Discover the World’s First Earthquake Detector, Invented in China 2,000 Years Ago

The Renais­sance did not, strict­ly speak­ing, occur in Chi­na. Yet it seems that the Mid­dle King­dom did have its Renais­sance men, so to speak, and in much ear­li­er times at that. We find one such illus­tri­ous fig­ure in the Han dynasty of the first and sec­ond cen­turies: a states­man named Zhang Heng (78–139 AD), who man­aged to dis­tin­guish him­self across a range of fields from math­e­mat­ics to astron­o­my to phi­los­o­phy to poet­ry. His accom­plish­ments in sci­ence and tech­nol­o­gy include invent­ing the first hydraulic armil­lary sphere for observ­ing the heav­ens, improv­ing water clocks with a sec­ondary tank, cal­cu­lat­ing pi fur­ther than it had been in Chi­na to date, and mak­ing dis­cov­er­ies about the nature of the moon. He also, so records show, put togeth­er the first-ever seis­mo­scope, a device for detect­ing earth­quakes.

A visu­al expla­na­tion of Zhang’s design appears in the Sci­ence­World video above. His seis­mo­scope, its nar­ra­tor says, “was called hòufēng dìdòngyí, which means ‘instru­ment for mea­sur­ing sea­son­al winds and move­ments of the earth,’ ” and it could “deter­mine rough­ly the direc­tion in which an earth­quake occurred.”

Each of its eight drag­on heads (a com­bi­na­tion of num­ber and crea­ture that, in Chi­na, could hard­ly be more aus­pi­cious) holds a ball; when the ground shook, the drag­on point­ing toward the epi­cen­ter of the quake drops its ball into the mouth of one of the dec­o­ra­tive toads wait­ing below. At one time, as his­to­ry has record­ed, it “detect­ed an earth­quake 650 kilo­me­ters, or 400 miles away, that was­n’t felt at the loca­tion of the seis­mo­scope.”

Not bad, con­sid­er­ing that nei­ther Zhang nor any­one else had yet heard of tec­ton­ic plates. But as all engi­neers know, prac­ti­cal devices often work just fine even in the absence of com­plete­ly sound the­o­ry. Though no con­tem­po­rary exam­ples of hòufēng dìdòngyí sur­vive from Zhang’s time, “researchers believe that inside the seis­mo­scope were a pen­du­lum, a bronze ball under the pen­du­lum, eight chan­nels, and eight levers that acti­vat­ed the drag­ons’ mouths.” Mov­ing in response to a shock wave, the pen­du­lum would release the ball in the oppo­site direc­tion, which would roll down a chan­nel and release the mouth at the end of it. How­ev­er inno­v­a­tive it was for its time, this scheme could, of course, pro­vide no infor­ma­tion about exact­ly how far away the earth­quake hap­pened, to say noth­ing of pre­dic­tion. For­tu­nate­ly, cen­turies of Renais­sance men still lay ahead to fig­ure all that out.

Relat­ed Con­tent:

How the Ancient Greeks Invent­ed the First Com­put­er: An Intro­duc­tion to the Antikythera Mech­a­nism (Cir­ca 87 BC)

The Advanced Tech­nol­o­gy of Ancient Rome: Auto­mat­ic Doors, Water Clocks, Vend­ing Machines & More

Behold Col­or Pho­tographs Tak­en Dur­ing the After­math of San Francisco’s Dev­as­tat­ing 1906 Earth­quake

China’s 8,000 Ter­ra­cot­ta War­riors: An Ani­mat­ed & Inter­ac­tive Intro­duc­tion to a Great Archae­o­log­i­cal Dis­cov­ery

What Ancient Chi­nese Phi­los­o­phy Can Teach Us About Liv­ing the Good Life Today: Lessons from Harvard’s Pop­u­lar Pro­fes­sor, Michael Puett

Based in Seoul, Col­in Marshall writes and broad­casts on cities, lan­guage, and cul­ture. He’s the author of the newslet­ter Books on Cities as well as the books 한국 요약 금지 (No Sum­ma­riz­ing Korea) and Kore­an Newtro. Fol­low him on the social net­work for­mer­ly known as Twit­ter at @colinmarshall.