Around 240 BC, Eratosthenes measured the Earth's circumference in Egypt, while Chinese chroniclers made the first sure record of Halley's Comet.
The events
- Eratosthenes measures the Earthc. 240 BC · Syene. 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.
- Earliest sure record of Halley's Comet240 BC · State of Qin. Chinese chronicles preserved in Sima Qian's Records of the Grand Historian note a comet in 240 BC, the first reliable sighting of Halley's Comet. The state of Qin was then ruled by young Ying Zheng, the future First Emperor.
More amazing facts
- 509 BC · 508 BC Rome expelled its last king in 509 BC and Athens got democracy from Cleisthenes in 508: republic and democracy were born almost side by side.
- 480 BC · 479 BC Confucius died in 479 BC — one year after the Greeks defeated the Persian fleet at Salamis.
- 323 BC · 322 BC India's Maurya Empire arose about a year after Alexander the Great died — and its founder, Chandragupta, is said to have met Alexander himself.
- 261 BC · 260 BC Almost simultaneously, Ashoka conquered Kalinga (261 BC) and repented the bloodshed, while China saw the Battle of Changping (260 BC), one of antiquity's bloodiest.
- 202 BC In 202 BC, empires were decided at both ends of Eurasia: Scipio defeated Hannibal at Zama, and Liu Bang founded the Han dynasty.
- 36 BC · 31 BC The earliest known Long Count calendar date in Mesoamerica is 36 BC — just five years before the Battle of Actium.