Definition of precession of the equinoxes in US English:

precession of the equinoxes


  • 1The slow retrograde, or westward, motion of equinoctial points along the ecliptic.

    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

    • ‘He was not the first Chinese astronomer to discover the precession of the equinoxes (Yu Xi did so in the fourth century) but he was the first to take this into account in calendar calculations.’
    • ‘Because of the precession of the equinoxes, the equinox and solstice points have each moved westward about 30 degrees in the last 2,000 years.’
    • ‘About fifty years after Liu's remarkable contributions, a major advance was made in astronomy when Yu Xi discovered the precession of the equinoxes.’
    • ‘The gravitational pull of the sun and moon cause a phenomenon known as the precession of the equinoxes, which makes the earth's axis move in a cone shape.’
    1. 1.1 The resulting earlier occurrence of equinoxes in each successive sidereal year.