Next occurrence on April 24 in 2016
Zero Shadow Day outreach programme organised by an NGO at DAV Public School, Velachery, on Tuesday.
Chennai: Most of you might not know that your shadow, your most devoted companion, disappears completely twice a year for a brief moment. Yes, Chennaiites experienced it on Tuesday at 12.13 pm. If you missed it, don’t worry. Your shadow will not accompany you again on April 24, 2016! It’s called ‘Zero Shadow Day’. This happens due to the tilt of the Earth’s axis of rotation. Remember that the Earth revolves round the Sun in the fixed plane of our solar system, and at the same time spins about an axis that’s not quite perpendicular to that plane. In reality, the Earth’s axis of rotation is tilted by about 23.4 degrees from vertical.
As a result, most of us pass through the plane of our solar system twice a year—each time resulting in a “zero shadow day”. If you live on the equator you’ll pass through that plane every six months. As you go north from the equator, you’ll experience two “zero shadow days” in closer and closer proximity, until you get to the Tropic of Cancer, where you’ll only touch the plane of our solar system once a year. If you go even further north, you will never experience a “zero shadow day”, Mr. Vijay Ravikumar, visiting faculty at Chennai Mathematical Institute, told Deccan Chronicle.
“It’s very easy to see and experiment. To feel the zero shadow moment next time, you can stand or place a vertical object in the sun around noon time and you will see the shadow getting shorter and shorter and eventually disappear, only to reappear later in about a minute’s time”, he said.
A. Prabhakaran, educator with Space Technology and Education Pvt. Ltd, said some places in Andhra Pradesh such as Tirupati and Tumkur in Karnataka located at 13.37 degrees N latitude experienced zero shadow day on Monday. Since, Chennai is located 13.18 degrees N latitude experienced the phenomenon on Tuesday. “For Chennai to experience it again, the city will have to wait till April 24 next year. People in Delhi never experience zero shadow day as the city does not fall between the tropics”.
Not all missed it: Not all missed it on Tuesday in Chennai. There are about 80 students in DAV Public School, Velachery, who had fun watching their shadows play hide and seek. The SPACE, which actively promotes astronomy education, had organised an outreach programme for the students and conducted few experiments to show how the zero shadow day occurred.
The students were also provided an opportunity to watch the Sun with solar view goggles and a big 8 inch Dobsonian reflector telescope using a solar filter. Principal and regional director of DAV Public School Minoo Aggarwal describe the event very informative that educated students as well as teachers about the ‘Zero shadow day’. Ananya Sreekanth, a class 8 students said: “Very interesting program. It was very informative and very useful. It gave us a lot of knowledge about astronomy and the Sun. It was great!”.
( Source : deccan chronicle )
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