…the two days in a year when our shadow leaves us alone?
Only two days in the year when the sun rises in the east direction. Similarly, there are only two days a year when the sun shines right over our head during the meridian!
Since childhood we are taught that the sun always rises in the east and the shadows always walk together. But actually it is not true, only two days in the year when the sun rises in the east direction. Similarly, there are only two days a year when the sun shines right over our head during the meridian. So during those two days in the middle of the afternoon our shadow leaves us. This event of not becoming a shadow is called `Zero Shadow Day’.
We know that our earth revolves around the sun and around its axis. The earth is leaning 23.5 degrees on its latitude, due to which the sun’s light does not always be alike on earth, and that is why the duration of the day and night is not even equal. Due to the earth rotating the Sun, the process of Uttarayan and Dakshayana of the Sun occurs and changes in seasons.
When the Sun moves north from the Capricorn line at 23.5 degree latitude in the Southern Hemisphere, it is called Uttarayan. On the 21st of June, moving north, the Sun reaches the top of the cancer line located at 23.5 degree latitude in the Northern Hemisphere. During this time, the rays of the sun are straight at some places in the center of the kraka line from the equator, due to which there is no shadow of vertical. During Uttarayan, heat starts increasing in the northern hemisphere, nights are short and day long, and on June 21, the smallest night and day is the largest.
When the Sun begins to move south, then it is called dakshinayana and around 22 December the sun shines above the Capricorn in the Southern Hemisphere. During this there is a hot summer and the days are long and the nights are small. During this time, the rays of Sun are straight in many places on the Makar line, located at 23.5 degree latitude in the south from the equator, while there is zero shadow day for a few moments during the meridian. Keep in mind that the occurrence of zero shadow day occurs only between the krka line and the makar line. There is zero shadow day in the north of the kraka line and south of the makar line.
Through the process of Uttarayan and Dakshinaayan of the Sun, it is clear that the center of the sunrise also varies changes. In this way, only two days (around 21 March and 21 September) the sun turns out in the real east direction. These two days are called Equinox. In the rest of the day, the center of the sunrise is north-east or south east. On June 21 and December 22, when the sun is on its top point in the northeast or south-east, it is called as solitary.
Many cities of India are witnessing ‘zero shadow day’ these days. Astronomers, students and curious people use different types of this day. They look at their shadow at midday, look at the glass inversion or look at the shadow of a pillar.