In mathematics, V stands for volume, which is a technical term of geometry. When the space occupied by an object is a three-dimensional space, the size of the space occupied is called the volume of the object. The international unit of volume system is cubic meters. One-dimensional space objects and two-dimensional space objects are all zero volumes. China, the first mathematician in the world who worked out the correct formula for calculating the volume of a sphere, was Zu Chongzhi in the Southern Dynasties, about a thousand years earlier than Europeans. He also carefully studied the art of celestial computing and perfected the calendar of the Ming Dynasty. After his repeated requests, it was officially promulgated on 5 10. He also made a variety of precision observation instruments such as copper sundial and clepsydra, which were adopted by later generations.