Braving the summer heat, Samyak and his friends are busy plotting points and recording the shadow movements as the size of the shadow reduces as each minute passes. Along with Samyak, several other children gathered at the Jawaharlal Nehru Planetarium in Bengaluru did the same, to find the exact minute when the Zero Shadow phenomenon is noticed.
On April 24th, Bengaluru experienced ‘Zero Shadow Day’ at 12:18 pm where the sun was at its zenith position and there was almost no visible shadow. The phenomenon occurs twice a year as the sun traces its path to the Tropic of Cancer and then retraces its path towards the south. Usually, the sun transits by small margins towards the north or south around noon. But on Zero Shadow Day, it was exactly overhead.
This phenomenon is used to calculate the circumference and the radius of the Earth. Speaking to TNM, Pramod Galgali, Director of Jawaharlal Nehru Planetarium, said, “Zero Shadow happens in an instant. It will happen in different cities at different times. Once we have the data, we will calculate the speed of Earth’s rotation.”
He adds that this activity is a coordinated effort with planetariums at Chennai, Mangaluru, Delhi, Jaipur, the Aryabhat Foundation based in Bhopal and the Science Teachers Association in Srinagar.
The Jawaharlal Nehru Planetarium in Bengaluru had also showcased demonstration models in an exhibition which was open for the public.
Many people thronged to these exhibits, taking photos and asking questions to the volunteers. A 3 feet-long pole was erected to demonstrate the Zero Shadow effect along with other poster exhibitions.
An experiment named ‘Hear’ was the crowd-puller, a unique experiment which is in the shape of a cannon. It has a convex lens placed above it and the lens would focus on the firecracker kept inside which would light it up. This concept was said to be used as a messaging system in ancient times.
Bengaluru experiences two Zero Shadow days in a year, with the next one on the 18th of August. However, Galgali said noticing this would be difficult because of the monsoon season and the month is usually clouded. Chennai and Mangaluru also experienced Zero Shadow day on April 24.