Looking at the Moon & Measuring the Earth (finishing up with the Sun)

Eratosthenes- An Ancient Astronomer who discovered the circumference of the Earth by observing the Sun at the bottom of a well in Aswan, Egypt (24degrees North Latitude) on the Summer Solstice and then noticing there was a shadow in Alexandria, Greece--Why was there a shadow in Alexandria and not in Aswan???

One way to try this with students:
Eratosthenes Experiment

How to Measure the Earth: Astronomy On-Line

And this On-Line and pdf Teacher's Guide to Follow in the Steps of Eratosthenes

More about Magnetic North vs Local Solar Noon --Which is true North?? I redid my measurements on Sunday October1, 2006: