Abu Raihan al-Biruni isn’t a household name in the West. But he should be. The Uzbek scholar’s phenomenal intellect and breathtaking discoveries should rank him alongside Aristotle, Galileo, and Newton in the pantheon of pre-modern scientific geniuses. His life was difficult. He never knew his father, and the region he lived in was going through a particularly war-torn period, forcing Biruni to frequently uproot himself and flee from various conflicts. Despite this, he managed to produce an astonishing 146 works. Only 22 of which have survived, but they are more than enough to secure his reputation for brilliance.
Hundreds of years before Copernicus, he demonstrated that it was possible for the Earth to revolve around the Sun rather than the other way around, although he concluded that he could not definitely prove it either way and called on mathematicians to do more work on the subject. Observing that fossils were sometimes found on remote mountains, he suggested that they had once been underwater, anticipating plate tectonics. In a move sure to endear him to modern skeptics, he dismissed astrological horoscopes as “sorcery.” His work on specific gravity was groundbreaking.
But Biruni’s greatest achievements lay in his work on latitude and longitude. A youthful interest in geography led him to begin collecting or calculating precise coordinates of various towns and cities across the known world. While still in his twenties, he used this data to calculate the precise circumference of the Earth, which he used to produce a new globe unparalleled until the Renaissance. Later in life, he developed a new technique using spherical trigonometry and the law of sines which allowed him to make even more accurate calculations. His ultimate estimate of the Earth’s circumference was only 10.44 miles off from our modern figures.
These calculations led Biruni to an astonishing realization. Once he knew the size of the Earth, Biruni could not help but notice that the known world, Asia, Europe, and Africa, only occupied a small part of it, two-fifths at best. So what was in the other three-fifths? Biruni dismissed the accepted view that the world consisted of one central landmass surrounded by a vast ocean—if a landmass had arisen in the known two-fifths of the world, he deduced, there was no logical reason why a similar process wouldn’t have occurred in the remaining three-fifths. Since the Eurasian/African landmass straddled the equator, Biruni reasoned that the mysterious other continent would likely do the same, since it would have arisen from the same processes. That meant that the new land would have a roughly similar climate and would almost certainly be capable of supporting human life.
Biruni made most of these discoveries in a hilltop fortress in what is now Pakistan, where he had fled to avoid the attentions of a particularly cruel local warlord. In a castle north of modern Islamabad, hundreds of miles from the sea, an 11th-century genius realized that the people of the Old World were not alone on this planet. In a way, his achievement was more impressive, if less world-shaking, than that of Columbus, who fully believed he could sail to Asia.