Zhang Heng

• Born: 78
• Died: 139

Zhang Heng was a Han Dynasty mathematician and scientist, famous for calculating the rough value of pi, and inventing the grid system for mapmaking, as well as a seismograph effective at detecting earthquakes even far from the capital.

References

• Conrad Schirokauer, et al, A Brief History of Chinese and Japanese Civilizations, Fourth Edition, Cengage Learning (2012), 60.