Media Release
Udupi, Apr 21: An astronomical phenomenon that is the easiest to observe is approaching. This week, on April 24 the people of Mangaluru and on April 25 the people of Udupi and surrounding areas will see their shadows disappear for a few minutes at 12:28 pm. This phenomenon is called Zero Shadow Day.
If you take a candle in a dark room and use it to create a shadow of your palm on the wall. The hand will cast a shadow on the wall as you move your hand and when you place your palm on the wall, you will see no shadow. This happens because the Sun, at this time shines exactly above our heads. In astronomy, we call this point the Zenith. The point in the sky directly above an observer at any given location. So it is quite clear now that on Zero Shadow Day, the Sun passes through the Zenith as a result of which, all objects will have minimal or no shadow if they are on the ground.
The reason this happens on some specific days is concerned with astronomy. The earth spins around on its own axis and causes days and nights. It also revolves around the Sun causing a year. But the seasons are caused because the axis is tilted at an angle of 23.5 degrees. It is because of this tilt that the Sun rises every day in the east gradually moving towards the north till June 21 and then slowly proceeding towards the south till December 21 every year, these days are called solstice. This means the sun shines between the tropic of Cancer and tropic of Capricorn every day passing by the equator on the days called the equinox.
As the earth moves around the Sun and revolves on its own axis, for all the people between Tropic of Cancer and Tropic of Capricorn, the Sun at noon moves father and closer to the Zenith passing through Zenith twice causing two Zero Shadow Days per year. People at Mangaluru will observe this on April 24 and August 18 every year and people at Udupi will observe this on April 25 and August 17 every year. Places with same latitudes will observe the same days of Zero Shadow but the time would vary with longitude. For example, people of Bengaluru as they share the latitude with Mangaluru will observe it on April 24. While the people of Mangaluru will observe their shadows disappear at 12:28 pm, people of Bengaluru will observe this at 12:17 pm. Places like Moodbidri, Bantwala, Sakleshpur and Hassan will also observe Zero shadows on April 24 along with Mangaluru and Bengaluru with little variation in time. Places like Brahmavar, Karkala, Sringeri, Kudremukha, Chickmagaluru will observe the Zero Shadow on the same day as Udupi on April 25.
People at Mangaluru will observe Zero Shadows at 12:28 pm on April 24 and at Udupi on April 25 at 12:29 pm.
In order to truly 'see no shadow,' the object casting the shadow must be symmetric or of equal or decreasing width from bottom to top. Humans, as we have a wider torso compared to the width of our legs, will notice a small amount of shadow. A cylinder or a cone (or household items of similar shape) placed on the floor would cast Zero Shadow at the above time.
This is perhaps one of the simplest observations that can be made from an astronomical phenomenon as one requires no instruments of any sorts. Poornaprajna Amateur Astronomers’ Club urges people to observe and enjoy this beautiful astronomical phenomenon. PAAC also has planned a live stream of the Zero Shadow moments of Mangaluru and Udupi on their website and Facebook page.