Zero Shadow Day: What Is The Science Behind It?

Before we dive into the phenomenon of Zero Shadow or No Shadow Day, let us first learn the basics and the science of shadow formation. Sure enough you must have a brief understanding of how shadows are formed, why they are formed differently at different times of the day, and such other easily available information. Now it’s time to deep dive and learn some more fascinating facts.

This Story also Contains

1. What Are Shadows?
2. Why Shadows Vary Throughout The Day
3. What Is No-Shadow Day?
4. Does No Shadow Day Occur Everywhere on Earth?
5. The Phenomenon Behind Zero Shadow Day

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What Are Shadows?

How is a shadow formed? When light falls on particular objects, they form shadows. These objects are called opaque objects because they do not allow light to pass through them, so light passes only through their outline while the middle part is blocked, thus forming a shadow.

For example, a person walking on the road in the daytime will have a shadow resembling their outline, and here, the light source is the sun.

Transparent objects like mirrors or water do not form shadows. This is because they allow the light to pass through them, and hence, light rays pass throughout the object and are not blocked.

Why Shadows Vary Throughout The Day

You must have noticed that the shadows change distinctively throughout the day. They are light and blurry in the morning but are extended and evident by the late afternoon. This is due to the variation in the position of the light source. The light source of nature is the sun, which gets wider as the day passes, and hence the shadows are darker and longer.

As we have learned, shadows are cast mainly due to the sun in nature, so the absence of the sun during rainy or cloudy weather will not form any shadows. The shadows can also be formed artificially by introducing an artificial light source like bulbs, torches, and more.

The Earth’s rotation on its axis and around the sun forms variable angles with the sun’s rays, and hence various lengths and directions of shadows can be observed throughout the year.

What Is No-Shadow Day?

A zero shadow day is the one on which the Sun does not cast a shadow of an object at solar noon when the sun will be exactly at the zenith position. For locations in the tropics, zero shadow days happen twice a year.

Certain cities in India, like Bengaluru and Mumbai, experienced or are going to experience no shadow day in August 2023. As the term states, no shadow is formed by the objects, but the interesting thing is that this phenomenon is occurring in the presence of the light source, i.e., the sun. So, how is it that the light rays are not casting any shadows?

This interesting celestial phenomenon where no shadows are being cast by the objects on the Earth’s surface is due to the presence of the sun directly above the objects. This phenomenon will usually occur during noon when the light rays will fall directly overhead of the objects, and thus the solar angle will be so low that little or no shadow will be formed.

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Does No Shadow Day Occur Everywhere on Earth?

No, not all cities or countries witness the no-shadow day. It occurs in the cities that lie between the Tropic of Cancer and Capricorn, primarily near the equator. Bengaluru in India is one of the cities that will witness this celestial phenomenon on August 18, 2023.

For Hyderabad, a no-shadow day was August 4, 2023. It is not that the shadow is not cast for the entire day but only for a brief period around noon time. This unique event became popular on social media, and people shared many pictures of Zero Shadow Day. Some regions of Telangana and Maharashtra also observed this phenomenon at similar times.

The Phenomenon Behind Zero Shadow Day

The Astronomical Society of India (ASI) proposed that the major reason for zero shadow days is the positioning of the sun. Since it is directly above or the light rays fall directly on top of objects, the solar angle is very low, thus producing no shadow. In other words, this phenomenon happens when the Sun's declination equals the location's latitude.

On a zero shadow day, when the sun crosses the local meridian, the sun’s rays are directly falling downward, exactly vertically, relative to an object on the ground. Thus, there is no declination, and hence the viewer, the sun, and the objects are at 90 degrees. The light rays are not bending after hitting the object, so no angle is present and no shadow is formed.

People can arrange experiments to witness the zero-shadow day by aligning the objects in the proper dimensions. Arranging them vertically and observing them at noon can enable one to see no shadow phenomenon.

Zero-shadow days are not similar everywhere, as they largely depend on the positioning of the sun, which varies across the globe. This unique celestial phenomenon can be observed twice a year as the sun lies overhead in regions near the equator. It must be noted that the zero-shadow phenomenon is mainly associated with vertical objects as they align with the sun's rays, thereby producing a low solar angle and no shadow. Some examples are tall buildings, trees, and poles whose shadow cannot be seen on the ground for a brief moment at noon.

No-shadow day enlightens us about the intricate movements of the planet and gives a sneak peek into the unbelievable wonders of celestial phenomena.

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