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The galactic year, also known as a cosmic year, is the duration of time required for the Sun to
orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...
once around the center of the Milky Way Galaxy.Cosmic Year
, Fact Guru, University of Ottawa
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) or 143 mi/s (514,000 mph) within its trajectory around the galactic center,http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question18.html NASA – StarChild Question of the Month for February 2000 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.Geologic Time Scale – as 18 galactic rotations
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Timeline of the universe and Earth's history in galactic years

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


See also

* Galactic Tick Day *
Geologic time scale The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochr ...


References

{{DEFAULTSORT:Galactic Year Milky Way Types of year