William Rowan Hamilton, while walking with his wife along the Royal Canal in Dublin, grasps the solution to the problem of generalizing complex numbers to three-dimensional space. He is so excited by the discovery that he carves the solution into a stone on the Brughma Bridge: i2=j2=k2=ijk=-1: quaternions. Quaternions are used in computer graphics, control theory, robotics, signal processing, attitude control, physics, bioinformatics, and orbital mechanics. For example, it is common for spacecraft attitude control systems to be commanded in terms of quaternions. Tomb Raider (1996) is often cited as the first mass-market computer game to use quaternions to achieve smooth 3D rotation.
