Cosmic Calendar

I’ve posted often on this blog about the Cosmic Calendar – a concept introduced by Carl Sagan which scales the entire history of the cosmos, from the big bang to the present moment, into a single year. Every day represents about 37.8 million years. It is a tool for conceptualizing deep time, as well as a fruitful source of science-based annual celebrations.

On this page, you can find many of the interesting landmarks in the Cosmic Calendar, as well as links to my blog posts about various events. If you use Google Calendars, here is one with the whole Cosmic Calendar already entered, with notes and reference links. I want to point out that, as I learn more, I update my calculations. So the dates in earlier blog entries may not correspond with later ones. I will keep this page and the Google Calendar updated with my latest calculations.

January, 13.8 to 12.6 billion years ago

  • 1 (13.8 billion years ago +/- 37 million): Big Bang. The cosmos springs from a singularity into an expanding mess of stuff.
    • 00:01:54 to 00:02:40 (50 000 to 70 000 years later): Matter begins to dominate the universe (relative to energy)
    • 00:14:22 to 00:18:33 (377000 to 487000 years after big bang): Recombination and decoupling allow radiation to travel unimpeded, giving us the CMBR.
  • 11 (13.4 billion years ago): First stars begin to form.
  • 16 (13.2 billion years ago): Oldest star in the Milky Way, HE 1523-0901 was formed. [B1] [B2]

February, 12.6 to 11.6 billion years ago (lazily assuming non-leap year, 28 days in February)

  • 17 (12 billion years ago): Hubble Deep Field penetration (the farthest in space and time that we’ve seen in visible light?).

March, 11.6 to 10.4 billion years ago

  • 16 (11 billion years ago): Universe transitions from heating up to cooling down. [ref]

April, 10.4 to 9.3 billion years ago

  • 8 (10.1 billion years ago): Early end of range for formation of Milky Way galaxy. [B]

May, 9.3 to 8.1 billion years ago

  • (I haven’t found anything notable yet for this month.)

June, 8.1 to 7.0 billion years ago

  • (I haven’t found anything notable yet for this month.)

July, 7.0 to 5.8 billion years ago

  • 13 (6.5 billion years ago): Late end of range for formation of Milky Way galaxy. [B]

August, 5.8 to 4.6 billion years ago

  • (I haven’t found anything notable yet for this month.)

September, 4.6 to 3.5 billion years ago

  • 1 (4.6 billion years ago): Solar system forms. [B1] [B2]
  • 3 (4.5 billion years ago): Earth forms. [B]
  • 11 (4.2 billion years ago): Liquid water on Earth (earliest possible origin of life)

October, 3.5 to 2.3 billion years ago

  • 29 (2.4 billion years ago): Definite fossil evidence of life (latest possible origin of life)

November, 2.3 to 1.2 billion years ago

  • 6 (2.1 billion years ago): Oldest plant fossils.
  • 27 (1.3 billion years ago): Oxygen atmosphere.
  • 30 (1.2 billion years ago): Earliest fossil evidence of sex. [ref]

December, 1.2 billion years ago to present

  • 17, 13:26 (542 million years ago): Ediacaran extinction.
  • 17, 14:43 (540 million years ago): Cambrian Explosion – a huge and (by cosmic standards) abrupt increase in biodiversity, especially among animals. [B1] [B2]
  • 17, 18:33 (534 million years ago): Earliest vertebrate fossils.
  • 17, 23:31 (530 million years ago): MRCA with lampreys and hagfish (jawless & limbless fish). [AT]
  • 18, 23:00 (493 million years ago): Plants colonize land.
  • 19, 19:57 (460 million years ago): MRCA with sharks. [AT]
  • 20, 01:02 (452 million years ago): First insects.
  • 20, 08:39 (440 million years ago): MRCA ray-finned fish. [AT]
  • 20, 18:11 (425 million years ago): MRCA coelocanths. [AT]
  • 20, 23:15 (417 million years ago): MRCA lungfish. [AT]
  • 21, 10:03 (400 million years ago): First winged insects. First amphibians.
  • 22, 05:06 (370 million years ago): Earliest trees. First reptiles.
  • 23, 00:09 (340 million years ago): MRCA amphibians. [AT]
  • 23, 07:08 (329 million years ago): First dinosaurs.
  • 23, 19:11 (310 million years ago): MRCA sauropsids. [AT]
  • 25, 08:01 (252 million years ago): Permian-Triassic extinction (killed over 90% of all species)
  • 26, 01:09 (225 million years ago): First mammals.
  • 27
    • 05:43 (180 million years ago): MRCA monotremes. [AT]
    • 21:36 (155 million years ago): First birds.
  • 28
    • 07:07 (140 million years ago): MRCA marsupials. [AT]
    • 16:38 (125 million years ago): First flowering plants. [B]
  • 29
    • 05:20 (105 million years ago): MRCA aardvarks & elephants. [AT]
    • 11:41 (95 million years ago): MRCA armadillos. [AT]
    • 18:02 (85 million years ago): MRCA laurasiatheres (cats, dogs, bats, hogs, etc). [AT]
  • 30
    • 00:23 (75 million years ago): MRCA rodents & rabbits. [AT]
    • 03:34 (70 million years ago): MRCA colugos & tree shrews. [AT]
    • 06:44 (65 million years ago): Dinosaurs go extinct.
    • 08:00 (63 million years ago): MRCA lemurs. [AT]
    • 11:11 (58 million years ago): MRCA tarsiers. [AT]
    • 13:05 (55 million years ago): Warm north pole.
    • 16:15 (50 million years ago): First cetaceans.
    • 22:36 (40 million years ago): MRCA new world monkeys. [AT]
  • 31
    • 08:08 (25 million years ago): MRCA old world monkeys. [AT]
    • 12:34 (18 million years ago): MRCA gibbons. [AT]
    • 15:07 (14 million years ago): MRCA orang utans. [AT]
    • 19:33 (7 million years ago): MRCA gorillas. [AT]
    • 20:11 (6 million years ago): MRCA chimpanzees. [AT]
    • 22:25 (2.5 million years ago): Ancestral humans.
    • 23:50:28 (250 000 years ago): Homo sapiens
    • 23:59:32 (12 000 years ago): Agriculture
    • Midnight: Present!

Here are some posts where I talk more generally about the Cosmic Calendar:

And here are some Cosmic Calendar resources that other people have put together:

Calendar to Cosmic time conversions:

  • One second = 438 years.
  • One minute = 26 thousand years.
  • One hour = 1.58 million years.
  • One day = 37.8 million years.
  • One week = 265 million years.
  • An average month = 1.15 billion years.

Cosmic to Calendar time conversions:

  • One year = 2.29 milliseconds
  • One thousand years = 2.29 seconds.
  • One million years = 38 minutes, 6 seconds.
  • One billion years = 26 days, 11 hours.

Reference:

[AT] The MRCA events refer to “most recent common ancestors” between humans and different groups of organisms. These events are derived from descriptions in Richard Dawkins & Yan Wong’s excellent book, The Ancestor’s Tale. If you want to learn more about any of these events on our calendar, I strongly recommend you read that book. Cover to cover.

One Response to “Cosmic Calendar”

  1. Back into the Cosmic Calendar | Friendly Humanist Says:

    […] you want to plan your own celebrations for any of the events, do check out my Cosmic Calendar page, where I list all of the events I have been able to identify and verify (already over fifty), with […]

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