Al-Biruni
Key Contribution:
Polymath who calculated Earth's radius with remarkable accuracy.
Preceded the West:
Calculated Earth's circumference 600 years before the West, with less than 1% error.
Abu Rayhan Muhammad ibn Ahmad al-Biruni was one of the greatest scholars in history, with contributions spanning mathematics, astronomy, physics, natural sciences, geography, history, and linguistics. He calculated the Earth's radius at 6,339.9 km — astonishingly close to the modern value of 6,371 km — using a method he devised by measuring the angle of depression from a mountaintop. He authored over 140 works. His Kitab al-Hind (Book of India) is considered the first work of comparative anthropology. He discussed the rotation of Earth on its axis, proposed that Earth revolves around the Sun (centuries before Copernicus), and made important contributions to trigonometry and the understanding of specific gravity.