Zero Shadow Day: Bengaluru to witness the 2nd astronomical miracle of 2023 today

Scientifically, Zero Shadow Day happens twice a year at places which fall between Tropic of Cancer and Tropic of Capricorn, encompassing latitudes of 23.5 and -23.5 degrees. (Representative Image/Twitter)

Bengaluru is gearing up today to witness the celestial astronomical phenomenon known as Zero Shadow Day for the second time in 2023. At 12:24 pm, timing arrived at by astronomer Alok Mandavgane, the city will experience a celestial fleeting moment when the Sun will be positioned directly overhead. During this time, vertical objects such as poles, sticks, and even people will not cast any shadow on the ground. When the sun reaches the zenith, you won't be able to see your shadow unless you jump.

Scientifically, Zero Shadow Day happens twice a year at places which fall between Tropic of Cancer and Tropic of Capricorn, encompassing latitudes of 23.5 and -23.5 degrees.

Earlier this year, Bengaluru encountered Zero Shadow Day on April 18, with the notable moment occurring at 12.17 pm when vertical objects momentarily lacked their shadows. Likewise, Hyderabad observed this phenomenon on August 3 at 12:23 pm and previously on May 9 this year.

To understand the mystical event, let's explore the fundamental scientific explanation that underlies this remarkable celestial occurrence.

Science behind the phenomenon

The Astronomical Society of India explains, "the Sun is almost never exactly overhead at noon, but usually transits a bit lower in altitude, a bit to the north or a bit to the south." Scientifically, it says "the Earth's rotation axis is inclined at 23.5 degrees to the plane of its revolution around the Sun, which is why we have seasons."

Furthermore, the ASI website says, "This also means that the Sun, in its highest point of the day, will move from 23.5 degrees south of the celestial equator to 23.5 degrees north of the equator (Uttarayan), and back again (Dakshinayan), in a year. For people living between +23.5 and -23.5 degrees latitude, the Sun's declination will be equal to their latitude twice - once during Uttarayan and once during Dakshinayan. On these two days, the Sun will be exactly overhead at noon and will not cast a shadow of an object on the ground."

Understanding the theory behind Zero Shadow Day (ZSD)

The path the sun takes across the sky changes over the course of a year. Imagine a vast dome-like structure in the sky. The zenith is located at this celestial dome's peak. Your shadow perfectly lines up beneath you when the sun reaches this peak. Only twice a year does this happen, and both times it only happens on Zero Shadow Days.

What time ZSD occurs

The occurrence of the Zero Shadow Day phenomenon is dependent upon the precise timing of solar noon at a specific location. The date and timing of this phenomenon varies for each location. While solar noon has traditionally been set at 12 PM, the precise time of solar noon fluctuates according to the location and the specific period of the year, as it is influenced by the Earth’s tilt and orbit around the Sun.

What time it will occur in Bengaluru on August 18

The Sun reaches exactly overhead at 12:24 pm in Bengaluru on August 18, 2023. The shadow of any vertical object would disappear at that moment.

How to witness Zero Shadow Day

As the anticipated time of solar noon draws near, you'll witness the gradual disappearance of your shadow. Objects adjacent to you, such as poles, will lack shadows, seemingly suspended in midair. You can set out items like water bottles, torchlights, bottles, rods, pipes, and more in the sunlight on your rooftop or the ground, and take note of their diminishing shadow lengths. Eventually, just a few seconds around 12:24 pm, the shadow will completely vanish. This moment marks the Zero Shadow time.