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Almost nobody thought the Earth was flat by the 19th century. Even as early as Columbus, the argument was not that the Earth was round, but that it was small enough to go to India from Spain (it wasn't). The ancient Greek mathematician Eratosthenes was able to calculate the circumference of the earth with relatively good accuracy i.e. not flat. Columbus used ...


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A friend of his named Heracleides wrote a biography, but it was lost so the details of his biography is unknown. But after reading its biography, (in my opinion ) I don't think he had any students. The quote below is from wikipedia Unlike his inventions, the mathematical writings of Archimedes were little known in antiquity. Mathematicians from ...


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He synchronised them to the solar zenith. Eratosthenes knew that on the day of the summer solstice, the sun passed vertically above Syene, which lies very close to the Tropics of Cancer. As the traditional account goes, the sun was directly above a vertical well at Syene, whereas at Alexandria the columns of the Library always leaves a shadow. Either way, ...


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Simple. While the earth moves around the year, the sun seemingly moves around between the Tropic of Cancer (north) and the Tropic of the Capricorn (south). In the north this is begin of summer and the sun reaches the highest point. The first city where the deep well exists is the city of Syene (now Assuan) which is almost exactly on the Tropic of Cancer, ...



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