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How The Diametre Of The Earth Was Measured

Before the technological era the diametre of the earth had already been estimated, have you ever wondered how? It is a very easy task just ask and you will definetly know the answer. So in 200 BC the earth's diametre was estimated to one percent accuracy. Just Imagine that high precision and the timeline. If you were told to do it now would you.

Erathosthenes was a genius of his own making. He used Aristotles idea that the earth was round and the stars would appear at different positions when observed from different latitudes. He knew that on first day of the summer the sun would pass directly overhead at Syene, Egypt. At midday the same day he measuted the sun's angular displacement at the city of Alexandria 5000 stadia away from Syene.

He found out the the angular displacement was 7.2 degrees, which is 1/50 of a circle. Geometry tells us that the ratio is the same as the ratio of the distance between Syene and Alexandria to the circumference of the earth. Thus the distance can be estimated by multipling the distance between the two cities, 50000 stadia by 50 stadia equalling to 250000 stadia. Which is about 40,000 Kilometres, and got the radius as 6366 Kilometres. And today the measured circumference is 40070 Kilometres and the radius is 6378 Kilometres. A very close estimation that is the beauty of science and scientists.

Content created and supplied by: Sheleonard (via Opera News )

Aristotles Egypt Erathosthenes


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