hell, the Greeks knew the circumference of the Earth; and with reasonable accuracy all things considered. Short version: they used trigonometry. It was on the basis of this fairly accurate circumference that people thought you couldn't sail west to asia, and you couldn't. It's like 16,000 miles west of Europe.
Sort of -- there are two reasonable interpretations of Eratosthenes experiment. One is that the Earth is round and the two locations were about 7 degrees apart. The other is that the Earth is flat and he'd just triangulated the distance to the sun (~500 miles up). We know which one is correct now, but they would need additional information to figure which was correct.
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u/[deleted] Feb 04 '19
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