Chennai: Chennai observed Zero Shadow Day on Wednesay with the help of Tamilnadu Science and Technology Centre. The sun will be exactly overhead and will cast almost no shadow of objects on the ground, two times a year. This is because the sun rays will hit the surface perpendicularly and your shadow will be totally beneath you which will make it look like there's no shadow. This is observed as Zero Shadow Day(ZSD). It occurs at different times in different places around the world. In India, it is usually observed between April and September.
In an interview to Deccan Chronicle, Dr S Soundara rajaperumal, Director in-charge of Tamilnadu Science and Technology Centre, said that around 60 school students came together and took part in observational experiments at Birla Planetarium to mark this day. They were given brief training on April 15 for the same. They observed the shadow cast by a gnomon (the vertical, cylindrical part of a sundial which casts a shadow) from 11 am for every 10 minutes. The length of the shadow kept decreasing and at 12.07 pm no shadow was observed. In scientific terms, this time is referred to as 'Local noon' - the time at which the shadow length is shortest and when the sun crosses the local meridian(the imaginary line connecting due north, overhead and due south). Similar events were conducted across the cities of Bangalore, Mangalore, Allahabad, Bhopal and Jaipur, Mr Soundara Rajaperumal said. Bangalore (which is to the west of Chennai) observed local noon at 12.17 pm and Mangalore (which is further west ) observed it at 12.28 pm. From the observations made, students calculated the linear velocity as well as the circumference of the earth at different latitudes. This phenomenon which occurs twice a year will again be observed on August 18. It occurs only at places located between Tropic of Cancer and Tropic of Capricorn which explains why places like Delhi, Allahabad and Srinagar (located away from the Tropic of Capricorn) have no zero shadow day.
