Water clock (clepsydra)
Clepsidra (reloj de agua)
- Date
- c. 1500 BCE · confidence high
- Place
- Karnak, Thebes, Egypt
- Credited to
- Amenemhat (according to his funerary inscription) and the priests of Karnak
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
A conical alabaster vessel with a calibrated lower hole through which water escapes at an approximately constant rate, with interior scales for each month. It allows time to be measured at night and in the temple, without the sun.
The oldest surviving clepsydra is that of Karnak (reign of Amenhotep III, c. 1400 BCE); Babylonian texts and tradition suggest parallel uses in Mesopotamia.
What it led to
- Timed night rites and military watches
- The first measurement of time independent of observing the sky
- A tradition of hydraulic clocks culminating in Hellenistic and Chinese automata
Built on
- Sexagesimal number systemc. 3000 BCE
- Sundial / shadow clockc. 1500 BCE
- Pottery and stone vessels
- Sexagesimal system
Made possible
- Advanced water clock (Ctesibius' clepsydra)c. 270 BCE
- Zhang Heng's water-powered armillary sphere125 CE
- Sinking-bowl water clock (ghati)c. 500
- Al-Muradi's epicyclic and segmental gearsc. 1050
- Su Song astronomical clock tower1092
- Mercury, water and candle clocks of the Libros del saber de astronomía1276-1279
- Jagyeongnu self-striking water clock1434
- Greek float water clock
- Ctesibius's water clock
- Chinese astronomical clock