Zu Chongzhi (429–500) was born into a family where his grandfather, Zu Chang, served as an official in charge of imperial construction projects during the Liu Song dynasty. Growing up in such an environment, Zu Chongzhi read extensively from a young age, and people widely praised him as a learned young man. He had a particular passion for studying mathematics and also enjoyed researching astronomy and calendrical science, frequently observing the movements of the sun and planets and making detailed records of his observations.
Upon hearing of his reputation, Emperor Xiaowu of the Song dynasty appointed Zu Chongzhi to work at the Hualin Xuesheng, a government institution dedicated to academic research. Although Zu had no interest in pursuing an official career, this position allowed him to focus even more deeply on his studies in mathematics and astronomy.
Throughout Chinese history, there had always been officials tasked with astronomical research, and calendars were created based on their findings. By the time of the Song dynasty, calendar systems had already made significant progress. However, Zu Chongzhi believed they were still not precise enough. Based on his long-term observations, he developed a new calendar called the "Daming Calendar" (Daming was the reign title of Emperor Xiaowu). The number of days he calculated for each tropical year (the time between two winter solstices) differed from modern scientific measurements by only fifty seconds. His calculation for the time the moon takes to complete one orbit around Earth differed by less than one second from modern measurements, demonstrating its remarkable accuracy.
In 462 AD, Zu Chongzhi petitioned Emperor Xiaowu to adopt his new calendar. The emperor convened a meeting of his ministers to discuss the proposal. At that time, a powerful minister named Dai Faxing, favored by the emperor, opposed the idea, accusing Zu Chongzhi of recklessly altering the ancient calendar and straying from traditional principles. Zu Chongzhi immediately countered Dai Faxing's arguments with the data from his research. Relying on the emperor's favor, Dai Faxing arrogantly declared, "The calendar was established by the ancients; later generations should not alter it." Zu Chongzhi remained unafraid. He responded solemnly, "If you have factual evidence, present it for debate. Don't try to intimidate others with empty words!" Emperor Xiaowu, wishing to support Dai Faxing, arranged for several officials knowledgeable in calendrical science to debate Zu Chongzhi, but one by one, they were all refuted by Zu. Nevertheless, Emperor Xiaowu still refused to promulgate the new calendar. It was only ten years after Zu Chongzhi's death that his Daming Calendar was finally adopted and implemented.
Despite the social unrest and instability of the era, Zu Chongzhi continued his scientific research with unwavering dedication. His greatest achievements lay in the field of mathematics. He wrote commentaries on the ancient mathematical text "The Nine Chapters on the Mathematical Art" and compiled another work titled "Zhui Shu" (Method of Continuation). His most outstanding contribution was determining a highly accurate value for pi. After prolonged and arduous research, he calculated pi to be between 3.1415926 and 3.1415927, making him the world's first scientist to compute the value of pi to seven decimal places.
Zu Chongzhi was a versatile inventor in the field of science. He built a south-pointing chariot; no matter how the vehicle turned, the bronze figure on it always pointed south. He also constructed a "thousand-li boat," which he tested on the Xinting River (southwest of present-day Nanjing), capable of sailing over a hundred li in a single day. Additionally, he harnessed water power to turn stone mills for husking rice and grinding grain, a device known as the "shui dui mo" (water-powered trip hammer and mill).
In his later years, the Song dynasty was overthrown by Xiao Daocheng, the commander of the imperial guards.