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The categorization of time into discrete named blocks is called periodization. This is a list of such named time periods as defined in various fields of study. Major categorization systems include cosmological (concerning the various time periods in the origin and evolution of our universe), geological (concerning time periods in the origin and evolution of earth ) and historical (concerning time periods in the origin, evolution of mankind).

Human time periods

Based on current and debatable evidence, the human species has found its origins starting from about 250,000 years ago - when homo began to develop. It is broadly divided into prehistorical (before history began to be recorded) and historical periods (when written records began to be kept).

Further information: Human evolution

Prehistorical periods

Main article: List of archaeological periods

In archaeology and anthropology, human prehistory is subdivided around the three-age system.

  • The Stone Age
    • In some regions the Stone Age is divided into the Paleolithic Age (Old Stone Age) and the Neolithic Age (New Stone Age).
    • In other regions the Stone Age is divided into the Paleolithic Age, the Mesolithic Age (Middle Stone Age, also called the Epipaleolithic Age), and the Neolithic Age.
  • The Copper Age (aka Chalcolithic Age). The Copper Age was not part of the original three-age system.
  • The Bronze Age
  • The Iron Age

The dates for each age can vary by region. On the geologic time scale, the Holocene epoch starts at the end of the most recent Ice age (about 9400 BC) and continues to the present. The beginning of Mesolithic is usually considered to correspond to the beginning of the Holocene epoch.

Historical periods

Further information: History of the world

Calendar systems

Various societies in the past have created calendars to record events, such as religious observances and agricultural tasks. A common characteristic of most known calendars is that they measure time in relation to a particular point in history, known as the epoch date. A period between epoch dates is known as a calendar era.

Mythological and astrological time periods

Cosmological time periods

13.7 billion years ago: The Big Bang

Main article: Timeline of the Big Bang

Because of the scales involved (both very large and very small), cosmological time periods are usually described in seconds. In this table, each row is defined in seconds after the Big Bang, with earliest at the top of the chart.

Seconds after the Big Bang Period
5.4 × 10−44 Planck time
10−43 to 10−35 Planck Epoch
10−35 to 10−33 Inflationary epoch
10−35 to 10−12 Epoch of Grand Unification
10−12 to 10−6 Electroweak Epoch
10−6 to 100 Hadron Epoch
1 to 100 Lepton Epoch

100 seconds to 300,000 years after the big bang - Epoch of Nucleosynthesis

300,000 years on from the Big Bang - Epoch of Galaxies

Formation of Population III stars

The first stars were formed from the Hydrogen and Helium formed in the Big Bang were short lived massive Population III stars. Nuclear processes in these stars converted the Hydrogen and Helium into metals and other heavier elements. As the Population III stars died these heavier elements were released.

Formation of Population II stars

Population II stars contain metals formed in the Population III stars. These were longer lived than the Population III stars and some of them are still around. In addition to the metals these inherited from the Population III stars the Population II stars also formed metals by nuclear reactions and when the stars died much of that material was returned to be used as the building blocks for the next generation of stars.

5 Billion Years ago - Formation of Population I stars

Population I stars are also known as metal rich stars. Our own sun is a Population I star and was formed about 5 billion years ago.

Geologic time periods

Main articles: Geologic time scale and List of Global Boundary Stratotype Sections and Points

The geologic time scale covers the extent of the existence of Earth, from about 4600 million years ago to the present day. It is marked by Global Boundary Stratotype Sections and Points. Geologic time units are (in order of descending specificity) eons, eras, periods, epochs, and ages; and the corresponding chronostratigraphic units, which measure "rock-time", are eonothems, erathems, systems, series, and stages.

The second and third timelines are each subsections of their preceding timeline as indicated by asterisks. The Cenozoic is sometimes divided into the Quaternary and Tertiary periods, although their use is no longer official.

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 id:tonian        value:rgb(0.796,0.643,0.424)  
 id:stratherian   value:rgb(1,1,0.8)   # light yellow
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 id:phanerozoic value:rgb(0.7019,0.886,0.819)
 id:proterozoic value:rgb(0.8,0.85,0.568)
 id:archean   value:rgb(0.6,0.6784,0.6745)
 id:hadean value:rgb(0.4,0.4,0.4)
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 at:      0   align:right  $markred
 at:   -542   align:left   $markred shift:(2,3)
 from: -542   till:    0   text:Phanerozoic  color:phanerozoic   
 from:-2500   till: -542   text:Proterozoic  color:proterozoic   
 from:-3800   till: -2500  text:Archean      color:archean   
 from: start  till: -3800  text:Hadean       color:hadean


 bar:era
 from:  -65.5 till:    0   text:C~z shift:(0,1.5)        color:cenozoic        
 from: -251   till:  -65.5 text:Meso~zoic shift:(0,1.5)  color:mesozoic        
 from: -542   till: -251 text:Paleo~zoic shift:(0,1.5)  color:paleozoic 
 from: -1000  till:  -542  text:Neoprote-~rozoic shift:(0,1.8) color:neoproterozoic   
 from:-1600   till:  -1000  text:Mesoproterozoic color:mesoproterozoic  
 from:-2500   till: -1600  text:Paleoproterozoic color:paleoproterozoic 
 from:-2800   till: -2500  text:Neo-~archean shift:(0,1.5)     color:neoarchean       
 from:-3200   till: -2800  text:Meso-~archean shift:(0,1.5)   color:mesoarchean      
 from:-3600   till: -3200  text:Paleo-~archean shift:(0,1.5) color:paleoarchean     
 from:-3800   till: -3600  text:Eoar-~chean shift:(0,0.5) color:eoarchean fontsize:6       
 from:start   till: -3800  color:white
 bar:period
 fontsize:6
 from:   -23.03 till:    0    color:neogene
 from:  -65.5 till:   -23.03  color:paleogene
 from: -145.5   till:  -65.5  color:cretaceous
 from: -199.6   till: -145.5  color:jurassic
 from: -251   till: -199.6    color:triassic
 from: -299   till: -251      color:permian
 from: -359.2   till: -299    color:carboniferous
 from: -416 till: -359.2      color:devonian
 from: -443.7 till: -416      color:silurian
 from: -488.3   till: -443.7  color:ordovician
 from: -542   till: -488.3    color:cambrian
 from: -630   till:  -542  text:Ed. color:ediacaran
 from: -850   till:  -630  text:Cryo-~genian color:cryogenian shift:(0,0.5)
 from: -1000  till:  -850  text:Ton-~ian color:tonian shift:(0,0.5)
 from: -1200  till:  -1000 text:Ste-~nian color:mesoproterozoic shift:(0,0.5)
 from: -1400  till:  -1200 text:Ect-~asian color:mesoproterozoic shift:(0,0.5)
 from: -1600  till:  -1400 text:Calym-~mian color:mesoproterozoic shift:(0,0.5)
 from: -1800  till:  -1600 text:Stath-~erian color:paleoproterozoic shift:(0,0.5)
 from: -2050  till:  -1800 text:Oro-~sirian color:paleoproterozoic shift:(0,0.5)
 from: -2300  till:  -2050 text:Rhy-~acian color:paleoproterozoic shift:(0,0.5)
 from: -2500  till:  -2300 text:Sid-~erian color:paleoproterozoic shift:(0,0.5)
 from: start  till:  -2500 color:white

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 id:cretaceous   value:rgb(0.5,0.764,0.1098)
 id:jurassic      value:rgb(0.302,0.706,0.5) 
 id:triassic    value:rgb(0.403,0.765,0.716) 
 id:permian   value:rgb(0.404,0.776,0.867) 
 id:carboniferous     value:rgb(0.6,0.741,0.855)
 id:devonian  value:rgb(0.6,0.6,0.788)
 id:silurian  value:rgb(0.694,0.447,0.714)
 id:ordovician      value:rgb(0.976,0.506,0.651)
 id:cambrian  value:rgb(0.984,0.5,0.373)
 id:cenozoic   value:rgb(1,1,0)
 id:mesozoic   value:rgb(0.5,0.6784,0.3176)
 id:paleozoic  value:rgb(0.5,0.7098,0.835)
 id:phanerozoic value:rgb(0.7019,0.886,0.819)
 id:black  value:black
 id:white  value:white
 id:darkgreen value:rgb(0,0.35,0)


Period = from:-542 till:0 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:100 start:-500 ScaleMinor = unit:year increment:10 start:-540

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 bar:eon
 at:      0   align:right  $markred 
 at:   -542   align:left   $markred shift:(2,3)
 from: -542   till:    0   text:Phanerozoic color:phanerozoic
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 at:      0   align:right  $markgreen
 at:    -65.5 align:left   $markgreen shift:(2,3)
 from:  -65.5 till:    0   text:Cenozoic color:cenozoic
 from: -251   till:  -65.5 text:Mesozoic color:mesozoic
 from: -542   till: -251   text:Paleozoic color:paleozoic
 bar:period fontsize:8
 from: -2.588  till: 0 color:quaternary
 from: -23.03    till:  -2.588     text:Neo-~gene shift:(0,0.5) color:neogene
 from: -65.5  till:  -23.03   text:Paleo-~gene shift:(0,0.5) color:paleogene
 from: -145.5   till:  -65.5 text:Cretaceous color:cretaceous
 from: -199.6   till: -145.5   text:Jurassic color:jurassic
 from: -251.4   till: -199.6   text:Triassic   color:triassic
 from: -299   till: -251.4   text:Permian      color:permian
 from: -359.2   till: -299   text:Carboniferous color:carboniferous
 from: -416 till: -359.2   text:Devonian        color:devonian
 from: -443.7 till: -416 text:Sil-~urian shift:(0,0.5) color:silurian
 from: -488.3   till: -443.7 text:Ordovician color:ordovician
 from: -542   till: -488.3   text:Cambrian   color:cambrian

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Colors =

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 id:neogene   value:rgb(0.99215,0.8,0.54)
 id:paleogene value:rgb(1,0.7019,0)
 id:cenozoic   value:rgb(1,1,0)
 id:holocene   value:rgb(1,1,0.702)
 id:pleistocene  value:rgb(1,0.922,0.384)
 id:pliocene     value:rgb(1,0.922,0.675)
 id:miocene      value:rgb(1,0.871,0)
 id:oligocene    value:rgb(0.918,0.776,0.447)
 id:eocene       value:rgb(0.918,0.678,0.263)
 id:paleocene    value:rgb(0.92,0.576,0.005)
 id:black  value:black
 id:white  value:white
 id:darkgreen value:rgb(0,0.35,0)

Period = from:-65.5 till:0 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:10 start:-60 ScaleMinor = unit:year increment:1 start:-65

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 align:center textcolor:black fontsize:8 mark:(line,black)  shift:(0,-5)
 bar:era
 at:     0  align:right $markgreen 
 at: start  align:left  $markgreen shift:(2,3)
 from:start  till:  0    text:Cenozoic color:cenozoic
 bar:period
 from: -2.588 till: 0   text:Q. color:quaternary
 from: -23.03   till:  -2.588   text:Neogene color:neogene
 from:start  till: -23.03   text:Paleogene color:paleogene
 bar:epoch
 from: -0.1  till:  0  color:holocene
 from: -1.80  till: -0.1  text:P color:pleistocene
 from: -5.332    till: -1.80  text:Plio-~cene shift:(0,1) color:pliocene fontsize:7
 from:-23.03    till: -5.332    text:Miocene color:miocene
 from:-33.9    till:-23.03    text:Oligocene color:oligocene
 from:-55.8    till:-33.9    text:Eocene     color:eocene
 from:start  till:-55.8    text:Paleocene    color:paleocene

Millions of Years


See also

References

This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia


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