Equinox Southern Hemisphere 2024. Earth’s tilt on its axis is what causes this northward shift of the. An equinox is one of two days in the year when the sun crosses the equator and day and night become equal in length.
On the day of the autumn (september) equinox, the sun, moving along the ecliptic, crosses the celestial equator, moving from the northern hemisphere to the southern. This sunday, the autumnal equinox is upon us, and with it, a shift to shorter days, longer nights and the astronomical start of fall in the.