In the coming days, as the Sun makes its way across the sky, moving towards the north with each passing day, depending upon where you live, the Sun will pass through the Zenith. This is Zero Shadow Day. Zenith is the point exactly above your head wherever you stand. Given the earth is a sphere-globe, this point varies from place to place with respect to the sky.
At any other point, with the Sun facing you at an angle, your shadow will be cast on the ground around you. As the sun reaches higher in the sky, the length of the shadow reduces and, on this day, when the sun is exactly above your head, it casts a shadow exactly below you. Since you stand on this shadow, you don’t really see your shadow making your shadow invisible… or Zero shadow.
With the Earth tilted at an angle of 23.5 degrees (as the globes are made), as the earth moves around the Sun, the sun appears to move from north to south, appearing at zenith on two days of the year for all people living between the Tropic of Cancer and Tropic of Capricorn. The two days occur in April-May and August every year, with August being the monsoon and April, a summer month, the chances of observing Zero Shadow Days are higher during this time.
This is one of the easiest astronomical phenomena that can be observed without the use of any instrument.
People at Mangaluru will observe Zero Shadows at 12:28pm on 24th of April and at Udupi on 25th April at 12:29pm. People in Bengaluru will have their Zero Shadow moment on the 24th of April at 12:18pm.
The following are the dates of Zero Shadow day for the rest of Karnataka:
22 Apr : Mysore, Madikeri
23 Apr : Mandya, Putt0ur
24 Apr : Mangalore (D.K.), Hassan, Bengaluru
25 Apr : Udupi, Chikamagaluru, Tumkur, Chikkaballapura
26 Apr : Kundapura, Thirthahalli, Gauribidanur
27 Apr : Bhatkal, Shivamogga, Channagiri
28 Apr : Honnavara, Kumta, Shikaripura, Chitradurga
29 Apr : Gokarna, Sirsi, Ranebennur, Davanagere
30 Apr : Karwar, Haveri 01 May : Hubli, Hospet, Bellari
02 May : Dharwad, Gadag, Koppala
03 May : Belagavi, Sindhanur
04 May : Gokak, Bagalkot, Raichur
06 May : Yadgir
07 May : Vijayapura
09 May : Kalburgi
10 May : Hunmabad
11 May : Bidar
The shadows for the above place will disappear for a minute between 12:15pm for eastern and 12:35pm for western parts of the state.
In order to observe Zero Shadow, an object needs to have an equal or increasing width from top to bottom, like a Cylinder, Cube or a Cone. Poles, Traffic Cones or an Inverted Glass Tumbler. Humans have a broader upper body than our lower half and hence would cast a very small amount of shadow which will be minimum on Zero Shadow Day.
Poornaprajna Amateur Astronomers’ Club urges people to observe and enjoy this beautiful astronomical phenomenon and we wish clear skies to all those who set out to see their shadows disappear.
- Atul Bhat
Co-ordinator, Poornaprajna Amateur Astronomers' Club, Udupi
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