precession of the equinoxes
noun
mass noun
1- Astronomy the slow retrograde motion of equinoctial points along the ecliptic【天文】（分点沿黄道的）缓慢逆行。
1.1
- the resulting earlier occurrence of equinoxes in each successive sidereal year岁差, 分点岁差。
As the earth rotates about its axis it responds to the gravitational attraction of the sun upon its equatorial bulge, so that its axis of rotation describes a circle in the sky, with a period of about 26, 000 years. The precession of the equinoxes was discovered by Hipparchus in c. 125 BC, when the vernal equinox was in Aries.