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February 3rd, 2012

The ‘Pitch Drop’ experiment is one for the generations

Published on February 3rd, 2012 | By: Eileen De Guire

 

Screenshot from live webcam of the “Pitch Drop Experiment” at the University of Queensland in Australia. The experiment, begun in 1927, demonstrates the fluid nature of tar pitch at room temperature. Credit: U. Queensland, Australia.

Would you start an experiment that took three years to set up, yielded it’s first result eight years later and generated an average of one data point per decade? Botanists make the news now and then when something like the stinky “corpse flower” blooms once every ten years, but in the physical world, things tend to happen faster.

 

In 1927, University of Queensland’s first physics professor, Thomas Parnell, want to demonstrate that materials are not always what they seem. Tar pitch, for example, appears to be a brittle solid at room temperature and will shatter if struck with a hammer.

 

To demonstrate that tar pitch is actually a fluid, Parnell heated a sample of pitch and poured it into a glass funnel with a sealed stem. He allowed three years for the pitch to settle into the funnel, cut the seal in 1930 and waited.

 

Parnell was a patient man.

 

The first drop of pitch fell from the funnel in 1938, and a drop has fallen about once per decade since then. The ninth drop fell in November 2000.

 

Nobody has ever seen any of the drops fall. According to a story in the Brisbane Times, efforts to record the 2000 drip were foiled when the webcam equipment failed. The current curator of the experiment, UQ physics professor John Mainstone, estimates that the next drop will fall sometime around 2013.

 

The Brisbane Times story reports that the Guinness Book of World Records has recognized it as the longest running experiment in the world. The record is unlikely to be broken. Mainstone estimates that there is enough pitch in the funnel for the experiment to last another century or so. That means a yet-to-be-born Parnell will have to finish the experiment that his great-great-great grandfather started.

 

And, for those who have lots of time on their hands, the experiment can be watched via live webcam at the university’s webpage about the experiment.

 


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