22/09/2023
Al-Biruni: The forgotten genius who measured the Earth
Al-Biruni (about 1,000 years ago) measured📏📐 the circumference of the Earth🌍 with an accuracy of 99.7% compared to today’s accepted value.
Al-Biruni was a Persian polymath who lived from 973 to 1048. He was a scholar of many fields, including astronomy, mathematics, geography, physics, and history.
In 1030, al-Biruni used trigonometry to measure the circumference of the Earth. His estimate was 6339.6 kilometers, which is within 0.3% of the modern accepted value of 6378.1 kilometers.
Al-Biruni's method was based on the principle that the Earth's curvature causes the horizon to appear lower from a mountaintop than it does from sea level. He measured the angle between the horizon and a plumb line at two different locations, and used this information to calculate the Earth's radius.
Al-Biruni's measurement of the Earth's circumference was one of the most accurate of its time. It was not surpassed until the 17th century, when the French mathematician and astronomer Jean Picard used a more precise method to measure the Earth's circumference.
