Zero shadow day

A zero shadow day is a day on which the Sun does not cast a shadow of an object at noon, when the sun will be exactly at zenith. Zero shadow day happens twice in a year for the places between +23.5 and -23.5 degrees of latitude. The dates will be different for different places on Earth. This phenomenon happens when the Sun's declination becomes equal to the latitude of the place.[1] On a zero shadow day, when the sun crosses the local meridian, the sun rays will fall exactly vertical to the objects on the ground and one can not observe any shadow of it.[2]

Students performing experiment on a zero shadow day