Science & Tech

What is Zero Shadow Day and why does it occur?

Since the sun was directly overhead at the moment, many cities in India are enjoying Zero Shadow Day.

What exactly is Zero Shadow Day?

  • The occurrence of Zero Shadow Day occurs twice a year at every point on Earth between the Tropics of Cancer and Capricorn.
  • Vertical objects appear to cast no shadow at local noon, when the sun is at its zenith exactly above the object, on Zero Shadow Day.
  • When the sun swings from 23.5°N to 23.5°S of the Earth’s equator and back, the shadow disappears beneath objects around local noon.

What causes this to happen?

  • It is caused by the sun’s journey from south to north during Uttarayan and back from north to south during Dakshinayan.
  • The Earth’s rotation axis is tilted at an angle of around 23.5° to the axis of revolution around the sun, causing this movement.
  • On that day, all locations whose latitude equals the angle between the location of the sun and the equator enjoy Zero Shadow Day, with the shadow dissipating at local noon.
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