The 100-Year-Old Pitch Drop Experiment Could Last Another Century

The Guinness World Record for the longest-running scientific experiment is currently held by the ‘Pitch Drop Experiment’ at the University of Queensland, Australia.

The experiment, initiated in 1927 by physicist Thomas Parnell, could continue for another century. Parnell’s objective was to demonstrate pitch’s high viscosity and fluid nature—a tar derivative historically used in ship waterproofing, considered the thickest fluid known.

Parnell began the experiment by heating the pitch, pouring it into a sealed glass funnel, and allowing it to settle for three years. He then opened the funnel in 1930, setting the stage for an experiment intended as a straightforward demonstration. Remarkably, the setup does not require specialized environmental conditions and is displayed in a cabinet, where temperature fluctuations across seasons influence the pitch’s flow rate.

Could be any minute now.

A pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. pic.twitter.com/KRfZ8vNoP5

— World of Engineering (@engineers_feed) February 17, 2024

Professor John Mainstone took over the stewardship of the experiment in 1961 and oversaw it for over five decades. The experiment’s slow progression saw the first drop fall after eight years, with subsequent drops taking decades to detach. To date, nine drops have fallen, and anticipation is building for another this decade, although no one has yet witnessed a drop fall in real-time.

Experiment’s Findings:

Despite appearing solid and even brittle at room temperature—such that it can shatter like glass when struck—the experiment has revealed that pitch’s viscosity is approximately 100 billion times that of water. The setup still contains enough pitch to continue for another hundred years potentially.

In recognition of their unique contribution to science, Mainstone and Parnell received the Ig Nobel Prize in 2005 posthumously. This humorous yet thought-provoking award celebrates unusual and trivial scientific achievements that first make people laugh and then think. The longevity and quirky nature of the Pitch Drop Experiment have secured its place in both scientific and popular discourse.