The waiting game: UQ’s pitch drop experiment

On a Friday afternoon in April 1979, John Mainstone, a physics professor at the University of Queensland, rang his wife at home. He wouldn’t be back that evening, he told her. For the previous 18 years, Mainstone had looked after the pitch drop experiment, a long-form demonstration of the extreme viscosity of pitch. For the first time since August 1970, the pitch was about to drip from its funnel, and Mainstone didn’t want to miss it.

Pitch is a resin: a viscoelastic substance derived from petroleum or coal tar, used in bitumen, and for waterproofing. Which is ironic, for as solid as it appears, pitch is fluid – at least, it is when you put it in a funnel, the sloping sides of which create a pressure gradient.

Mainstone stayed up all that Friday night. He continued to keep watch on the Saturday, eventually ringing his wife back to tell her he wouldn’t be home that night, either. Still, the globule of (literally) pitch-black liquid hung by a thread from the bottom of its funnel. On Sunday evening, exhausted by his vigil, he went home. By the time he returned to work on a sleep-deprived Monday morning, the pitch had dropped into its beaker.… Read more..