Monday, December 02, 2013


galactic year

(2.25 – 2.5)×108 a
定義 太陽系の銀河中心に対する公転周期

Estimates of the length of one orbit range from 225 to 250 million "terrestrial" years.[

According to NASA, the Solar System is traveling at an average speed of 828,000 km/h (230 km/s) or 514,000 mph (143 mi/s) relative to the galactic center,[3] which is about one 1300th of the speed of light. If you could travel at that speed in a jet aircraft along the equator, you would go all the way around the world in approximately 2 minutes and 54 seconds.

18.4 galactic years ago Birth of the Sun
17-18 galactic years ago Oceans appear on Earth
15 galactic years ago Life begins on Earth


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