You are an astronomer on planet Nearth, which orbits a distant star. It has recently been accepted that Nearth is spherical in shape, though no one knows its size. One day, while studying in the library of Alectown, you learn that on the equinox your sun is directly overhead in the city of Nyene, located 1200 kilometers due north of you. On the equinox, you go outside in Alectown and observe that the altitude of your sun is 79 ∘. What is the circumference of Nearth?
Hint: Apply the technique used by Eratosthenes to measure Earth’s circumference.