Ele Willoughby, PhD

Another of scientists without a known birthday: my #linocut of ancient Chinese Han Dynasty #polymath & statesman Zhang Heng (78-139) who invented a seismoscope (simplified seismometer which does not make a record of earth motions) to detect distant earthquakes & indicate their direction, 2000 years ago! Here with a reconstruction of his seismoscope, schematic of how it might have worked & 🧵

https://minouette.etsy.com/listing/1383517882

#histsci #printmaking #ZhangHeng #EarthScience #seismology #mastoArt

Jan 4 at 12:59pmWeb
Show threadEle Willoughby, PhDJan 4
horizontal earthquake surface waves (Rayleigh waves in particular). A career civil servant in Nanyang, Zhang Heng was also an #astronomer, #mathematician, #seismologist, hydraulic engineer, #inventor, geographer, cartographer, ethnographer, artist, #poet, philosopher, politician & literary scholar. He was a bit of a controversial figure politically, sparing over calendar reform & with rivals amongst the palace eunuchs. But both his poetry & famous inventions are still remembered. He also 🧵2/
Show threadEle Willoughby, PhDJan 4

improved the Chinese approximation for pi & made an extensive star catalog. He understood that the Sun & Moon are spherical, & that the Moon merely reflects the light of the Sun. He also explained the nature of solar & lunar eclipses, invented the world’s first water-powered armillary sphere for astronomical observation, improved the inflow water clock by adding another tank.

According to the Book of Later Han (compiled by Fan Ye in the 5th century), his bronze urn-shaped device, 🧵3/

Show threadEle Willoughby, PhDJan 4
with a swinging pendulum inside, was able to detect the direction of an earthquake 100s of km away. The outside of the device was described as having 8 dragons with balls in their mouths & 8 open-mouthed frogs around the base which could catch fallen balls (& indicate direction to the source). The device was triggered by an event, which was too subtle for people to feel but that the west-facing dragon drop its ball. Officials doubted the device worked as intended, but several days later 🧵4/5
Show threadEle Willoughby, PhDJan 4

a messenger arrived from the west & reported that an earthquake had occurred in Longxi (modern Gansu Province). So, the court acknowledged it in fact worked.

Unfortunately, no ancient seismoscopes have survived & details of the mechanism are sparse so this is a best guess.

🧵5/5

Show threadSellaTheChemistJan 4
@minouette Nice. There's a very good account of Chang Hêng's instrument in Volume 3 of Joseph Needham's Science and Civilization in China.