You are an astronomer on planet Neo, which orbits a distant star. It has recently been accepted that Neo is spherical in shape, though no one knows its size. One day, while studying in the library of Town A, you learn that on the equinox your sun is directly overhead in Town B, located 1200 kilometers due north of you.On the equinox, you go outside in Town A and observe that the altitude of your sun is 78?.
What is the circumference of Neo? (Hint: Apply the technique used by Eratosthenes to measure Earth's circumference.)