Offline edby

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On the size and distance of the sun and moon
« on: May 11, 2018, 02:39:15 PM »
A page on the FE wiki (here) tries to refute Eratosthenes' proof (3rd century BC) of the round earth. It notes
Eratosthenes' model depends on the assumption that the earth is a globe and that the sun is far away and therefore produces parallel rays of light all over the earth.
Correct. The article then tackles the parallel assumption, arguing that his observation can be explained if the sun is only approximately 2000 miles above the earth.

OK. But why did Eratosthenes assume the sun was much further? To understand that, we must go back to an earlier Greek astronomer Aristarchus, and his book On the Sizes and Distances (of the Sun and Moon). Using easily replicated observations based on the half moon, Aristarchus showed that the distance of the sun from the earth must be 20 times that of the earth to the moon. What an elegant and beautiful argument.

None of the Greek science was based on complex instrumentation or NASA. Just simple observations, and trigonometry.