Pioneering Muslim scientist Abu Rayan Al-Biruni developed a genuinely extraordinary and clever way to determine the radius of the world (and subsequently its circumference).
Only four measurements were needed for this procedure to be precise; the solution was then reached by using a trigonometric equation. The west did not discover what Biruni discovered in the 10th century with unparalleled accuracy and precision.
When the Abbasid Caliphate extended from Spain to the Indus River in present-day Pakistan, the necessity to determine the extent of the earth became apparent for the first time. Being far from the Kaaba does not exempt a Muslim from the requirement to offer prayers facing the direction of the Kaaba. Therefore, in order to pray, Muslims needed to know the precise direction of the Kaaba, regardless of their distance from it.
They needed to know the earth’s curvature in order to complete this task effectively and learning this required knowledge of the size of the planet. The Caliph, incidentally, was equally interested in the size of his dominion.
As a result, Abbasid Caliph Al-Mamun assembled a group of eminent academics and gave them the duty of estimating the size of the earth. They began by calculating the radius from which size could be inferred by multiplying the distance over which the sun’s angle at midday varied by one degree. Within 4% of the actual amount, they calculated a value. The issue with this system was that it was difficult to measure long straight lines between two sites in the sweltering desert; instead, they may have only needed to count steps.
Al-Biruni came up with a more complex and dependable strategy to accomplish this goal.
By using his formula, Biruni was able to calculate the earth’s circumference to within 200 miles of its actual value of 24,902 miles, or less than 1% error. The radius given by Biruni, 6335.725 km, is likewise fairly similar to the initial value.
