Final answer:
During the September equinox, the Sun's vertical rays hit the Earth at the equator, marking a time of equal day and night, and the transition of seasons.
Step-by-step explanation:
During the September equinox, the vertical rays of the Sun are striking the Earth directly at the equator. This happens when the Sun crosses the celestial equator, around September 21, resulting in nearly equal amounts of day and night across the globe. Every place on Earth experiences approximately 12 hours of daylight and 12 hours of darkness due to this equinoctial position.
The equinox marks a time when Earth's tilt is neither away from nor towards the Sun, causing the Sun to illuminate both hemispheres equally. This celestial event happens twice a year, once in March (vernal equinox) and once in September (autumnal equinox). On these dates, the Sun is directly above the equator at noon, symbolizing the transition between seasons for both hemispheres.