The Sun Is Directly Above You and Your Shadow Has the Day Off - Welcome to Zero Shadow Day

On certain days of the year, step outside at noon and look down - your shadow will have completely vanished. This is Zero Shadow Day (ZSD), a fascinating astronomical event when the sun reaches its zenith, or highest point directly overhead, causing the rays to hit the Earth at a precise 90-degree angle. The result - shadows of vertical objects fall directly underneath them, effectively disappearing from sight for a brief window of time.

The Science Behind The Disappearing Shadow

Zero Shadow Day occurs because of Earth's axial tilt of 23.5 degrees and its revolution around the sun. As the sun appears to move north and south throughout the year, there are specific days when its declination - the angle between the sun and the equator - becomes exactly equal to the latitude of a particular location. When this alignment happens at local solar noon, the sun is positioned at a perfect right angle overhead, erasing all shadows momentarily.

Which Cities In India Experience It

The phenomenon is restricted to locations situated between the Tropic of Cancer (+23.5 degrees) and the Tropic of Capricorn (-23.5 degrees). In India, this means cities south of Ranchi qualify - including Bengaluru, Chennai, Hyderabad, Mumbai, Pune, and Mangaluru. Each qualifying city experiences ZSD twice a year - once during Uttarayan (sun moving northward) and once during Dakshinayan (sun moving southward). For Bengaluru, the two dates fall on April 24 and August 18, with the event observable at precisely 12:17 PM local time.

Celestial Phenomenon Highlights

• Zero Shadow Day occurs twice a year for all locations between the Tropic of Cancer and Tropic of Capricorn
• The phenomenon lasts only a brief moment but its visible effects can be observed for up to two minutes
• Earth's 23.5-degree axial tilt is the primary reason this event occurs
• In 2026, Bengaluru experienced Zero Shadow Day on April 24 at exactly 12:17 PM
• Bengaluru's second ZSD of 2026 will fall on August 18
• Cities north of Ranchi - including New Delhi - do not experience Zero Shadow Day at all
• The Indian Institute of Astrophysics (IIA) and the Astronomical Society of India (ASI) actively promote public outreach events around ZSD
• The event can be easily observed using any vertical object - a pole, a bottle, or even a person standing straight

Sources: Indian Express, Times of India, Hindustan Times, Indian Institute of Astrophysics - PIB, Astronomical Society of India, ABP Live, GeeksforGeeks