Galactic year

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Panoramic image of the Milky Way, taken from Death Valley.

The galactic year, also known as a cosmic year, is the duration of time required for the solar system to orbit once around the center of the Milky Way galaxy.[1] Estimates of the length of one orbit range from 225 to 250 million "terrestrial" years.[2]

The galactic year provides a conveniently "graspable" unit for thinking about cosmic and geological time periods. (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.) [3]

[edit] Timeline of earth's history in galactic years

In this list, 1 galactic year (GY) = 225 million years

[edit] See also

Crab Nebula.jpg Astronomy portal

[edit] References

  1. ^ Cosmic Year, Fact Guru, University of Ottawa
  2. ^ Leong, Stacy (2002). "Period of the Sun's Orbit around the Galaxy (Cosmic Year)". The Physics Factbook. http://hypertextbook.com/facts/2002/StacyLeong.shtml. 
  3. ^ Geologic Time Scale - as 18 galactic rotations
Retrieved from "http://en.wikipedia.org/wiki/Galactic_year"
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