Stokes' law, viscometry, and the Stokes falling sphere clock

Abstract

Clocks run through the history of physics. Galileo conceived of using the pendulum as a timing device on watching a hanging lamp swing in Pisa cathedral; Huygens invented the pendulum clock; and Einstein thought about clock synchronization in his Gedankenexperiment that led to relativity. Stokes derived his law in the course of investigations to determine the effect of a fluid medium on the swing of a pendulum. I sketch the work that has come out of this, Stokes drag, one of his most famous results. And to celebrate the 200th anniversary of George Gabriel Stokes’ birth I propose using the time of fall of a sphere through a fluid for a sculptural clock—a public kinetic artwork that will tell the time. This article is part of the theme issue ‘Stokes at 200 (part 2)’.