How did Eratosthenes determine the circumference of the Earth?

1 Answer
chandramohanPanakkal
May 5, 2016

Eratosthenes lived in Alexandria of Egypt in BC 240.. He found out the diameter of Earth thorough geometry and mathematics.

Explanation:

On summer solstice Eratosthenes came to know that there is no shadow in the well at the town of syene which is 5000 stadia from his home.(This is equivalent to about 800 kilometers in present day units).
.This means Sun is just vertically above that place o n particular time..He know that the tower in Alexandria have a shadow of 7.2 degree..7.2 is 1/50th of 360 degree. So calculated the distance of 360 degree..Since his measure stadia in not correctly known.But his calculation was 1% error only with the present day value of 40,000 kilometers.enter image source here unit
Picture credit wired.com.

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