The Ancient Greek Water Clock That Kept the Most Accurate Time for 1,800 Years

Today, we’re sur­round­ed by tech­nolo­gies we could jus­ti­fi­ably describe as time thieves. In ancient Greece, those who want­ed to know where their time was going con­sult­ed a device they called a “water thief.” The roots of the clep­sy­dra, or water clock, go back as far as the six­teenth cen­tu­ry BC, with evi­dence of such devices found in mod­ern-day Iraq, Iran, and Egypt, and more ambigu­ous evi­dence unearthed in places like India and Chi­na. The mech­a­nism in the ear­li­est exam­ples takes not much more com­plex a form than a bowl out of which water slow­ly drips, albeit not at a reg­u­lar pace. That nat­ur­al imped­i­ment to hydraulic time­keep­ing was­n’t cor­rect­ed until the third cen­tu­ry BC, when a Greek inven­tor called Cte­si­bius set about mak­ing his own improve­ments.

Cte­si­bius’ auto­mat­ic water clock used a ver­ti­cal cylin­der, rotat­ing once year­ly, marked with straight ver­ti­cal lines rep­re­sent­ing the months of the year and curved hor­i­zon­tal lines rep­re­sent­ing the hours of the day. A point­er next to it indi­cat­ed the cur­rent hour, its posi­tion changed by the water lev­el of the cylin­der in which it float­ed. That cylin­der was filled through a feed­ing reser­voir, itself con­stant­ly sup­plied with water.

The idea behind this arrange­ment was to keep the rate of flow steady, and thus the speed of the point­er con­stant. To emp­ty the reser­voir with­out the need for human inter­ven­tion, Cte­si­bius incor­po­rat­ed a siphon that let water out every 24 hours, reset­ting the clock­’s dai­ly cycle. A water wheel attached to a sim­ple sys­tem of gears kept the cylin­der turn­ing, so that its “dis­play” could keep up with the ever-chang­ing length of the day­light-based ancient Greek hour.

All this is explained with detailed visu­al aids in the ani­mat­ed Decon­struct­ed video above. “In a world with­out elec­tric­i­ty, dig­i­tal log­ic, or even mechan­i­cal clocks,” says its nar­ra­tor, “this ancient inven­tion laid the foun­da­tion for automa­tion and time­keep­ing as we know them today.” Indeed, Cte­si­bius’ clep­sy­dra “kept bet­ter time than any­thing else on Earth for 1800 years,” until Chris­ti­aan Huy­gens invent­ed the pen­du­lum clock in 1656. There’s some­thing in the swing­ing of such a mech­a­nism that appeals to the innate human attrac­tion to rhythm, and the metaphor­i­cal val­ue of the grains of sand pass­ing through an hour­glass (an inter­me­di­ary inven­tion between Cte­si­bius and Huy­gens) remains strong even now. But it’s prob­a­bly not a coin­ci­dence that the flow of time and the flow of water, at least from the human per­spec­tive, feel like two aspects of the same pri­mal phe­nom­e­non.

Relat­ed Con­tent:

The Plan­e­tar­i­um Table Clock: Mag­nif­i­cent 1775 Time­piece Tracks the Pass­ing of Time & the Trav­el of the Plan­ets

An Ani­mat­ed Intro­duc­tion to the Antikythera Mech­a­nism: The World’s First Ana­log Com­put­er from Ancient Greece

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

How Medieval Islam­ic Engi­neer­ing Brought Water to the Alham­bra

Ancient Egypt­ian Pyra­mids May Have Been Built with Water: A New Study Explore the Use of Hydraulic Lifts

How Clocks Changed Human­i­ty For­ev­er, Mak­ing Us Mas­ters and Slaves of Time

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.