For most people, the first thing that comes to mind when they think of Leonardo da Vinci is the Mona Lisa, or his sketches of the Vitruvian man. Fans of pulp fiction or popular cinema might even find their minds drifting to memories of The Da Vinci Code, the mystery thriller. Not me, though. I’m engaged in the study of friction, the force resisting the relative motion between surfaces. What most people may not realise is that Leonardo was responsible for the first systematic study of friction.