View source for Astronomy:Cosmic Calendar

{{short description|Method to visualize the chronology of the universe}}
[[Image:Cosmic Calendar (extended by "The Final Second").png|thumb|right|upright=2.8|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 [[Astronomy:Chronology of the universe|chronology of the universe]], scaling its [[Astronomy:Age of the universe|currently understood age]] of 13.8 billion years to a single [[Year|year]] in order to help intuit it for pedagogical purposes in science education or popular science.

In this visualization, the [[Astronomy:Big Bang|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.<ref name="astrosocietyorg">{{cite web |author=Blanchard |first=Therese Puyau |year=1995 |title=The Universe At Your Fingertips Activity: Cosmic Calendar |url=http://www.astrosociety.org/education/astro/act2/cosmic.html |url-status=dead |archive-url=https://web.archive.org/web/20071216233615/http://www.astrosociety.org/education/astro/act2/cosmic.html |archive-date=2007-12-16 |access-date=2007-12-15 |publisher=[[Organization:Astronomical Society of the Pacific|Astronomical Society of the Pacific]]}}</ref> 
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 [[Biography:Carl Sagan|Carl Sagan]] in his 1977 book ''The Dragons of Eden'' and on his 1980 television series ''Cosmos''.<ref>[https://www.youtube.com/watch?v=Pa1ImgOcOPM&t=52m55s ''Cosmos'', episode 1 (1980)]</ref> 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".<ref>[https://www.youtube.com/watch?v=Pa1ImgOcOPM&t=53m38s Episode 1: The Shores of the Cosmic Ocean (''Cosmos: A Personal Voyage'', Carl Sagan)]</ref> 

A similar analogy used to visualize the [[Earth:Geologic time scale|geologic time scale]] and the [[Biology:History of life|history of life on Earth]] is the [[Astronomy:Geologic Calendar|Geologic Calendar]].

== Cosmology ==
{| class="wikitable"
|-
!   Date !! [[Year#Abbreviations yr and ya|Gya (billion years ago)]] !! Event
|-
|  1 Jan || 13.8 || [[Astronomy:Big Bang|Big Bang]], as seen through [[Astronomy:Cosmic microwave background|cosmic background radiation]], which would have been last emitted 14 minutes after midnight
|-
|19 Jan
|13.1
|Oldest known [[Astronomy:GRB 090423|Gamma Ray Burst]]
|-
|26 Jan
|12.85
|First galaxies form<ref>{{Cite web|title = First Galaxies Born Sooner After Big Bang Than Thought|url = http://www.space.com/11386-galaxies-formation-big-bang-hubble-telescope.html|website = Space.com| date=14 April 2011 |access-date = 2015-11-07}}</ref>
|-
| 16 Mar || 11 || Milky Way Galaxy formed
|-
| 13 May || 8.8 || [[Astronomy:Thin disk|Milky Way Galaxy disk]] formed
|-
| 2 Sep  || 4.57 || Formation of the Solar System
|-
| 6 Sep  || 4.4 || [[Physics:Oldest dated rocks|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 ==
{{anchor|Life birth}}
{| class="wikitable"
|-
!   Date !! [[Year#Abbreviations yr and ya|Gya (billion years ago)]] !! Event
|-
| 14 Sep || 4.1 || First known remains of [[Chemistry:Biotic material|biotic life]] (discovered in 4.1 billion-year-old rocks in Western Australia).<ref name="AP-20151019">{{cite news |last=Borenstein |first=Seth |date=19 October 2015 |title=Hints of life on what was thought to be desolate early Earth |work=[[Company:Excite (web portal)|Excite]] |publisher=Mindspark Interactive Network |agency=Associated Press |location=Yonkers, New York |url=http://apnews.excite.com/article/20151019/us-sci--earliest_life-a400435d0d.html |access-date=2015-10-20}}</ref><ref name="PNAS-20151014-pdf">{{cite journal |last1=Bell |first1=Elizabeth A. |last2=Boehnike |first2=Patrick |last3=Harrison |first3=T. Mark |last4=Mao |first4=Wendy L. |display-authors=3 |date=19 October 2015 |title=Potentially biogenic carbon preserved in a 4.1 billion-year-old zircon |url=http://www.pnas.org/content/early/2015/10/14/1517557112.full.pdf |journal=Proc. Natl. Acad. Sci. U.S.A. |doi=10.1073/pnas.1517557112 |issn=1091-6490 |access-date=2015-10-20 |pmid=26483481 |pmc=4664351 |volume=112 |issue=47 |pages=14518–21|bibcode = 2015PNAS..11214518B |doi-access=free }} Early edition, published online before print.</ref>
|-
|-
| 30 Sep  || 3.4 || [[Earth:Photosynthesis|Photosynthesis]]
|-
| 29 Oct || 2.4 || [[Earth:Great Oxygenation Event|Oxygenation of atmosphere]]
|-
|  9 Nov || 2 || Complex cells (Eukaryotes)
|-
|  5 Dec || 0.8 || First [[Biology:Multicellular organism|multicellular life]]<ref name="PTRS-2015">{{cite journal |last1=Erwin |first1=Douglas H. |title=Early metazoan life: divergence, environment and ecology |journal=Phil. Trans. R. Soc. B |date=9 November 2015 |volume=370 |issue=20150036|pages=20150036 |doi=10.1098/rstb.2015.0036 |pmid=26554036 |pmc=4650120 }}</ref>
|-
| 7 Dec || 0.67 || Simple [[Biology:Animal|animal]]s
|-
| 14 Dec || 0.55 || Arthropods (ancestors of insects, arachnids)
|-
| 17 Dec || 0.5 || Fish and Proto-amphibians
|-
| 20 Dec || 0.45 || [[Biology:Evolutionary history of plants|Land plants]]; [[Earth:Ordovician–Silurian extinction events|Ordovician–Silurian extinction events]]
|-
| 21 Dec || 0.4 || Insects and seeds
|-
| 22 Dec || 0.36 || Amphibians; [[Earth:Late Devonian extinction|Late Devonian extinction]]
|-
| 23 Dec || 0.3 || Reptiles
|-
| 24 Dec || 0.25 || [[Earth:Permian–Triassic extinction event|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; [[Biology:Triassic–Jurassic extinction event|Triassic–Jurassic extinction event]]
|-
| 27 Dec || 0.15 || Birds (avian dinosaurs)
|-
| 28 Dec || 0.13 || Flowers
|-
| 30 Dec, 06:24 || 0.065 || [[Earth:Cretaceous–Paleogene extinction event|Cretaceous–Paleogene extinction event]], non-avian dinosaurs die out<ref>{{Cite web |url=http://www.hulu.com/watch/604551 |title=Cosmos: A Spacetime Odyssey (@35min) |access-date=2014-03-11 |archive-url=https://web.archive.org/web/20140311104905/http://www.hulu.com/watch/604551 |archive-date=2014-03-11 |url-status=dead }}</ref>
|}

== Human evolution ==
{{anchor|Primate evolution}}
{| class="wikitable"
|-
! Date ''/'' time  !! [[Year#Abbreviations yr and ya|Mya (million years ago)]] !! Event
|-
| 30 Dec           || 65 || [[Biology:Primates|Primates]]
|-
| 31 Dec, 06:05    || 15 || Apes
|-
| 31 Dec, 14:24    || 12.3 || [[Biology:Hominidae|Hominids]]
|-
| 31 Dec, 22:24    || 2.5 || Primitive humans and [[History:Oldowan|stone tools]]
|-
| 31 Dec, 23:44    || 0.4 || [[Biology:Control of fire by early humans|Domestication of fire]]
|-
| 31 Dec, 23:52    || 0.2 || Anatomically modern humans
|-
| 31 Dec, 23:55    || 0.11 || [[Earth:Last glacial period|Beginning of most recent Glacial Period]]
|-
| 31 Dec, 23:58    || 0.035 || Sculpture and painting
|-
| 31 Dec, 23:59:32 || 0.012 || [[History:Neolithic Revolution|Agriculture]]
|}

== History begins ==
{{anchor|Emperors and gods}} {{anchor|voyages of discovery}}
{| class="wikitable"
|-
! Date ''/'' time  !! [[Year#Abbreviations yr and ya|kya (thousand years ago)]] !! Event
|-
| 31 Dec, 23:59:33 || 12.0 || End of the [[Earth:Last glacial period|last Ice Age]]
|-
| 31 Dec, 23:59:41 || 8.3 || Flooding of [[Earth:Doggerland|Doggerland]]
|-
| 31 Dec, 23:59:46 || 6.0 || [[Chemistry:Chalcolithic|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 || [[Social:Alphabet|Alphabet]], Akkadian Empire, wheel
|-
| 31 Dec, 23:59:51 || 4.0 || Code of Hammurabi, [[History:Middle Kingdom of Egypt|Middle Kingdom of Egypt]]
|-
| 31 Dec, 23:59:52 || 3.5 || Late Bronze Age to early Iron Age; [[Earth:Minoan eruption|Minoan eruption]]
|-
| 31 Dec, 23:59:53 || 3.0 || [[History:Iron Age|Iron Age]]; beginning of [[History:Classical antiquity|classical antiquity]]
|-
| 31 Dec, 23:59:54 || 2.5 || [[Biography:Gautama Buddha|Buddha]], Mahavira, [[Biography:Zoroaster|Zoroaster]], [[Biography:Confucius|Confucius]], [[Place:Achaemenid Empire|Achaemenid Empire]], Qin Dynasty, Classical Greece, [[History:Ashoka|Ashokan Empire]], [[Religion:Vedas|Vedas]] Completed, [[Biography:Euclid|Euclid]]ean geometry, [[Biography:Archimedes|Archimedean]] Physics, Roman Republic
|-
| 31 Dec, 23:59:55 || 2.0 || [[History:Ptolemaic Kingdom|Ptolemaic]] astronomy, Roman Empire, Christ, invention of numeral 0, [[History:Gupta Empire|Gupta Empire]]
|-
| 31 Dec, 23:59:56 || 1.5 || [[Biography:Muhammad|Muhammad]], Maya civilization, Song Dynasty, rise of [[Place:Byzantine Empire|Byzantine Empire]]
|-
| 31 Dec, 23:59:58 || 1.0 || Mongol Empire, [[Place:Maratha Empire|Maratha Empire]], [[Religion:Crusades|Crusades]], Christopher Columbus voyages to the Americas, [[Philosophy:Renaissance|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.
|}

==See also==
{{col div|colwidth=35em}}
* {{annotated link|Astronomy:Geologic Calendar}} 
* {{annotated link|Biology:Big History}}
* {{annotated link|Detailed logarithmic timeline}}
* [[History:List of timelines|List of timelines]]
* {{annotated link|History:Timeline of ancient history}}
* {{annotated link|Biology:Timeline of the evolutionary history of life}}
* {{annotated link|Unsolved:Timeline of the far future}}
* {{annotated link|Biology:Timeline of human evolution}}
* {{annotated link|History:Timeline of human prehistory}}
* {{annotated link|History:Timelines of modern history}}
* {{annotated link|Earth:Timeline of natural history}}
* {{annotated link|Biology:Timeline of plant evolution}}
* {{annotated link|Astronomy:Chronology of the universe}}
* {{annotated link|History:Timeline of the Middle Ages}}
* {{annotated link|Astronomy:Cosmic time}}
* {{annotated link|Earth:History of Earth}}
{{colend}}

==References==
{{reflist|30em}}

==External links==
*[http://www.cosmiccalendar.net More information on the image used for this article.]
*[https://www.google.com/calendar/embed?src=k5g0mosd8l1jvofagvmkquaqtk%40group.calendar.google.com&ctz=America/Los_Angeles The Cosmic Calendar in a Google Calendar format]
*[https://twitter.com/Cosmic_Calendar The Cosmic Calendar relayed in real time.]

{{Chronology}}
[[Category:Units of time]]
[[Category:Physical cosmology|Calendar]]
[[Category:Time in astronomy]]

{{Sourceattribution|Cosmic Calendar}}