Pitch Drop Experiment

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Audio question

1. AA Queensland physicist set up the experiment in 1927 to demonstrate that pitch, though it shatters like a solid, flows as an extremely viscous liquid. Drops have fallen only about once a decade since 1938, long going unobserved by anyone, and the drip timing suggests pitch is vastly more viscous than water, illustrating how blurred the solid–liquid boundary is.
2. BThomas Parnell began the experiment in 1927 and personally observed each of the drops that fell during his lifetime, using the roughly annual drips to calculate that pitch is about a hundred billion times more viscous than water. The demonstration convinced his students that pitch is a true solid despite its appearance.
3. CThe main point of the lecture is that scientific instruments such as webcams have transformed how experiments are monitored. Because early researchers lacked such technology, the pitch drop experiment was abandoned for decades until modern cameras allowed the University of Queensland to resume it and finally record the first drop in 1938.
4. DThe lecture explains how a long-running Queensland experiment measuring the flow of pitch has become an important tool for the asphalt industry, since the viscosity data gathered from each drop helps engineers design road surfaces. The custodian John Mainstone recorded every drop over fifty years to build the dataset.

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Source: Pearson, PTE Academic & UKVI test format, Part 3: Listening, checked 9 October 2026.