Guest post by Tina Baradaran, an astronomer and educator at the Sydney Observatory.
Have you been wondering why the days are getting longer during this time of the year? Every year when the Sun reaches its most southerly position, the summer solstice occurs in the southern hemisphere and the winter solstice in the northern hemisphere.
On Monday 21st December 2020 at 9:02 pm Australian Eastern Daylight saving Time, the summer solstice occurs in Sydney, Australia. When the Sun appears at its most southerly position for the year, in the southern hemisphere, it marks the longest day of the year. In Sydney, the Sun will be above the horizon for 14 hours and 25 minutes.
The summer solstice occurs once a year in December when the Sun’s path across the Australian sky reaches its highest point. It is the day with the most daylight hours in the year. The summer solstice usually occurs on 22 December but can occur between 21 and 23 December, depending on the leap year. The winter solstice is the day of the year that has the least daylight hours of any in the year and usually occurs on 22 June but can occur between 21 and 23 June.
The summer solstice is not the day with the earliest sunrise or the latest sunset. It is the day with the longest time from sunrise to sunset. If you live in Sydney, the earliest sunrise and the latest sunset are about a month apart with the solstice in the middle. Throughout late December the days become slightly longer until the solstice, then start to shorten, however throughout the whole time, sunset and sunrise become later and later until January 7. After that date, the sun begins to set earlier. This fact is caused by the combination of the Earth’s tilt of 23.5 degrees and its elliptical orbit around the sun.
For people in the northern hemisphere, the December solstice marks the ‘turning of the Sun’ as the days slowly get longer. Celebrations of the lighter days to come have been common throughout history with feasts, festivals, and holidays around the December solstice celebrated by various cultures across the globe.
Yalda or Shab-e Yalda (‘night of Yalda) is a Persian festival celebrated on the “longest and darkest night of the year” which is the night of the winter solstice in the northern hemisphere.
Every year, on the eve of the Winter solstice, Persians celebrate the arrival of winter, the renewal of the Sun, and the victory of light over darkness on Yalda Night.
Ancient Persians believed that the dawning of each year is marked with the re-emergence or rebirth of the sun, an event that falls on the first day of the month of Dey in the Persian calendar (December 21). On this day, the sun was salvaged from the claws of the devil, which is represented by darkness, and gradually spread its rays all over the world to symbolise the triumph of good over evil. Family members get together (most often in the house of the eldest member) and stay awake all night long in Yalda.
Pomegranate, watermelon, and dried nuts are served as a tradition and classic poetry and old mythologies are read in the gatherings.
Central Asian countries such as Afghanistan, Tajikistan, Uzbekistan, Turkmenistan, and some Caucasian states such as Azerbaijan and Armenia share the same tradition as well and celebrate Yalda Night annually at this time of the year.
Although in the southern hemisphere, the night may not be long-lasting our companionship is. We wish everyone a safe and joyous festive session, a cool summer solstice in the southern hemisphere, and a warm winter solstice in the northern hemisphere.