High school teacher Joe Howard made another excellent math video. This time, he shows how Eratosthenes calculated the circumference of the Earth in 200 BC. In one of the dopest displays of critical thinking in history, Erotosthenes estimated the circumference of the Earth. All he had was a pole, the sun, knowledge of a famous well in Egypt, and potentially money to pay someone to walk the distance between two cities. This story demonstrates the beauty of trigonometry.