The galactic year, also known as a cosmic year, is the total time needed 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) in an arc-like orbit around the galactic center.[3] At this speed, an object could travel around the Earth's equator in 2 minutes and 54 seconds and that speed is still about 1/1300 of the speed of light.

The orbit of the Sun (yellow circle ring) around the galactic center

The galactic year provides an easily usable unit for showing cosmic and geological time periods together. Very differently, a "billion-year" scale does not allow for useful difference between geologic events, and a "million-year" scale needs some very large numbers.[4]

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
source: http://simple.wikipedia.org/wiki/Galactic_year