Beyond Words - Language Blog

The Autumnal Point or the First Point of Libra: Language of the Equinox

For those of you in the Northern Hemisphere, today marks the autumnal equinox, otherwise known as the first day of fall (for those of you in the Southern Hemisphere, the first day of Spring). While for many, the first day of fall is mentally linked with the beginning of the school year or with some long-awaited day when the weather might actually drop below the 90s, the actual start of the fall season corresponds to the tilt of the Earth’s axis.

Occurring in autumn and spring, the equinox is when the earth’s axis is tilted neither towards the Sun (in the summer) nor away from the sun (in the winter), but aligned so the Sun is in the same plane as the Equator. Apart from these two days, Earth’s axis tilts toward or away from the sun, creating the seasons as we know them — autumn, winter, spring, and summer.

The word equinox is derived from the Latin aequus (meaning “equal”) and nox (meaning “night”). The equinox, then, is the equality of night and day — during the equinox daylight is roughly 12 hours and nighttime is 12 hours. At some point during the day, the sun is directly overhead in its subsolar point, another anomaly that sets equinox apart and signals the equality between the darker and lighter halves of the day.

Other names are used for the autumnal equinox — autumnal stemming from the Latin autumnus (meaning “fall,” “autumn,” or the third season of the Roman calendar):

  • September equinox is a term that is sometimes used, but mostly by technical writers who choose to avoid a Northern Hemisphere bias (Remember: The seasons are opposite in the Northern and Southern Hemisphere — what is autumn in New York is actually spring in Christchurch, NZ).
  • Southward equinox is another term that can be used and refers to the seen motion of the Sun at the time of the equinox — i.e. it appears to be moving southward from the Northern Hemisphere.
  • Autumnal point refers to the point in the celestial sphere where the sun appears to be located during the autumnal equinox (again, a problematic reference to the Northern Hemisphere, but one that is generally acknowledged).
  • First Point of Libra, the archaic name for the equinox used by navigators and astrologers, signifies the position of navigational stars, thus emphasizing Libra’s role in the night sky. However, due to the precession of the equinoxes, or the orbital paths of celestial bodies, the astrological signs where these equinoxes are located no longer corresponds to the actual constellations once ascribed to them. The equinox is currently located in Virgo — not Libra.
  • Whatever you choose to call your day — the autumn equinox, September equinox, the First Point of Libra, or even just Wednesday — happy autumn for those of you in the Northern Hemisphere, and happy spring to those of you in the Southern one!