Al-Biruni

Al-Biruni worked at the Ghazni court in what is now Afghanistan, producing more than a hundred works across astronomy, mathematics, geography, geology and comparative religion. He calculated the radius of the Earth to within about one percent of its modern value using the angle of dip to the horizon measured from a mountain of known height, a method requiring only trigonometry and one careful observation rather than an expedition. He also wrote one of the first systematic comparative studies of religion, describing Indian belief and practice from direct study of Sanskrit texts rather than secondhand report. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/