Two of my favorites on his list are Roger Bacon and Robert Grosseteste.

FORBES: Rick Santorum and the 13th Century

In 1267, legendary English scientist Roger Bacon published a recipe for gunpowder, and by the late 1300s, handheld, muzzle-loading pistols were common in Europe.

FORBES: No. 7 The Rifle

Until then, the Catholic Church branded as heretics scientific investigators who, like the 13th-century English friar Roger Bacon, calculated that the current calendar year was over-running the solar year by a whole day every 125 years.

ECONOMIST: Late for the date