Related Topic in KAS Prelims Syllabus:
Geography [Paper-I]: Solar system, Motion of Earth
Why in News?
In 2019, the winter solstice will occur on 22nd December.
What is Winter Solstice?
- On 22nd December, the Tropic of Capricorn receives direct rays of the sun as the South Pole tilts towards it.
- As the sun’s rays fall vertically at the Tropic of Capricorn (23° S), a larger portion of the Southern Hemisphere gets light.
- Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights. The reverse happens in the Northern Hemisphere.
- This position of the earth is called the Winter Solstice.
Why are the hours of daylight not the same every day?
- The Earth’s axis of rotation is tilted at an angle of 23.5 degrees away from the perpendicular.
- This tilt, combined with factors such as Earth’s spin and orbit, leads to variations in the duration of Sunlight that any location on the planet receives on different days of the year.
- 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.
- Winter Solstice is the day when the North Pole is most tilted away from the Sun.
- The tilt is also responsible for the different seasons that we see on Earth. Day occurs on the side facing the Sun, and changes to night as Earth continues to spin on its axis.
About Summer Solstice
- On 21st June, the Northern Hemisphere is tilted towards the sun.
- The rays of the sun fall directly on the Tropic of Cancer. As a result, these areas receive more heat.
- The areas near the poles receive less heat as the rays of the sun are slanting.
- The North Pole is inclined towards the sun and the places beyond the Arctic Circle experience continuous daylight for about six months.
- Since a large portion of the Northern Hemisphere is getting light from the sun, it is summer in the Northern Hemisphere. The longest day and the shortest night at these places occur on 21st June.
- The reverse happens in the Southern Hemisphere. It will be winter season there and thus the nights are longer than the days.
- This position of the earth is called the Summer Solstice.
[Source: NCERT, Indian Express]