Measurement of Earth circumference
Medida de la circunferencia terrestre
- Date
- c. 240 BCE · confidence medium
- Place
- Alexandria, Egypt
- Credited to
- Eratosthenes of Cyrene
- People
- 👤 Eratóstenes276 BCE–194 BCE
- Field
- Knowledge & symbols
What was discovered
By comparing the shadow at Syene and Alexandria at the solstice, he deduced that the arc between them was 1/50 of a circumference and estimated the Earth at about 250,000 stadia, with an error under 15 per cent. The first geometric measurement of a planetary object.
Accuracy depends on the value of the stadion, which is not known with certainty. Merged with «Measurement of Earth's circumference», «Measurement of Earth's radius» (duplicate, 23-09-2026).
What it led to
- geodesy
- cartography with latitude and longitude
- mathematical geography
- mathematical geography and the latitude/longitude system
- the calculation of ocean distances (Columbus used a flawed estimate that was too small)
- modern geodesy
- the estimation of celestial distances in terrestrial units
- expectations of the globe's size in the Age of Discovery
Built on
- Sphericity of the Earthc. 350 BCE
- Euclidean axiomatic geometryc. 300 BCE
- Euclidean geometry
- Babylonian astronomy
Made possible
- Strabo's Geographyc. 20 (obra de entre 7 BCE y 23)
- Ujjain meridian (prime meridian of Indian astronomers)c. 500
- Snellius's triangulation (Eratosthenes Batavus)1615-1617
- scale maps
- ocean navigation
- World map with parallels and meridians
- Geodesy
- Maps with scale