The pitch drop experiment is a long-term experiment which measures the flow of a piece of pitch over many years. Pitch is the name for any of a number of highly viscous liquids which appears solid, most commonly bitumen. Unlike glass, tar pitch flows at room temperature, albeit very very slowly. The experiment began in 1927 when Professor Thomas Parnell of the University of Queensland in Brisbane poured a sample of pitch into a sealed funnel and allowed it to settle for three years. In 1930, the seal at the neck of the funnel was broken, allowing the pitch to start flowing. Large droplets form and fall over the period of about a decade. The eighth drop fell on November 28 2000, allowing experimenters to calculate that the pitch has a viscosity approximately 100 billion times that of water.
The experiment is not carried out under any special controlled atmospheric conditions, meaning that the viscosity can vary throughout the year with fluctuations in temperature.
This is recorded in the Guinness Book of Records as the world's longest continuously running laboratory experiment, and it is expected that there is enough pitch in the funnel to allow it to continue for at least another hundred years.
It has been claimed this experiment is pre-dated by two other scientific devices, The Beverly Clock and The Oxford Electric Bell .
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