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{| class="wikitable"
{| class="wikitable"
! Time
! Time
!
! Event
! Event
|-
|-
!colspan="2" align="center"|'''Past'''
! colspan="3" align="center" |'''Past'''
|-
|-
|align="right"|About 61.32 galactic years ago||[[Big Bang]]
|align="right"|About 61.32 galactic years ago
| ||[[Big Bang]]
|-
|-
|align="right"|About 54 galactic years ago||Birth of the [[Milky Way]]
|align="right"|About 54 galactic years ago
| ||Birth of the [[Milky Way]]
|-
|-
|align="right"|20.44 galactic years ago||Birth of the [[Sun]]
|align="right"|20.44 galactic years ago
| ||Birth of the [[Sun]]
|-
|-
|align="right"|17–18 galactic years ago||Oceans appear on Earth
|align="right"|17–18 galactic years ago
| ||Oceans appear on Earth
|-
|-
|align="right"|16.889 galactic years ago||[[Timeline of the evolutionary history of life|Life begins on Earth]]
|align="right"|16.889 galactic years ago
| ||[[Timeline of the evolutionary history of life|Life begins on Earth]]
|-
|-
|align="right"|15.555 galactic years ago||[[Prokaryotes]] appear
|align="right"|15.555 galactic years ago
| ||[[Prokaryotes]] appear
|-
|-
|align="right"|12 galactic years ago||[[Bacteria]] appear
|align="right"|12 galactic years ago
| ||[[Bacteria]] appear
|-
|-
|align="right"|10 galactic years ago||Stable continents appear
|align="right"|10 galactic years ago
| ||Stable continents appear
|-
|-
|align="right"|6.8 galactic years ago||[[Multicellular]] organisms appear
|10 galactic years ago
|2250 Ma
|[[Eukaryian]] period<ref name="El_Albani_2014">{{cite journal |last1=El Albani |first1=Abderrazak |last2=Bengtson |first2=Stefan |last3=Canfield |first3=Donald E. |last4=Riboulleau |first4=Armelle |last5=Rollion Bard |first5=Claire |last6=Macchiarelli |first6=Roberto |display-authors=etal |year=2014 |title=The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity |journal=PLOS ONE |volume=9 |issue=6 |pages=e99438 |bibcode=2014PLoSO...999438E |doi=10.1371/journal.pone.0099438 |pmc=4070892 |pmid=24963687 |doi-access=free}}</ref><ref name="El_Albani_2010">{{cite journal |last1=El Albani |first1=Abderrazak |last2=Bengtson |first2=Stefan |last3=Canfield |first3=Donald E. |last4=Bekker |first4=Andrey |last5=Macchiarelli |first5=Roberto |last6=Mazurier |first6=Arnaud |last7=Hammarlund |first7=Emma U. |display-authors=etal |year=2010 |title=Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago |url=http://www.afrikibouge.com/publications/Article%20Albani.pdf |journal=Nature |volume=466 |issue=7302 |pages=100–104 |bibcode=2010Natur.466..100A |doi=10.1038/nature09166 |pmid=20596019 |s2cid=4331375}}{{Dead link|date=February 2022|bot=InternetArchiveBot|fix-attempted=yes}}</ref> first appearance of eukaryotes<ref name="GTS2012">{{Cite book |author=F. M. Gradstein |url=https://www.worldcat.org/oclc/808340848 |title=The geologic time scale 2012. Volume 2 |date=2012 |publisher=Elsevier |isbn=978-0-444-59448-8 |edition=1st |location=Amsterdam |oclc=808340848}}</ref>
|-
|-
|align="right"|6.666 galactic years ago||[[Eukaryotes]] appear
| align="right" |6.8 galactic years ago
| ||[[Multicellular]] organisms appear
|-
|-
|align="right"|2.4 galactic years ago||[[Cambrian explosion]] occurs
| align="right" |6.666 galactic years ago
| ||[[Eukaryotes]] appear
|-
|-
|align="right"|2 galactic years ago||The first brain structure appears in worms
| align="right" |2.4 galactic years ago
| ||[[Cambrian explosion]] occurs
|-
|-
|align="right"|1.11 galactic year ago||[[Permian–Triassic extinction event]]
| align="right" |2 galactic years ago
| ||The first brain structure appears in worms
|-
|-
|align="right"|0.2933 galactic years ago||[[Cretaceous–Paleogene extinction event]]
| align="right" |1.11 galactic year ago
| ||[[Permian–Triassic extinction event]]
|-
|-
|align="right"|0.0013 galactic years ago||Emergence of [[anatomically modern humans]]
| align="right" |0.2933 galactic years ago
| ||[[Cretaceous–Paleogene extinction event]]
|-
|-
⚫
| align="right" |0.0013 galactic years ago
⚫
!colspan="2" align="center"|'''Future'''
| ||Emergence of [[anatomically modern humans]]
|-
|-
⚫
! colspan="3" align="center" |'''Future'''
⚫
|align="right"|0.15 galactic year from now
|-
| align="right" |0.15 galactic year from now
|
|Mean time between impacts of asteroidal bodies in the order of magnitude of the [[K/Pg impactor]] has elapsed.<ref>Lunar and Planetary Institute (2010), https://www.lpi.usra.edu/features/chicxulub/</ref>
|Mean time between impacts of asteroidal bodies in the order of magnitude of the [[K/Pg impactor]] has elapsed.<ref>Lunar and Planetary Institute (2010), https://www.lpi.usra.edu/features/chicxulub/</ref>
|-
|-
|align="right"|1 galactic year from now
| align="right" |1 galactic year from now
|
|All the continents on Earth may fuse into a [[supercontinent]]. Three potential arrangements of this configuration have been dubbed [[Amasia (continent)|Amasia]], [[Novopangaea]], and [[Pangaea Ultima]].<ref>{{cite web |last1=Williams |first1=Caroline |last2=Nield |first2=Ted |date=2007-10-17 |title=Pangaea, the comeback |work=New Scientist |accessdate=2014-01-02 |url=https://www.newscientist.com/article/mg19626261-500-pangaea-the-comeback/ }}</ref>
|All the continents on Earth may fuse into a [[supercontinent]]. Three potential arrangements of this configuration have been dubbed [[Amasia (continent)|Amasia]], [[Novopangaea]], and [[Pangaea Ultima]].<ref>{{cite web |last1=Williams |first1=Caroline |last2=Nield |first2=Ted |date=2007-10-17 |title=Pangaea, the comeback |work=New Scientist |accessdate=2014-01-02 |url=https://www.newscientist.com/article/mg19626261-500-pangaea-the-comeback/ }}</ref>
|-
|-
|align="right"|2–3 galactic years from now
| align="right" |2–3 galactic years from now
|
|[[Tidal acceleration]] moves the Moon far enough from Earth that [[total solar eclipse]]s are no longer possible
|[[Tidal acceleration]] moves the Moon far enough from Earth that [[total solar eclipse]]s are no longer possible
|-
|-
|align="right"|4 galactic years from now
| align="right" |4 galactic years from now
|
|Carbon dioxide levels fall to the point at which [[C4 photosynthesis]] is no longer possible. Multicellular life dies out<ref>{{cite journal| last1=Franck | first1=S. | last2=Bounama | first2=C. | last3=von Bloh | first3=W. | title=Causes and timing of future biosphere extinction |journal=Biogeosciences Discussions| publisher=Copernicus GmbH |volume=2|issue=6| date=2005-11-07 | doi=10.5194/bgd-2-1665-2005 | page=1665-1679|bibcode=2006BGeo....3...85F| s2cid=3619702 | doi-access=free }}</ref>
|Carbon dioxide levels fall to the point at which [[C4 photosynthesis]] is no longer possible. Multicellular life dies out<ref>{{cite journal| last1=Franck | first1=S. | last2=Bounama | first2=C. | last3=von Bloh | first3=W. | title=Causes and timing of future biosphere extinction |journal=Biogeosciences Discussions| publisher=Copernicus GmbH |volume=2|issue=6| date=2005-11-07 | doi=10.5194/bgd-2-1665-2005 | page=1665-1679|bibcode=2006BGeo....3...85F| s2cid=3619702 | doi-access=free }}</ref>
|-
|-
|align="right"|15 galactic years from now
| align="right" |15 galactic years from now
|
|Surface conditions on [[Earth]] are comparable to those on [[Venus]] today
|Surface conditions on [[Earth]] are comparable to those on [[Venus]] today
|-
|-
|align="right"|22 galactic years from now||The Milky Way and [[Andromeda Galaxy]] [[Andromeda–Milky Way collision|begin to collide]]
| align="right" |22 galactic years from now
| ||The Milky Way and [[Andromeda Galaxy]] [[Andromeda–Milky Way collision|begin to collide]]
|-
|-
|align="right"|25 galactic years from now||Sun ejects a [[planetary nebula]], leaving behind a [[white dwarf]]
| align="right" |25 galactic years from now
| ||Sun ejects a [[planetary nebula]], leaving behind a [[white dwarf]]
|-
|-
| align="right" |30 galactic years from now
|align="right"|30 galactic years from now||The Milky Way and Andromeda complete their merger into a giant [[elliptical galaxy]] called [[Milkomeda]] or [[Milkdromeda]]<ref>{{cite journal | last1=Cox | first1=T. J. | last2=Loeb | first2=Abraham | title=The collision between the Milky Way and Andromeda | journal=Monthly Notices of the Royal Astronomical Society | publisher=Oxford University Press (OUP) | volume=386 | issue=1 | date=2008-05-01 | issn=0035-8711 | doi=10.1111/j.1365-2966.2008.13048.x | pages=461–474|bibcode=2008MNRAS.386..461C|arxiv=0705.1170| s2cid=14964036 }}</ref>
| ||The Milky Way and Andromeda complete their merger into a giant [[elliptical galaxy]] called [[Milkomeda]] or [[Milkdromeda]]<ref>{{cite journal | last1=Cox | first1=T. J. | last2=Loeb | first2=Abraham | title=The collision between the Milky Way and Andromeda | journal=Monthly Notices of the Royal Astronomical Society | publisher=Oxford University Press (OUP) | volume=386 | issue=1 | date=2008-05-01 | issn=0035-8711 | doi=10.1111/j.1365-2966.2008.13048.x | pages=461–474|bibcode=2008MNRAS.386..461C|arxiv=0705.1170| s2cid=14964036 }}</ref>
|-
|-
| align="right" |500 galactic years from now
|align="right"|500 galactic years from now||The Universe's expansion causes all galaxies beyond the Milky Way's [[Local Group]] to disappear beyond the [[cosmic light horizon]], removing them from the observable universe<ref>{{cite journal | last=Loeb | first=Abraham | title=Cosmology with hypervelocity stars | journal=Journal of Cosmology and Astroparticle Physics | publisher=IOP Publishing | volume=2011 | issue=4 | date=2011-04-18 | issn=1475-7516 | doi=10.1088/1475-7516/2011/04/023 | pages=023|arxiv=1102.0007| bibcode=2011JCAP...04..023L | s2cid=118750775 }}</ref>
| ||The Universe's expansion causes all galaxies beyond the Milky Way's [[Local Group]] to disappear beyond the [[cosmic light horizon]], removing them from the observable universe<ref>{{cite journal | last=Loeb | first=Abraham | title=Cosmology with hypervelocity stars | journal=Journal of Cosmology and Astroparticle Physics | publisher=IOP Publishing | volume=2011 | issue=4 | date=2011-04-18 | issn=1475-7516 | doi=10.1088/1475-7516/2011/04/023 | pages=023|arxiv=1102.0007| bibcode=2011JCAP...04..023L | s2cid=118750775 }}</ref>
|-
|-
| align="right" |2000 galactic years from now
|align="right"|2000 galactic years from now||Local Group of 47 galaxies<ref>{{cite web |title=The Local Group of Galaxies |work=University of Arizona |first1=Hartmut |last1=Frommert |first2=Christine |last2=Kronberg |publisher=Students for the Exploration and Development of Space |date=2007-06-05 |accessdate=2009-10-02 |url=http://www.seds.org/messier/more/local.html |archiveurl=https://web.archive.org/web/20090907170724/http://www.seds.org/messier/more/local.html |archivedate=2009-09-07 }}</ref> coalesces into a single large galaxy<ref>{{cite journal | last1=Adams | first1=Fred C. | last2=Laughlin | first2=Gregory | title=A dying universe: the long-term fate and evolutionof astrophysical objects | journal=Reviews of Modern Physics | volume=69 | issue=2 | date=1997-04-01 | issn=0034-6861 | doi=10.1103/revmodphys.69.337 | pages=337–372|bibcode=1997RvMP...69..337A|arxiv=astro-ph/9701131| s2cid=12173790 }}</ref>
| ||Local Group of 47 galaxies<ref>{{cite web |title=The Local Group of Galaxies |work=University of Arizona |first1=Hartmut |last1=Frommert |first2=Christine |last2=Kronberg |publisher=Students for the Exploration and Development of Space |date=2007-06-05 |accessdate=2009-10-02 |url=http://www.seds.org/messier/more/local.html |archiveurl=https://web.archive.org/web/20090907170724/http://www.seds.org/messier/more/local.html |archivedate=2009-09-07 }}</ref> coalesces into a single large galaxy<ref>{{cite journal | last1=Adams | first1=Fred C. | last2=Laughlin | first2=Gregory | title=A dying universe: the long-term fate and evolutionof astrophysical objects | journal=Reviews of Modern Physics | volume=69 | issue=2 | date=1997-04-01 | issn=0034-6861 | doi=10.1103/revmodphys.69.337 | pages=337–372|bibcode=1997RvMP...69..337A|arxiv=astro-ph/9701131| s2cid=12173790 }}</ref>
|}
|}
{{Css Image Crop
{{Css Image Crop

Revision as of 22:29, 9 May 2023

Approximate orbit of the Sun (yellow circle) around the Galactic Centre
Approximate orbit of the Sun (yellow circle) around the Galactic Centre

The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy.[1] One galactic year is 230 million Earth years.[2] The Solar System is traveling at an average speed of 230 km/s (828,000 km/h) or 143 mi/s (514,000 mph) within its trajectory around the galactic center,[3] a speed at which an object could circumnavigate the Earth's equator in 2 minutes and 54 seconds; that speed corresponds to approximately 1/1300 of the speed of light.

The galactic year provides a conveniently usable unit for depicting cosmic and geological time periods together. By contrast, a "billion-year" scale does not allow for useful discrimination between geologic events, and a "million-year" scale requires some rather large numbers.[4]

Timeline of the universe and Earth's history in galactic years

Main articles: Timeline of the early universe, Timeline of natural history, and Timeline of the far future
The orientation of the Solar System's motion

The following list assumes that 1 galactic year is 225 million years.

Time Event
Past
About 61.32 galactic years ago Big Bang
About 54 galactic years ago Birth of the Milky Way
20.44 galactic years ago Birth of the Sun
17–18 galactic years ago Oceans appear on Earth
16.889 galactic years ago Life begins on Earth
15.555 galactic years ago Prokaryotes appear
12 galactic years ago Bacteria appear
10 galactic years ago Stable continents appear
10 galactic years ago 2250 Ma Eukaryian period[5][6] first appearance of eukaryotes[7]
6.8 galactic years ago Multicellular organisms appear
6.666 galactic years ago Eukaryotes appear
2.4 galactic years ago Cambrian explosion occurs
2 galactic years ago The first brain structure appears in worms
1.11 galactic year ago Permian–Triassic extinction event
0.2933 galactic years ago Cretaceous–Paleogene extinction event
0.0013 galactic years ago Emergence of anatomically modern humans
Future
0.15 galactic year from now Mean time between impacts of asteroidal bodies in the order of magnitude of the K/Pg impactor has elapsed.[8]
1 galactic year from now All the continents on Earth may fuse into a supercontinent. Three potential arrangements of this configuration have been dubbed Amasia, Novopangaea, and Pangaea Ultima.[9]
2–3 galactic years from now Tidal acceleration moves the Moon far enough from Earth that total solar eclipses are no longer possible
4 galactic years from now Carbon dioxide levels fall to the point at which C4 photosynthesis is no longer possible. Multicellular life dies out[10]
15 galactic years from now Surface conditions on Earth are comparable to those on Venus today
22 galactic years from now The Milky Way and Andromeda Galaxy begin to collide
25 galactic years from now Sun ejects a planetary nebula, leaving behind a white dwarf
30 galactic years from now The Milky Way and Andromeda complete their merger into a giant elliptical galaxy called Milkomeda or Milkdromeda[11]
500 galactic years from now The Universe's expansion causes all galaxies beyond the Milky Way's Local Group to disappear beyond the cosmic light horizon, removing them from the observable universe[12]
2000 galactic years from now Local Group of 47 galaxies[13] coalesces into a single large galaxy[14]
Visualisation of the orbit of the Sun (yellow dot and white curve) around the Galactic Centre (GC) in the last galactic year. The red dots correspond to the positions of the stars studied by the European Southern Observatory in a monitoring programme.[15]
Visualisation of the orbit of the Sun (yellow dot and white curve) around the Galactic Centre (GC) in the last galactic year. The red dots correspond to the positions of the stars studied by the European Southern Observatory in a monitoring programme.[15]

See also

References

  1. ^ Cosmic Year Archived 2014-04-12 at the Wayback Machine, Fact Guru, University of Ottawa
  2. ^ Leong, Stacy (2002). "Period of the Sun's Orbit around the Galaxy (Cosmic Year)". The Physics Factbook.
  3. ^ http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question18.html NASA – StarChild Question of the Month for February 2000
  4. ^ Geologic Time Scale – as 18 galactic rotations
  5. ^ El Albani, Abderrazak; Bengtson, Stefan; Canfield, Donald E.; Riboulleau, Armelle; Rollion Bard, Claire; Macchiarelli, Roberto; et al. (2014). "The 2.1 Ga Old Francevillian Biota: Biogenicity, Taphonomy and Biodiversity". PLOS ONE. 9 (6): e99438. Bibcode:2014PLoSO...999438E. doi:10.1371/journal.pone.0099438. PMC 4070892. PMID 24963687.
  6. ^ El Albani, Abderrazak; Bengtson, Stefan; Canfield, Donald E.; Bekker, Andrey; Macchiarelli, Roberto; Mazurier, Arnaud; Hammarlund, Emma U.; et al. (2010). "Large colonial organisms with coordinated growth in oxygenated environments 2.1 Gyr ago" (PDF). Nature. 466 (7302): 100–104. Bibcode:2010Natur.466..100A. doi:10.1038/nature09166. PMID 20596019. S2CID 4331375.[permanent dead link]
  7. ^ F. M. Gradstein (2012). The geologic time scale 2012. Volume 2 (1st ed.). Amsterdam: Elsevier. ISBN 978-0-444-59448-8. OCLC 808340848.
  8. ^ Lunar and Planetary Institute (2010), https://www.lpi.usra.edu/features/chicxulub/
  9. ^ Williams, Caroline; Nield, Ted (2007-10-17). "Pangaea, the comeback". New Scientist. Retrieved 2014-01-02.
  10. ^ Franck, S.; Bounama, C.; von Bloh, W. (2005-11-07). "Causes and timing of future biosphere extinction". Biogeosciences Discussions. 2 (6). Copernicus GmbH: 1665-1679. Bibcode:2006BGeo....3...85F. doi:10.5194/bgd-2-1665-2005. S2CID 3619702.
  11. ^ Cox, T. J.; Loeb, Abraham (2008-05-01). "The collision between the Milky Way and Andromeda". Monthly Notices of the Royal Astronomical Society. 386 (1). Oxford University Press (OUP): 461–474. arXiv:0705.1170. Bibcode:2008MNRAS.386..461C. doi:10.1111/j.1365-2966.2008.13048.x. ISSN 0035-8711. S2CID 14964036.
  12. ^ Loeb, Abraham (2011-04-18). "Cosmology with hypervelocity stars". Journal of Cosmology and Astroparticle Physics. 2011 (4). IOP Publishing: 023. arXiv:1102.0007. Bibcode:2011JCAP...04..023L. doi:10.1088/1475-7516/2011/04/023. ISSN 1475-7516. S2CID 118750775.
  13. ^ Frommert, Hartmut; Kronberg, Christine (2007-06-05). "The Local Group of Galaxies". University of Arizona. Students for the Exploration and Development of Space. Archived from the original on 2009-09-07. Retrieved 2009-10-02.
  14. ^ Adams, Fred C.; Laughlin, Gregory (1997-04-01). "A dying universe: the long-term fate and evolutionof astrophysical objects". Reviews of Modern Physics. 69 (2): 337–372. arXiv:astro-ph/9701131. Bibcode:1997RvMP...69..337A. doi:10.1103/revmodphys.69.337. ISSN 0034-6861. S2CID 12173790.
  15. ^ "Milky Way Past Was More Turbulent Than Previously Known". ESO News. European Southern Observatory. 2004-04-06. After more than 1,000 nights of observations spread over 15 years, they have determined the spatial motions of more than 14,000 solar-like stars residing in the neighbourhood of the Sun.
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