COSMIC CALENDAR

The image below is a photo of the exhibit poster. Following it is a transcript of the poster.

Photo of the panel from the exhibit.
Approximate dimensions: H:36 in W:24 in

Pomegranate Communications;
original version published in The Dragons of Eden (1977 Carl Sagan)
Images from NASA and The Hubble Heritage Team (STScl); Designed by Mariah Lander.

How can we humans, who live a century at most, hope to grasp the immense time scales of cosmic history?

The astonomer Carl Sagan proposed a simple device to help us comprehend the vast expanse of time. He condensed the entire history of the cosmos into a single Cosmic Year. The birth of our universe in the Big Bang occurs on January 1 in the Cosmic Year, and the present time corresponds to the stroke of midnight on December 31.

We know the dates of some events, such as the origin of Earth, with a fair degree of accuracy. But for most events in the Cosmic Calendar, such as the formation of the Milky Way Galaxy, or the origin of life on Earth, the dates are imprecise estimates, to be refined and revised as we continue to learn. We have only begun to use the methods of science to reconstruct our distant past. Still, the Cosmic Calendar is a useful tool for getting a sense of the grand story of the universe as revealed by science.

-- Ann Druyan & Steven Soter

The best estimate for the age of our universe is 13.7 billion years, plus or minus a few hundred million years. Taking that as our baseline, we have

1 year of the Cosmic Calendar = 13.7 billion years in real time
1 month = 1.14 billion years
1 week = 263 million years
1 day = 37.5 million years
1 hour = 1.56 million years
1 minute = 26,000 years
1 second = 430 years

JANUARY

  • 1 -- 12:00 a.m. -- Big Bang
  • 1 -- 12:15 a.m. -- Neutral atoms form; space becomes transparent
  • 6 -- First stars ignite
  • 26 -- First galaxies form

FEBRUARY

MARCH

  • 13 -- Formation of the Milky Way Galaxy

APRIL

MAY

JUNE

JULY

AUGUST

SEPTEMBER

  • 1 -- Origin of our solar system and Earth
  • 16 -- Oldest surviving rocks on Earth
  • 21 -- First stirrings of life
  • 29 -- Oldest stromatolites

OCTOBER

NOVEMBER

  • 8 -- Significant oxygen atmosphere
  • 30 -- Invention of sex by multicellular algae

DECEMBER

  • 5 -- Seaweed appears
  • 11 -- First amoebas with shells
  • 15 -- Multicellular animals (e.g., sponges and jellyfish) appear
  • 17 -- Cambrian explosion; first hard-bodied organisms
  • 18 -- First fish
  • 19 -- Algae begin to live on the land
  • 21 -- First land animals (millipedes)
  • 22 -- First sharks; first flying insects, ferns, and plants with roots
  • 23 -- Rise of amphibians
  • 24 -- First reptiles
  • 25 -- Permian mass extinction; age of dinosaurs begins; first bees and mammals
  • 26 -- First birds
  • 28 -- First flowering plants; Africa separates from South America
  • 30 -- Impact ends Cretaceous period; dinosaurs become extinct; first rodents, horses, grasslands
  • 31 -- 1:00 a.m. Primitive apes
  • 31 -- 12:00 p.m. -- Early dogs
  • 31 -- 2:00 p.m. -- Asteroid makes Ries crater in Germany
  • 31 -- 6:00 p.m. -- Early cats
  • 31 -- 9:00 p.m. -- First hominids
  • 31 -- 10:30 p.m. -- Stone tools
  • 31 -- 11:00 p.m. -- Domestication of Fire
  • 31 -- 11:48 p.m. -- Symbolic language
  • 31 -- 11:54 p.m. Homo sapiens appears
  • 31 -- 11:58 p.m. -- Seafarers settle Australia
  • 31 -- 11:59 p.m. -- Extensive cave paintings
  • 31 -- 11:59:37 p.m. -- Invention of Agriculture
  • 31 -- 11:59:46 p.m. -- Rise of Sumer
  • 31 -- 11:59:48 p.m. -- Bronze Age begins; writing invented
  • 31 -- 11:59:51 p.m. -- Code of Hammurabi in Babylon; Middle Kingdom in Egypt
  • 31 -- 11:59:52 p.m. -- Moses leads enslaved Hebrews out of Egypt
  • 31 -- 11:59:53 p.m. -- Trojan War; Olmec culture; Iron Age; Carthage founded
  • 31 -- 11:59:54 p.m. -- Founding of Rome; Ashokan India; Chin dynasty; Periclean Athens; birth of Buddha
  • 31 -- 11:59:55 p.m. -- Euclidean geometry; Archimediean physics; Ptolemaic astronomy; birth of Jesus
  • 31 -- 11:59:57 p.m. -- Zero and decimals invented in India; Muslim conquest
  • 31 -- 11:59:58 p.m. -- Mayan civilization; Sung Dynasty China; Byzantine Empire; Mongol invasion; Crusades
  • 31 -- 11:59:59 p.m. -- Copernicus; voyages of discovery; emergence of experimental method in science

WE ARE NOW ENTERING THE FIRST SECOND OF A NEW COSMIC YEAR, a time of unprecedented danger and promise for life on our planet. We are taking our first steps to explore the universe and to trace the ancient continuity of cosmic evolution of which we are a part. What happens next in our Cosmic Calendar depends on how we use our intelligence ... on what we do now.