Defining the World

The Earth

If the Earth is so large, why did Columbus think that India was close enough to reach by sailing west from Europe?

The Greek geographer Posidonus did not believe Eratosthenes’ earlier calculation, so he performed his own measurement of the Earth’s circumference and arrived at the figure of 18,000 miles (28,962 kilometers). Columbus used the circumference estimated by Posidonus when he argued his plan before the Spanish court. The 7,000 mile (11,263 kilometer) difference between the actual circumference and the one Columbus used led him to believe he could reach India rather quickly by sailing west from Europe.


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