This is a story about the ever-changing surface of our planet and how and why that happens. The first author was thanked by Hess (1960 preprint), but he only watched the theory’s growth from the sidelines. The 10 years that followed brought forth a deluge of evidence. Now 55 years later, no net torque amongst the plates remains, but still without a mechanism. Bowin (2010) demonstrated plate tectonics conserves angular momentum, but few appear to note its existence. This clarifies the mechanism.