Bengaluru recently experienced its inaugural ‘Zero Shadow Day’ (ZSD) of the year, marked by scientific enthusiasts engaging in talks, workshops, and interactive sessions. This phenomenon occurs when the sun reaches a position directly overhead, causing vertical objects to cast no shadows. On this particular day, it happened at local noon (12.17 pm), impacting locations like Bengaluru, Mangaluru, and Chennai, which share the same latitude.
Zero Shadow Day, explained by the Indian Institute of Astrophysics (IIA), is a consequence of Earth’s tilt. The sun doesn’t always rise directly in the east, set in the west, or pass exactly overhead due to the Earth’s axis being tilted at 23.5 degrees relative to its orbit. This tilt is responsible for seasons and influences the sun’s apparent path across the sky throughout the year.
This phenomenon occurs twice a year for locations between the Tropic of Cancer and Tropic of Capricorn, with the exact days varying with latitude. Over 60 people, including students, gathered at IIA’s Koramangala campus to track shadow changes using simple sticks stuck in the ground (gnomons). At 12.17 pm, when the sun was directly overhead, the gnomons cast no shadows, confirming ZSD.
IIA collaborated with the Aryabhat Foundation in Bhopal, roughly at Bengaluru’s longitude, where students measured the length of the shadow at Bengaluru’s local noon and calculated its value. The Jawaharlal Nehru Planetarium also organized demonstrations and interactive sessions. Bengaluru’s next Zero Shadow Day is anticipated on August 18.
