Zero Shadow Day is a fascinating phenomenon that occurs in locations between the Tropic of Cancer and the Tropic of Capricorn. On April 25, the Sun will be directly overhead in Bengaluru, India, causing any vertical object to cast no shadow at 12:17 p.m. local time. This phenomenon occurs twice a year, on April 25 and August 18, for Bengaluru.
To celebrate this occasion, the Indian Institute of Astrophysics is organizing a public talk and hands-on activities at their campus. Visitors will have the opportunity to observe the effect of changing shadow length on objects and measure the length of the shadow. Additionally, the Institute will be coordinating with a school in a different location to measure the Earth’s diameter collaboratively.
It’s worth noting that the Sun is almost never exactly overhead at noon, but usually transits a bit lower in altitude, a bit to the north or a bit to the south. This annual celestial phenomenon occurs twice a year for places between +23.5 and -23.5 degrees latitude.