Why is dawn delayed after the winter solstice? Jeddah Astronomy Society explains

The head of the Jeddah Astronomical Society, Engineer Majid Abu Zahra, revealed the scientific explanation for an astronomical phenomenon that has puzzled many with the onset of winter: the continued delay in dawn and sunrise, despite the winter solstice having passed and the days gradually lengthening. He clarified that the common belief that increased daylight hours necessarily mean an immediate earlier sunrise is astronomically inaccurate.

The paradox of the winter solstice

Abu Zahra explained that the winter solstice marks the shortest day and longest night of the year, and after this date, the days do indeed begin to gain extra minutes. However, this initial increase comes solely from a later sunset, not an earlier sunrise. Consequently, dawn and sunrise continue to be delayed for several days or even weeks after the solstice before the astronomical cycle begins to reverse and sunrise begins to advance, which explains why people feel that the morning is still dark even though the peak of winter has passed.

Physical causes: the equation of time

Regarding the precise scientific reason, the head of the Jeddah Astronomical Society pointed to two main factors controlling this phenomenon: the tilt of the Earth's axis of rotation at an angle of 23.5 degrees, and the elliptical (oval) shape of the Earth's orbit around the sun, rather than a circular one. These two factors lead to what is known astronomically as the "equation of time," where the apparent speed of the sun changes across the sky, creating a discrepancy between solar noon and the time measured on a clock, resulting in a lack of synchronization between the earlier sunrise and the later sunset.

Astronomical context and historical significance

It is worth noting that the winter solstice is a significant astronomical event observed by human civilizations since ancient times. Ancient peoples relied on it to determine the planting and harvesting seasons and the astronomical beginning of winter. This phenomenon is particularly important in regions that depend on solar time for their religious practices and daily activities, such as determining prayer times, as worshippers may notice a slight or consistent delay in the timing of the Fajr (dawn) prayer during this period, despite the changing seasons.

The impact of geographical location and misconceptions

Abu Zahra pointed out that the impact of this phenomenon varies significantly depending on geographical location. Areas near the equator experience only slight changes, while the difference becomes more pronounced as one moves towards higher latitudes, both north and south. He also corrected some misconceptions, emphasizing that atmospheric factors such as clouds and fog, or the moon's movement, are unrelated to astronomical calculations of dawn time, but only affect visual visibility. He stressed that the change begins gradually and becomes noticeable to everyone during the first few weeks of winter.