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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).
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).
In archaeology and anthropology, human prehistory is subdivided around the three-age system.
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.
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.
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
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.
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.
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.
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.
Colors =
id:neogene value:rgb(0.99215,0.8,0.54) id:paleogene value:rgb(1,0.7019,0) 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:neoproterozoic value:rgb(0.792,0.647,0.583) id:mesoproterozoic value:rgb(0.867,0.761,0.533) id:paleoproterozoic value:rgb(0.702,0.698,0.369) id:eoarchean value:rgb(0.5,0.565,0.565) id:paleoarchean value:rgb(0.6,0.592,0.569) id:mesoarchean value:rgb(0.698,0.65,0.6) id:neoarchean value:rgb(0.796,0.804,0.784) id:ediacaran value:rgb(0.918,0.847,0.737) id:cryogenian value:rgb(0.863,0.671,0.667) id:tonian value:rgb(0.796,0.643,0.424) id:stratherian value:rgb(1,1,0.8) # light yellow id:calymmian value:rgb(1,1,0.8) # light yellow id:orosirian value:rgb(1,1,0.8) # light yellow id:rhyacian value:rgb(1,1,0.8) # light yellow id:siderian value:rgb(1,1,0.8) # light yellow id:ectasian value:rgb(1,1,0.8) # light yellow id:stenian value:rgb(1,1,0.8) # light yellow 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: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) id:precambrian value:rgb(0.9,0.9,0.9) id:black value:black id:white value:white
Period = from:-4567.17 till:0 TimeAxis = orientation:horizontal ScaleMajor = unit:year increment:500 start:-4500 ScaleMinor = unit:year increment:100 start:-4500
Define $markred = text:"*" textcolor:red shift:(0,3) fontsize:10
PlotData=
align:center textcolor:black fontsize:8 mark:(line,black) shift:(0,-5)
bar:supereon
from: start till: -542 text:Precambrian color:precambrian
bar:eon
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
Colors =
id:quaternary value:rgb(0.9,0.9,0.5) id:neogene value:rgb(0.99215,0.8,0.54) id:paleogene value:rgb(1,0.7019,0) 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
Define $markred = text:"*" textcolor:red shift:(0,3) fontsize:10 Define $markgreen = text:"*" textcolor:darkgreen shift:(0,3) fontsize:10
PlotData=
align:center textcolor:black fontsize:8 mark:(line,black) shift:(0,-5)
bar:eon at: 0 align:right $markred at: -542 align:left $markred shift:(2,3) from: -542 till: 0 text:Phanerozoic color:phanerozoic
bar:era 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
Colors =
id:quaternary value:rgb(0.9,0.9,0.5) 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
Define $markgreen = text:"*" textcolor:darkgreen shift:(0,3) fontsize:10
PlotData=
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
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