Nothing in my many years of reading about the Middle Ages had led me to suspect that the pope in the year 1000 was the leading mathematician and astronomer of his day.
Nor was his science just a sidelight. According to a chronicler who knew him, he rose from humble beginnings to the highest office in the Christian Church “on account of his scientific knowledge.”
To my mind, scientific knowledge and medieval Christianity had nothing in common. I was wrong.
... was the first Christian known to teach math using the nine Arabic numerals and zero. He devised an abacus, or counting board, that mimics the algorithms we use today for adding, subtracting, multiplying, and dividing. ...
Like a modern scientist, Gerbert questioned authority. He experimented. To learn which of two rules best calculated the area of an equilateral triangle, he cut out square inches of parchment and measured the triangle with them. To learn why organ pipes do not behave acoustically like strings, he built models and devised an equation. ...
Gerbert made sighting tubes to observe the stars and constructed globes on which their positions were recorded relative to lines of celestial longitude and latitude. He (or more likely his best student) wrote a book on the astrolabe, an instrument for telling time and making measurements by the sun or stars. You could even use it to calculate the circumference of the earth, which Gerbert and his peers knew very well was not flat like a disc but round as an apple.
Pope Sergius IV, who had been Gerbert’s papal librarian, wrote his epitaph [posted at St. John Lateran]. It reads, in part: “The emperor, Otto III, to whom he was always faithful and devoted, loved him greatly and offered him this church of Rome. They illuminated their time, emperor and pope, by the brilliance of their wisdom. The century rejoiced.” Upon Gerbert’s death, Sergius said, “the world was darkened and peace disappeared.”
How prophetic those words, written in 1009, now sound. Less than a hundred years later, a pope would launch the first Crusade, and The Scientist Pope would be branded a sorcerer and devil-worshipper for having taught the science that had come into Christian Europe from Islamic Spain.
"The world was darkened." That says a lot, dunnit? One of the great scientists of the tenth century was branded as a sorcerer in the 11th -- and, by the way, the brand stuck; only recently has Sylvester's reputation begun to recover.
In the same way, we have sometimes observed, the Renaissance gets a free pass. Witch-hunting, for example, was not (as some people still imagine) a product of the early medieval era; it began slowly in the 1300s and reached its fever pitch during the 16th and 17th centuries. That is to say, during the Reformation, and among Protestants as much as Papists.