Note4Students
From UPSC perspective, the following things are important :
Prelims level: Zero Shadow Day
Mains level: Not Much
Central idea: Many cities across India are experiencing Zero Shadow Day since the sun was directly overhead at that time.
What is Zero Shadow Day?
- Zero Shadow Day is a phenomenon that occurs twice a year at every point on Earth located between the Tropic of Cancer and the Tropic of Capricorn.
- During Zero Shadow Day, vertical objects appear to cast no shadow at local noon, when the sun is at its zenith directly above the object.
- It occurs when the sun’s location moves from 23.5°N to 23.5°S of Earth’s equator and back, causing the shadow to disappear beneath objects at local noon.
Why does it happen?
- It occurs due to the movement of the sun from south to north during the Uttarayan and back from north to south during Dakshinayan.
- This movement is caused by Earth’s rotation axis being tilted at an angle of roughly 23.5° to the axis of revolution around the sun.
- All places whose latitude equals the angle between the sun’s location and the equator on that day experience Zero Shadow Day, with the shadow disappearing at local noon.
Try this PYQ:
On 21st June, the Sun-
(a) Does not set below the horizon at the Arctic Circle
(b) Does not set below the horizon at Antarctic Circle
(c) Shines vertically overhead at noon on the Equator
(d) Shines vertically overhead at the Tropic of Capricorn
Post your answers here.
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