Autumnal Equinox: Day and Night Not Actually Equal Due to Optical Illusion

The autumnal equinox, marking the start of astronomical autumn in the Northern Hemisphere, will occur tonight at 3:05 AM. Contrary to its name, the equinox does not feature precisely equal hours of daylight and darkness globally. This discrepancy is attributed to an optical illusion, according to the Meteorological Service, which causes the sun to appear about 0.6 degrees above the horizon even when it is at the 90-degree angle over the equator in the Pacific Ocean's El Niño region.

This effect means that daylight is longer than night even on the equinox. The difference widens closer to the poles, where the sun remains visible above the horizon for 24 hours on the equinox. In Israel, daylight will be shorter than 12 hours starting September 27th and continuing until March 16th, totaling 171 days, or 47% of the year.

An additional observation compares the two equinoxes: sunrise and sunset times on the autumnal equinox are about 15 minutes earlier than on the vernal equinox, disregarding daylight saving time. This means light durations are not identical even between the two equinoxes.

Despite the astronomical nuances, the autumnal equinox signifies the beginning of autumn in terms of weather. Nights are becoming cooler than in mid-summer, and rains typically do not begin until late September. However, this year saw rains as early as mid-August, significantly before the usual period.