New Delhi (India), April 25, 2023: Residents of Bengaluru were treated to a rare astronomical phenomenon on Tuesday, as their shadows vanished from the ground at 12:17 pm, marking the occurrence of Zero Shadow Day.
The unique event is a result of the Earth’s axial tilt on its axis and takes place twice a year in certain parts of the globe. The phenomenon is observed in regions between +23.5- and -23.5-degrees latitude.
The Astronomical Society of India explains that the Sun is typically not directly overhead at noon and instead usually passes slightly lower in altitude or to the north or south. This is due to the Earth’s rotational axis being inclined at an angle of 23.5 degrees to the plane of its orbit around the Sun.
For individuals residing within +23.5- and -23.5-degree latitudes, the Sun’s declination corresponds to their latitude twice annually. On these two specific days, the Sun is directly overhead at noon and does not cast a shadow on any object on the ground.
During the spring and fall equinoxes, when the Sun’s rays hit the Earth at a 90-degree angle along the equator, there are no shadows. As the Earth’s axial tilt changes, the Sun’s position in the sky varies, causing different shadow lengths throughout the year.
Overall, the phenomenon of Zero Shadow Day offers a unique opportunity to observe the Earth’s axial tilt and the resulting effects on sunlight and shadows on the planet’s surface.
