Bhubaneswar residents on Friday witnessed Zero Shadow Day, a rare celestial phenomenon wherein no shadow of any object or being is observed. Generally, the event occurs twice a year when the sun remains at its peak in the sky. The event takes place when the sun comes exactly overhead over all the regions between the Tropic of Cancer and the Tropic of Capricorn. Due to this, the shadow of objects and beings almost vanish during the day and hence, it is known as Zero Shadow day. The celestial phenomenon started at 11.43 am in Bhubaneswar and continued for a brief period of 3 minutes.
Deputy Director of Pathani Samanta Planetarium in Bhubaneswar, Subhendu Patnaik explained the phenomenon. According to him, the event takes place when the rotation axis of the Earth is tilted at an angle of 23.5° to the axis of revolution around the sun.
Patnaik said that Zero Shadow Day can be seen using white paper by placing it on flat ground, keeping some vertical object like a bottle on it and studying the movement of its shadow.
He further said that when the location of the sun moves from 23.5° N to 23.5° S of Earth’s equator, then “all places whose latitude equals the angle between the location of the Sun and the equator will experience Zero Shadow Days.”
During the sun’s apparent North to South and South to North movement, there are two days in a calendar year when the sun’s declination and the latitude of a place within the tropics align briefly, making shadows disappear for a short while.
