Geography & Planet Earth
How long is Earth's equator, in km (1 km ≈ 0.6 mi)?
Answer
40,075 km
The Greek scholar Eratosthenes estimated Earth's circumference around 240 BC using shadows and a well — and got remarkably close, more than 1,700 years before anyone sailed around the planet.
Source: NASA / IUGG reference ellipsoid (40,075.017 km)
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