The 3rd century BC Greek mathematician Eratosthenes found that identical objects cast different shadows at noon across the world, proving that the Earth’s surface is curved. The variations in shadow lengths led him to calculate the circumference of the Earth as being 40 000km. Nearly 2 000 years later, satellites found the exact circumference to be 40 030km! Despite centuries of evidence, however, some conspirators still believe that the Earth is flat.

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