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The city witnessed the celestial event of Zero Shadow Day on Wednesday (April 24) afternoon. Shadows vanished from 12.17 to 12.23 p.m. as the Sun aligned perfectly overhead.
At the Indian Institute of Astrophysics, Koramangala, more than 60 people gathered to conduct hands-on experiments and listen to a talk on the subject.
According to IIA, the Sun does not rise exactly in the east or set exactly in the west every day, and neither does it pass directly overhead every day. This is because of the Earth’s axial tilt of 23.5 degrees, which is also the cause of seasons. The Sun is directly over the Tropic of Cancer on June 21 (the summer solstice in the northern hemisphere) and then journeys southwards as seen from the Earth, called Dakshinayana.
The Sun then comes directly over the Equator on September 23 (autumnal equinox for the northern hemisphere) and is over the Tropic of Capricorn on December 22. It is then seen to journey northwards, called Uttarayana, and is overhead the Equator again on March 21, and so on. Hence, the Sun is directly over locations between the two tropics twice a year, and this day varies with latitude.
When the Sun is directly overhead, the shadow of a vertical object falls under it, and hence, no shadow will be seen. Therefore, this is called Zero Shadow Day. In Bengaluru and places at the same latitude, like Mangaluru and Chennai, the phenomenon occurs on April 24 and August 18.
