Here is an interesting piece of history we thought we’d share with our readers. More than 2,000 years ago, Eratosthenes, a Greek mathematician, used Sunlight to measure the Earth’s circumference.

#### How did Eratosthenes measure the Earth’s circumference?

He measured the angle between a stick and its shadow in two different cities at the same time of the day. Using the fact that the Sunlight reaches the earth in form of parallel rays and some simple math calculations, Eratosthenes estimated the radius of the Earth as 40,000 KM. He was just 75 KM off from the correct circumference of the Earth, known to be 40,075 KM today.

Checkout the video below for a description of his calculations. Maybe you could try this experiment with help from a friend living in a different city.

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