The Middle Ages were not only a time of endless wars and epidemics, but also an era of scientific discoveries and a disinterested pursuit of knowledge. Medieval thinkers and practitioners explored the world around them, founded the first universities, invented mechanical clocks and devices for observing celestial bodies. In this book, our guide to the world of medieval science will be a real person, a monk named John Westwick, who lived in the 14th century and was educated in the largest monastery in England. The fascinating history of his scientific works allowed the author to show not the ceremonial world of star names and discoveries, but the atmosphere of the scientific search of that time, to present the ideas and achievements of the nameless majority of people with a scientific mindset, which so often escape the attention of historians. Traveling with Brother John in Britain and beyond, we will meet curious characters of those years: an English watchmaker abbot, a French artisan turned spy, a Persian polymath who founded the most advanced observatory in the world. We will find out how these people navigated by the stars, multiplied Roman numerals, treated diseases and determined the time with the help of an astrolabe, and reconsider the attitude to the Middle Ages as to dark times.