What is The Concept Behind Winter Solstice?

Context

December 22 is Winter Solstice in the Northern Hemisphere. Whereas in the Southern Hemisphere, it is the Summer Solstice in places like Australia, New Zealand, or South Africa.

Probable Question

Explain the concepts of “Solstice” and “Equinox”. (150 words, 10 marks)

About the Winter Solstice

• The word "solstice" comes from the Latin word "solstitium," which roughly translates to "sun standing still."
• The hemisphere experiencing the Winter Solstice has the shortest day and the longest night of the year.
• The situation reversed in six months on June 21, and both the Northern and Southern Hemisphere will experience the vice versa of the solstice they are experiencing currently.
• The Winter Solstice is experienced by the Northern Hemisphere on December 21 or 22 and by the Southern Hemisphere on June 21.
• Due to Earth's tilt toward the Sun, which is approximately 23.5 degrees, the winter solstice happens.

Reasons for the Change in the Hours of Daylight

• Every planet in the Solar System is tilted at different angles at different times. Similarly, the change in the hours of daylight every day is due to the Earth’s tilt.
• The Earth’s axis of rotation is tilted at an angle of 23.5° away from the perpendicular. 
• Earth's Tilt: 

This tilt is combined with factors such as Earth’s spin and orbit and leads to variations in the duration of Sunlight that any location on the planet receives on different days of the year.

The tilt is also responsible for the different seasons that we see on Earth. The day occurs on the side facing the Sun, and changes to night as Earth continues to spin on its axis.

The Northern Hemisphere spends half the year tilted in the direction of the Sun, getting direct sunlight during long summer days. During the other half of the year, it tilts away from the Sun, and the days are shorter.

The Earth’s tilt helps define some familiar imaginary lines, which are also key to determining when a Solstice occurs. These are latitudes, which are a measure of a location’s distance from the Equator.

• Poles:

The Earth’s North Pole points towards the North Star over an extended period, as the Earth moves around the Sun over the course of a year.

Winter Solstice, December 22, is the day when the North Pole is most tilted away from the Sun.

During summer in either hemisphere, that pole is tilted towards the Sun and the polar region receives 24 hours of daylight for months. Likewise, During winter, the region is in total darkness for months.

• Equator: On the Equator, day and night are equal. The closer one moves toward the poles, the more extreme the variation. 
• Latitudes: 

At latitudes of 23.5° (matching the tilt) 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 higher than 66.5° (in either direction) that days of constant darkness or light occur.

Winter Solstice in India

• In India, the shortest day and longest night of the year will fall on December 22. 
• Over the Tropic of Capricorn, the Sun is directly overhead. 
• As Earth revolves around the Sun, the tilt causes the Northern and Southern Hemispheres to receive varying dosages of sunlight throughout the entire year. 
• This is why we experience four different seasons throughout the whole year.

News Source: The Indian Express and the DNA India

https://indianexpress.com/article/explained/understanding-the-winter-solstice-the-shortest-day-of-the-year-6179628/

https://www.dnaindia.com/lifestyle/report-winter-solstice-2022-today-marks-the-shortest-day-of-the-year-here-s-why-3012162

If you want to enhance your IAS preparation and crack the UPSC CSE examination, download the PrepLadder app and get access to the finest study material curated by India’s top UPSC faculty.

You can also join our Telegram channel for UPSC coaching and to stay updated with the latest information about the UPSC exam.