars at
    the same rate as before.[254]
    |]
    "",

    CalendarEntry (4.4 & billionYearsAgo) Nothing
    "Formation of the moon"
    "A collision of the planet Theia with Earth creates the moon"
    [text|
    Astronomers think the collision between Earth and Theia happened at about
    4.4 to 4.45 bya; about 0.1 billion years after the Solar System began to
    form.[15][16] In astronomical terms, the impact would have been of moderate
    velocity. Theia is thought to have struck Earth at an oblique angle when
    Earth was nearly fully formed. Computer simulations of this "late-impact"
    scenario suggest an initial impactor velocity at infinity below 4 kilometres
    per second (2.5 mi/s), increasing as it fell to over 9.3 km/s (5.8 mi/s) at
    impact, and an impact angle of about 45°.[17] However, oxygen isotope
    abundance in lunar rock suggests "vigorous mixing" of Theia and Earth,
    indicating a steep impact angle.[3][18] Theia's iron core would have sunk
    into the young Earth's core, and most of Theia's mantle accreted onto
    Earth's mantle. However, a significant portion of the mantle material from
    both Theia and Earth would have been ejected into orbit around Earth (if
    ejected with velocities between orbital velocity and escape velocity) or
    into individual orbits around the Sun (if ejected at higher velocities).
    Modelling[19] has hypothesised that material in orbit around Earth may have
    accreted to form the Moon in three consecutive phases; accreting first from
    the bodies initially present outside Earth's Roche limit, which acted to
    confine the inner disk material within the Roche limit. The inner disk
    slowly and viscously spread back out to Earth's Roche limit, pushing along
    outer bodies via resonant interactions. After several tens of years, the
    disk spread beyond the Roche limit, and started producing new objects that
    continued the growth of the Moon, until the inner disk was depleted in mass
    after several hundreds of years.
    |]
    [text|
    https://en.wikipedia.org/wiki/Giant-impact_hypothesis#Basic_model
    https://www.psi.edu/epo/moon/moon.html
    |],

    CalendarEntry (3.77 & billionYearsAgo) Nothing
    "Life on Earth"
    ""
    [text|
    The earliest time for the origin of life on Earth is at least 3.77 billion
    years ago, possibly as early as 4.28 billion years,[2] or even 4.41 billion
    years[4][5]—not long after the oceans formed 4.5 billion years ago, and
    after the formation of the Earth 4.54 billion years ago.[2][3][6][7]
    |]
    "https://en.wikipedia.org/wiki/Earliest_known_life_forms",

    CalendarEntry (3.42 & billionYearsAgo) Nothing
    "Earliest known life on Earth"
    "The fossil record begins"
    [text|
    The earliest known life forms on Earth are putative fossilized
    microorganisms found in hydrothermal vent precipitates, considered to be
    about 3.42 billion years old.[1][2] The earliest time for the origin of life
    on Earth is at least 3.77 billion years ago, possibly as early as 4.28
    billion years,[2] or even 4.41 billion years[4][5]—not long after the oceans
    formed 4.5 billion years ago, and after the formation of the Earth 4.54
    billion years ago.[2][3][6][7] The earliest direct evidence of life on Earth
    is from microfossils of microorganisms permineralized in
    3.465-billion-year-old Australian Apex chert rocks.[8][9]
    |]
    "https://en.wikipedia.org/wiki/Earliest_known_life_forms",

    CalendarEntry (3.4 & billionYearsAgo) Nothing
    "First photosynthetic bacteria"
    "(Still no Oxygen)"
    [text|
    They absorbed near-infrared rather than visible light and produced sulfur or
    sulfate compounds rather than oxygen. Their pigments (possibly
    bacteriochlorophylls) were predecessors to chlorophyll.
    |]
    "https://www.scientificamerican.com/article/timeline-of-photosynthesis-on-earth/",

    CalendarEntry (2.7 & billionYearsAgo) Nothing
    "Oxygen from photosynthesis"
    [text|
    Cyanobacteria (blue-green algae) initiates "rusting of the Earth"
    The resulting Ozone layer will make life possible on land
    |]
    [text|
    These ubiquitous bacteria were the first oxygen producers. They absorb
    visible light using a mix of pigments: phycobilins, carotenoids and several
    forms of chlorophyll.

    The Great Oxidation Event (GOE), also called the Great Oxygenation Event,
    the Oxygen Catastrophe, the Oxygen Revolution, and the Oxygen Crisis, was a
    time interval when the Earth's atmosphere and the shallow ocean first
    experienced a rise in the amount of oxygen. This occurred approximately
    2.4–2.0 Ga (billion years) ago, during the Paleoproterozoic era.[2]
    Geological, isotopic, and chemical evidence suggests that
    biologically-produced molecular oxygen (dioxygen, O2) started to accumulate
    in Earth's atmosphere and changed it from a weakly reducing atmosphere
    practically free of oxygen into an oxidizing atmosphere containing abundant
    oxygen.[3]

    The sudden injection of toxic oxygen into an anaerobic biosphere caused the
    extinction of many existing anaerobic species on Earth.[4] Although the event is
    inferred to have constituted a mass extinction,[5] due in part to the great
    difficulty in surveying microscopic species' abundances, and in part to the
    extreme age of fossil remains from that time, the Oxygen Catastrophe is
    typically not counted among conventional lists of "great extinctions", which are
    implicitly limited to the Phanerozoic eon.

    The event is inferred to have been caused by cyanobacteria producing the
    oxygen, which may have enabled the subsequent development of multicellular
    life-forms.[6]

    The current scientific understanding of when and how the Earth's atmosphere
    changed from a weakly reducing to a strongly oxidizing atmosphere largely
    began with the work of the American geologist Preston Cloud in the 1970s.[9]
    Cloud observed that detrital sediments older than about 2 billion years ago
    contained grains of pyrite, uraninite,[9] and siderite,[12] all minerals
    containing reduced forms of iron or uranium that are not found in younger
    sediments because they are rapidly oxidized in an oxidizing atmosphere. He
    further observed that continental redbeds, which get their color from the
    oxidized (ferric) mineral hematite, began to appear in the geological record
    at about this time. Banded iron formation largely disappears from the
    geological record at 1.85 billion years ago, after peaking at about 2.5
    billion years ago.[14] Banded iron formation can form only when abundant
    dissolved ferrous iron is transported into depositional basins, and an
    oxygenated ocean blocks such transport by oxidizing the iron to form
    insoluble ferric iron compounds.[15] The end of the deposition of banded
    iron formation at 1.85 billion years ago is therefore interpreted as marking
    the oxygenation of the deep ocean.[9] Heinrich Holland further elaborated
    these ideas through the 1980s, placing the main time interval of oxygenation
    between 2.2 and 1.9 billion years ago, and they continue to shape the
    current scientific understanding.[10]
    |]
    [text|
    https://www.scientificamerican.com/article/timeline-of-photosynthesis-on-earth/
    https://en.wikipedia.org/wiki/Great_Oxidation_Event
    |],

    CalendarEntry (2.05 & billionYearsAgo) Nothing
    "Eukaryotic cells"
    "Cells with nucleus (inner membrane holding DNA)"
    [text|
    Eukaryotes (/juːˈkærioʊts, -əts/) are organisms whose cells have a nucleus
    enclosed within a nuclear envelope.[1][2][3] They belong to the group of
    organisms Eukaryota or Eukarya; their name comes from the Greek εὖ (eu,
    "well" or "good") and κάρυον (karyon, "nut" or "kernel").[4] The domain
    Eukaryota makes up one of the three domains of life; bacteria and archaea
    (both prokaryotes) make up the other two domains.[5][6] The eukaryotes are
    usually now regarded as having emerged in the Archaea or as a sister of the
    Asgard archaea.[7][8] This implies that there are only two domains of life,
    Bacteria and Archaea, with eukaryotes incorporated among archaea.[9][10]
    Eukaryotes represent a small minority of the number of organisms;[11]
    however, due to their generally much larger size, their collective global
    biomass is estimated to be about equal to that of prokaryotes.[11]
    Eukaryotes emerged approximately 2.3–1.8 billion years ago, during the
    Proterozoic eon, likely as flagellated phagotrophs.[12][13]
    |]
    "https://en.wikipedia.org/wiki/Eukaryote",

    CalendarEntry (1.2 & billionYearsAgo) Nothing
    "Red and brown algae"
    ""
    [text|
    These organisms have more complex cellular structures than bacteria do. Like
    cyanobacteria, they contain phycobilin pigments as well as various forms of
    chlorophyll.
    |]
    "https://www.scientificamerican.com/article/timeline-of-photosynthesis-on-earth/",

    CalendarEntry (0.75 & billionYearsAgo) Nothing
    "Green algae"
    ""
    [text|
    Green algae do better than red and brown algae in the strong light of
    shallow water. They make do without phycobilins.
    |]
    "https://www.scientificamerican.com/article/timeline-of-photosynthesis-on-earth/",

    CalendarEntry (0.475 & billionYearsAgo) Nothing
    "First land plants"
    ""
    [text|
    Mosses and liverworts descended from green algae. Lacking vascular structure
    (stems and roots) to pull water from the soil, they are unable to grow
    tall.
    |]
    "https://www.scientificamerican.com/article/timeline-of-photosynthesis-on-earth/",

    CalendarEntry (0.423 & billionYearsAgo) Nothing
    "Vascular plants"
    ""
    [text|
    These are literally garden-variety plants, such as ferns, grasses, trees and
    cacti. They are able to grow tall canopies to capture more light.
    |]
    "https://www.scientificamerican.com/article/timeline-of-photosynthesis-on-earth/",

    CalendarEntry (750 & millionYearsAgo) Nothing
    "Bones and shells"
    ""
    [text|
    A series of spectacularly preserved, 750-million-year-old fossils represent
    the microscopic origins of biomineralization, or the ability to convert
    minerals into hard, physical structures. This process is what makes bones,
    shells, teeth and hair possible, literally shaping the animal kingdom and
    even Earth itself.

    The fossils were pried from ancient rock formations in Canada's Yukon by
    earth scientists Francis Macdonald and Phoebe Cohen of Harvard University.
    In a June Geology paper, they describe their findings as providing "a unique
    window into the diversity of early eukaryotes."

    Using molecular clocks and genetic trees to reverse-engineer evolutionary
    histories, previous research placed the beginning of biomineralization at
    about 750 million years ago. Around that time, the fossil record gets
    suggestive, turning up vase-shaped amoebas with something like scales in
    their cell walls, algae with cell walls possibly made from calcium carbonate
    and sponge-like creatures with seemingly mineralized bodies.
    |]
    "https://www.wired.com/2011/06/first-shells/",

    CalendarEntry (440 & millionYearsAgo) Nothing
    "Fish with jaws"
    ""
    [text|
    Prehistoric armoured fishes called placoderms were the first fishes to have
    jaws. They arose some time in the Silurian Period, about 440 million years
    ago, to become the most abundant and diverse fishes of their day.

    Placoderms dominated the oceans, rivers and lakes for some 80 million years,
    before their sudden extinction around 359 million years ago. This is possibly
    due to the depletion of trace elements in our oceans.
    |]
    "",

    CalendarEntry (518 & millionYearsAgo) Nothing
    "Vertebrates"
    "Animals with backbones"
    [text|
    Vertebrates (/ˈvɜːrtəbrɪts, -ˌbreɪts/)[3] comprise all animal taxa within
    the subphylum Vertebrata (/ˌvɜːrtəˈbreɪtə/)[4] (chordates with backbones),
    including all mammals, birds, reptiles, amphibians, and fish. Vertebrates
    represent the overwhelming majority of the phylum Chordata, with currently
    about 69,963 species described.[5]
    |]
    "",

    CalendarEntry (385 & millionYearsAgo) Nothing
    "Insects"
    ""
    [text|
    Comprising up to 10 million living species, insects today can be found on
    all seven continents and inhabit every terrestrial niche imaginable. But
    according to the fossil record, they were scarce before about 325 million
    years ago, outnumbered by their arthropod cousins the arachnids (spiders,
    scorpions and mites) and myriapods (centipedes and millipedes).

    The oldest confirmed insect fossil is that of a wingless, silverfish-like
    creature that lived about 385 million years ago. It’s not until about 60
    million years later, during a period of the Earth’s history known as the
    Pennsylvanian, that insect fossils become abundant.
    |]
    "https://earth.stanford.edu/news/insects-took-when-they-evolved-wings",

    CalendarEntry (368 & millionYearsAgo) Nothing
    "Amphibians"
    ""
    [text|
    The earliest well-known amphibian, Ichthyostega, was found in Late Devonian
    deposits in Greenland, dating back about 363 million years. The earliest
    amphibian discovered to date is Elginerpeton, found in Late Devonian rocks
    of Scotland dating to approximately 368 million years ago. The later
    Paleozoic saw a great diversity of amphibians, ranging from small legless
    swimming forms (Aistopoda) to bizarre "horned" forms (Nectridea). Other
    Paleozoic amphibians more or less resembled salamanders outwardly but
    differed in details of skeletal structure. Exactly how to classify these
    fossils, and how they might be related to living amphibians, is still
    debated by paleontologists. Shown at the right is Phlegethontia, an aistopod
    from the Pennsylvanian.

    The familiar frogs, toads, and salamanders have been present since at least
    the Jurassic Period. (The fossil frog pictured to the left is much younger,
    coming from the Eocene, only 45 to 55 million years ago). Fossil caecilians
    are very rare; until recently the oldest known caecilians were Cenozoic in
    age (that is, less than 65 million years old), but recent finds have pushed
    back the ancestry of the legless caecilians to Jurassic ancestors that had
    short legs. The rarity of fossil caecilians is probably due to their
    burrowing habitat and reduced skeleton, both of which lessen the chances of
    preservation.
    |]
    "https://ucmp.berkeley.edu/vertebrates/tetrapods/amphibfr.html",

    CalendarEntry (320 & millionYearsAgo) Nothing
    "Reptiles"
    ""
    [text|
    Reptiles, in the traditional sense of the term, are defined as animals that
    have scales or scutes, lay land-based hard-shelled eggs, and possess
    ectothermic metabolisms.

    Though few reptiles today are apex predators, many examples of apex reptiles
    have existed in the past. Reptiles have an extremely diverse evolutionary
    history that has led to biological successes, such as dinosaurs, pterosaurs,
    plesiosaurs, mosasaurs, and ichthyosaurs.
    |]
    [text|
    https://en.wikipedia.org/wiki/Evolution_of_reptiles
    https://www.thoughtco.com/the-first-reptiles-1093767
    |],

    CalendarEntry (335 & millionYearsAgo) Nothing
    "Pangea forms"
    ""
    [text|
    Pangaea or Pangea (/pænˈdʒiː.ə/)[1] was a supercontinent that existed during
    the late Paleozoic and early Mesozoic eras.[2] It assembled from the earlier
    continental units of Gondwana, Euramerica and Siberia during the
    Carboniferous approximately 335 million years ago, and began to break apart
    about 200 million years ago, at the end of the Triassic and beginning of the
    Jurassic.[3] In contrast to the present Earth and its distribution of
    continental mass, Pangaea was centred on the Equator and surrounded by the
    superocean Panthalassa and the Paleo-Tethys and subsequent Tethys Oceans.
    Pangaea is the most recent supercontinent to have existed and the first to
    be reconstructed by geologists.
    |]
    "https://en.wikipedia.org/wiki/Pangaea",

    CalendarEntry (243 & millionYearsAgo) Nothing
    "Dinosaurs"
    ""
    [text|
    For the past twenty years, Eoraptor has represented the beginning of the Age
    of Dinosaurs. This controversial little creature–found in the roughly
    231-million-year-old rock of Argentina–has often been cited as the earliest
    known dinosaur. But Eoraptor has either just been stripped of that title, or
    soon will be. A newly-described fossil found decades ago in Tanzania extends
    the dawn of the dinosaurs more than 10 million years further back in time.

    Named Nyasasaurus parringtoni, the roughly 243-million-year-old fossils
    represent either the oldest known dinosaur or the closest known relative to
    the earliest dinosaurs. The find was announced by University of Washington
    paleontologist Sterling Nesbitt and colleagues in Biology Letters, and I
    wrote a short news item about the discovery for Nature News. The paper
    presents a significant find that is also a tribute to the work of Alan
    Charig–who studied and named the animal, but never formally published a
    description–but it isn’t just that. The recognition of Nyasasaurus right
    near the base of the dinosaur family tree adds to a growing body of evidence
    that the ancestors of dinosaurs proliferated in the wake of a catastrophic
    mass extinction.
    |]
    [text|
    https://www.smithsonianmag.com/science-nature/scientists-discover-oldest-known-dinosaur-152807497/
    |],

    CalendarEntry (210 & millionYearsAgo) Nothing
    "Mammals"
    ""
    [text|
    The earliest known mammals were the morganucodontids, tiny shrew-size
    creatures that lived in the shadows of the dinosaurs 210 million years ago.
    They were one of several different mammal lineages that emerged around that
    time. All living mammals today, including us, descend from the one line that
    survived.
    |]
    "https://www.nationalgeographic.com/science/article/rise-mammals",

    CalendarEntry (150 & millionYearsAgo) Nothing
    "Birds"
    ""
    [text|
    The first birds had sharp teeth, long bony tails and claws on their hands.
    The clear distinction we see between living birds and other animals did not
    exist with early birds. The first birds were in fact more like small
    dinosaurs than they were like any bird today.

    The earliest known (from fossils) bird is the 150-million-year-old
    Archaeopteryx, but birds had evolved before then. A range of birds with more
    advanced features appeared soon after Archaeopteryx. One group gave rise to
    modern birds in the Late Cretaceous.
    |]
    "https://australian.museum/learn/dinosaurs/the-first-birds/",

    CalendarEntry (130 & millionYearsAgo) Nothing
    "Flowers"
    ""
    [text|
    Today, plants with flowers--called angiosperms--dominate the landscape.
    Around 80 percent of green plants alive today, from oak trees to grass, are
    flowering plants. In all of these plants, flowers are part of the
    reproductive system. But 130 million years ago, flowering plants were rare.
    Most plants reproduced with spores, found today on ferns, or with seeds and
    cones, found today on pine trees. The plant fossils found in Liaoning,
    China, show evidence of plants with spores or seeds--and perhaps one of the
    first flowering plants.

    Researchers have found an ancient plant in Liaoning, Archaefructus, that has
    very small, simple flowers and could be one of the first flowering plants.
    Archaefructus lived around 130 million years ago and probably grew in or
    near the water.
    |]
    "https://www.amnh.org/exhibitions/dinosaurs-ancient-fossils/liaoning-diorama/when-flowers-first-bloomed",

    CalendarEntry (85 & millionYearsAgo) Nothing
    "Tyranosaurids"
    "The Tyrant Lizards"
    [text|
    The name says it all. This group of huge carnivores must have tyrannically
    ruled the land during the last part of the Cretaceous, 85 to 65 million
    years ago. Short but deep jaws with banana-sized sharp teeth, long hind
    limbs, small beady eyes, and tiny forelimbs (arms) typify a tyrannosaur. The
    Tyrannosauridae included such similar animals (in rough order of increasing
    size) as Albertosaurus, Gorgosaurus, Daspletosaurus, Tarbosaurus, and of
    course Tyrannosaurus rex.

    T. rex was one of the largest terrestrial carnivores of all time. It stood
    approximately 15 feet high and was about 40 feet in length, roughly six tons
    in weight. In its large mouth were six-inch long, sharp, serrated teeth.

    Just about two dozen good specimens of these animals have been found and
    these finds are from highly restricted areas in western North America. Henry
    Fairfield Osborn, of the American Museum of Natural History in New York
    City, first described Tyrannosaurus rex in 1905. This first specimen of
    Tyrannosaurus is now on display at the Carnegie Museum of Natural History in
    Pittsburgh, Pennsylvania.
    |]
    "",

    CalendarEntry (445 & millionYearsAgo) Nothing
    "The first mass extinction"
    "Fluctuating sea levels cause mass die-off of marine invertebrates"
    [text|
    The earliest known mass extinction, the Ordovician Extinction, took place at
    a time when most of the life on Earth lived in its seas. Its major
    casualties were marine invertebrates including brachiopods, trilobites,
    bivalves and corals; many species from each of these groups went extinct
    during this time. The cause of this extinction? It’s thought that the main
    catalyst was the movement of the supercontinent Gondwana into Earth’s
    southern hemisphere, which caused sea levels to rise and fall repeatedly
    over a period of millions of years, eliminating habitats and species. The
    onset of a late Ordovician ice age and changes in water chemistry may also
    have been factors in this extinction.
    |]
    "https://www.amnh.org/shelf-life/six-extinctions",

    CalendarEntry (370 & millionYearsAgo) Nothing
    "Late Devonian Extinction"
    "The Kellwasser Event and the Hangenberg Event combine to cause an enormous loss in biodiversity"
    [text|
    Given that it took place over a huge span of time—estimates range from
    500,000 to 25 million years—it isn’t possible to point to a single cause for
    the Devonian extinction, though some suggest that the amazing spread of
    plant life on land during this time may have changed the environment in ways
    that made life harder, and eventually impossible, for the species that died
    out.

    The brunt of this extinction was borne by marine invertebrates. As in the
    Ordovician Extinction, many species of corals, trilobites, and brachiopods
    vanished. Corals in particular were so hard hit that they were nearly wiped
    out, and didn’t recover until the Mesozoic Era, nearly 120 million years
    later. Not all vertebrate species were spared, however; the early bony
    fishes known as placoderms met their end in this extinction.
    |]
    "https://www.amnh.org/shelf-life/six-extinctions",

    CalendarEntry (252 & millionYearsAgo) Nothing
    "The Great Dying"
    "Mass extinction kills more than 95 percent of marine species and 70 percent of land-dwelling vertebrates"
    [text|
    So many species were wiped out by this mass extinction it took more than 10
    million years to recover from the huge blow to global biodiversity. This
    extinction is thought to be the result of a gradual change in climate,
    followed by a sudden catastrophe. Causes including volcanic eruptions,
    asteroid impacts, and a sudden release of greenhouse gasses from the
    seafloor have been proposed, but the mechanism behind the Great Dying
    remains a mystery.
    |]
    "https://www.amnh.org/shelf-life/six-extinctions",

    CalendarEntry (201 & millionYearsAgo) Nothing
    "Triassic-Jurassic Extinction"
    "Death of more than a third of marine species and of most large amphibians"
    [text|
    This extinction occurred just a few millennia before the breakup of the
    supercontinent of Pangaea. While its causes are not definitively
    understood—researchers have suggested climate change, an asteroid impact, or
    a spate of enormous volcanic eruptions as possible culprits—its effects are
    indisputable.

    More than a third of marine species vanished, as did most large amphibians
    of the time, as well as many species related to crocodiles and dinosaurs.
    |]
    "https://www.amnh.org/shelf-life/six-extinctions",

    CalendarEntry (66 & millionYearsAgo) Nothing
    "Dinosaurs extinct"
    "Mammals take over land & sea"
    [text|
    An asteroid more than 6 miles across strikes the Yucatan Peninsula,
    triggering the fifth mass extinction in the world’s history.

    Some of the debris thrown into the atmosphere returned to Earth, the
    friction turning the air into an oven and sparking forest fires as it landed
    all over the world. The intensity of the heat pulse gave way to a prolonged
    impact winter, the sky blotted out by soot and ash as temperatures fell.

    More than 75 percent of species known from the end of the Cretaceous period,
    66 million years ago, didn’t make it to the following Paleogene period. The
    geologic break between the two is called the K-Pg boundary, and beaked birds
    were the only dinosaurs to survive the disaster.|]
    [text|
    https://www.smithsonianmag.com/science-nature/why-birds-survived-and-dinosaurs-went-extinct-after-asteroid-hit-earth-180975801/,
    https://www.amnh.org/shelf-life/six-extinctions
    |],

    CalendarEntry (27.5 & millionYearsAgo) Nothing
    "Apes and monkeys split"
    ""
    [text|
    Studies of clock-like mutations in primate DNA have indicated that the split
    between apes and Old World monkeys occurred between 30 million and 25
    million years ago.
    |]
    "https://www.nsf.gov/news/news_summ.jsp?cntn_id=127930",

    CalendarEntry (12.1 & millionYearsAgo) Nothing
    "Humans and chimpanzees split"
    ""
    [text|
    A 2016 study analyzed transitions at CpG sites in genome sequences, which
    exhibit a more clocklike behavior than other substitutions, arriving at an
    estimate for human and chimpanzee divergence time of 12.1 million years.[20]
    |]
    [text|
    https://en.wikipedia.org/wiki/Chimpanzee%E2%80%93human_last_common_ancestor
    |],

    CalendarEntry (4.4 & millionYearsAgo) Nothing
    "Humans first walk upright"
    ""
    [text|
    The earliest hominid with the most extensive evidence for bipedalism is the 4.4-million-year-old Ardipithecus ramidus.
    |]
    [text|
    https://www.smithsonianmag.com/science-nature/becoming-human-the-evolution-of-walking-upright-13837658/
    |],

    CalendarEntry (300 & thousandYearsAgo) Nothing
    "Modern humans evolve"
    ""
    [text|
    Among the oldest known remains of Homo sapiens are those found at the
    Omo-Kibish I archaeological site in south-western Ethiopia, dating to about
    233,000[2] to 196,000 years ago,[3] the Florisbad site in South Africa,
    dating to about 259,000 years ago, and the Jebel Irhoud site in Morocco,
    dated about 300,000 years ago.
    |]
    [text|
    https://en.wikipedia.org/wiki/Early_modern_human
    |],

    CalendarEntry (100 & thousandYearsAgo) Nothing
    "Human migration out of Africa"
    ""
    [text|
    Between 70,000 and 100,000 years ago, Homo sapiens began migrating from the
    African continent and populating parts of Europe and Asia. They reached the
    Australian continent in canoes sometime between 35,000 and 65,000 years ago.

    Map of the world showing the spread of Homo sapiens throughout the Earth
    over time.
    |]
    [text|
    https://www.khanacademy.org/humanities/world-history/world-history-beginnings/origin-humans-early-societies/a/where-did-humans-come-from
    |],

    CalendarEntry (600 & millionYearsAgo) Nothing
    "Multicellular life"
    ""
    [text|
    |]
    "",

    CalendarEntry (2.6 & millionYearsAgo) Nothing
    "First Stone Tools"
    [text|
    Mode I: The Oldowan Industry
    Stone flakes with sharp edges for cutting
    |]
    [text|
    The earliest known Oldowan tools yet found date from 2.6 million years ago,
    during the Lower Palaeolithic period, and have been uncovered at Gona in
    Ethiopia.[16] After this date, the Oldowan Industry subsequently spread
    throughout much of Africa, although archaeologists are currently unsure
    which Hominan species first developed them, with some speculating that it
    was Australopithecus garhi, and others believing that it was in fact Homo
    habilis.[17]

    Homo habilis was the hominin who used the tools for most of the Oldowan in
    Africa, but at about 1.9-1.8 million years ago Homo erectus inherited them.
    The Industry flourished in southern and eastern Africa between 2.6 and 1.7
    million years ago, but was also spread out of Africa and into Eurasia by
    travelling bands of H. erectus, who took it as far east as Java by 1.8
    million years ago and Northern China by 1.6 million years ago.
    |]
    "",

    CalendarEntry (1.8 & millionYearsAgo) Nothing
    "First major transition in stone tool technology"
    [text|
    Mode II: The Acheulean Industry
    Stone hand-axes shaped symmetrically from two sides
    |]
    [text|
    From the Konso Formation of Ethiopia, Acheulean hand-axes are dated to about
    1.5 million years ago using radiometric dating of deposits containing
    volcanic ashes.[6] Acheulean tools in South Asia have also been found to be
    dated as far as 1.5 million years ago.[7] However, the earliest accepted
    examples of the Acheulean currently known come from the West Turkana region
    of Kenya and were first described by a French-led archaeology team.[8] These
    particular Acheulean tools were recently dated through the method of
    magnetostratigraphy to about 1.76 million years ago, making them the oldest
    not only in Africa but the world.[9] The earliest user of Acheulean tools
    was Homo ergaster, who first appeared about 1.8 million years ago. Not all
    researchers use this formal name, and instead prefer to call these users
    early Homo erectus.[3]
    |]
    "",

    CalendarEntry (160 & thousandYearsAgo) Nothing
    "Second major transition in stone tool technology"
    [text|
    Mode III: The Levallois technique; The Mousterian Industry
    Stone scrapers, knives, and projectile points
    |]
    [text|
    Levallois is a "prepared-core" technique: one face of a stone core is fully
    shaped by knapping in perparation. Then a large sharp flake is created by
    cracking off the entire prepared face in one final stroke.

    The technique is first found in the Lower Palaeolithic but is most commonly
    associated with the Neanderthal Mousterian industries of the Middle
    Palaeolithic. In the Levant, the Levallois technique was also used by
    anatomically modern humans during the Middle Stone Age. In North Africa, the
    Levallois technique was used in the Middle Stone Age, most notably in the
    Aterian industry to produce very small projectile points. While Levallois
    cores do display some variability in their platforms, their flake production
    surfaces show remarkable uniformity. As the Levallois technique is
    counterintuitive, teaching the process is necessary and thus language is a
    prerequisite for such technology.[2]

    The Mousterian (or Mode III) is a techno-complex (archaeological industry)
    of stone tools, associated primarily with the Neanderthals in Europe, and to
    a lesser extent the earliest anatomically modern humans in North Africa and
    West Asia. The Mousterian largely defines the latter part of the Middle
    Paleolithic, the middle of the West Eurasian Old Stone Age. It lasted
    roughly from 160,000 to 40,000 BP. If its predecessor, known as Levallois or
    Levallois-Mousterian, is included, the range is extended to as early as c.
    300,000–200,000 BP.[2] The main following period is the Aurignacian (c.
    43,000–28,000 BP) of Homo sapiens.
    |]
    "",

    CalendarEntry (115 & thousandYearsAgo) (Just $ 11.7 & thousandYearsAgo)
    "The Ice Age begins"
    "Glaciers cover most land on Earth, joining Asia to North America"
    [text|
    The Last Glacial Period (LGP), also known colloquially as the last ice age
    or simply ice age,[1] occurred from the end of the Eemian to the end of the
    Younger Dryas, encompassing the period c. 115,000 – c. 11,700 years ago. The
    LGP is part of a larger sequence of glacial and interglacial periods known
    as the Quaternary glaciation which started around 2,588,000 years ago and is
    ongoing.[2] The definition of the Quaternary as beginning 2.58 million years
    ago (Mya) is based on the formation of the Arctic ice cap. The Antarctic ice
    sheet began to form earlier, at about 34 Mya, in the mid-Cenozoic
    (Eocene–Oligocene extinction event). The term Late Cenozoic Ice Age is used
    to include this early phase.[3]
    |]
    "https://en.wikipedia.org/wiki/Last_Glacial_Period",

    CalendarEntry (50 & thousandYearsAgo) Nothing
    "Third major transition in stone tool technology"
    [text|
    Mode IV: The Aurignacian Industry
    Long stone blades
    |]
    [text|
    The widespread use of long blades (rather than flakes) of the Upper
    Palaeolithic Mode 4 industries appeared during the Upper Palaeolithic
    between 50,000 and 10,000 years ago, although blades were produced in small
    quantities much earlier by Neanderthals.[20] The Aurignacian culture seems
    to have been the first to rely largely on blades.[21] The use of blades
    exponentially increases the efficiency of core usage compared to the
    Levallois flake technique, which had a similar advantage over Acheulean
    technology which was worked from cores.
    |]
    "https://en.wikipedia.org/wiki/Stone_tool#Mode_IV:_The_Aurignacian_Industry",

    CalendarEntry (35 & thousandYearsAgo) Nothing
    "Last major transition in stone tool technology"
    [text|
    Mode V: The Microlithic Industries
    Stone blades fastened to wood or bone handles
    |]
    [text|
    Mode 5 stone tools involve the production of microliths, which were
    used in composite tools, mainly fastened to a shaft.[22] Examples include
    the Magdalenian culture. Such a technology makes much more efficient use of
    available materials like flint, although required greater skill in
    manufacturing the small flakes. Mounting sharp flint edges in a wood or bone
    handle is the key innovation in microliths, essentially because the handle
    gives the user protection against the flint and also improves leverage of
    the device.
    |]
    "https://en.wikipedia.org/wiki/Stone_tool#Mode_V:_The_Microlithic_Industries"
    ,

    CalendarEntry (12 & thousandYearsAgo) Nothing
    "Agriculture leads to permanent settlements"
    "Neolithic age (\"new stone age\")"
    [text|
    Wild grains were collected and eaten from at least 105,000 years ago.[2]
    However, domestication did not occur until much later. The earliest evidence
    of small-scale cultivation of edible grasses is from around 21,000 BC with
    the Ohalo II people on the shores of the Sea of Galilee.[3] By around 9500
    BC, the eight Neolithic founder crops – emmer wheat, einkorn wheat, hulled
    barley, peas, lentils, bitter vetch, chickpeas, and flax – were cultivated
    in the Levant.[4] Rye may have been cultivated earlier, but this claim
    remains controversial.[5] Rice was domesticated in China by 6200 BC[6] with
    earliest known cultivation from 5700 BC, followed by mung, soy and azuki
    beans. Rice was also independently domesticated in West Africa and
    cultivated by 1000 BC.[7][8] Pigs were domesticated in Mesopotamia around
    11,000 years ago, followed by sheep. Cattle were domesticated from the wild
    aurochs in the areas of modern Turkey and India around 8500 BC. Camels were
    domesticated late, perhaps around 3000 BC.
    |]
    "https://en.wikipedia.org/wiki/History_of_agriculture",

    CalendarEntry (6.5 & thousandYearsAgo) Nothing
    "First copper tools"
    ""
    ""
    "",

    CalendarEntry (5.3 & thousandYearsAgo) Nothing
    "First bronze tools, first written language"
    "The Bronze Age"
    ""
    "",

    CalendarEntry (3000 & yearsBeforeCommonEra) (Just $ 2350 & yearsBeforeCommonEra)
    "Corded Ware culture"
    "Indo-European languages spread across Europe and Asia"
    [text|
    The Corded Ware culture comprises a broad archaeological horizon of Europe
    between ca. 3000 BCE – 2350 BCE, thus from the late Neolithic, through the
    Copper Age, and ending in the early Bronze Age.[2] Corded Ware culture
    encompassed a vast area, from the contact zone between the Yamnaya culture
    and the Corded Ware culture in south Central Europe, to the Rhine on the
    west and the Volga in the east, occupying parts of Northern Europe, Central
    Europe and Eastern Europe.[2][3] The Corded Ware culture is thought to have
    originated from the westward migration of Yamnaya-related people from the
    steppe-forest zone into the territory of late Neolithic European cultures
    such as the Globular Amphora and Funnelbeaker cultures,[4][5][6] and is
    considered to be a likely vector for the spread of many of the Indo-European
    languages in Europe and Asia.[1][7][8][9]

    Corded Ware encompassed most of continental northern Europe from the Rhine
    on the west to the Volga in the east, including most of modern-day Germany,
    the Netherlands, Denmark, Poland, Lithuania, Latvia, Estonia, Belarus, Czech
    Republic, Austria, Hungary, Slovakia, Switzerland, northwestern Romania,
    northern Ukraine, and the European part of Russia, as well as coastal Norway
    and the southern portions of Sweden and Finland.[2] In the Late
    Eneolithic/Early Bronze Age, it encompassed the territory of nearly the
    entire Balkan Peninsula, where Corded Ware mixed with other steppe
    elements.[11]

    Archaeologists note that Corded Ware was not a "unified culture," as Corded
    Ware groups inhabiting a vast geographical area from the Rhine to Volga seem
    to have regionally specific subsistence strategies and economies.[2]: 226 
    There are differences in the material culture and in settlements and
    society.[2] At the same time, they had several shared elements that are
    characteristic of all Corded Ware groups, such as their burial practices,
    pottery with "cord" decoration and unique stone-axes.[2]
    |]
    "",

    CalendarEntry (2800 & yearsBeforeCommonEra) (Just $ 1800 & yearsBeforeCommonEra)
    "Bell Beaker culture"
    [text|
    copper daggers, v-perforated buttons, stone wrist-guards
    copper, bronze, and gold working
    long-distance exchange networks, archery
    social stratification and the emergence of regional elites
    |]
    [text|
    The Bell Beaker culture (also described as the Bell Beaker complex or Bell
    Beaker phenomenon) is an archaeological culture named after the
    inverted-bell beaker drinking vessel used at the very beginning of the
    European Bronze Age. Arising from around 2800 BC, it lasted in Britain until
    as late as 1800 BC[1][2] but in continental Europe only until 2300 BC, when
    it was succeeded by the Unetice culture. The culture was widely dispersed
    throughout Western Europe, being present in many regions of Iberia and
    stretching eastward to the Danubian plains, and northward to the islands of
    Great Britain and Ireland, and was also present in the islands of Sicily and
    Sardinia and some small coastal areas in north-western Africa. The Bell
    Beaker phenomenon shows substantial regional variation, and a study[3] from
    2018 found that it was associated with genetically diverse populations.

    In its mature phase, the Bell Beaker culture is understood as not only a
    collection of characteristic artefact types, but a complex cultural
    phenomenon involving metalwork in copper and gold, long-distance exchange
    networks, archery, specific types of ornamentation, and (presumably) shared
    ideological, cultural and religious ideas, as well as social stratification
    and the emergence of regional elites.[6][7] A wide range of regional
    diversity persists within the widespread late Beaker culture, particularly
    in local burial styles (including incidences of cremation rather than
    burial), housing styles, economic profile, and local ceramic wares
    (Begleitkeramik). Nonetheless, according to Lemercier (2018) the mature
    phase of the Beaker culture represents "the appearance of a kind of Bell
    Beaker civilization of continental scale."[8]

    Bell Beaker people took advantage of transport by sea and rivers, creating a
    cultural spread extending from Ireland to the Carpathian Basin and south
    along the Atlantic coast and along the Rhône valley to Portugal, North
    Africa, and Sicily, even penetrating northern and central Italy.[50] Its
    remains have been found in what is now Portugal, Spain, France (excluding
    the central massif), Ireland and Great Britain, the Low Countries and
    Germany between the Elbe and Rhine, with an extension along the upper Danube
    into the Vienna Basin (Austria), Hungary and the Czech Republic, with
    Mediterranean outposts on Sardinia and Sicily; there is less certain
    evidence for direct penetration in the east.
    |]
    "https://en.wikipedia.org/wiki/Bell_Beaker_culture",

    CalendarEntry (11.7 & thousandYearsAgo) Nothing
    "Ice Age ends"
    ""
    ""
    "https://en.wikipedia.org/wiki/Last_Glacial_Period",

    CalendarEntry (1600 & yearsBeforeCommonEra) Nothing
    "Dynastic China"
    "History begins"
    [text|
    The earliest known written records of the history of China date from as
    early as 1250 BC, from the Shang dynasty (c. 1600–1046 BC), during the king
    Wu Ding's reign

    The state-sponsored Xia–Shang–Zhou Chronology Project dated them from c.
    1600 to 1046 BC based on the carbon 14 dates of the Erligang site.
    |]
    "",

    CalendarEntry (480 & yearsBeforeCommonEra) Nothing
    "Old Testament, Buddha"
    ""
    ""
    "",

    CalendarEntry (6 & yearsBeforeCommonEra) Nothing
    "Christ born"
    ""
    ""
    "",

    -- CalendarEntry (300 & yearsBeforeCommonEra) Nothing
    -- "Eratosthenes calculates the circumference of Earth"
    -- ""
    -- ""
    -- "",

    CalendarEntry (theYear 570) Nothing
    "Muhammad born"
    ""
    ""
    "",

    CalendarEntry (theYear 1492) Nothing
    "Columbus arrives in America"
    ""
    ""
    ""
  ]