Cosmic Calendar Countdown

Carl Sagan’s Cosmic Calendar maps the entire history of our cosmos onto a single year.  You can follow the entire calendar here at HP.  As you imagine, things speed up considerably as the year advances.  After the Big Bang on January 1, we have to wait until May for the Milky Way to form and September for our own Sun to form.  But things got really busy in December:

Dec 5  First multicellular life 1 bya

Dec 14  Our First Animal Ancestors 0.67 bya

Dec 14  Arthropods emerge 0.55 bya

Dec 18  Our First Ancestors with Backbones (Fish) 0.5 bya

Dec 20  Land plants emerge 0.45 bya

Dec 21  Insects and seeds emerge 0.4 bya

Dec 22  Our Ancestors crawl onto land 0.36 bya

Dec 23  Reptiles and dinosaurs emerge 0.3 bya

Dec 26  Ancestors with Hair (Mammals) 0.2 bya

Dec 27  Birds emerge 0.15 bya

Dec 28  Flowers emerge 0.13 bya

Dec 30  Cretaceous-Paleogene extinction event (non-avian dinosaurs die out) 65 mya

Dec 30 Ancestors with hands (Primates) 65 mya

Dec 31  Upright Ancestors with bigger brains (Hominids) 15 mya

When December 31st arrives, we have an especially fun way to count down to the New Year with Sagan’s Cosmic Calendar.  Jon Cleland Host shares the experience with his children, calling out momentous events by the tick of a watch, as history whizzes by in the last few seconds before midnight.  Try it out!  (Skip some as you like). This is so much more fun than just sitting around waiting for the ball to start moving, and much more meaningful than yet another singer on stage amid fireworks!  Because these go so fast in the last few seconds, it works better to try out a practice run sometime during the day by yourself just to see how it works.

Human evolution

Date / time mya Event
31 Dec, 06:05 15 Apes
31 Dec, 14:24 6 hominids
31 Dec, 22:24 2.5 primitive humans and stone tools
31 Dec, 23:20 1.0 Domestication(1) of fire by Homo erectus
31 Dec, 23:52 0.2 Anatomically modern humans
31 Dec, 23:55 0.11 Beginning of most recent glacial period
31 Dec, 23:58 0.035 sculpture and cave painting
31 Dec, 23:59:32 0.012 Winter Solstice Celebrations,  Agriculture

Written records begin

Date / time kya Event
31 Dec, 23:59:47 5.5 Native American Circles, First writing,  beginning of the Bronze Age
31 Dec, 23:59:48 5.0 First dynasty of EgyptEarly Dynastic period in SumerAstronomy, 
31 Dec, 23:59:49 4.5 Stonehenge, AlphabetAkkadian EmpireWheel
31 Dec, 23:59:51 4.0 Code of HammurabiEgyptian Pyramids Built
31 Dec, 23:59:52 3.5 Mycenaean GreeceOlmec civilization; Iron Age in Near East, India, and Europe; founding of Carthage
31 Dec, 23:59:53 3.0 Ancient Olympic games
31 Dec, 23:59:54 2.5 BuddhaConfuciusQin DynastyClassical GreeceAshokan EmpireVedas completed, Euclidean geometry, Archimedean physics, Roman Republic
31 Dec, 23:59:55 2.0 Ptolemaic astronomy, CeasarChrist, invention of numeral 0
31 Dec, 23:59:56 1.5 MuhammadMaya civilizationSong Dynasty, rise of Byzantine Empire
31 Dec, 23:59:58 1.0 Mongol EmpireCrusadesChristopher Columbus voyages to the Americas, Renaissance in Europe

The current second

Date / time kya Event
31 Dec, 23:59:59 0.5 Modern Science and technology, American RevolutionFrench revolutionWorld War IWorld War IIApollo Moon landing

Below is a video of Carl Sagan explaining the Cosmic Calendar.


One Comment on “Cosmic Calendar Countdown

  1. Or you can recalibrate the Cosmic Calendar to include the future. A little hard to calibrate because the future is a little less predicatable than the past is postdictable (to coin a word). But if you call the end of the universe the predicted end to star formation due to the pollution of galactic clouds with helium, then you get an end date of 150 trillion years in the future. Then all of Sagan’s calendar happens in the first hour or so after midnight on the first of January. So right after you do the last hour count from Sagan’s calendar as outlined above, you can do the first hour count based on 150 trillion year calendar and get another perspective. Time doesn’t end with us. The universe is still very young relatively speaking.


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