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(Top) 1 Cosmology 2 Evolution of life on Earth 3 Human evolution 4 History begins 5 See also 6 References 7 External links

Cosmic Calendar

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A graphical view of the Cosmic Calendar, featuring the months of the year, days of December, the final minute, and the final second

The Cosmic Calendar is a method to visualize the chronology of the universe, scaling its currently understood age of 13.8 billion years to a single year in order to help intuit it for pedagogical purposes in science educationorpopular science.

In this visualization, the Big Bang took place at the beginning of January 1 at midnight, and the current moment maps onto the end of December 31 just before midnight.^[1] At this scale, there are 437.5 years per cosmic second, 1.575 million years per cosmic hour, and 37.8 million years per cosmic day.

The concept was popularized by Carl Sagan in his 1977 book The Dragons of Eden and on his 1980 television series Cosmos.^[2] Sagan goes on to extend the comparison in terms of surface area, explaining that if the Cosmic Calendar were scaled to the size of a football field, then "all of human history would occupy an area the size of [his] hand".^[3]

A similar analogy used to visualize the geologic time scale and the history of life on Earth is the Geologic Calendar.

Cosmology[edit]

Date	Gya (billion years ago)	Event
1 Jan	13.8	Big Bang, as seen through cosmic background radiation, which would have been last emitted 14 minutes after midnight
19 Jan	13.1	Oldest known Gamma Ray Burst
26 Jan	12.85	First galaxies form^[4]
16 Mar	11	Milky Way Galaxy formed
13 May	8.8	Milky Way Galaxy disk formed
2 Sep	4.57	Formation of the Solar System
6 Sep	4.4	Oldest rocks known on Earth

Date in year calculated from formula

T(days) = 365 days * ( 1- T_Gya/13.797 )

Evolution of life on Earth[edit]

Date	Gya (billion years ago)	Event
14 Sep	4.1	First known remains of biotic life (discovered in 4.1 billion-year-old rocks in Western Australia).^[5]^[6]
21 Sep	3.8	First Life (Prokaryotes)^[7]^[8]^[9]
30 Sep	3.4	Photosynthesis
29 Oct	2.4	Oxygenation of atmosphere
9 Nov	2	Complex cells (Eukaryotes)
5 Dec	0.8	First multicellular life^[10]
7 Dec	0.67	Simple animals
14 Dec	0.55	Arthropods (ancestors of insects, arachnids)
17 Dec	0.5	Fish and Proto-amphibians
20 Dec	0.45	Land plants; Ordovician–Silurian extinction events
21 Dec	0.4	Insects and seeds
22 Dec	0.36	Amphibians; Late Devonian extinction
23 Dec	0.3	Reptiles
24 Dec	0.25	Permian–Triassic extinction event; 57% of all biological families and 83% of all genera die
25 Dec	0.23	Dinosaurs
26 Dec	0.2	Mammals; Triassic–Jurassic extinction event
27 Dec	0.15	Birds (avian dinosaurs)
28 Dec	0.13	Flowers
30 Dec, 06:24	0.065	Cretaceous–Paleogene extinction event, non-avian dinosaurs die out^[11]

Human evolution[edit]

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Date / time	Mya (million years ago)	Event
30 Dec	65	Primates
31 Dec, 06:05	15	Apes
31 Dec, 14:24	12.3	Hominids
31 Dec, 22:24	2.5	Primitive humans and stone tools
31 Dec, 23:44	0.4	Domestication of fire
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 painting
31 Dec, 23:59:32	0.012	Agriculture

History begins[edit]

Date / time	kya (thousand years ago)	Event
31 Dec, 23:59:33	12.0	End of the last Ice Age
31 Dec, 23:59:41	8.3	Flooding of Doggerland
31 Dec, 23:59:46	6.0	Chalcolithic
31 Dec, 23:59:47	5.5	Early Bronze Age; Proto-writing; Building of Stonehenge Cursus
31 Dec, 23:59:48	5.0	First Dynasty of Egypt, Early Dynastic period in Sumer, beginning of Indus Valley civilisation
31 Dec, 23:59:49	4.5	Alphabet, Akkadian Empire, wheel
31 Dec, 23:59:51	4.0	Code of Hammurabi, Middle Kingdom of Egypt
31 Dec, 23:59:52	3.5	Late Bronze Agetoearly Iron Age; Minoan eruption
31 Dec, 23:59:53	3.0	Iron Age; beginning of classical antiquity
31 Dec, 23:59:54	2.5	Buddha, Mahavira, Zoroaster, Confucius, Achaemenid Empire, Qin Dynasty, Classical Greece, Ashokan Empire, Vedas Completed, Euclidean geometry, Archimedean Physics, Roman Republic
31 Dec, 23:59:55	2.0	Ptolemaic astronomy, Roman Empire, Christ, invention of numeral 0, Gupta Empire
31 Dec, 23:59:56	1.5	Muhammad, Maya civilization, Song Dynasty, rise of Byzantine Empire
31 Dec, 23:59:58	1.0	Mongol Empire, Maratha Empire, Crusades, Christopher Columbus voyages to the Americas, Renaissance in Europe, Classical music to the time of Johann Sebastian Bach
31 Dec, 23:59:59	0.5	Modern History; the last 437.5 years before present.

References[edit]

^ Blanchard, Therese Puyau (1995). "The Universe At Your Fingertips Activity: Cosmic Calendar". Astronomical Society of the Pacific. Archived from the original on 2007-12-16. Retrieved 2007-12-15.

^ Cosmos, episode 1 (1980)

^ Episode 1: The Shores of the Cosmic Ocean (Cosmos: A Personal Voyage, Carl Sagan)

^ "First Galaxies Born Sooner After Big Bang Than Thought". Space.com. 14 April 2011. Retrieved 2015-11-07.

^ Borenstein, Seth (19 October 2015). "Hints of life on what was thought to be desolate early Earth". Excite. Yonkers, New York: Mindspark Interactive Network. Associated Press. Retrieved 2015-10-20.

^ Bell, Elizabeth A.; Boehnike, Patrick; Harrison, T. Mark; et al. (19 October 2015). "Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon" (PDF). Proc. Natl. Acad. Sci. U.S.A. 112 (47): 14518–21. Bibcode:2015PNAS..11214518B. doi:10.1073/pnas.1517557112. ISSN 1091-6490. PMC 4664351. PMID 26483481. Retrieved 2015-10-20. Early edition, published online before print.

^ Ohtomo, Yoko; Kakegawa, Takeshi; Ishida, Akizumi; Nagase, Toshiro; Rosing, Minik T. (8 December 2013). "Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks". Nature Geoscience. 7 (1): 25–28. Bibcode:2014NatGe...7...25O. doi:10.1038/ngeo2025.

^ Borenstein, Seth (13 November 2013). "Oldest fossil found: Meet your microbial mom". AP News. Retrieved 15 November 2013.

^ Noffke, Nora; Christian, Daniel; Wacey, David; Hazen, Robert M. (8 November 2013). "Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia". Astrobiology. 13 (12): 1103–24. Bibcode:2013AsBio..13.1103N. doi:10.1089/ast.2013.1030. PMC 3870916. PMID 24205812.

^ Erwin, Douglas H. (9 November 2015). "Early metazoan life: divergence, environment and ecology". Phil. Trans. R. Soc. B. 370 (20150036): 20150036. doi:10.1098/rstb.2015.0036. PMC 4650120. PMID 26554036.

^ "Cosmos: A Spacetime Odyssey (@35min)". Archived from the original on 2014-03-11. Retrieved 2014-03-11.

External links[edit]

Wikibooks has a book on the topic of: General Astronomy/Short History of the Universe

Wikibooks has a book on the topic of: High School Earth Science

Chronology

Key topics

Periods

Eras

Epochs

Calendar eras

Human Era
Ab urbe condita
Anno Domini / Common Era
Anno Mundi
Bosporan era
Bostran era
Byzantine era
Seleucid era
Era of Caesar (Iberia)
Before present
Hijri
Egyptian
Sothic cycle
Hindu units of time (Yuga)
Mesoamerican
- Long Count
- Short Count
- Tzolk'in
- Haab'

Regnal year

Era names

Calendars

Pre-Julian / Julian	Pre-Julian Roman Original Julian Proleptic Julian Revised Julian
Gregorian	Gregorian Proleptic Gregorian Old Style and New Style dates Adoption of the Gregorian calendar Dual dating
Astronomical	Lunisolar (Hebrew, Hindu) Solar Lunar (Islamic) Astronomical year numbering
Others	Chinese sexagenary cycle Geologic Calendar Iranian ISO week date Mesoamerican Maya Aztec Winter count New Earth Time

Astronomic time

Geologic time

Concepts

Standards

Methods

Chronological
dating

Absolute dating

Relative dating

Genetic methods

Molecular clock

Linguistic methods

Glottochronology