Measuring Earth's radius in greek style || Maths+Sun rays

Here we go today i am going to explain How To Measure Earth's radius ? 

you just need a mountain & stop watch  don't able to afford a mountain alright just know the distance between two cities confused by the end of the article you will be able to understand everything just relaxed. So let's get started

Around the time 275BC there lived a greek Mathematician by the name of Eratosthenes born in cyrene (Modern day Libya).

 

So How Eratosthenes calculated earth's radius ?

Eratosthenes calculated the distance by the help of knowing the distance between two cities of egypt syene & Alexandria which is about 500 stadia (~ 800km) approx. from each other &these assumptions.

1.Syene is at the tropic of cancer (sun rays straight overhead)
2.The earth is a perfect sphere

3. The alexandria is due north of syene

4.The sun rays coming to earth are parallel

so 7/360 is equals to 800km of the circumference.

By this Eratosthenes able to calculate The circumference hence The radius of earth.

Which was not accurate at that time later other mathematician were able to calculate it.

Fun Fact you can see the sun rise 2 times if you are lying on a beach and suddenly sun started coming into the horizon just pop up frequently you will see the sun rise again !!

At the end Thank you Eratosthenes (276-194) BC and thanks for reading !!