Eratosthenes measures the Earth
Two shadows and geometry reveal the size of the planet
Eratosthenes, head of the Library of Alexandria, compared noon shadows at Syene and Alexandria on the summer solstice and calculated the Earth's circumference. His result was remarkably close to the true value.
Wikipedia (Russian) · Wikipedia (English) · 3rd century BC
Did you know
Around 240 BC, Eratosthenes measured the Earth's circumference in Egypt, while Chinese chroniclers made the first sure record of Halley's Comet.
Meanwhile around the world (±25 years)
Europe
- 218 BC Hannibal crosses the Alps — 22 years later
- 216 BC Battle of Cannae — 24 years later
Asia
- c. 261 BC Kalinga War — 21 years earlier
- 221 BC Qin Shi Huang unifies China — 19 years later
Alive at the time
- Archimedes (aged 47)
- Qin Shi Huang (aged 19)
- Hannibal (aged 7)
- Ashoka (aged 64)
- Eratosthenes (aged 36)
- Liu Bang (Emperor Gaozu of Han) (aged 16)
- Empress Lü (Lü Zhi) (aged 1)