Earth size estimate
In Aswan, the sun is directly overhead. By comparing it to the 7 deg offset in Alexandria and using the cities' relative location Eratosthenes estimated earth circumference to be 25k miles.
In Aswan, the sun is directly overhead. By comparing it to the 7 deg offset in Alexandria and using the cities' relative location Eratosthenes estimated earth circumference to be 25k miles.