$i$ demystifying Cover image generated with Bing's AI My son Mats has just learned about the complex numbers in high school! I was myself flabbergasted when I encountered the imaginary number back in 1985. How could you possibly come up with a kind of number called $i$ that squares to minus one , so $i^2=-1$? At SIGGRAPH 2001 - a conference for professional computed graphics - I learned about Geometric Algebra. This is an amazing forgotten framework from the 19th century, that is recently gaining in popularity again, because from a mathematical point of view, it is sheer beauty. It unifies so many seemingly different topics ( vectors, points, lines, planes, volumes, circles, spheres, complex numbers, quaternions, dual quaternions, determinants, intersections, homogenous coordinates, space-time algebra, spinors, tensors, ... ) in one coherent s