Folha: 'The life of Pi in ancient China'

Reproduction of Marcelo Viana's column in Folha de S. Paulo. I'm not a big fan of social media and I don't think I ever will be: the cost-benefit ratio is simply bad. But the other day I came across something interesting on Instagram: a mention of the mathematician Zu Chongzhi (429–500), who lived in China during the Liu Song dynasty. His grandfather and father were dignitaries at court, so Zu had a privileged upbringing, with access to the best education, especially in mathematics and astronomy. The fame of the young man's talent reached the ears of the emperor, who had him study at the imperial university in Nanjing. In 464, he moved to the region where the city of Shanghai is located today. In the following years, he produced his most famous works. In 465, he developed the Daming calendar, the most advanced of its time, which was officially adopted by the imperial court. Zu estimated that the solar year corresponds to 365.2428 days, which is very close to the currently accepted value: 365.2422 days. He also incorporated advanced mathematical and astronomical methods into his calendar, including precise measurements of the Moon's movement that greatly facilitated the prediction of astronomical phenomena, such as eclipses. Read more: Registrations for the 20th OBMEP 2025 end on March 17th 'Bigger than expected,' says Campos about the event at IMPA Visgraf video unites avatars of Aristotle and Steve Jobs Zu's main scientific results were collected in the book "Zhui Shu," which unfortunately has been lost. It must not have been an easy text to read: comments from other authors suggest that Zu's methods were so advanced for the time that mathematicians of later generations considered them confusing. Some historians speculate that "Zhui Shu" included methods for solving the cubic equation, a problem that would only be completely solved in the Renaissance. We know that Zu measured the length of a Jupiter year, concluding that it corresponded to 11.858 Earth years, very close to the value of 11.962 accepted today. He also formulated and used the idea that solids that have the same height and whose cross-sectional areas at each height are equal necessarily have the same volume. Today this idea is called Cavalieri's Principle, in honor of the Italian Bonaventura Cavalieri (1598–1647), who rediscovered it more than a thousand years later. Zu used it to find the formula for the volume of a sphere: v = ^πd³ /6, where d represents the diameter.