Zhang Heng
Zhang Heng lived during the Han dynasty and was an expert in subjects such as astronomy, mathematics, hydraulics, and science, being one of the most famous people in ancient China. Zhang did not come from a royal family but he was taught Confucianism and, after self-education in various fields, he held the position of chief astronomer and later imperial palace guard. Despite the opportunity to work at a higher level, he refused to accept these positions, saying that he was not ambitious enough. In ancient times, famous astrologers like Zhang used to write calendars for kings. Calendars were intended to guide the emperor in the way in which he should rule, but they had little to do with the emperor's ruling strategies and were largely based on what astrologers wanted. Zhang's refusal to draw the Chinese calendar illegally for the government made him unusually popular.
Zhang Heng invented a water-powered sphere that was used to calculate altitude and longitude. He also theorized about the moon and its relationship to the sun. He studied the 3 × 3 magic square and found a number close to π. He stated that π is approximately the square root of 10 and is equivalent to 3.162. He deduced equations for the volumes of three-dimensional objects such as spheres and enclosing cubes. This level of math was unprecedented at the time. He also contributed to the literary field by writing many poems and stories, an interest he developed during his time at the imperial court because of his access to a wide range of books and major literary works.
- Born and died: 78–139 AD
- Known as: Scientist
