(Jon of the Clue Crew points to an astronomical diagram on the monitor.)  In the 200s B.C. Eratosthenes calculated Earth's girth using the difference in the angle of the Sun's rays between Aswan & this Egyptian city
By noting the angles of shadows in two cities 
on the Summer ... right calculations using his knowledge of geometry and the 
distance ... angle between Alexandria and Syene as measured from the Earth's... [DOC] [TLE] Eratosthenes of Cyrene | 4.3Ways of Knowing: Our Solar System ... [PAR] Eratosthenes also calculated the distance from the Earth to the Moon and to the 
Sun, ... well in the Egyptian city of Swenet (Syene in Greek, and now known as 
Aswan), ... Recognizing the curvature of the Earth and knowing the distance 
between the ... Eratosthenes could measure the angle of the Sun's rays off the 
vertical by... [DOC] [TLE] Eratosthenes - Wikipedia [PAR] Eratosthenes of Cyrene was a Greek mathematician, geographer, poet, 
astronomer, and music ...