This describes a famous experiment conducted by the Greek scholar Eratosthenes around 240 BCE to measure the size of the Earth.Observation: Eratosthenes noticed that at noon on the summer solstice, the Sun was directly overhead in Syene (modern-day Aswan), casting no shadow down a deep well. At the same time in Alexandria, further north, he observed that a vertical stick (gnomon) did cast a shadow.
He measured the angle of this shadow, which was approximately 7.2 degrees, or 1/50th of a circle.
By assuming the distance between the two cities was roughly 5,000 stadia (about 800 kilometers) and multiplying that distance by 50, he calculated the Earth's circumference to be about 40,000 kilometers, a value remarkably close to modern calculations.
But do NOT equate belief in a flat earth (obviously preposterous as so many celestial events make clear) and questioning that humans have left near earth orbit and have traveled successfully to the moon. They are independent issues.
ReplyDeleteI know lots of trivia like this. I wish I was smart enough to come up with the next great invention.
ReplyDeleteB.C.
ReplyDeleteQuestion from a dumb guy....
ReplyDeleteOK, how did he know when it was midday? Isn't that generally calculated by the sun's being directly overhead?