 "The Winter Solstice is today. Why is it the shortest day of the year?")
The Winter Solstice is here.
Already the cold is seeping in and the atmosphere is turning festive with Christmas decorations being put up.
Those in the northern hemisphere who prefer summer and can’t get enough sunlight can try to escape to the southern hemisphere. Or they can wait.
From Sunday onwards, days will begin to get longer and longer – which will go on until late June.
Let’s take a closer look at the phenomenon of the Winter Solstice.
Why does the solstice occur?
As the Earth travels around the Sun, it does so at an angle. For most of the year, the Earth’s axis is tilted toward or away from it. That means the Sun’s warmth and light fall unequally on the northern and southern halves of the planet.
The solstices occur at that time of the year when the Earth’s axis is tilted at its most extreme either towards or away from the sun.
Thus, the hemispheres receive different amounts of sunlight leading to days and nights in the opposite hemisphere at their most unequal.
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During the Northern Hemisphere’s winter solstice, the upper half of the Earth is tilted away from the sun, creating the shortest day and longest night of the year. The winter solstice falls between December 20 and 23. Meanwhile, at the summer solstice, the Northern Hemisphere is toward the sun, leading to the longest day and shortest night of the year. This solstice falls between June 20 and 22.
The purpose of the equinox
When the Earth’s axis and orbit line up so that both hemispheres receive equal amounts of sunlight, it is known as the equinox.
Interestingly, the word is a combination of two Latin words meaning equal and night. It has been named thus because on the equinox, day and night last almost the same amount of time — though one may get a few extra minutes depending on where you are on the planet.
Also Read: Explained: The science behind why 21 June is the longest day of the year
Equinox takes place in spring or autumn. The Northern Hemisphere’s spring or vernal equinox can land between March 19 and 21, depending on the year. Its fall or autumnal equinox can land between September 21 and 24.
When is the Winter Solstice taking place this year?
This year the winter solstice will take place on December 21 (Saturday) in the Northern Hemisphere.
According to NASA, at 4:20 am ET (2:50 am IST), the solstice will take place, marking “the beginning of winter in the Northern Hemisphere and summer in the Southern Hemisphere.”
Difference between meteorological and astronomical seasons
These are just two different ways to carve up the year. Meteorological seasons are defined by the weather. They break down the year into three-month seasons based on annual temperature cycles. By that calendar, spring starts on March 1, summer on June 1, fall on September 1 and winter on December 1.
Astronomical seasons depend on how the Earth moves around the sun. Solstices kick off summer and winter. Equinoxes mark the start of spring and autumn.
With inputs from AP
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