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Pitch drop experiment

  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 appear solid, most commonly bitumen. Tar pitch flows at room temperature, albeit very very slowly, eventually forming a drop.

The pitch drop experiment at the University Of Queensland

The most famous version of the experiment was started in 1927 by Professor Thomas Parnell of the University of Queensland in Brisbane, Australia, to demonstrate to students that some substances that appear to be solid are in fact very-high-viscosity fluids. Parnell 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 28 November 2000,[1] allowing experimenters to calculate that the pitch has a viscosity approximately 100 billion times that of water.

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. This experiment is pre-dated by two other still-active scientific devices, the Beverly Clock and the Oxford Electric Bell.

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.

  In October 2005, John Mainstone and the late Thomas Parnell were awarded the Ig Nobel Prize in Physics, a parody of the Nobel Prize, for the pitch drop experiment.[2]

To date, no one has ever actually witnessed a drop fall. The experiment is in the view of a webcam although technical problems prevented the most recent drop from being recorded.[3]


Date Event
1927Experiment set up
1930The stem was cut
December 19381st drop fell
February 19472nd drop fell
April 19543rd drop fell
May 19624th drop fell
August 19705th drop fell
April 19796th drop fell
July 19887th drop fell
November 28, 20008th drop fell


  1. ^ Edgeworth, R., Dalton, B.J. & Parnell, T.. The Pitch Drop Experiment (html). Retrieved on 2007-10-15.
  2. ^ John Mainstone's article on the eighth drop
  3. ^ University of Queensland page on the Pitch Drop experiment (links to webcam)
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Pitch_drop_experiment". A list of authors is available in Wikipedia.
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