Sundial introduction: The sundial, also known as the "sundial", is a timing instrument in ancient China that uses the shadow of the sun to measure time. It usually consists of a copper pointer and a stone disk. The copper pointer is called the "dial needle", which passes vertically through the center of the disc and plays the role of the neutral pole of the watch. Therefore, the sundial needle is also called the "dial", and the stone disc is called the "dial surface".