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Explorations an Introduction to Astronomy Thomas T. Arny | ||||||||
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Chapter
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Chapter 1, Figure 17
Figure
1.17
Eratosthenes's
calculation of the circumference of the Earth. The Sun is directly overhead
on the summer solstice at Syene, in southern Egypt. On that same day, Eratosthenes
found the Sun to be 7° from the vertical in Alexandria, in northern Egypt.
Eratosthenes deduced that the angle between two verticals placed in northern
and southern Egypt must be 7°.
