Geodesy

Around 240 BC, Eratosthenes compared the Sun's shadow angle at Alexandria with the overhead Sun at Syene, then scaled up the distance between them to get Earth's circumference.

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Earth bulges at the equator because it spins. Chimborazo sits almost on the equator, so its summit is about 2.1 km farther from the center than Everest's, though Everest is higher above sea level.

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