Zero Shadow Day occurs when the sun reaches its zenith position—directly above a specific location—causing vertical objects to cast no visible shadows. This happens because the sun’s rays strike the Earth at a 90-degree angle, making shadows fall directly beneath objects and effectively rendering them invisible to the human eye. This phenomenon is observable in regions situated between the Tropic of Cancer and the Tropic of Capricorn. In Bengaluru, located at approximately 13°N latitude, Zero Shadow Day typically occurs twice a year: around April 24–25 and again around August 18.
Why Does It Happen?
The Earth’s axial tilt of approximately 23.5 degrees and its orbit around the sun cause the sun’s apparent position in the sky to change throughout the year. As a result, the sun is directly overhead at different latitudes at different times. When the sun’s declination matches the latitude of a location, it reaches the zenith at solar noon, leading to Zero Shadow Day.
Where Else Does It Occur?
Zero Shadow Day isn’t exclusive to Bengaluru. Cities situated between the Tropic of Cancer and the Equator, such as Chennai and Mangaluru, also experience this phenomenon twice a year. The specific dates vary depending on the city’s latitude.
How to Observe It
To witness Zero Shadow Day, step outside at 12:17 PM on April 24 and observe the base of vertical objects like poles or your own shadow. You’ll notice that the shadow is either absent or falls directly beneath the object, making it nearly invisible. This brief event offers a unique opportunity to observe the interplay between the sun’s position and shadow formation.
Educational Significance
Zero Shadow Day serves as an excellent educational opportunity to understand Earth’s movements, the concept of solar declination, and the impact of Earth’s tilt on sunlight distribution. Schools and science enthusiasts often use this day to conduct experiments and observations related to astronomy and Earth’s geometry.
Bengaluru Set To Experience Zero Shadow: Date and Time
Bengaluru Set To Experience Zero Shadow: Date and Time Bengaluru is set to witness the fascinating celestial event known as Zero Shadow Day on April 24, 2025, at exactly 12:17 PM. During this brief moment, vertical objects will cast no visible shadow as the sun will be positioned directly overhead.
Cities That Experience Zero Shadow Day
Zero Shadow Day is experienced in places located between the Tropic of Cancer and the Tropic of Capricorn, where the sun passes directly overhead twice a year. On these days, vertical objects cast no shadows at solar noon because the sun is at its highest point in the sky.
In India, cities like Bengaluru, Chennai, Hyderabad, Pune, Mumbai, Ahmedabad, Mangaluru, Kochi, and Thiruvananthapuram all experience Zero Shadow Day. For instance, in Bengaluru and Chennai, it happens around April 24 and again around August 18. In cities like Pune and Mumbai, it typically occurs in May and July.
Globally, cities close to the equator—such as Nairobi in Kenya, Quito in Ecuador, Singapore, Kuala Lumpur in Malaysia, Bangkok in Thailand, and Jakarta in Indonesia—also experience this phenomenon twice a year. Zero Shadow Day – ASI POEC
These dates vary depending on the latitude of the city. The closer a location is to the equator, the more evenly spaced these dates are. It’s a fascinating celestial event that helps illustrate the Earth’s tilt and orbit in a real and visible way.
The significance of Zero Shadow Day goes beyond just being a cool natural event — it blends science, education, and wonder. Here’s why it’s important:
1. Demonstrates Earth’s Geometry
Zero Shadow Day is a vivid demonstration of how the Earth’s tilt (23.5°) and its orbit around the sun affect how sunlight reaches different parts of the globe. It makes abstract astronomical concepts like solar declination and zenith position feel real and tangible.
2. Great for Science Education
This phenomenon is a perfect opportunity for schools, students, and science enthusiasts to learn through direct observation. Experiments related to sun angles, shadow lengths, and Earth’s curvature can be conducted in real time — making it a practical and memorable science lesson.
3. Cultural and Architectural Insights
In ancient times, civilizations used similar observations to design temples, clocks, and calendars. Even today, solar alignment in architecture (like sun temples in India) echoes these principles. Zero Shadow Day reminds us of our deep-rooted connection to celestial cycles.
4. Encourages Curiosity About Astronomy
It sparks curiosity and encourages people to look up — literally. It’s often the first step for many toward learning more about astronomy, space, and Earth sciences. It’s a “wow” moment that makes science feel magical.
5. Citizen Science & Public Engagement
Events like these promote citizen science, where ordinary people participate in data collection and experiments. Organizations and science centers often organize public events, workshops, and outreach sessions, bringing communities together.
In short, Zero Shadow Day is not just a moment when shadows disappear—it’s a chance for people to connect with the cosmos, understand planetary motion, and celebrate the elegance of science in everyday life.
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