Pune: The lands on the surface of the earth, are not always aligned with the position of the sun. In a tropical country like India, the sun travels in the sky at a shifted angle. The sun shifts northwards and southward as the earth revolves around the sun, in a middle of which, the Sun comes directly overhead, causing shadows to fall directly below the object. This is celebrated as the Zero Shadow day (ZSD), which in Pune will be on May 13.
“In collaboration with a large number of local science communication groups in each state, as the ZSD line progresses northwards, each state has seen dozens of events in schools, where students observe the lack of shadow of a vertical pole at local noon,” says Niruj Ramanujam, an astrophysicist and a member of the Astronomical Society of India, Public Outreach and Education Committee (ASI POEC).
The ASI POEC has created a special mobile app so that anyone can know the ZSD timings in their location. “Our app has many interactive demos to helps students and teachers understand ZSD and also plan their events. Our website (bit.ly/zsd2018) has information for any teacher or student to plan their own event,” Ramanujam says, adding, “We would like school students to do something as simple and cost-effective, as measuring the shadow length of a vertical stick throughout the day, for many days in a year.”
“This simple experiment based on a stick can actually allow the student to measure the cardinal directions, the time of local noon, and with some additional data, even the latitude and longitude of their location. If they work together with students in other latitudes, they can calculate the diametre of the earth itself, quite precisely,” Ramanujam says adding, “Understanding and performing these calculations uses the students knowledge of geography, trigonometry, geometry and optics, and hence we feel that this simple, no-cost exercise is something every school in India should
“We want to create curiosity in the minds of the people. By using the ZSD as an occasion, that curiosity will make them come up with questions like how shadows fall, why they move etc., and will understand the nature of the universe,” says Aniket Sule, Chairman of ASI POEC. He further adds, “Our app will become a good educational tool for students and an interesting tool for the curious minds.”
“As an Android developer, most of the apps I have commercially designed have been for astronomy-related projects. I have myself been involved in outreach programmes and so I happily agreed to design the ZSD app,” says Alok Mandavgane, the creator of the app, adding, “Earlier, there used to be a compiled list of the date and time of the ZSD for major cities. Now with the app, anyone from any location can know their local ZSD accompanied with various visualisations and interesting features.” The Zero Shadow Day app is available on Google Play Store.