Updated: December 21, 2020 8:50:57 pm
In Delhi, the sun rose at 7.10am and set at 5.29pm, which made the day last 10 hours, 19 minutes, and 3 seconds. (Representation image: AP)
Today, December 21, is the winter solstice, the shortest day of the year in the Northern Hemisphere. In Delhi, the sun rose at 7.10am and set at 5.29pm, which made the day last 10 hours, 19 minutes and 3 seconds.
Tuesday, December 22, will be a second longer, at 10:19:04 in Delhi.
In the southern hemisphere, by contrast, today is the summer solstice; In places like Australia, New Zealand, and South Africa, therefore, December 21 is the longest day of the year. So in Melbourne, the Sun rose at 5.54am on Monday and set at 8.41pm, marking a day 14:47:19 in length.
This situation will be reversed within six months: on June 21, 2021, the northern hemisphere will see the summer solstice, when the day will be the longest of the year. And the southern hemisphere will see the shortest day of the year or the longest night.
Why are the hours of daylight not the same every day?
The explanation lies in the tilt of the Earth. And it’s not just Earth, all the planets in the Solar System are tilted relative to their orbits, all at different angles.
The axis of rotation of the Earth is inclined at an angle of 23.5 ° with respect to its orbital plane. This tilt, combined with factors such as the spin and orbit of the Earth, leads to variations in the duration of sunlight that any place on the planet receives on different days of the year.
The Northern Hemisphere spends half the year tilted in the direction of the Sun, receiving direct sunlight during long summer days. During the other half of the year, it moves away from the Sun and the days are shorter. The winter solstice, December 21, is the day the North Pole is tilted the most outward from the Sun.
The tilt is also responsible for the different seasons we see on Earth. The side facing the Sun experiences day, which turns into night as the Earth continues to rotate on its axis.
In Ecuador, day and night are the same. The closer one gets to the poles, the more extreme the variation. During the summer in any hemisphere, that pole is tilted towards the Sun and the polar region receives 24 hours of light for months. Also, during winter, the region remains in total darkness for months.
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The tilt of the Earth helps define some familiar imaginary lines, which are also key in determining when a solstice occurs. These are latitudes, which are a measure of the distance from a location to the equator.
At latitudes of 23.5 ° (which coincide with the inclination) are the Tropics of Cancer and Capricorn, north and south of the Equator. At 66.5 ° (or 90 ° minus 23.5 °) are the Arctic and Antarctic circles, to the north and south. It is at latitudes above 66.5 ° (in any direction) that days of constant darkness or light occur.
Celebrations associated with the winter solstice
For centuries this day has held a special place in various communities due to its astronomical significance and is celebrated in many ways around the world.
The Jews call the winter solstice ‘Tekufat Tevet’, which marks the beginning of winter. The ancient Egyptians celebrated the birth of Horus, the son of Isis (divine mother goddess) for 12 days in mid-winter. In China, the day is celebrated by families gathering for a special meal.
In Iran and neighboring Afghanistan, Uzbekistan, Tajikistan, Turkmenistan, Azerbaijan, and Armenia, the winter solstice is celebrated as Yalda or Shab-e-Yalda. The festival marks the last day of the Persian month of Azar, and is seen as the victory of light over darkness. It is also the birthday of the sun god Mithras, a pre-Islamic deity. Families celebrate Yalda late into the night with special foods such as ajeel nuts, pomegranates and watermelon, and recite works by the 14th century Sufi poet Hafiz Shirazi.
Among the monuments linked to the winter solstice is Stonehenge in England. (Photo: AP)
In the southern hemisphere, where the winter solstice in June, Peru celebrates the day with a festival called Inti Raymi, which means “festival of the sun” in the Quechua language. Before the colonization of Peru by Spain, the Inca civilization honored the sun god Inti by fasting for three days, and the fourth day was celebrated with festivals and sacrifices. The festival was banned under Spanish rule, but was later revived in the 20th century and continues today, with mock sacrifices.
In pre-Christian Europe, the solstice was celebrated as the beginning of winter. People slaughtered their farm animals so they wouldn’t have to feed them. The wine made during the summer months was also ready for consumption. Thus, the solstice became an occasion for a party, often communal, before snow covered most of the land and people were forced to spend time indoors.
In the Vedic tradition, the movement of the north of the Earth in the celestial sphere is implicitly recognized in the Surya Siddhanta, which describes the Uttarayana (the period between Makar Sankranti and Karka Sankranti). Therefore, the winter solstice is the first day of Uttarayana.
The Yule festival, which used to be celebrated in pre-Christian Scandinavian lands for 12 days, was later associated with Christmas as the Yule tide.
The winter solstice also influenced culture to the extent that ancient peoples built various architectural structures aligned with the phenomenon. Some of these structures include Stonehenge and Glastonbury (England), Chichen Itza (Mexico), Goseck Circle (Germany), and the Temple of Karnak (Egypt).
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