[Mycroft Holmes]

In 200 BC, travelers told the head of the Alexandria Library, Eratosthenes, about a well near present-day Aswan. The bottom of the well was lit by the sun at noon during the summer solstice. At that moment the sun was straight overhead. Eratosthenes realized he could measure the shadow cast by a tower in Alexandria while no shadow was being cast in Aswan. Then, knowing the distance to Aswan, it'd be simple to calculate Earth's radius.

Due to some erroneous assumptions he was off by about 15%. Not too shabby for the time.

[Sherman Logan]

Fascinating story. Given the paucity of their equipment, the Greeks did some amazing scientific-like work.

OTOH, huge amounts of their speculations were wildly off, but we remember the ones that were reasonably close to the truth. Like Eratosthenes and Democritus.

[Ernest_at_the_Beach]

Thanks....

This would be a great story to use with a Geometry class.