Bengaluru is bracing for a remarkable celestial occurrence known as ‘Zero Shadow Day’ on Wednesday, during which all vertical structures in the city will briefly cast no shadow. The event is scheduled to take place at 12:17 pm local time, with the effects observable until approximately 12:23 pm. In anticipation of this rare event, the Indian Institute of Astrophysics (IIA) in Bengaluru’s Koramangala area has organised various activities on its campus to commemorate the occasion
The institute posted an invitation on social media, urging people to join in the celebrations and participate in shadow length measurements and demonstrations. Additionally, collaborative efforts with Bhopal and Chennai are underway to calculate the Earth’s diameter and rotation speed.
Zero Shadow Day marks a unique celestial event when the sun is positioned directly overhead, causing objects to cast no shadows at noon. This phenomenon primarily occurs in regions located near the equator, where the sun’s angle is nearly perpendicular to the Earth’s surface, resulting in the absence of shadows.
As the Earth orbits the sun, its position in the sky changes, reaching its zenith at different latitudes during various times of the year. This orbital movement creates the changing seasons and causes the sun to transition from 23.5 degrees south of the equator to 23.5 degrees north, and vice versa, annually.
According to the Astronomical Society of India, Zero Shadow Day occurs twice a year in locations situated between the latitudes of +23.5 and -23.5 degrees.
According to the ASI, Zero Shadow Day occurs when the Sun’s declination matches the latitude of the location. This alignment lasts only momentarily but has a visible impact for up to two minutes.
"Join us on 24 April to celebrate #ZeroShadowDay #ZSD for locations at #Bengaluru latitude. Measure shadow lengths & check out our cool demos! We will work with Bhopal & Chennai to calculate Earth's diameter and rotation speed!" The IIA posted
Bengaluru witnessed Zero Shadow Days on April 25 and August 18 last year, marking significant celestial events in the city’s calendar.
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