Egypt, with later development in Greece, China and the Islamic world
Associated with
Egyptian and later Greek, Chinese and Islamic craftspeople
Developed and refined the device over many centuries
Plate 019
c. 1400 BCE
Egypt, with later development in Greece, China and the Islamic world
No photograph is shown for this exhibition. The museum displays an image only where it can show the object honestly.
About this date
The oldest surviving water clock, found at Karnak in Egypt, is dated to about 1400 BCE. Written sources hint at older ones.
About credit
No single inventor is known. Later makers such as Ctesibius of Alexandria (3rd century BCE) and Su Song in 11th-century China greatly improved the design.
Chapter II
The world before
Life before the Water Clock
Time was told by sun and shadow, which fails at night and when the sky is overcast.
II
The human achievement
How it came about
The Egyptian version was a bowl with a small hole near the base; as water drained, marks on the inside showed how much time had passed. Later makers added floats, gears and figures that struck bells, turning the device into one of the first machines to regulate itself.
III
Understanding the invention
How it works
The Water Clock, explained in two steps.
01
Step 01 of 02
A steady flow
Water leaves a bowl at a rate that depends on how full it is. Designers shaped the bowl, or kept the water level constant with a header tank, to make the rate steady.
A steady flow
Marks and mechanisms
IV
The transformation
What changed for humanity
Law and ritual
Speeches in Athenian courts were timed with water clocks.
Astronomy
Reliable timing helped astronomers make observations at night.
Measuring time independently of the sun made it possible to schedule work, court sessions and ceremonies, and prepared the ground for mechanical clocks.
V
Before and after
Life before and after The Water Clock
Before
Only by daylight.
After
By day or night, indoors or out.
On larger screens, drag the divider (or use the arrow keys) to give more room to the world before or after.
Huygens’s clock made timekeeping far more accurate.
VII
Human stories
The people and the moments
Su Song’s clock tower
In the early 1090s the Chinese scholar-official Su Song completed a clock tower in Kaifeng driven by a water wheel, with an escapement and an armillary sphere on top. It is documented in his own written description.
Where accounts differ, this museum follows the documented record and says so.