The galactic year, also known as a cosmic year, is the length of time needed for the Sun to orbit once around the center of the Milky Way Galaxy. One galactic year is 230 million Earth years. The Solar System is traveling at an average speed of 230 km/s (828,000 km/h) within its arc-like path around the galactic center, a speed at which an object could travel around the Earth's equator in 2 minutes and 54 seconds; that speed goes along with about 1/1300 of the speed of light.
The galactic year provides a conveniently 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 rather large numbers.
References[change | change source]
- Cosmic Year Archived 2014-04-12 at the Wayback Machine, Fact Guru, University of Ottawa
- Leong, Stacy (2002). "Period of the Sun's Orbit around the Galaxy (Cosmic Year)". The Physics Factbook.
- http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question18.html NASA – StarChild Question of the Month for February 2000
- Geologic Time Scale – as 18 galactic rotations