Australia / Modern science
The Pitch Drop Experiment
At the University of Queensland, pitch that looks and feels solid has been flowing through a glass funnel since 1930. Only nine drops have completed the journey.
The apparatus stretches an ordinary physical process across human lifetimes. It makes viscosity visible while recording how temperature and experimental conditions shape a measurement.
A CLOSER LOOK
Physics professor Thomas Parnell began the demonstration in 1927. He heated pitch, poured it into a glass funnel with a sealed stem, and left it to settle for three years. In 1930 he cut the stem. The first drop took eight more years to fall.
Pitch is a tar-derived material once used for waterproofing boats. At room temperature it can be hard enough to shatter under a hammer, yet the experiment shows that it continues to flow. University measurements place this sample’s viscosity at roughly 100 billion times that of water.
Nine drops have fallen. The ninth touched the eighth in April 2014, and the accumulated material required a fresh receiving beaker. Long gaps make each event difficult to witness: earlier custodians found a completed drop after the fact, and a power failure prevented a camera from recording the eighth drop in 2000.
The apparatus was built as a lecture demonstration and does not have tightly controlled laboratory conditions. Seasonal temperature changes, air conditioning, display lighting, the shrinking mass in the funnel, and contact between drops have all affected its rate. The irregular timing is part of the record, so estimates for the next drop remain uncertain.
FOLLOW THE EVIDENCE
University of Queensland School of Mathematics and PhysicsPitch Drop experimentUniversity of Queensland Physics Museum1927 – Famous Pitch Drop ExperimentOriginal explanation based on the sources above. Images carry their own reuse terms.