This incredibly accurate science experiment was centuries ahead of its time. | Business Insider

2.8K views · 20 reactions | Eratosthenes measured Earth’s circumference mathematically using two surface points to make the calculation. He noted that the Sun’s rays fell vertically at noon in Syene (now Aswān), Egypt, at the summer solstice. In Alexandria, also in Egypt, at the same date and time, sunlight fell at an angle of about 7.2° from the vertical. | Encyclopaedia Britannica | Facebook