Article:
Understanding the key geography concepts of Summer Solstice, Winter Solstice, and Equinox is crucial in comprehending our planet’s dynamics. Notably, these phenomena have significant effects on the Earth’s climatic conditions due to the different lengths of days they bring about.
Introduction to Solstices
The term solstice originated from the Latin word ‘solstitium’ meaning ‘sun standing still’. This refers to the time when the sun appears to have stopped moving north or south. Solstices occur twice a year, once during summer and once during winter, for each hemisphere of the Earth. These solstices represent the longest and shortest days of the year. For instance, the Northern Hemisphere experiences its longest day and shortest night on the Summer Solstice, which typically falls on 21st June.
Understanding the Summer Solstice
During the Summer Solstice, the countries within the Northern Hemisphere are closest to the Sun with the Sun shining overhead along the Tropic of Cancer (23.5° North). During this time, the Earth’s axis is tilted such that the North Pole leans towards the sun and the South Pole moves away from it. The tilt of the axis, which is constant at 23.5 degrees relative to the Sun, plays a crucial role in this occurrence.
The Energy Distribution
Characteristic of the Summer Solstice is the abundance of energy received from the sun. As per NASA, the amount of incoming solar energy Earth receives on the Summer Solstice is 30% more at the North Pole than at the Equator. Consequently, the Northern Hemisphere gets the maximum amount of sunlight around 20th, 21st, or 22nd June. In contrast, the Southern Hemisphere receives most sunlight on 21st, 22nd, or 23rd December, marking the Winter Solstice for the Northern Hemisphere, which experiences its longest nights during this time.
The Geography Behind Solstices
The Earth’s axial tilt, in combination with its spin and orbit, causes variations in the amount of daylight each location on Earth receives. This leads to different lengths of days throughout the year. The Northern Hemisphere spends half the year tilting towards the Sun, experiencing long summer days of direct sunlight. For the remainder of the year, it tilts away from the Sun, leading to shorter days. This tilt is what brings about the different seasons on Earth.
Equinox Explained
On the other hand, the term equinox, which denotes ‘equal night,’ refers to the periods when the Earth’s axis is perpendicular to the incoming sun rays. As such, all latitudes on Earth experience nearly equal amounts of day and night. The Northern Hemisphere encounters the vernal or spring equinox on around 20th or 21st March, while the autumnal or fall equinox occurs around 22nd or 23rd September.
Interesting Facts: Previous Years Questions (PYQ)
In the UPSC Civil Services examination of 2019, a question related to these phenomena was presented as follows;
“On 21st June, the Sun –
(a) does not set below the horizon at the Arctic Circle
(b) does not set below the horizon at Antarctic Circle
(c) shines vertically overhead at noon on the Equator
(d) shines vertically overhead at the Tropic of Capricorn?”
The correct answer was option (a). Here’s why; On the Summer Solstice, which falls on 21st June, the Northern Hemisphere experiences its longest day, while the Southern Hemisphere has its shortest day. During this period, the Earth’s North Pole tilts maximally toward the Sun and so the Sun seems to be directly overhead at 23.5º North latitude, along the Tropic of Cancer. Consequently, at the Arctic Circle, which lies in the Northern Hemisphere, the sun does not set below the horizon during the Summer Solstice.
