Cardano, Dee, and Napier |

John Dee Exhibit, Royal College of Physicians, London 2016 |

John Dee's crystal ball |

Prior to my first sabbatical I had not heard of John Dee -- embarrassing to admit, but there it is. Thankfully, while I was in London the Royal College of Physicians was hosting a John Dee exhibit along with a variety of other Dee events. I found myself captivated. A book on display there linked John Dee with one of my favorite Italian mathematicians, Girolamo Cardano. I later learned that they had met, despite a quarter-century difference in their ages and despite living at such a distance from each other at a time when long-distance travel was onerous, to say the least! This link was the seed of the idea for this second sabbatical.

Dee's copy, with his marginal notes, of Scaliger's "critique" of Cardano |

Additionally during those first travels I learned more of John Napier -- also a Renaissance-era mathematician with a reputation for dabbling in the dark arts. How could I resist opportunity to study these three more deeply and in conjunction with each other? (And if any mathematicians are going to capture the imaginations of my students, wouldn't it be these three?! Crystal balls, castles, the Spanish Inquisition, codes, feuds, spy-craft, the occult, lost treasure, etc., etc., etc.)

John Napier's Tower House/Castle, Edinburgh, Scotland 2019 |

Beginning March 12, 2020, I will be "walking in the footsteps" of these mathematicians as closely as possible. I will be visiting places where they lived, studied, worked, worshiped, and died. I will read in library and museum archives, focusing especially on original documents such as diaries and letters. I will attend any and all talks, tours and events that I can find relating to these mathematicians.

Mathematically I will be studying their work on their terms, as they wrote it and understood it. The Renaissance Era was as much a rebirth and flowering of mathematics as it was of art, music and literature. These three mathematicians were deeply involved in this flowering that gave rise to the mathematics (and thus the technology) that we have today. For example, in 1545 Girolamo Cardano published

*Ars Magna*, or*The Great Art*, an extremely influential mathematics text that is a basis of our modern algebra. John Napier created logarithms, an invention that so shortened the time needed for calculations that he is said to have “doubled the life of the astronomer.” John Dee worked with mathematics relating to navigation and calendar reform and is the first person to have used the term “British Empire,” a phrase he coined in his role as adviser to Queen Elizabeth I.Though their mathematical contributions are profound, there is much more than mathematics that attracted me to these three. John Dee may have been a spy for Queen Elizabeth I and is thought to have inspired Ian Fleming’s James Bond character as well as Shakespeare’s Prospero and Marlowe’s Dr. Faustus. What kind of life must he have lived to have inspired such a diversity of fictional characters?! Girolamo Cardano was the second most renowned physician of his day and was also a gambler and an astrologer who was imprisoned by the Inquisition for, ostensibly, casting a horoscope of Jesus Christ. John Napier was an elder in his church, but he was also considered a sorcerer by his neighbors. That was a very fine line to walk, particularly in the 16

^{th}century when people were burned at the stake for witchcraft. Because of his reputation as a sorcerer, he was contracted to use his skills to search for treasure in Scotland’s Fast Castle.

There is a great deal more to what I am doing and exploring, but hopefully that gives a sense of the journey -- enough to tempt you to follow along!

In Italy my focus is

*mainly*Cardano (though while I'm there I'll also look into Bruno, Fibonacci, Pacioli, Somerville, etc.). I will be, at the very least, visiting the cities of**Rome**

**Naples**

**Florence**

**Vinci**

**Pisa**

**Bologna**

**Urbino**

**Venice**

**Padua**

**Milan**

**Sirmione**

**Pavia**

*mainly*on Dee, and in Scotland I'll focus

*mainly*on Napier. The cities I'll be visiting, at the very least, in the United Kingdom are

**London**

**Oxford**

**Eyemouth**

**Edinburgh**

**Gartness**

**St. Andrews**

I have been researching this with varying levels of intensity since my last sabbatical, and this research has now shifted into very high gear. I need to go in with a lot of knowledge in order to get as much out of this as I possibly can. I plan to begin regular blog posts a few days after landing in Rome on March 12, so watch this space in order to learn about those "Sorcerer Mathematicians of the Renaissance!"

**PS**This blog is a continuation from my previous sabbatical, so all the posts from those travels can be found below.