Mathematics and Society - OS X Lion Server

.. ~(CONT'>-lUe:O)3.In the city of Aswan, Eratosthenes observed that at noon on the longest day of theyear the Sun was directly overhead. It illuminated the bottom of a deep well. Atexactly the same time in Alexandria, the Sun was not directly overhead and caused atall pillar to cast a shadow.measuring the pillar and shadow,Eratosthenes found the anglebetweenlthe Sun and the zenithByto be 75°' Pacers had found thedistance from Alexandria to Aswanto be 790 km. Knowing thatlight rays from the Sun strikingthe Earth seem to be parallel,Eratosthenes was able to calculatethe size of the Earth./ISHADOW·SUtJ 1Il0TOVERH£AD1SUI\)OVER\4t:ADIILOCATE A