If Earth Is Round, the Mn Must be Round T 21
approximately 925 km (575 miles). Then he used the following formula to determine the
circumference of Earth.
575 miles (925 km) 28,750 miles (46,250 km)×
°
°
360
72.
=
Although we now know that the circumference of Earth is 40,000 km (24,855 miles),
Eratosthenes’ calculation is remarkably close.
Another version of the story says that Eratosthenes got his idea by seeing the Sun’s
rays reach the bottom of a well rather than observing the shadow cast by a rod. Neverthe-
less, it is generally accepted that he calculated Earth's circumference as being approximately
25,000 miles, which is roughly accurate.
If ...
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