Zero Shadow Day

Zero Shadow Day occurs when the sun’s rays are directly overhead, causing objects to cast no shadows, typically observed near the equator twice a year, showcasing celestial phenomena. It happens in all locations where the latitude aligns with the angle between the Sun’s position and the equator on that specific day.

In this article, we will understand the meaning of zero shadow day, facts about zero shadow day, and the phenomenon behind the zero shadow day.

Zero Shadow Day Overview

Facts about Zero Shadow Day	Information
Occurrence	It happens in all locations where the latitude aligns with the angle between the Sun’s position and the equator on that specific day.
Shadow Position	At local noon, the shadow is directly beneath an object, resulting in minimal or no shadow.
Scientific Basis	Zero Shadow Day is attributed to the Earth’s tilt concerning the Sun, impacting the angle and position of sunlight.
Seasonal Connection	Earth’s axial tilt, responsible for seasons, also influences the distribution of sunlight on Zero Shadow Day.
Sun’s Direct Overhead	On Zero Shadow Day, the sun is positioned directly overhead, causing the shadow length to be 0.
Cultural Significance	Recognized in various regions, particularly during solstices, marking a unique alignment of the Sun and Earth.

Zero Shadow Day – Concept

Zero Shadow Days, or ZSD, occur biannually when the sun rises directly in the east and sets directly in the west. During this phenomenon, the sun reaches its zenith, or highest point in the sky, resulting in objects casting no shadows for a brief period.

This happens when the sun’s rays, known as the subsolar point, hit the Earth’s surface at a 90-degree angle. ZSD typically occur between the Tropic of Cancer and the Tropic of Capricorn. Regions within this zone, like Chennai, Mumbai, and Pune, are likely to experience Zero Shadow Days, while areas outside this range, such as New Delhi, do not observe this phenomenon.

Facts About Zero Shadow Day

Some facts about zero shadow day are:

• The Earth is tilted at an angle, making the Sun appear higher or lower in the sky at different times of the year.

• Zero Shadow Day occurs twice a year when the Sun is directly above certain places on Earth.

• It occurs when you’re in a location between two imaginary lines on the globe which is called the Tropic of Cancer and the Tropic of Capricorn.

• During Zero Shadow Day, the objects don’t cast shadows for a short time because the Sun is right above them.

• This special day occurs in May and either July or August.

• Even though Zero Shadow Day lasts for a very short moment, one can see its effects for about one to one-and-a-half minutes.

The Phenomenon Behind Zero Shadow Day

• The Astronomical Society of India (ASI) suggests that the main reason for zero shadow days is how the sun is positioned.

• When the sun is right above or its light directly hits objects, the solar angle is very low, resulting in no shadows. This happens when the Sun’s declination matches the location’s latitude.

• On a zero-show day, when the sun passes the local meridian, its rays fall straight down, perfectly vertical to an object on the ground.

• This means there’s no declination, and the viewer, the sun, and the objects form a 90-degree angle. Since the light rays don’t bend after hitting the object, there’s no angle, and hence, no shadow is cast.

• Zero-shadow days vary in different places due to the sun’s position, which changes globally. This event happens twice a year when the sun is directly above regions near the equator.

• It’s important to know that the zero-shadow effect is mostly seen with vertical objects aligning with the sun’s rays, causing a low solar angle and no shadow. This includes tall buildings, trees, and poles whose shadows vanish briefly at noon.

When is Zero Shadow Day at your location? 

Here’s the Zero Shadow Day (ZSD) information for various places, now formatted into a table for clarity. This phenomenon occurs due to the sun’s position directly overhead, causing no shadow for objects at solar noon. The dates provided are for two occurrences each year for the specified locations:

ZSD Dates	Places
6 Apr & 5 Sep	Indira Point
10 Apr & 1 Sep	Kanyakumari, Nagercoil, Kudankulam, Trinket Island
11 Apr & 31 Aug	Kovalam, Trivandrum, Kazhakoottam, Nedumangadu, Sathankulam, Tiruchendur
12 Apr & 30 Aug	Varkala, Ponmudai, Paravur, Kollam, Kottarakara, Punalur, Tenkasi, Tirunelveli, Thoothukudi
13 Apr & 29 Aug	Kayankulam, Adoor, Thiruvalla, SankaranKoil, Kovilpatti, Rameshwaram, Ramanathapuram, Car Nicobar
14 Apr & 28 Aug	Alappuzha, Kottayam, Vaikom, Pala, Sabarimala, Cumbum, Rajapalayam, Sivakasi, Virudhunagar, Paramakudi
15 Apr & 27 Aug	Kochi, Vypin, Thodupuzha, Idukki, Munnar, Theni, Andipatti, Tirumangalam, Madurai, Sivaganga, Karaikudi
16 Apr & 26 Aug	Paravur, Aluva, Chalakudy, Valparai, Kodaikanal, Dindigul, Pudukottai, Pattukottai, Vedaranyam
17 Apr & 25 Aug	Guruvayur, Ponnani, Thrissur, Ottapalam, Palakkad, Pollachi, Mettupalayam, Udumalpet, Palani, Trichy, Thanjavur, Thiruvarur, Nagapattinam, Little Andaman
18 Apr & 24 Aug	Kottakal, Malappuram, Coimbatore, Gudalur, Palladam, Tiruppur, Kangayam, Karur, Kumbakonam, Mayiladuthurai, Karaikal, Poompuhar
19 Apr & 23 Aug	Kozhikode, Koyilandy, Thamarassery, Ooty, Kotagiri, Avinashi, Erode, Tiruchengode, Namakkal, Sirkazhi, Chidambaram
20 Apr & 22 Aug	Vadakara, Mahe, Thalassery, Perambra, Wayanad, Mudumalai, Bhavani, Mettur, Salem, Kallakuruchi, Neyveli, Panruti, Cuddalore, Port Blair
21 Apr & 21 Aug	Kannur, Payyanur, Taliparamba, Dharmapuri, Sankarapuram, Villupuram, Pondicherry, Havelock Island
22 Apr & 20 Aug	Kanhangad, Kasargod, Madikeri, Mysore, Srirangapatna, Shuivanasamudra, Chengam, Tiruvannamalai, Tindivanam, Long Island
23 Apr & 19 Aug	Uppala Gate, Puttur, Arakalagud, Krishnarajapete, Melkote, Mandya, Channapatna, Ramanagara, Attibele, Hosur, Krishnagiri, Tirupattur, Vanaiyambadi, Kavalur, Ambur, Arani, Kanchipuram, Chengalpattu, Mahabalipuram, Kelambakkam
24 Apr & 18 Aug	Mangalore, Moodabidri, Bantwal, Sakleshpur, Hassan, Shravanabelagola, Bidadi, Bangalore, Dasarahalli, Bangarapet, Kolar, Gudiyattam, Vellore, Arcot, Arakkonam, Sriperumbudur, Tiruvallur, Avadi, Chennai, Interview Island, Sound Island
25 Apr & 17 Aug	Udupi, Brahmavar, Karkala, Sringeri, Kudremukha

Conclusion

Zero Shadow Day is a celestial event that occurs twice a year near the equator when the sun is directly overhead. This results in objects casting no shadows. This phenomenon is linked to the Earth’s tilt and the sun’s position, which creates a unique alignment.

The associated facts and explanations contribute to a deeper understanding of this natural occurrence, emphasizing its significance in various regions. As a momentary spectacle, Zero Shadow Day showcases the intricate relationship between Earth and the Sun, leaving a lasting impression on those fortunate enough to witness it.

The event’s frequency, cultural recognition, and the science behind it add layers to the appreciation of this intriguing celestial phenomenon

Zero Shadow Day – FAQs

What is No Shadow Day?

No Shadow Day happens when objects don’t make shadows because the sun is right above them, so there are no angles to create shadows.

When Does Zero Shadow Day happen?

Zero Shadow Day happens when the sun is directly above a place, usually twice a year near the equator, making it seem like there are no shadows.

Why Do Vertical Objects Not Cast on Zero Shadow Day?

Vertical things like buildings or trees don’t make shadows on Zero Shadow Day because the sunlight hits them straight down, so there are no angles to create shadows.

How Often Does Zero Shadow Day Occur?

Zero Shadow Day occurs twice a year near the equator when the sun is directly overhead, but it can vary in other places depending on the sun’s position.

Is Zero Shadow Day the Same Everywhere in The World?

No, Zero Shadow Day is different in other parts of the world because it depends on where you are and how the sun is positioned. It happens more often near the equator but less frequently in other places.