Final answer:
The sun is directly overhead at the Earth's equator during the September Equinox, which occurs around September 21st, resulting in nearly equal day and night durations worldwide.
Step-by-step explanation:
During the September Equinox, the sun overhead is directly above the Earth's equator. This occurs around September 21st and marks a point in time when the Sun crosses the celestial equator. This crossing means that the Sun's position is neither in the Northern nor the Southern Hemisphere, leading to approximately equal lengths of day and night across the globe.
The description of how celestial objects appear from the North Pole indicates that the Sun rises at the vernal equinox and sets at the autumnal equinox, showing a direct relationship between the position of the Sun and the equinoxes. During the September Equinox, the Earth experiences a moment of equatorial alignment where the Sun is overhead at the zenith (90°) at noon for observers located on the equator.