出典:Wiktionary
出典:Wikipedia
出典:『Wikipedia』 (2011/04/05 00:16 UTC 版)
In the history of astronomy, a Great Year often refers to one complete precession of the equinox, but may also refer to any real or imagined cycle with astronomical or astrological significance. The most common Great Year (sometimes confused with the Platonic year) is the time required for one complete cycle of the precession of the equinoxes, presently about 25,765 years. The Greeks sometimes called the period of time required for the naked eye planets to realign, a Great Year; this was an important concept in ancient Stoicism.