Galactic year

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The galactic year is the period of time it requires 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, and the present age of the solar system is estimated at between 18 and 22 galactic years. [2]. Because a billion-year scale does not allow for useful discrimination between geologic events, and a million-year scale generates some very large numbers, the galactic year is a good unit for measuring events which occur over a long duration of time.[3] This scale may occasionally be referred to as the "cosmic year", though that term is more commonly used to describe the scale popularized by Carl Sagan.

[edit] References

  1. ↑  Astronomy Knowledge Base
  2. ↑  Hypertextbook.org
  3. ↑  Geologic Time Scale
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