The formation and variations of the seasons are attributed to the revolution of the earth around the sun, whereas, the changes in the night and day patterns are attributed to the rotational-spinning of the Earth about its own axis. The Earth’s axis of rotation is not perpendicular to its orbital plane, but makes an angle of around 24 degrees, and hence the axis keep on changing its orientation with the frame of reference. As a consequence, for half the year the Northern Hemisphere is inclined toward the Sun while for the other half year the Southern Hemisphere has this distinction. The two moments when the inclination of Earth’s rotational axis has maximum effect are the solstices.
The word “solstice” comes from the Latin terms “sol” (the sun) and “stitium” (to stop), which reflects the fact that the sun appears to stop or remains for a longer duration, on this day. June 20 to June 22,and notably June 21,marks the Summer Solstice (also known as June Solstice) and beginning of the summer season in the Northern Hemisphere and the Winter Solstice (also known as December Soltice) in the Southern Hemisphere, and is the day of the year with the most hours of daylight in the northern hemisphere and the fewest hours of daylight in the southern hemisphere. The date of June solstice varies between June 20 and June 22 ,depending on the days in the leap year(365 or 366 days), and accordingly with respect to the different calendars, followed in different cultures and nations.
In June, rotation of the earth about the sun would be in such a way that the countries which are located above the equator, lying in the Northern hemisphere, would be directly exposed to the sunlight, and those lying below the equator, in the Southern hemisphere, would recede in the shadow of the sun and would experience winters. On June 21, the locus of the sun and earth would be drawn in such a manner, that these countries lying in the Northern hemisphere, would receive maximum sunlight,and for extraordinarily longer durations, even reaching upto 15 or 16 hours daylight. The intensity and duration of light would vary with the latitudinal variations. Those living in the North of Arctic Circle are able to see the “midnight sun”, where sun remains visible throughout the night as well.During the same time of summer solstice, countries that lie on the equator ,experience equal lengths of day and night time and experience the same temperature in the night and day.
On June 21, the sun does not rise precisely in the east, but rises to the north of east and sets to the north of west, therefore, remains on the sky for the longer period of time ,and hence June 21 is called the longest day of the year. In the southern hemisphere, June 21,is known as the shortest day of the year. This is so because the sun has reached its furthest point from the equator and marks the first day of winter.
Apart from these geographical and astronomical observations, let’s discuss about a few historical facts and cultural myths. In ancient times, solstices were important in guiding people to develop and maintain calenders, as well as helping them to grow crops. The concept of solstices was found in the ancient Greek Celestial Navigation.The Latenate names Estival solstice (summer) and Hibernal (winter) are sometimes used to the same effect. Over the centuries , the June solstice was a time when festivals ,celebrations and other festivities were celebrated. The traditional East Asian calendars divide a year into 24 solar terms.Many cultures celebrate various combinations of the winter and summer solstices, and various holidays are observed around these events. The Aymara people of Bolivia, celebrate their New Year on June 21,a celebration occurs at sunrise. The Mapuche people of South America, celebrate We Tripantu(the New Year),around June 21.The Atacama people ,in the Northern Hemisphere, formerly celebrated this day with a noise festival.
One of the most popular summer solstice celebrations occurs at Stonehenge in Wiltshire,England, a place that is believed to have been used as a religious site by Britons four million years ago. On June 21,thousands of people descend on the monument in wild clothing, there. The Japanese celebrate the start of summer solstice, June 21,with an occurrence, known as Setsubun. In Scandinavia, June 21 is commemorated with pre-Christian celebration of Midsummer Eve, and a national holiday is observed in Sweden and Finland. Swedes celebrate the event by singing and dancing.
Many countries including Canada, USA ,New Zealand and those of Central and Northern Europe, have recently adopted the custom of using these solstices to mark the beginning of the summer and winter. In Hindu calendar, the Karkat Sankranti ,occurs around june-July ,each year. It also signifies the movement of the Sun along a fixed Zodiac, to yield a zodiacal sign that corresponds to Cancer.
Geographically, Pakistan is located between 24 and 37 degrees North latitudes, and from 61 to 76.5 degrees East, therefore lying in the Northern Hemisphere. The duration of daylight on June 21, on the average is recorded to be of 14 hours. Figure, below, illustrates the usual sunrise and sunset patterns , on June 21, in Pakistan.