Gnomon and graduated sundial
Gnomon y reloj de sol graduado
- Date
- c. 560 BCE · confidence low
- Place
- Miletus and Sparta, Turkey / Greece
- Credited to
- Anaximander of Miletus (introduction to Greece); Babylon
- People
- 👤 Anaximandro620 BCE–547 BCE
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What it is
A vertical rod whose shadow on a graduated scale marks hours, solstices and equinoxes. A basic instrument of observational astronomy and mathematical geography.
Herodotus says the Greeks took the gnomon from Babylon; China independently used gnomons (biao) at least since the Zhou dynasty.
What it led to
- Determination of latitudes and of the obliquity of the ecliptic
- Eratosthenes' measurement of the size of the Earth
- Division of the day into civil hours in Greek and Roman cities
- Cartography based on astronomical observation
Built on
- Egyptian obelisk
- Babylonian astronomy
- Geometry
Made possible
- Advanced water clock (Ctesibius' clepsydra)c. 270 BCE
- Armillary spherec. 255 BCE
- Measurement of Earth's circumference (Eratosthenes)c. 240 BCE
- Julian calendar45 BCE
- Early planispheric astrolabec. 150 CE
- Map projection with coordinates (Ptolemy's Geography)c. 150 CE
- Polar-axis sundial of the Umayyad Mosque1371
- Angbuilgu bowl sundial1434
- Measurement of Earth's circumference