Mathematician Alain Goriely, Professor of Mathematical Modelling at Oxford, explains why a cracking whip makes such a loud sound by building the mathematics behind it. Starting from simple demonstrations of whips and a chain fountain spilling over a pulley, he shows how naive energy and momentum arguments fail to explain the whip's motion, then constructs a proper model of a moving rope whose solutions blow up to infinity. He connects this to a 1927 experiment proving that whip tips break the sound barrier, and to the long-standing puzzle of why the tip moves at roughly twice the speed of sound. Along the way he brings in ancient whips, the debated idea of supersonic dinosaur tails, and finishes by linking the same mathematics to sperm motion and octopus arms. Delivered at Gresham College, the lecture moves from simple demonstrations to full simulations that match experimental data closely.