Question

what is a sundial??..

Answer 1

A instrument showing by time by the shadow of a pointer cast by the sun on a plate marked with the hours of the day is called sundial...

Answer 2

$\color{red} \looparrowright$The first devices for measuring time were sundials the which are based on the fact that the position and length of the shadow cast by an object changes with the time during the day.

$\color{red} \looparrowright$A simple sundial consists of a horizontal circular board with a triangular plate of metal fixed vertically on it. The plate is kept along north-south direction. The plate casts its shadow falls at different angles during different times of the day. The position of the shadow is utilised to mark the time of the day.