Cosmic Calendar

The Cosmic Calendar is a method to visualize the chronology of the universe, scaling its current age of 13.8 billion years to a single year in order to help intuit it for pedagogical purposes in science education or popular 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 second, 1.575 million years per hour, and 37.8 million years per day.

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

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

The Cosmic Year

The Cosmic Calendar shows the time-scale relationship of the universe and all events on Earth as plotted along a single 12-month, 365-day, year:


Date Bya(Billion Years Ago) Event
1 Jan 13.8 Big Bang, as seen through cosmic background radiation
14 Jan 13.1 Oldest known Gamma Ray Burst
22 Jan 12.85 First galaxies form[4]
16 Mar 11 Milky Way Galaxy formed
12 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 * 0.100/13.797 ( 1- T_Gya/13.797 )

Evolution of life on Earth

Date Bya(Billion Years Ago) Event
14 Sep 4.1 First known "remains of biotic life" found 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
21 Dec 0.4 Insects and Seeds
22 Dec 0.36 Amphibians
23 Dec 0.3 Reptiles
24 Dec 0.25 Permian-Triassic Extinction Event, 90% of Species Die Out
25 Dec 0.23 Dinosaurs
26 Dec 0.2 Mammals
27 Dec 0.15 Birds
28 Dec 0.13 Flowers
30 Dec, 06:24 0.065 Cretaceous–Paleogene extinction event, Non-avian Dinosaurs Die Out[11]

Human evolution

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

Date / time kya(Thousand Years Ago) Event
31 Dec, 23:59:33 12.0 End of the 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 Age to Early 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, 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

The current second

Date / time kya(Thousand Years Ago) Event
31 Dec, 23:59:59 0.5 Modern History; the last 437.5 years before present.


Future of the Earth and Solar System ("Year 2")

Date / time kyr(Thousand years), myr (Million years), and Byr (billion years) Event
1 Jan, 00:00:01 0.5 Anthropocene Epoch
1 Jan, 00:00:23 10.0 Antares explodes into a supernova
1 Jan, 00:00:50 20.0 Chernobyl finally becomes safe
1 Jan, 00:00:57 20.0 The Arecibo message finally reaches the M13 cluster
1 Jan, 00:01:54 50.0 Niagara Falls finally erodes away
1 Jan, 00:03:48 100.0 Proper motion makes all constellations unrecognizable
1 Jan, 00:11:24 300.0 WR 104 explodes
1 Jan, 00:19:02 500.0 Earth likely hit by 1 km asteroid
1 Jan, 00:38:05 1.0 Pyramids of Giza erode away
1 Jan, 04:34:17 7.2 Mount Rushmore erodes away
3 Jan 100.00 Saturn loses its rings
5 Jan 180.00 Earth's day becomes one hour longer
7 Jan 240.00 Solar System completes one galactic year
16 Jan 600.00 Solar eclipses no longer possible
16 Apr 4.0 Global surface temperatures reach 1330 deg C, hot enough to melt lead
28 Jul 7.9 Sun destroys the Earth

Future of the Universe ("Year 3" and beyond)

Date / time Byr (billion years) and above Event
Year 8, 1 Apr 100.0 Galaxies disappear beyond light horizon
Year 7247, 13 Dec 100 trillion Star formation ends
Year 72,479, 11 Jul 1 quadrillion Sun cools down to -268 deg C
Year 7.94*10^35 3*10^43 Black Hole Era
Year 4.54*10^98 1.7*10^98 Dark Era
Year 10^1500 Iron stars
Year 10^10^50 Boltzmann brain appears
Year 10^10^78 Last black holes evaporate
Year 10^10^120 Final entropy state
Year 10^10^10^56 Possible new Big Bang occurs

See also


  1. ^ Therese Puyau Blanchard (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.
  2. ^ Cosmos, episode 1 (1980)
  3. ^ Episode 1: The Shores of the Cosmic Ocean (Cosmos: A Personal Voyage, Carl Sagan)
  4. ^ "First Galaxies Born Sooner After Big Bang Than Thought". Retrieved 2015-11-07.
  5. ^ Borenstein, Seth (19 October 2015). "Hints of life on what was thought to be desolate early Earth". Excite. Yonkers, NY: Mindspark Interactive Network. Associated Press. Retrieved 2015-10-20.
  6. ^ 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.
  7. ^ Yoko Ohtomo; Takeshi Kakegawa; Akizumi Ishida; Toshiro Nagase; Minik T. Rosing (8 December 2013). "Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks". Nature Geoscience. 7: 25–28. Bibcode:2014NatGe...7...25O. doi:10.1038/ngeo2025.
  8. ^ Borenstein, Seth (13 November 2013). "Oldest fossil found: Meet your microbial mom". AP News. Retrieved 15 November 2013.
  9. ^ 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.
  10. ^ 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.
  11. ^ Cosmos: A Spacetime Odyssey (@35min)

External links

Carl Sagan Memorial Award

The Carl Sagan Memorial Award is an award presented jointly by the American Astronautical Society and The Planetary Society to an individual or group "who has demonstrated leadership in research or policies advancing exploration of the Cosmos." The annual award, first presented in 1997, was created in honor of American astronomer, astrobiologist and science popularizer, Carl Sagan (1934–1996).


Chronostratigraphy is the branch of stratigraphy that studies the age of rock strata in relation to time.

The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geological region, and eventually, the entire geologic record of the Earth.

The standard stratigraphic nomenclature is a chronostratigraphic system based on palaeontological intervals of time defined by recognised fossil assemblages (biostratigraphy). The aim of chronostratigraphy is to give a meaningful age date to these fossil assemblage intervals and interfaces.


Circa (from Latin, meaning 'around, about') – frequently abbreviated c., ca. or ca and less frequently circ. or cca. – signifies "approximately" in several European languages and as a loanword in English, usually in reference to a date. Circa is widely used in historical writing when the dates of events are not accurately known.

When used in date ranges, circa is applied before each approximate date, while dates without circa immediately preceding them are generally assumed to be known with certainty.


1732–1799: Both years are known precisely.

c. 1732 – 1799: The beginning year is approximate; the end year is known precisely.

1732 – c. 1799: The beginning year is known precisely ; the end year is approximate.

c. 1732 – c. 1799: Both years are approximate.

Era (geology)

A geologic era is a subdivision of geologic time that divides an eon into smaller units of time. The Phanerozoic Eon is divided into three such time frames: the Paleozoic, Mesozoic, and Cenozoic (meaning "old life", "middle life" and "recent life") that represent the major stages in the macroscopic fossil record. These eras are separated by catastrophic extinction boundaries, the P-T boundary between the Paleozoic and the Mesozoic and the K-Pg boundary between the Mesozoic and the Cenozoic. There is evidence that catastrophic meteorite impacts played a role in demarcating the differences between the eras.

The Hadean, Archean and Proterozoic eons were as a whole formerly called the Precambrian. This covered the four billion years of Earth history prior to the appearance of hard-shelled animals. More recently, however, the Archean and Proterozoic eons have been subdivided into eras of their own.

Geologic eras are further subdivided into geologic periods, although the Archean eras have yet to be subdivided in this way.


Floruit (UK: , US: ), abbreviated fl. (or occasionally flor.), Latin for "he/she flourished", denotes a date or period during which a person was known to have been alive or active. In English, the word may also be used as a noun indicating the time when someone flourished.

Fluorine absorption dating

Fluorine absorption dating is a method used to determine the amount of time an object has been underground.

Fluorine absorption dating can be carried out based on the fact that groundwater contains fluoride ions. Items such as bone that are in the soil will absorb fluoride from the groundwater over time. From the amount of absorbed fluoride in the item, the time that the item has been in the soil can be estimated.

Many instances of this dating method compare the amount of fluorine and uranium in the bones to nitrogen dating to create more accurate estimation of date. Older bones have more fluorine and uranium and less nitrogen. But because decomposition happens at different speeds in different places, it's not possible to compare bones from different sites.

As not all objects absorb fluorine at the same rate, this also undermines the accuracy of such a dating technique. Although this can be compensated for by accommodating for the rate of absorption in calculations, such an accommodation tends to have a rather large margin of error.

In 1953 this test was used to easily identify that the 'Piltdown Man' was forged, almost 50 years after it was originally 'unearthed'.

Galactic Tick Day

Galactic Tick Day is an awareness and education day that celebrates the movement of the Solar System around the Milky Way galaxy.

Geologic Calendar

The Geologic Calendar is a scale in which the geological lifetime of the earth is mapped onto a calendrical year; that is to say, the day one of the earth took place on a geologic January 1 at precisely midnight, and today's date and time is December 31 at midnight. On this calendar, the inferred appearance of the first living single-celled organisms, prokaryotes, occurred on a geologic February 25 around 12:30pm to 1:07pm, dinosaurs first appeared on December 13, the first flower plants on December 22 and the first primates on December 28 at about 9:43pm. The first Anatomically modern humans did not arrive until around 11:48 p.m. on New Year's Eve, and all of human history since the end of the last ice-age occurred in the last 82.2 seconds before midnight of the new year.

Geological period

A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place.

These periods form elements of a hierarchy of divisions into which geologists have split the Earth's history.

Eons and eras are larger subdivisions than periods while periods themselves may be divided into epochs and ages.

The rocks formed during a period belong to a stratigraphic unit called a system.

Graphical timeline of the Big Bang

This timeline of the Big Bang shows a sequence of events as currently theorized by scientists.

It is a logarithmic scale that shows second instead of second. For example, one microsecond is . To convert −30 read on the scale to second calculate second = one millisecond. On a logarithmic time scale a step lasts ten times longer than the previous step.

Graphical timeline of the universe

This more than 20-billion-year timeline of our universe shows the best estimates of major events from the universe's beginning to anticipated future events. Zero on the scale is the present day. A large step on the scale is one billion years; a small step, one hundred million years. The past is denoted by a minus sign: e.g., the oldest rock on Earth was formed about four billion years ago and this is marked at -4e+09 years, where 4e+09 represents 4 times 10 to the power of 9. The "Big Bang" event most likely happened 13.8 billion years ago; see age of the universe.

Law of superposition

The law of superposition is an axiom that forms one of the bases of the sciences of geology, archaeology, and other fields dealing with geological stratigraphy. It is a form of relative dating. In its plainest form, it states that in undeformed stratigraphic sequences, the oldest strata will be at the bottom of the sequence. This is important to stratigraphic dating, which assumes that the law of superposition holds true and that an object cannot be older than the materials of which it is composed.


Limmu was an Assyrian eponym. At the beginning of the reign of an Assyrian king, the limmu, an appointed royal official, would preside over the New Year festival at the capital. Each year a new limmu would be chosen. Although picked by lot, there was most likely a limited group, such as the men of the most prominent families or perhaps members of the city assembly. The Assyrians used the name of the limmu for that year to designate the year on official documents. Lists of limmus have been found accounting for every year between 892 BC and 648 BC.

During the Old Assyrian period, the king himself was never the limmum, as it was called in their language. In the Middle Assyrian and Neo-Assyrian periods, however, the king could take this office.

New Earth Time

New Earth Time (or NET) is an alternative naming system for measuring the time of day. In NET the day is split into 360 NET degrees, each NET degree is split into 60 NET minutes and each NET minute is split into 60 NET seconds. One NET degree is therefore equivalent to four standard minutes, and one standard hour is equivalent to 15 NET degrees.

NET is equivalent to the UTC read from a 24-hour analog clock as the clockwise angle past midnight of the hour hand. For example, noon is 180°0'0" NET and at that time the hour hand is pointing straight down forming a 180° angle when measured from the top, at midnight. A full circle is 360 degrees and one NET day.

Nitrogen dating

Nitrogen dating is a form of relative dating which relies on the reliable breakdown and release of amino acids from bone samples to estimate the age of the object. For human bones, the assumption of about 5% nitrogen in the bone, mostly in the form of collogen, allows fairly consistent dating techniques.Compared to other dating techniques, Nitrogen dating can be unreliable because leaching from bone is dependent on temperature, soil pH, ground water, and the presence of microorganism that digest nitrogen rich elements, like collagen. Some studies compare nitrogen dating results with dating results from methods like fluorine absorption dating to create more accurate estimates. Though some situations, like thin porous bones might more rapidly change the dating created by multiple methods.

Proleptic Gregorian calendar

The proleptic Gregorian calendar is produced by extending the Gregorian calendar backward to dates preceding its official introduction in 1582. In countries that adopted the Gregorian calendar later, dates occurring in the interim (between 1582 and the local adoption) are sometimes "Gregorianized" as well. For example, George Washington was born on February 11, 1731 (Old Style), as Great Britain and its possessions were using the Julian calendar with English years starting on March 25 until September 1752. After the switch, that day became February 22, 1732, which is the date commonly given as Washington's birthday.

Standing Up in the Milky Way

"Standing Up in the Milky Way" is the first aired episode of the American documentary television series Cosmos: A Spacetime Odyssey. It premiered on March 9, 2014, simultaneously on various Fox television networks, including National Geographic Channel, FX, Fox Life, and others. The episode is presented by the series host astrophysicist Neil deGrasse Tyson, directed by Brannon Braga, produced by Livia Hanich and Steven Holtzman, and written by Ann Druyan and Steven Soter.

The series represents a follow-up of the 1980s television series Cosmos: A Personal Voyage by Carl Sagan, now hosted by Tyson, and explores astronomy, space and time, astrophysics, biology, and other diverse areas of science. In this episode, Tyson takes a tour of the Solar System and the Milky Way galaxy, explores the life of Renaissance philosopher Giordano Bruno and his vision of the cosmos, goes through a Cosmic Calendar from the beginning of the universe until the present, and ends with a tribute to Carl Sagan. The episode was first presented with a brief introduction by the President of the United States Barack Obama.The episode received positive reviews by critics, but was criticized on issues like the historical accuracy in the presentation of Giordano Bruno's life. It was also nominated for Primetime Emmy Award for Outstanding Music Composition for a Series at the 66th Primetime Creative Arts Emmy Awards, an award it won.


A stratotype or type section is a geological term that names the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the standard of reference for unlayered rocks is the type locality.

Key topics
Astronomic time
Geologic time
Genetic methods
Linguistic methods
Related topics
Scientific career
Science books
Sagan Prizes

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