‘Zero Shadow Day’ observed in Mysuru

COSMOS, Mysuru of the Indian Institute of Astrophysics organised hands-on experiments and demonstrations, at Vignana Bhavan in Manasagangotri, to mark Zero Shadow Day on Tuesday.
| Photo Credit: M.A. Sriram

The Cosmology Education and Research Training Center (COSMOS), Mysuru, of the Indian Institute of Astrophysics on Tuesday observed ‘Zero Shadow Day’ at Vignana Bhavan, Manasagangotri here. Amoghavarsha N., Project Associate of COSMOS, IIA, delivered a lecture on the science behind Zero Shadow Day.

Later, hands-on experiments and demonstrations were shown to participants by the SCOPE Team of IIA, led by Vikranth Pulamathi. Participants were asked to take readings of the length of the shadow made by the Gnomons (Shanku Yantra) every five minutes from 11.45 a.m. to 1.00 p.m. to note down changes in the shadow. Zero shadow phenomenon was observed at 12.22 p.m., demonstrated by a hollow cylinder on a glass plate along with the Gnomons, according to COSMOS.

Yashaswini K.S. and Renjithmon A.A. of IIA showed the sunspots to the participants. The event concluded with participants calculating the declination of the sun, finding the true north, and noting down the zero shadow phenomena, followed by a question and answer session.

Zero Shadow Day (ZSD) occurs when the sun is directly overhead (i.e., at the zenith). At this moment, any object held vertically will not cast any shadow on the ground, since the sun’s rays fall straight down on it, rather than at an angle. On other days, the sun is not exactly overhead at noon, a press release from COSMOS explained.

“Only locations lying between the Tropic of Cancer and the Tropic of Capricorn will experience ZSD, which will occur twice a year, corresponding to the northern and southern movements. Since the Earth is tilted on its axis by about 23.5 degrees, as it revolves around the sun, the sun can pass overhead only for locations whose latitude lies between 23.5° N and 23.5° S. Hence, different locations experience ZSD on different days. ZSD for Mysuru is on April 22 and August 19,” the organisation said.