Science
The pitch drop experiment

588px-Pitch_drop_experiment_with_John_Mainstone.jpg

In 1927 Dr. Thomas Parnell at the University of Queensland heated a sample of petroleum pitch, also called bitumen, and poured it into a glass funnel, with a sealed neck, set in a ring stand. Three years later, in 1930, he broke the neck off the funnel and set it aside. It took eight years for the first drop of pitch to fall. The experiment has been running continuously ever since, and has produced a total of eight drops to date. The man shown in the photograph above is Dr. John Mainstone, who is the experiment’s current custodian.

The most recent drop fell in November 2000, which means the next one should be falling sometime in the next couple of years. The funnel contains enough pitch to run, it is estimated, at least another hundred years. To date, no one has ever witnessed or photographed a drop falling, but that’s likely to change with the next one. The University of Queensland maintains a webcam showing a live view of the experiment at all times. The photograph below shows a screenshot I captured of it just this morning:

pitch drop experiment webcam capture.jpg

16 thoughts on “The pitch drop experiment

  1. They are directly measuring the viscosity of pitch at room temperature, which, because it is effectively a solid (if you strike it with a hammer, it will shatter like glass), has probably not been done before, and certainly not on such a large scale.

  2. I used to walk past this everyday on the way to Physics class in my first year, back then it was set out in the hall/building foyer between two lecture theater doors. Always made me think about science, as knowledge that one generation passes on to the next and the idea that not everything has to have a fast answer. Plus it just kinda cool in a geeky way.

  3. I believe that nobody thought that the glass of the funnel and of the bell cover is also amourphous, so there is enough glass to drip for 1 millions years :). Probably nobody witnessed yet a glass drop…  

    1. Hate to ruin your fun, but glass doesn’t flow =). Amorphous doesn’t mean that the material will flow, it simply means that the solid isn’t formed by crystalisation. This makes it generally more brittle, but doesn’t allow the solid to flow.

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I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and makezine.com. My work has also appeared in ReadyMade, c't – Magazin für Computertechnik, and The Wall Street Journal.

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