The Cosmic Timeline

Astrophysicists have deduced the age of the Universe
(dated from the Big Bang) to be

Imagine that the entire history of the universe is compressed into one year - with the Big Bang corresponding to the first second of the New Year's Day, and the present time to the last second of December 31st (midnight).

Using this scale of time, each month would equal a little over a billion years. Here's a closer look at when important events would occur when we imagine the universe in one year:

The Universe in One Year was inspired by the late astronomer, Carl Sagan (1934-1996). Sagan was the first person to explain the history of the universe in one year-as a "Cosmic Calendar"-in his television series, Cosmos.

Let us look at the calendar in a bit more detail:

Cosmic Calendar (From The Dragons of Eden - Carl Sagan)

Pre-December Dates

Big Bang January 1
Origin of Milky Way Galaxy May 1
Origin of the solar systemSeptember 9
Formation of the EarthSeptember 14
Origin of life on Earth~ September 25
Formation of the oldest rocks known on EarthOctober 2
Date of oldest fossils (bacteria and blue-green algae)October 9
Invention of sex (by microorganisms)~ November 1
Oldest fossil photosynthetic plantsNovember 12
Eukaryotes (first cells with nuclei) flourishNovember 15


Sunday MondayTuesdayWednesdayThursdayFridaySaturday

Significant oxygen atmosphere begins to develop on Earth.

2 345

Extensive vulcanism and channel formation on Mars.



8 910111213



First Worms.


Precambrian ends. Paleozoic Era and Cambrian Period begin. Invertebrates flourish.


First oceanic plankton. Trilobites flourish.


Ordovician Period. First fish, first vertebrates.


Silurian Period. First vascular plants. Plants begin colonization of land.


Devonian Period begins. First insects. Animals begin colonization of land.



First amphibians. First winged insects.


Carboniferous Period. First trees. First reptiles.


Permian Period begins. First dinosaurs.


Paleozoic Era ends. Mesozoic Era Begins.


Triassic Period. First mammals.


Jurassic Period. First birds.


Cretaceous Period. First flowers. Dinosaurs become extinct.



Mesozoic Era ends. Cenozoic Era and Tertiary Period begin. First cetaceans. First primates.


First evolution of frontal lobes in the brains of primates. First hominids. Giant mammals flourish.


End of Pliocene Period. Quaternary (Pleistocene and Holocene) Period. First humans.



December 31

Origin of Proconsul and Ramapithecus, probable ancestors of apes and men ~ 1:30 p.m.
First humans~ 10:30 p.m.
Widespread use of stone tools11:00 p.m.
Domestication of fire by Peking man11:46 p.m.
Beginning of most recent glacial period11:56 p.m.
Seafarers settle Australia11:58 p.m.
Extensive cave painting in Europe11:59 p.m.
Invention of agriculture11:59:20 p.m.
Neolithic civilization; first cities11:59:35 p.m.
First dynasties in Sumer, Ebla and Egypt; development of astronomy11:59:50 p.m.
Invention of the alphabet; Akkadian Empire11:59:51 p.m.
Hammurabic legal codes in Babylon; Middle Kingdom in Egypt11:59:52 p.m.
Bronze metallurgy; Mycenaean culture; Trojan War; Olmec culture; invention of the compass11:59:53 p.m.
Iron metallurgy; First Assyrian Empire; Kingdom of Israel; founding of Carthage by Phoenicia11:59:54 p.m.
Asokan India; Ch'in Dynasty China; Periclean Athens; birth of Buddha11:59:55 p.m.
Euclidean geometry; Archimedean physics; Ptolemaic astronomy; Roman Empire; birth of Christ11:59:56 p.m.
Zero and decimals invented in Indian arithmetic; Rome falls; Birth of Islam and the Islamic Civilization 11:59:57 p.m.
Mayan civilization; Sung Dynasty China; Byzantine empire; Mongol invasion; Crusades11:59:58 p.m.
Renaissance in Europe; voyages of discovery from Europe and from Ming Dynasty China; emergence of the experimental method in science11:59:59 p.m.
Widespread development of science and technology; emergence of global culture; acquisition of the means of self-destruction of the human species; first steps in spacecraft planetary exploration and the search of extraterrestrial intelligenceNow: The first second of New Year's Day


Within the scheme of the Cosmic Calendar, an average human life of 70-80 years is equivalent to approximately 0.16 cosmic seconds!