Zero Shadow Day:
A group of students was provided a first-hand experience of the Zero Shadow Day (ZSD) phenomenon at an event organised by the Pondicherry Science Forum (PSF).
- Zero Shadow Day is a sub-solar point where the sun is directly overhead at a particular latitude.
- When the sun is at the zenith (the highest point in the sky) its rays will be hitting a particular point exactly perpendicular to the surface.
- This will make the shadow of a person exactly under him, making it look like there are no shadows.
- There are two zero shadow days every year in May and July/August, observed in places that lie between the tropic of Cancer and the tropic of Capricorn.
- One falls during the Uttarayan (when the Sun moves northwards), and the other is during Dakshinayan (when the Sun moves southwards).
- It lasts for a small part of a second, but the effect can be seen for a minute to a minute-and-a-half.
