Zhang Heng was a celebrated astronomer of ancient China. An inventor of the seismograph and armillary sphere, he made great contributions to the development of astronomy in ancient China. Zhang Heng wrote altogether 32 works on science, philosophy and literature, of which Ling Xian (a summary of astronomical theories at the time) and The Map of Ling Xian are astronomical works.

Zhang Heng was born in a renowned literary family in 78 A. D. in Henan Province during the Eastern Han Dynasty. His grandfather was an honest and upright official; therefore, though Zhang Heng was brought up in an eminent family, the economic condition of the family was not very good. Growing in such an environment, Zhang Heng had set an ambitious and lofty goal at an early age and worked very hard for it. He used to be a local official in charge of writ-writing. Outstanding in both virtue and talent, he was later promoted as a key official in the imperial court, responsible for drawing up writs, compiling history records, and supervising astronomy and calendar as well as ancestor-worshipping. He was an upright and diligent official and had achieved great accomplishments in his administrative career, yet he preferred to conduct researches on astronomy and other branches of science. He took advantage of his official privilege and read extensively the ancient research works. Diligent in observing and experimenting, and versed in research, he learnt from previous experiences and made brilliant achievements in astronomy, seismology, mechanical technology, math, and so on. In addition, Zhang Heng did well in such fields as philosophy, literature, and painting. He was a rare talent versed in multiple fields in the Chinese history.

As a distinguished scientist in ancient China, Zhang Heng not only made eminent achievements in scientific theories, but also was good at making various scientific instruments to facilitate his scientific research. His invention of the seismograph and armillary sphere fully demonstrated the intelligence of the scientists in ancient China. Zhang Heng was indifferent to fame and fortune, erudite and diligent in his study, and lofty and noble in setting his goal. All these virtues have exerted great influence on the later generations and inspired Chinese learners of all dynasties.