Updated: May 15, 2019
One of the perks of my ongoing internship at IUCAA Science Center is helping in celebrating Zero Shadow Day in Pune at IUCAA.
Generally, the Sun is almost never exactly overhead at noon, but usually transits a bit lower in altitude, a bit to the north or a bit to the south. We have all studied in school that the Earth's rotation axis is inclined at 23.5 degrees to the plane of its revolution around the Sun, which is why we have seasons. This also means that the Sun, in its highest point of the day, will move from 23.5 degrees south of the celestial equator to 23.5 degrees north of the equator (Uttarayan), and back again (Dakshinayan), in a year. Of course, the northern most and southern most points are the two solstices, and the crossing of the Sun across the equator are the two equinoxes.
For people living between +23.5 and -23.5 degrees latitude, which is nothing but 'Tropic of Cancer' and 'Tropic of Capricorn', the Sun's declination will be equal to their latitude twice - once during Uttarayan and once during Dakshinayan. On these two days, the Sun will be exactly overhead at noon and will not cast a shadow of an object on the ground.
As Pune latitude is at 18.5 degrees, the ZSD occurred on 13th May 2019 at 12:31 p.m. which is local noon of Pune. And we had a very beautiful opportunity to celebrate this event.
We took a table and placed some supports on which we kept clean glass slab. On that few symmetrical objects were placed in order to observe to the Zero Shadow Phenomena. Also, we took a equatorial mount tripod stand of a telescope and positioned it in such way that it's tube holding rings were perpendicular to the ground. By this, we were able to actually track the ZSD phenomena more prominently.
In short, today was actually fun and was worth every moment.