CIRCUMFERENCE OF THE EARTH

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CIRCUMFERENCE OF THE EARTH
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In the third century BC, the Greek mathematician
Eratosthenes was asked to find the circumference
of the earth.
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He knew that the rays of the sun fall to earth in
parallel lines.
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He knew that when parallel lines
are cut by a transversal
alternate interior angles have the same measure
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He knew that if he went to the city of syene at
noon on June 19
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He knew that if he went to the city of syene at
noon on June 19 he would see light shining out of
the famous well.
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WELCOME TO SYENE HOME OF FAMOUS WELL
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The sunlight reflects only if the sun is
directly overhead!
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The rays of the sun are perpendicular to
the earth at this point
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I know the distance between Syene and
Alexandia. On June 19 I will be in
Alexandria. There I will erect a flagpole
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flagpole at Alexandria
well at Syene
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1/50 of a circle
1/50 of a circle
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Fifty times the distance between Syene and
Alexandia is the circumference of the earth!