Al-Biruni measures the earth

1013

At a fort in northern India, the Khwarezmian polymath used a clever geometrical method involving the angle of declination from a mountain peak to estimate the earth's radius with remarkable accuracy. His result, computed on a scrap of paper, was within a few percent of modern values. The technique, requiring only a mountaintop and an astrolabe, was elegant proof that brilliance needs no elaborate apparatus.