Zero Shadow Day

Zero Shadow is a phenomenon when the sun is exactly overhead and the shadows of symmetrical and vertical objects vanishes. This happens for locations between the tropics and is caused by the northern and southern motion of the sun during the course of a year. This app helps you find the Zero Shadow Day for any location.

If you are between Tropic of Cancer and Tropic of Capricorn, then on a particular day (one during Uttarayan and other during Dakshinayan) the Sun will pass directly overhead at local noon. At local noon on this day, a vertical pole will cast no shadow. These are called Zero Shadow Days, or ZSD. This app is an aid to the campaign by the Public Outreach and Education Committee of the Astronomical Society of India for celebrating ZSD.

Inputs and Content by
Dr. Niruj Mohan Ramanujam, ASI POEC
Translations by:
Kannada - Dr B.S. Shylaja of Jawaharlal Nehru Planetarium Bengaluru and Mrs. Jyotsna
Telugu - Teja Teppala
Marathi - Dr. Aniket Sule, HBCSE, ASI POEC.
Hindi - Alok Mandavgane
Spanish - Alvaro Jose Cano Mejia from Colombia
Portuguese Brazilian - José Roberto Vasconcelos Costa