Lesson 28: This lesson is really complicated!!! Basically a guy named Eratosthenes around 3rd century BC was able to understand that the world is round, and then he used some crazy math to calculate the circumference of the earth. He was able to do this by measuring the angles of shadows in different cities. In one city at exactly noon on a certain day, the shadow was not there because the sun was directly overhead, and the next year, on the exact same day and time, he measured the shadow of a pole. He used this to calculate what degree of change of tilt there was from one pole to the other pole, and then also the distance between the two cities to figure out the circumference of the earth. I didn’t really understand how the math part worked out, so I’m excited to see it in class!
Lesson 29:Hipparchus and the Moon
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