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sun’s apparent path in the heavens–i.e., he
measured the obliquity of the ecliptic, mak-
ˆ
ing it 23A 51’, confirming our knowledge
of its continuous diminution during histor-
ical times. He measured an arc of merid-
ian, from Alexandria to Syene (Assuan),
and found the difference of latitude by the
length of a shadow at noon, summer sol-
stice. He deduced the diameter of the earth,
96
