The pitch drop experiment is a long-term experiment measuring the flow of pitch over many years. The most famous version of the experiment was started in 1927 by Professor Thomas Parnell of the University of Queensland in Brisbane, Australia, demonstrating that some substances that appear to be solid are in fact very-high-viscosity fluids1. Pitch was heated and poured into a sealed funnel and allowed to settle. In 1930, the seal was cut to allow the pitch to start flowing. The duration of time between drops allows scientists to determine the viscosity of pitch is approximately 230 billion (2.3×1011) times that of water2.
This is recorded in Guinness World Records as the world's longest continuously running laboratory experiment, it is predicted that there is enough pitch in the funnel to allow it to continue for at least another hundred years3. This experiment is predated by only two other still-active scientific devices, the Oxford Electric Bell (1840) and the Beverly Clock (1864), but both have experienced interruptions. The experiment is monitored by a webcam (a livefeed can be viewed here) but technical problems prevented the November 2000 drop from being recorded. Professor John Mainstone died on 23 August 2013 following a stroke4. He was 78. A similar experiment started at Trinity College, Dublin in October 1944 dripped on July 11th, 2013, marking the first time a pitch drop was successfully filmed5.
This experiment has become so well known that it has even been an influence to art, where artist Julie Mecoli creates sculptures from substances similar to pitch like bitumen, which initially seems to act like a solid, but then can begin to slowly flow, transforming the sculpture.