Bengaluru is set to witness a unique celestial phenomenon called ‘Zero Shadow Day’ tomorrow on April 25 – when all the vertical objects in the city will not have a shadow for a short period of time. According to reports, the event will take place at 12:17 pm.
The Indian Institute of Astrophysics (IIA) at Bengaluru’s Koramangala will mark the occasion by organising events at its campus. “Come celebrate Zero Shadow Day #ZSD at our Koramangala campus on 25 Apr from 10 AM-1 PM. Sun will be directly overhead at 12:17,” the IIA tweeted.
Zero shadow day is a special celestial event that occurs twice a year at places between +23.5 and -23.5 degrees latitude. During this time, no shadows appear of any object or living being when the sun is at its highest point in the sky. According to the Astronomical Society of India (ASI), the Sun will not cast a shadow on an object – when it is exactly at the zenith position.

“For people living between +23.5 and -23.5 degrees latitude, the Sun’s declination will be equal to their latitude twice – once during Uttarayan and once during Dakshinayan. On these two days, the Sun will be exactly overhead at noon and will not cast a shadow of an object on the ground,” the ASI wrote on its website.
This phenomenon occurs when the Sun’s declination becomes equal to the latitude of the location. While this happens only for a second, its effect can be seen for up to two minutes.

Every year on the zero shadow days, students and astrophile who are located between the two Tropics erect vertical poles, and different objects, and sometimes even stand outside to see for themselves the cosmic event. The moment can be witnessed without any special equipment or instruments.

The next Shadow Day in Bengaluru will be observed on August 18. The dates of Zero Shadow Day vary depending on the location and time zone.