zhang heng


The First Seismoscope was invented in 132 AD by a Chinese astronomer, mathematician, engineer, and inventor called Zhang Heng.  The device was remarkably accurate in detecting earthquakes from afar, and did not rely on shaking or movement in the location where the device was situated.  Zhang’s seismoscope was a giant bronze vessel, resembling a samovar almost 6 feet in diameter. Eight dragons snaked face-down along the outside of the barrel, marking the primary compass directions. In each dragon’s mouth was a small bronze ball. Beneath the dragons sat eight bronze toads, with their broad mouths gaping to receive the balls. The sound of the ball striking one of the eight toads would alert observers to the earthquake and would give a rough indication of the earthquake’s direction of origin. 

In 2005, scientists in Zengzhou, China [which was also Zhang’s hometown] managed to replicate Zhang’s seismoscope and used it to detect simulated earthquakes based on waves from four different real-life earthquakes in China and Vietnam. The seismoscope detected all of them. As a matter of fact, the data gathered from the tests corresponded accurately with that gathered by modern-day seismometers!


Zhang Heng (Chinese: t 張衡, s 张衡, p Zhāng Héng; AD 78–139), “was a Chinese polymath from Nanyang who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, mathematician, inventor, geographer, cartographer, artist, poet, statesman, and literary scholar.

Zhang Heng began his career as a minor civil servant in Nanyang. Eventually, he became Chief Astronomer, Prefect of the Majors for Official Carriages, and then Palace Attendant at the imperial court. His uncompromising stances on certain historical and calendrical issues led to Zhang becoming a controversial figure, which prevented him from rising to the status of Grand Historian. His political rivalry with the palace eunuchs during the reign of Emperor Shun (r. 125–144) led to his decision to retire from the central court to serve as an administrator of Hejian in Hebei. He returned home to Nanyang for a short time, before being recalled to serve in the capital once more in 138. He died there a year later, in 139.

Zhang applied his extensive knowledge of mechanics and gears in several of his inventions. He invented the world’s first water-powered armillary sphere to assist astronomical observation; improved the inflow water clock by adding another tank; and invented the world’s first seismometer, which discerned the cardinal direction of an earthquake 500 km (310 mi) away. He improved previous Chinese calculations for pi. In addition to documenting about 2,500 stars in his extensive star catalog, Zhang also posited theories about the Moon and its relationship to the Sun: specifically, he discussed the Moon’s sphericity, its illumination by reflected sunlight on one side and the hidden nature of the other, and the nature of solar and lunar eclipses. His fu (rhapsody) and shi poetry were renowned in his time and studied and analyzed by later Chinese writers….”