This document discusses measuring the circumference of the Earth using observations of shadows cast at different locations on the summer solstice. It notes that Eratosthenes was able to measure the circumference by comparing shadow lengths in Syene and Alexandria, Egypt, breaking the challenge into constituent parts that could be observed and measured locally.

1. Eratosthane
s
Our ‘Old Greek
Guy’

2. Has it, or something very similar, been
measured before?

4. Sesame Street

5. What are the observable consequences
of the thing that we are interested in
measuring?

7. A Piano Tuner…

8. Can we break down our ‘impossible
measure’ into constituent parts?

9. A hungry Blue Whale