Why do we have two Yalda nights this year – RCO News Agency

Dr. Amir Mohammad Gomini, a researcher of the history of astronomy at Tehran University, in a conversation with Mehr reporter, explained about the Yalda astronomical event and said: the angle of rotation of the earth around itself and its rotation around the sun are not parallel to each other, and the earth has a certain angle to its path around the sun, and this It causes the sun to get high in the sky on one side of the path and the sun to get low on the other side of the path. How much the sun goes up and down during the day depends on these two paths and angles.

This researcher of the history of astronomy at Tehran University added: The more the sun angle in the sky, the longer it stays in the sky, that’s why the days in the first half of the year are long and the nights are short, and vice versa in the second half of the year. The days are short and the nights are long. As the length of the day gets longer and longer from the first of April and until the end of June, when the days reach their maximum length, the length of the day becomes shorter and the length of the day and night become equal on the first of October, after that the length of the night increases until the first of January. We reach the shortest day and the longest night, although it is not much longer than the nights before and after it and is only a few minutes.

Referring to the coincidence of Yalda night with the occurrence of “winter revolution” in the sky, he said: winter solstice means the time when the sun is at its southernmost point on the dome of the sky from the point of view of an earthly observer, and it is the longest night of the year, and the moment of winter solstice is 1403 hours. It happens at 12:50 pm on the first of December.

This year we have two Yalda nights

He explained that since the moment of the winter solstice this year is January 1, astronomically in some places we have 2 nights of Yalda in 1403, he explained about the reason and said: For some parts of the earth, including for the residents of Tehran, the night of January 1 The moon is one second longer than the night of Azar 30 (Iranian Yalda night), but for other places such as the northernmost village of Iran or the southernmost village of Iran, the length of the Yalda night (Azar 30) is exactly equal to the length of the night of the 1st of January, and even Not even a second difference.

Stating that Yalda night has deep roots in ancient Iranian astronomy and history, Gomini noted: In ancient Iranian culture, Yalda was revered as a symbol of the end of darkness and the beginning of increasing light. Ancient Iranians celebrated this astronomical event with special rituals, because they considered the return of the sun at the end of the Yalda night and the beginning of the increasing process of day length after this night as a sign of rebirth and the power of nature.