Roger Bacon was born in England maybe about 1210 AD. It was late in the reign of King John. (That’s the one in Robin Hood.) England was just beginning to get richer from raising and selling high quality wool cloth on the Silk Road. In addition, a warmer climate – the Medieval Warm period – was making England a richer, nicer place to live. Roger’s own family was rich enough to send him to school, where he learned Latin and Greek and logic and the scientific method. When he grew up, Roger Bacon taught at Oxford University. He specialized in Aristotle. A few years later, he left Oxford to teach at the University of Paris, where he also taught astronomy, math, and music. He met a brilliant student, Thomas Aquinas, there. Roger Bacon never married or had children.
Around 1247 AD, when he was about forty years old, Bacon left his position in Paris and went back to England. But when he was about fifty he became a Franciscan monk, like his older mentor Robert Grosseteste. When Bacon was almost 60, in 1266, he wrote his Opus Majus (the Big Work), almost all of it in one very hard-working year. The book covers a lot of different subjects. Bacon built on his reading of Greek and Islamic astronomers to show that the medieval calendar year of 365 1/4 days was not accurate enough. He suggested adding a day every 125 years. And that’s more or less what eventually happened.
Roger Bacon also thought (wrongly) that the world was mostly dry land, not oceans. He may have drawn a map of the world, updating Ptolemy based on Islamic research. But if he did, it has been lost. Like the Chinese scientist Shen Gua, who lived a little earlier, Bacon also summarized and explained the works of many earlier scientists, especially ibn al-Hatham‘s work on eyes and light. Roger Bacon got optics added to the European university curriculum. He was the first European to describe gunpowder and firecrackers, and what the ingredients were. Along with copies of his book, Bacon also sent the Pope an early glass lens (this was just about the same time that Italian glassmakers were making the first eyeglasses).
Roger Bacon spent most of the rest of his life at Oxford, where he probably died around 1295, when he was more than eighty years old.